Looks like it has been a week since my last post. This is not because I have not been working on the plane. This past week has been heavy with research, calling Vans to get answers to various questions, searching VAF to see how others have done things concerning the fuel tanks, and then the holidays managed to rear their ugly head once head, severely impeding what would otherwise be pretty good progress on the fuel tanks.
I ended up getting involved in one particular project that I managed to finish up today, that at face value does not seem to have anything to do with airplane building. More about that later.First I need to pick up where I left off, which was with the fabrication and match drilling of the stiffeners for both fuel tanks.
After that I took a deep dive into the plans and diagrams again, and started hitting up VAF pretty hard in search of answers to some very specific questions. It started when I was looking at the steps to fabricate and drills the rivet holes and holes for the fuel fittings and the vent line. I'll start with the vent line:
Q: The plans for the capacitive senders said to run the wires attached to each sender plate through the SB437-4 bushings that simply insert into the holes at the top of each rib that support the 1/4 inch OD hollow aluminum tubing from one end the tank to the other. The plans say to drill a small hole in the inner portion of the outer flange of this bushing to route the 18 ga. wire along side the vent line tubing. When you look at the snap bushing you just laugh, because Vans instructions are ridiculous. The question to them was how to drill this magical hole without exposing the wiring to the sharp edges of the hole in the tank rib where the snap bushing snaps into it. (There ain't a lot of room between the vent line and the snap bushing.
A: I was told by Vans to take a solid piece of 1/4 inch rod an insert it into each of the several snap bushings and then drill a hole on the inner surface of the bushing right next to the rod.
NOTE: I have since found out from my buddy Mike Rettig that the REAL way that most builders have done this is to take a jewelers circular file and file a small depression in the inner wall of the bushing - just enough to allow the wire to be inserted right next to the vent line. This needs to be done for each bushing through about 5 of the tank ribs.
Now, after having spent all this time writing up that little gem. you'll LOVE this:
As soon as I asked the above question to Vans, there was a pause on the other end of the phone for several seconds, and the next thing I heard was this:
"You must have ordered your wing kit with the capacitive sender kit a long time ago." Yes, I said, about 2010 as I recall. "Can I give you some advice?" Sure. "Take that capacitve sender kit that we sent you and throw it all away." Your kidding-right? " Nope. They have had so many problems that we stopped providing it as an option about 4-5 years ago (2012).
So there I was - all but ready to start working on the sender kit, and now I was being told not to use it. The reasons why were numerous. The most important reason was that different fuels with different blends have different capacitance values. If you ever plan to run auto gas and/or 100LL or some other type of approved avgas, the the capacitance is different for each type. Since most avionics and fuel gauges out there require calibration of the fuel system, the capacities and fuel gauges will all be calibrated with whatever fuel you put into the tanks at the time all this is done. If you then go and change fuels, your calibrations will be off, because the senders will be dealing with a different capacitance value due to the the different fuel. SO basically this will render your fuel gauges completely useless, unless you plan on recalibrating them every time you switch fuels.
I would also suspect that deposits from different fuel blends and additives might even contaminate the plates over time. Next, I was told a story about one of the Vans employees that still flies to work every morning in his RV, which also has the capacitive senders. Each day he flies past a group of three very tall radio towers, and every time he does this his fuel gauges drop to NOTHING due to some sort of RF interference playing havoc with the capacitve senders and electronics involved with the fuel gauges in his avionics system.
SO you might say - well I don't ever plan on switching fuels, so that shouldn't bother me. Well, how do you know what kind of fuel you are getting from place to place as you travel the country side in your new plane? Answer - you NEVER know exactly what kind of fuel you're getting, unless YOU were the one that refined it, tranported it to the airport, put it in the fueling truck, and fueled the airplane your self. Just because a fuel truck says it has 100LL in its tank does not mean that 100LL is what you are getting.
Anyway, the problems begin as soon as you end up with a mix of different fuels in your tanks. Between that issue and the stories of RF interference wreaking havoc on the system, I have decided that I am NOT going to install these stupid things. I'll give you one last consideration about all this, which VFR pilots will just never understand. If you are going to fly in IFR conditions, there will come a time when the weather throws you a curve ball, and you are going to have to make some decisions WHILE YOU ARE IN THE AIR about selecting and navigating to a NEW alternate airport. NOT the one that you filed you flight plan with because at the time when you were planning your flight your original selected alternate airport was within alternate minimums, but the NEW one you are going to have to determine if you ave enough fuel to get to safely, when all the "expected" weather conditions got crap on you while you are airborne.
If you cannot rely on what your fuel system is tellling you, then you have no business flying in IFR conditions in the first place IMHO.SO----now I ahve to purchase VANs fuel senders, which are standard float-type senders with essentially a potentiometer integrated into them. Another slight "hitch" to all this is that since I plan on putting a flop tube in my left tank for some added insurance during aerobatic maneuvering, the flop tube is long enough that it can interfere with the float sender arm, so instead of mounting the float sender in the normal location in the most inboard bay of the fuel tank, you have to mount it in the next bay over from the rear of the baffle plate. Vans plans show where this mod should be done, and the only thing I ponder is access to that unit for repair, removal, or replacement should the need arise - and it WILL arise at some point.
The only way to service the sender from this location, without having to remove the fuel tank from the wing, is from one of the access plate openings under the wing. I need t make sure that I can get to the screws and do whatever is necessary to remove any sealant material for that sender in order to get it out of the tank.
This will take me to the discussion/research about sealants, and some different things that various builders have done to facilitate "ease of maintenance" when the time comes. But it's late, and this post is already long enough with a week's worth of other stuff to report on, so I will end here for tonight. More to come this week. Like I said, lots of research and decisions to make at this stage of the build. Lot's of other experience to evaluate from others that have come before.
Other topics I will cover later:
Fabrication of the T405 and T410 tan k attach and support brackets
Sequence of installing AN833 6D and 4D AN elbow fittings
All about different types of sealant, applications methods, types of sealant to use inside and outside the tank, and more..
Semco Sealant gun and cartridges
Cutting large tank access holes in tank ribs using a fly wheel cutter in a drill press (That was scary and interesting all at the same time).
Using torque or allan head screws for the tank access plate instead of standard Phillips head #8 screws, as well as a different type of sealant for this area than standard proseal
What to do about planning for and putting in a fuel return (purge) line now - if anything?
Bung kit install procedures from SafeAir for extended fuel tank "readiness."
Searching for a piece of hinge material for the infamous "trap door," and what that is all about, and having to get up on my garage shelf for the first time in years to locate the flap hinges to borrow the hinge material I need for this.
Figuring the pivot point/radius from my tubing bending tool, which I will have to use once I start working on the vent lines.
Decisions to make about my standard Vans Fuel caps, i.e. to keep and use those or get some different ones
Bending and fabricating the standard fuel pickup tube from the 3/8 inch tubing supplied by Vans.
Relearning how to flare the ends of the tubing with the flaring tool.
And I'm just gettin' started.......... I'll get around to explaining what I mean by the title for this post in the next post, just to keep y'all guessing!
Till next time,
KPR.
Monday, December 11, 2017
Sunday, December 3, 2017
Clecoed, Match Drilled, and Deburred All Stiffener Holes
Today I used my #40 reamer and the quick change drill to match drill all the stiffener holes. After drilling each one I had to mark them carefully to ensure that the forward and rear stiffeners are easily identified and their positions preserved, and that the bays for each of the T711-B stiffeners are correctly identified as well. Even though the holes should be the same fr similar stiffener parts, I have learned over time that it is possible for slight variations to occur, so it is best to ensure that the parts that were drilled together are able to be matched together again when the time comes for riveting.
In my previous post I was perhaps a bit premature in my statements about how close I am to completing the tank. The truth is that I have many many more preparatory steps to complete, including some fabrication of various parts, mounting of fuel pickup lines, scuffing and cleaning the contact areas for the proseal, and dimpling all the parts for rivets and screw holes, etc.
My left tank will incorporate a flop tube pick up line that I will use when performing any aerobatics, while the right tank will have a standard pickup tube. The flop tube assembly is a bit different from the standard fuel pickup assembly, but they both accomplish the same basic objective - keep fuel flowing to the engine at all times, no matter what flight attitude you may be in.
I removed and marked all the stiffeners as described above, then I deburred all the holes, including the inner and outer skin holes, and the front and rear of each set of stiffener flange holes.
So it looks like I now need to disassemble the tank parts again and begin the process of fabricating the brackets and drilling the holes for the fuel line and vent line fittings, and the filler port and fuel drain fittings, and start working on the capacitive fuel sender for the left tank.
KPR
In my previous post I was perhaps a bit premature in my statements about how close I am to completing the tank. The truth is that I have many many more preparatory steps to complete, including some fabrication of various parts, mounting of fuel pickup lines, scuffing and cleaning the contact areas for the proseal, and dimpling all the parts for rivets and screw holes, etc.
My left tank will incorporate a flop tube pick up line that I will use when performing any aerobatics, while the right tank will have a standard pickup tube. The flop tube assembly is a bit different from the standard fuel pickup assembly, but they both accomplish the same basic objective - keep fuel flowing to the engine at all times, no matter what flight attitude you may be in.
I removed and marked all the stiffeners as described above, then I deburred all the holes, including the inner and outer skin holes, and the front and rear of each set of stiffener flange holes.
So it looks like I now need to disassemble the tank parts again and begin the process of fabricating the brackets and drilling the holes for the fuel line and vent line fittings, and the filler port and fuel drain fittings, and start working on the capacitive fuel sender for the left tank.
KPR
Cut, Formed, and Clecoed Tank Stiffeners onto the Lower Skin of the Fuel Tank
Before I get started about the stiffeners, here is a pic showing the quick change chuck and several collets with different bits and reamers in them:
The small dimples near the root of the collet are the recessed holes where the ball bearings in the chuck lock it in place. The nice thing about this tool set is that they give you 3 each #40 and #30 sized collets, so you can mount a drill bit in one, a reamer in another one, and a clearance or pilot bit in another one. then all you have to do is change the collet when you need a different tool. The only thing I don't like about it much is that it takes two different sized wrenches to tighten the bits in each collet.But since you should only have to do that every once in a while it's not that big of a deal.
Now on the stiffeners. I never thought I would get as much done on these as I did today. especially after attending the annual Parade of Lights in downtown Denver last night and hitting a couple of bars afterward. Was a fun night, but a really late one as well.
Preparing stiffeners always means cutting the basic parts from specially prepared aluminum angle that is pre-punched at the factory with a system of guide holes, notches, and grooves. These locations are then used to mark the positions where 90 degree angle cuts are made to separate each stiffener from the angle stock, and then t make the angular tapered cuts on one side that are designed to reduce stress concentrations and diffuse them across the entire part. I commented further about these when I did the rudder and the elevators long ago. The process for the making the fuel tank stiffeners is exactly the same.
Since I use a Dremel cutoff wheel to separate each stiffener from the common 3-4 foot long piece of aluminum angle, Safety is paramount. There are all sorts of ways to hurt yourself badly when making these parts. I ALWAYS where ear muffs AND safety goggles when I fab these parts.
Here is how I started out - Two clamps securing the first of 4 separate angles that must be cut to produce all of the stiffeners for each fuel tank. You can also see the dremel tool with the flex shaft and the cutting wheel in the distance on the floor.
Lines have been drawn by connecting all the notches. Then you use these as guides for making the rough cut of each stiffener. Then you start cutting. I extended the angle out from the edge of the bench far enough to allow room for the dremel tool to make the angular cuts as well as the separation cuts. As you cut each stiffener you remove the clamps, move the angle a bit more, and cut the next one, then wash, rinse, repeat.
Here is shot of the smallest of the stiffeners after cutting. Lots of sharp and raggedy edges on these, so be careful when you pick them up from the floor
When you get to the very last stiffener on the supplied angle, you need to reposition it to a different orientation on the bench so you can cut the last angle on the end. All I had to do was clamp it to the other edge at the corner of my work bench:
And here are all the individual stiffeners immediately after cutting them from the angle
And here is the dangerous mess that it leaves on the floor. Be sure that you don't do this job in your bare or stocking feet. You should also know that even though I wear the safety goggles, you have to get used to being pelted by metal particles when using a dremel cutoff wheel. It just happens, so you just need to deal with it. Nothing is large enough to puncture the skin, but you definitely feel it when they hit your face. So eye protection is absolutely necessary.
Trust me, those remnants are all razor sharp. I have never found a good use for any of this scrap metal, so the best place for this stuff is in the aluminum recycling bin.
After they are all cut, then next steps is to debur all the edges on the scotchbrite wheel. There are 6 bays per fuel tank, and two stiffeners on the bottom skin per bay, for a total of 12 stiffeners per fuel tank, or 24 total. So it takes a while to get all the edges nice and smooth, but when you do, you end up with a stack that looks like this:
Each of these four sets of stiffeners, marked T711 A through D, are different lengths. the longer ones are either 8 inches, just under 8 inches by varying amounts. So it is important to make sure that you cut and trim them as closely as possible to the expected dimensions, and even more important to label them properly, since they need to go in the proper bay of the fuel tank. The T711B stiffeners are place in 3 of the 6 bays in each tank, so there are more of them than the any other stiffener. All others will consist of a total of 4 stiffeners each for the A,C, and D parts.
The next step is clecoing them to the bottom of the fuel tank. Vans shows the basic orientaion of each one, which is to have the flange with the rivet holes facing forward, and the "stiffening" angle toward the rear of the tank. However, then they have a note somewhere on the plans that states that it is OK to change the orientation of the stiffeners by reversing them to make it easier to apply the proseal and back rivet them in place. Here are the pics with each stiffener clecoed in place:
Next step is to match drill the rivet holes for each stiffener and debur them. Then I need to start masking them with electrical tape and start getting my proseal routine, supplies, and procedures in order. Then the fuel filler port and fuel sump drain flange need to be positioned and drilled into the skin. So it was a good day at the factory since I was able to fab all of the tank stiffeners. This tank is rapidly getting to a point where it will be ready for the "goop" and riveting pretty soon.
KPR
Now on the stiffeners. I never thought I would get as much done on these as I did today. especially after attending the annual Parade of Lights in downtown Denver last night and hitting a couple of bars afterward. Was a fun night, but a really late one as well.
Preparing stiffeners always means cutting the basic parts from specially prepared aluminum angle that is pre-punched at the factory with a system of guide holes, notches, and grooves. These locations are then used to mark the positions where 90 degree angle cuts are made to separate each stiffener from the angle stock, and then t make the angular tapered cuts on one side that are designed to reduce stress concentrations and diffuse them across the entire part. I commented further about these when I did the rudder and the elevators long ago. The process for the making the fuel tank stiffeners is exactly the same.
Since I use a Dremel cutoff wheel to separate each stiffener from the common 3-4 foot long piece of aluminum angle, Safety is paramount. There are all sorts of ways to hurt yourself badly when making these parts. I ALWAYS where ear muffs AND safety goggles when I fab these parts.
After they are all cut, then next steps is to debur all the edges on the scotchbrite wheel. There are 6 bays per fuel tank, and two stiffeners on the bottom skin per bay, for a total of 12 stiffeners per fuel tank, or 24 total. So it takes a while to get all the edges nice and smooth, but when you do, you end up with a stack that looks like this:
The next step is clecoing them to the bottom of the fuel tank. Vans shows the basic orientaion of each one, which is to have the flange with the rivet holes facing forward, and the "stiffening" angle toward the rear of the tank. However, then they have a note somewhere on the plans that states that it is OK to change the orientation of the stiffeners by reversing them to make it easier to apply the proseal and back rivet them in place. Here are the pics with each stiffener clecoed in place:
KPR
Friday, December 1, 2017
Wrestled the Tank back together and countersunk the skin-to-baffle holes
Last night I was able to get the tank clecoed back together. It took a while, but seemed to go together fairly well. After I got the rear baffled re-installed, I did a trial fit with my microstop countersink tool and noticed that it was a bit difficult to get the pilot of the bit into the rivet holes. After pondering that for a day I decided to run a #40 reamer through each of the rivet holes to ensure that the pilot of the countersink cutter could be easily inserted into the hole.
Vans instructs you to countersink the skin in this area so that you don't have to deal with proseal and dimples later on. This could make it difficult to fit the rear baffle onto the tank and ensure that it is properly sealed up. If you countersink the skin holes then the holes in the baffle plate can remain as is, with no dimples. THis makes it easier to slide the baffle plate into position and rivet it in place when the time comes.
Tonight, after I ran the reamer through all those rivet holes, I took a piece of .032 scrap and .025 scrap and clamped them together. Then drilled #40 holes, deburred them, and then took the MS countersinl bit and did a test to ensure that the rivets would be set to the proper depth. In a phone conversation with Vans today they told me to set the depth so that these rivets would sit flush with the surface of the skin. I asked about this because was not sure if I needed to countersink them a bit deeper to allow for proseal that might fill the rivet holes. They said to keep them flush with the skin surface because these rivets should NOT be exposed to proseal.
So I verified that the test resulted in the rivets sitting flush with the tank skin. Then the fun began. The fuel was in the cradle, and the cradle was clamped to my work table. I then started to countersink ALL of those rivet holes. I spot checked the depth every so often with an AN426AD3 rivet, and they all looked like they were going to sit nice and flush.
This also took a while, and by the time I was finished with both sides, it was pretty flippin' cold in the garage. Too cold for pics in fact. SO I called it a night. Next step is to cut and fabricate the stiffeners, cleco those to the tank and match drill the rivet holes.
During my call to Vans I asked all of the questions I mentioned in a previous post. Here are the answers:
1. Countersink all the skin-to-baffle rivets so they are flush with the tank skin.
2. Do create a void in the T-405 tank attach bracket to ensure that there is enough room to clear the few rivets that will be protruding through the rib flange after the tank skin is riveted to the inboard tank rib.
3. Totally OK to leave the T-712 Z bracket flange UNPRIMED where it will be riveted to the rear baffle plate, and put proseal on the entire flange. Also need to leave the area o the baffle plate where that flange will be placed unprimed as well.
4. Perfectly OK to scuff out any scratches in the inside of the tank and leave them unprimed. When I asked if there was a concern about corrosion in the tank since I would be removing the alclad layer, I was told that the tank will have fuel in it most of the time, and it will be sealed except for the vent line, so corrosion from exposure to the air and moisture is not much of a concern for the inside of the fuel tank.
5. It is OK to scuff an area of the tank skin that is somewhat larger than the width of the rib flanges. Proseal will only be placed in an area relatively close to the rib flanges, bt for the same reason as described previously, scuffing and cleaning an area on the surface of the skin that is a bit wider is just fine.
6. Countersinking the .032 tank skin might result in "just touching" the metal of the baffle plate as well per Vans. Normally you do not think about countersinking something unless it is .040 inches thick or greater, but in this case you are instructed to do it by Vans for reasons previously stated. However, this means that almost the entire thickness of the .032 tank skin will be countersunk, and perhaps a small amount of the baffle flange that sits behind it. I will be curious to see how that worked out when I remove the baffle plate again to fit the stiffeners in place.
So I will scuff out the deeper scratches and don't need to worry about leaving the surface exposed after removing the alclad layer. That makes me feel a bit better. I have already been scuffing the inner surfaces of all my skins in a very similar manner anyway, so this will be like a normal routine for me anyway.
I also decided to remove the jacobs chuck in my older air drill and attach the quick change chuck, so that I could try it out and see how well that works. I did not want to remove the standard chuck in my Sioux air drill because I was concerned about not being able to use any drill bit sizes that did not have a matching quick change collet for them. However, that is when I learned that one of the attachments I received with the quick change set was an extension collet that has another 1/4-28 threaded shaft on the end, so that you can put that collet in the quick change chuck and then attach the standard jacobs chuck to the end of that collet, so you can still use any size drill bit by using this adapter. Even so, I still wanted to leave the original chuck in my sioux drill for now. I'll add more pics of all that tool stuff tomorrow.
KPR
Vans instructs you to countersink the skin in this area so that you don't have to deal with proseal and dimples later on. This could make it difficult to fit the rear baffle onto the tank and ensure that it is properly sealed up. If you countersink the skin holes then the holes in the baffle plate can remain as is, with no dimples. THis makes it easier to slide the baffle plate into position and rivet it in place when the time comes.
Tonight, after I ran the reamer through all those rivet holes, I took a piece of .032 scrap and .025 scrap and clamped them together. Then drilled #40 holes, deburred them, and then took the MS countersinl bit and did a test to ensure that the rivets would be set to the proper depth. In a phone conversation with Vans today they told me to set the depth so that these rivets would sit flush with the surface of the skin. I asked about this because was not sure if I needed to countersink them a bit deeper to allow for proseal that might fill the rivet holes. They said to keep them flush with the skin surface because these rivets should NOT be exposed to proseal.
So I verified that the test resulted in the rivets sitting flush with the tank skin. Then the fun began. The fuel was in the cradle, and the cradle was clamped to my work table. I then started to countersink ALL of those rivet holes. I spot checked the depth every so often with an AN426AD3 rivet, and they all looked like they were going to sit nice and flush.
This also took a while, and by the time I was finished with both sides, it was pretty flippin' cold in the garage. Too cold for pics in fact. SO I called it a night. Next step is to cut and fabricate the stiffeners, cleco those to the tank and match drill the rivet holes.
During my call to Vans I asked all of the questions I mentioned in a previous post. Here are the answers:
1. Countersink all the skin-to-baffle rivets so they are flush with the tank skin.
2. Do create a void in the T-405 tank attach bracket to ensure that there is enough room to clear the few rivets that will be protruding through the rib flange after the tank skin is riveted to the inboard tank rib.
3. Totally OK to leave the T-712 Z bracket flange UNPRIMED where it will be riveted to the rear baffle plate, and put proseal on the entire flange. Also need to leave the area o the baffle plate where that flange will be placed unprimed as well.
4. Perfectly OK to scuff out any scratches in the inside of the tank and leave them unprimed. When I asked if there was a concern about corrosion in the tank since I would be removing the alclad layer, I was told that the tank will have fuel in it most of the time, and it will be sealed except for the vent line, so corrosion from exposure to the air and moisture is not much of a concern for the inside of the fuel tank.
5. It is OK to scuff an area of the tank skin that is somewhat larger than the width of the rib flanges. Proseal will only be placed in an area relatively close to the rib flanges, bt for the same reason as described previously, scuffing and cleaning an area on the surface of the skin that is a bit wider is just fine.
6. Countersinking the .032 tank skin might result in "just touching" the metal of the baffle plate as well per Vans. Normally you do not think about countersinking something unless it is .040 inches thick or greater, but in this case you are instructed to do it by Vans for reasons previously stated. However, this means that almost the entire thickness of the .032 tank skin will be countersunk, and perhaps a small amount of the baffle flange that sits behind it. I will be curious to see how that worked out when I remove the baffle plate again to fit the stiffeners in place.
So I will scuff out the deeper scratches and don't need to worry about leaving the surface exposed after removing the alclad layer. That makes me feel a bit better. I have already been scuffing the inner surfaces of all my skins in a very similar manner anyway, so this will be like a normal routine for me anyway.
I also decided to remove the jacobs chuck in my older air drill and attach the quick change chuck, so that I could try it out and see how well that works. I did not want to remove the standard chuck in my Sioux air drill because I was concerned about not being able to use any drill bit sizes that did not have a matching quick change collet for them. However, that is when I learned that one of the attachments I received with the quick change set was an extension collet that has another 1/4-28 threaded shaft on the end, so that you can put that collet in the quick change chuck and then attach the standard jacobs chuck to the end of that collet, so you can still use any size drill bit by using this adapter. Even so, I still wanted to leave the original chuck in my sioux drill for now. I'll add more pics of all that tool stuff tomorrow.
KPR
Tuesday, November 28, 2017
Coming up with a Better Mousetrap for Deburring Rib Flanges
Tonight I set out to debur the inner rib flange holes of all 7 tank ribs, and reassemble the tank with the baffle plate. After suffering through yet another trip to the dentist where they had to shoot me up 3 times to refill a cracked filling, and then biting my tongue pretty bad in the process, when the drug finally wore off I was not feeling quite 100%. So I decided to keep the plan activity to a minimum by only deburring the rivet holes in the rib flanges.
However, this seemingly small task re-opened another nagging problem that I have encountered before, but never really managed to solve. That task is trying to find a tool with a 90 degree angle that has a small enough profile to be able to insert a deburring bit and properly debur the holes in the inner rib flanges. The problem is that there is only about 5/16ths of an inch clearance from the rib web to the rivet hole, and although this task must be performed a rather significant number of times, nobody seems to make a custom tool specifically for this purpose. So everyone seems to come up with their own creation to try to accomplish this task.
In my case, I was simply going to take my deburring bit in my fingers and clean each rivet hole manually, and then spend the next several days recovering from the pain in my fingers, just like I did for the similar rivet holes in the main wing ribs a long time ago. Then, just as I got started on the first rib, I had a moment of clarity. For some reason I was thinking about back riveting the rib flange holes and the top main wing skins, and the fact that I still needed to order a 12 inch extended shaft back rivet set in order to do this.
That's when I had the brilliant idea that could use a similar extended shaft with a hex insert for the deburring bit. There would still be a slight angle of the bit against the rivet hole, but the low angle still allowed the holes to be deburred adequately. I taped the bit in place in the extension to keep it from falling out:
Before I settled on the above solution, I was also pondering a couple of other ideas. The first one was to use my drill-driven 90 degree angle drill attachment that I ordered with my tool kit when I started this crazy project. It has a fitting that will accept the screw shaft of that 3 flute deburring bit on the end of the yellow-handled tool I reviewed in my previous post. Unfortunately, just as I had mentioned at the beginning of this post, the width of the tool is just too wide to allow the bit to reach the hole properly:
And then I had another thought. I had also ordered a set of quick disconnect bits with a chuck that was designed to replace the chuck in my air drill. I have never used any of them because I never got around to deciding to remove the standard chuck from the air drill. These last two pics are of the bits that came with the 90 degree drill attachment shown above, and then the quick disconnect bits. The quick disconnect chuck and collets have a design that is very similar to my edge deburring tool. The collet shaft has a set of divets in it that fit the ball bearings inside the chuck and locks the collet in place. the pic below shows the 1/4 inch collet with one of my 1/4 inch drill bits inserted and secured with the collet nut. Think of it as a big Dremel tool attachment with a special shaft insertion and locking design with multiple collets of different sizes for different sizes of commonly used drill bits.
These would certainly be easier and quicker to change out than having to use the manual chuck key to change bits each time. The only problem is that they use a specialized chuck, and once you remove the standard chuck and replace it with this chuck you pretty much have to use the collets for that chuck from that point on. Luckily I now have two air drills, so I can keep the standard chuck in one of them and the quick disconnect chuck in the other one:
Unfortunately the quick disconnect set does not come with a deburring bit, nor does the 90 degree angle drill set. Anyway, it had been way too long since I had even looked at these other tools so I decided to break them out to "refresh" my memory about them. I may decide to get brave and figure out how to replace the standard chuck in one of my air drills with the quick disconnect chuck. I seem to recall that I have instructions for that lying around somewhere - I'll have to look.
So I managed to get the inner rib flange holes deburred, and I also manged to use my edge deburring tool to smooth the edges of the remaining tooling holes in each rib. Apparently I discovered that I had deburred the larger holes in the inner ribs that are designed to allow fuel to pass through from each bay of the tank as it empties from the most outboard bay near the fuel cap toward the inboard bay where the fuel pick up tube resides.
However, this seemingly small task re-opened another nagging problem that I have encountered before, but never really managed to solve. That task is trying to find a tool with a 90 degree angle that has a small enough profile to be able to insert a deburring bit and properly debur the holes in the inner rib flanges. The problem is that there is only about 5/16ths of an inch clearance from the rib web to the rivet hole, and although this task must be performed a rather significant number of times, nobody seems to make a custom tool specifically for this purpose. So everyone seems to come up with their own creation to try to accomplish this task.
In my case, I was simply going to take my deburring bit in my fingers and clean each rivet hole manually, and then spend the next several days recovering from the pain in my fingers, just like I did for the similar rivet holes in the main wing ribs a long time ago. Then, just as I got started on the first rib, I had a moment of clarity. For some reason I was thinking about back riveting the rib flange holes and the top main wing skins, and the fact that I still needed to order a 12 inch extended shaft back rivet set in order to do this.
That's when I had the brilliant idea that could use a similar extended shaft with a hex insert for the deburring bit. There would still be a slight angle of the bit against the rivet hole, but the low angle still allowed the holes to be deburred adequately. I taped the bit in place in the extension to keep it from falling out:
These would certainly be easier and quicker to change out than having to use the manual chuck key to change bits each time. The only problem is that they use a specialized chuck, and once you remove the standard chuck and replace it with this chuck you pretty much have to use the collets for that chuck from that point on. Luckily I now have two air drills, so I can keep the standard chuck in one of them and the quick disconnect chuck in the other one:
So I managed to get the inner rib flange holes deburred, and I also manged to use my edge deburring tool to smooth the edges of the remaining tooling holes in each rib. Apparently I discovered that I had deburred the larger holes in the inner ribs that are designed to allow fuel to pass through from each bay of the tank as it empties from the most outboard bay near the fuel cap toward the inboard bay where the fuel pick up tube resides.
Monday, November 27, 2017
Deburred the tank rib flange to skin holes
Today I managed to start deburring the rivet holes for the tank rib flanges and the tank skin. The first order of business was to start removing the ribs one at a time with the tank in the cradle. This fuel tank has been clecoed together for over 3.5 years. This is the first time (aside from the removal of the inboard and outboard ribs to drill the tank baffle to the Z brackets) that the fuel tank has been completely disassembled since that time.
After removing all the tank ribs, I was bit surprized by the amount of "residue" sitting in the bottom of the tank skin. This is the result of all the match drilling and deburring that had taken place so far:
If only that were gold dust in there!
The next shot was simply to show the removal of the blue vinyl along the rivet lines for the ribs. I am leaving most of the vinyl covering over the holes for the stiffeners until those have been match drilled.
And of course this next pic has to come out blurry. I was trying to get a shot of a problem area that I will actually have to call Vans about tomorrow. Unfortunately, long ago when I was first wrestling the tank together, this resulted in some unsightly scratches that extend a bit wider than the typical inch or so on either side of the rivet hole center lines where I scuff and clean the line for primer. This usually does not phase me too much because I can always scuff the scratches out and prime over then since the alcad layer is removed during the scuffing process.
For the fuel tanks, no primer or other anti-corrosion treatment can be applied because it might not ply well with 100LL avgas. So now I need to find out just how wide I nee to scuff everything, because I HAVE to do it to prepare for proseal, but what I don't know is if I am supposed to ONLY scuff enough material to be as wide as the rib flanges, but no wider than that. Most other builders logs the that I review show that they have scuffed quite a bit more material, much wider than the width of the rib flange, but I don't think that proseal is applied to the area that is wider than the rib flange. Anyway, I have to check this because worst case is I will need a new tank skin.
Next is the stack of ribs that were already marked for each position inside the skin. As I pulled then out of the skin it was obvious that I need to do a bit more deburring and maybe touch up a few edges here and there on certain ribs.But the main task for tonight was to get as many holes deburred as possible.
I was able to debur the both sides of the fuel tank skin for each rivet line of each rib. I did the outer holes with the skin still in the cradle. For the inner holes, I wanted to try to continue to use my standard deburring bit in my electric screw driver, but to do so meant that I needed to remove the skin frm the cradle and place it on top of the dimpling table on my work bench. This would allow the skin to open up enough to be able to use the screwdriver to debur the holes.
I also was able to finish deburring all of the #19 screw holes for the joiner plate attachment on the outboard edge of the tank skin as well as the holes along the top and bottom edges of the skin where they attach to the main wing spar flange. To do this I used a combination of my standard deburring bit, and my edge deburring tool. These screw holes are about the same size as the tooling holes that are used to hydroform each of the ribs at the factory. I found that they were large enough that I could use the edge deburring tool to go around the edges of each hole to make sure they are truly smooth and free of burs.
Why is this so important? If the edges of these holes are not extremely smooth, when you try to dimple them with the #8 dimple die they can crack or end up having rough edges that could lead to stress cracks later on. So it is vital that these holes are super smooth. Here are the tools I am talking about:
The one on the left is my standard deburring bit from Cleaveland tools. It fits in my small electric screwdriver (NOT DRILL!!) DO NOT use this in a drill - only a screw driver with a slow setting. Usually 2 squeezes of the trigger does the job for #30 and #40 holes. It only has one single flute on the tip.
The center tool is the edge deburring tool with a fine hardened small blade. It is normally used for deburring straight edges in skins, but works pretty well in these larger sized bolt and screw holes.
The tool on the right is a speed deburring bit, similar to the one on the left, but with 3 cutting flutes instead of one. All I can say about this tool is to AVOID using it all costs. It tends to chatter when used, leaving uneven edges around the hole, and it can also take off too much material too quickly, which will leave the hole basically countersunk instead of deburred if you are not careful. Needless to say I don't like this tool very much and therefore do NOT use it very often.
I'm sure I have reviewed the use of these tools before, but it never hurts to do a refresher now and then. I managed to debur the outer flanges of all 7 tank ribs, so tomorrow I still need to debur the inner flanges, which, unfortunately, I have found I need to do by hand with my standard deburring bit. This is because I have not found a good reliable method for using an angle drill that would actually fit in the small space without marring up the rib web in the process. So I just do these holes by hand, painful as it sounds.
Lastly, I did some research on the T-405 tank attach bracket. Turns out there are some tricks to this assembly that also need to be taken into account when this is fabricated and positioned inside the nose section of the inboard tank rib.
Questions for Vans that need to be asked tomorrow are:
1. Scratches in the tank skin beyond the edges of the rib flanges - can I scuff those out without compromising the skin?
2. Z bracket prep for proseal and primer - do I plan to proseal the entire T-712 Z bracket flange that will sit against the rear baffle plate, or do I prime this flange, but only in the areas where proseal is not applied, i.e. about 1/2 inch around each rivet hole.
3. Method for clearing rivets when fabricating and positioning the T-405 tank attach bracket? Notches? Reduce the edge enough for dimple and rivet shop head clearance where the skin attaches to the rib?
After I get all the inner rib holes deburred, I need to put everything back together so I can countersink the rear baffle plate holes where they attach to the tank skin. I kind of did this out of order from the instructions because I wanted to remove all the burs first before I countersink these skin holes, to make sure everything is fitting together properly. I probably should have just countersunk the holes in hindsight before I removed the ribs - oh well - so it goes.
So deburring the inner rib flange holes and hopefully rough cutting the stiffeners are next on the list for tomorrow.
KPR
After removing all the tank ribs, I was bit surprized by the amount of "residue" sitting in the bottom of the tank skin. This is the result of all the match drilling and deburring that had taken place so far:
The next shot was simply to show the removal of the blue vinyl along the rivet lines for the ribs. I am leaving most of the vinyl covering over the holes for the stiffeners until those have been match drilled.
For the fuel tanks, no primer or other anti-corrosion treatment can be applied because it might not ply well with 100LL avgas. So now I need to find out just how wide I nee to scuff everything, because I HAVE to do it to prepare for proseal, but what I don't know is if I am supposed to ONLY scuff enough material to be as wide as the rib flanges, but no wider than that. Most other builders logs the that I review show that they have scuffed quite a bit more material, much wider than the width of the rib flange, but I don't think that proseal is applied to the area that is wider than the rib flange. Anyway, I have to check this because worst case is I will need a new tank skin.
I also was able to finish deburring all of the #19 screw holes for the joiner plate attachment on the outboard edge of the tank skin as well as the holes along the top and bottom edges of the skin where they attach to the main wing spar flange. To do this I used a combination of my standard deburring bit, and my edge deburring tool. These screw holes are about the same size as the tooling holes that are used to hydroform each of the ribs at the factory. I found that they were large enough that I could use the edge deburring tool to go around the edges of each hole to make sure they are truly smooth and free of burs.
Why is this so important? If the edges of these holes are not extremely smooth, when you try to dimple them with the #8 dimple die they can crack or end up having rough edges that could lead to stress cracks later on. So it is vital that these holes are super smooth. Here are the tools I am talking about:
The center tool is the edge deburring tool with a fine hardened small blade. It is normally used for deburring straight edges in skins, but works pretty well in these larger sized bolt and screw holes.
The tool on the right is a speed deburring bit, similar to the one on the left, but with 3 cutting flutes instead of one. All I can say about this tool is to AVOID using it all costs. It tends to chatter when used, leaving uneven edges around the hole, and it can also take off too much material too quickly, which will leave the hole basically countersunk instead of deburred if you are not careful. Needless to say I don't like this tool very much and therefore do NOT use it very often.
I'm sure I have reviewed the use of these tools before, but it never hurts to do a refresher now and then. I managed to debur the outer flanges of all 7 tank ribs, so tomorrow I still need to debur the inner flanges, which, unfortunately, I have found I need to do by hand with my standard deburring bit. This is because I have not found a good reliable method for using an angle drill that would actually fit in the small space without marring up the rib web in the process. So I just do these holes by hand, painful as it sounds.
Lastly, I did some research on the T-405 tank attach bracket. Turns out there are some tricks to this assembly that also need to be taken into account when this is fabricated and positioned inside the nose section of the inboard tank rib.
Questions for Vans that need to be asked tomorrow are:
1. Scratches in the tank skin beyond the edges of the rib flanges - can I scuff those out without compromising the skin?
2. Z bracket prep for proseal and primer - do I plan to proseal the entire T-712 Z bracket flange that will sit against the rear baffle plate, or do I prime this flange, but only in the areas where proseal is not applied, i.e. about 1/2 inch around each rivet hole.
3. Method for clearing rivets when fabricating and positioning the T-405 tank attach bracket? Notches? Reduce the edge enough for dimple and rivet shop head clearance where the skin attaches to the rib?
After I get all the inner rib holes deburred, I need to put everything back together so I can countersink the rear baffle plate holes where they attach to the tank skin. I kind of did this out of order from the instructions because I wanted to remove all the burs first before I countersink these skin holes, to make sure everything is fitting together properly. I probably should have just countersunk the holes in hindsight before I removed the ribs - oh well - so it goes.
So deburring the inner rib flange holes and hopefully rough cutting the stiffeners are next on the list for tomorrow.
KPR
Friday, November 24, 2017
Drilling and Deburring the Remaining Fuel Tank Rivet and Screw holes
Spent almost a whole day match drilling and deburring the remaining rivet holes for the left fuel tank. It never seems like much work until you start doing it, and you suddenly realize just how many holes there are.
I also decided to go ahead drill the #19 holes for the all the remaining screw holes along the bottom of the fuel tank skin that attach it to both sides of the main wing spar flanges. This has come up in several build logs over the years as something that many are not sure how to tackle. Some will step drill these holes until they get to the final #19 bit, and others will just drill using the #19 bit without any upsizing the hole whatsoever. I chose to do the latter. The reason why some decide to step up the hole a little at a time is because if you follow Vans instructions, they would have you believe that you just run a drill bit through the skin without any kind of backing behind it.
Problem is - anyone who has been building for a while, which would be most of us if you are at this stage of the build, would know from experience that drilling aluminum sheet without anything backing it up is prone to leave some very nasty burs on the back side of the hole. Some of them can be a pain to remove. So, as a rule, it is always best to have something behind the metal when you drill to help prevent this from happening, or at least keep the burs as small as possible. SO was my solution to this problem. I found a piece of wood lying around the garage that was just ling enough and wide enough to fit behind the fuel tank skin just above the rear baffle.
I was able to match drill all the screw holes, and almost all of the rivet holes. The only rivet holes I have not drilled yet are for the stiffeners on the bottom of the fuel tank skin. I have not fabricated the stiffeners yet (on my list of to-do's for this weekend). So I don't want to drill those holes in the skin until I have the stiffeners clecoed in place per the instructions. However, I did manage to get all the rib flange to skin rivet holes drilled.
So next steps at this point are to fab the tank skin stiffeners and cleco and match drill them to the skin. Then I can start deburring the rib holes and the stiffener holes after I disassemble the ribs. I was able to debur and disassemble the rear baffle plate, and this allowed me to also resolve another pesky problem I encountered after going through all that "special method" to position and drill the rear flanges of the inboard and outboard ribs and baffle plate holes to the Z brackets on the wing spar.
When I reassembled the tank assembly and tried to cleco all the rib flange holes back to the skin, the forward most hole on the top and bottom rib flanges of the outboard fuel tank rib would not align with the holes in the skin. With the tank completely closed up it was impossible to get those small tab holes in the rib to line up with the skin holes for some reason. Usually this is a sign that more rib straightening and fluting may be necessary, but I was pretty sure 3+ years ago that all the tank ribs had been straightened adequately.Then again, with these leading edge, stressed skins, anything is possible. I did not want to start match drilling any holes in this rib until that forward-most set of holes was lined up and clecoed in place again.
Anyway, to solve this little problem, before I removed the rear baffle plate, I wanted to see if I could realign the holes in those tabs in the rib flanges without removing the rib, since I still needed it to remain in place so I could match drill all the rib flange holes. I decided to leave the baffle plate in place, but to remove the clecoes that were holding it in place in that outboard bay along the flanges of the baffle plate, and then I removed all the clecoes from the rib flanges for that outboard rib. This meant that the tank was still closed up, but only loosely "closed" in that bay. So I could not just easily reach down from the rear and move the front of the rib around, but things were now lose enough that could manipulate the rib a bit to try to line up those forward holes with the skin.
How did I do this? Well, I thought my solution was quite ingenious. I took the largest and longest allen wrench that I own - about 3/8s of an inch as I recall, and 6 inches long. Then I realized that the rib in question was right next to the hole in the skin for the fuel tank fill port. So I was able to take that allen wrench and slip it inside the fuel port hole in the skin, and turn it so that the small "L" portion of the wrench was parallel to the rib web, and positioned it as low toward the front the rib as possible, and lightly tapped on the rib web. I'll be darned if that did not align the holes right up. SO I immediately clecoed all the rib flange holes, starting with those and working my way toward the rear.
Then I was able to match drill all the rib flange holes in that rib - FINALLY! After that the rear baffle plate was able to come off for deburring. So ends another fun-filled day of airplane building.
KPR.
I also decided to go ahead drill the #19 holes for the all the remaining screw holes along the bottom of the fuel tank skin that attach it to both sides of the main wing spar flanges. This has come up in several build logs over the years as something that many are not sure how to tackle. Some will step drill these holes until they get to the final #19 bit, and others will just drill using the #19 bit without any upsizing the hole whatsoever. I chose to do the latter. The reason why some decide to step up the hole a little at a time is because if you follow Vans instructions, they would have you believe that you just run a drill bit through the skin without any kind of backing behind it.
Problem is - anyone who has been building for a while, which would be most of us if you are at this stage of the build, would know from experience that drilling aluminum sheet without anything backing it up is prone to leave some very nasty burs on the back side of the hole. Some of them can be a pain to remove. So, as a rule, it is always best to have something behind the metal when you drill to help prevent this from happening, or at least keep the burs as small as possible. SO was my solution to this problem. I found a piece of wood lying around the garage that was just ling enough and wide enough to fit behind the fuel tank skin just above the rear baffle.
So next steps at this point are to fab the tank skin stiffeners and cleco and match drill them to the skin. Then I can start deburring the rib holes and the stiffener holes after I disassemble the ribs. I was able to debur and disassemble the rear baffle plate, and this allowed me to also resolve another pesky problem I encountered after going through all that "special method" to position and drill the rear flanges of the inboard and outboard ribs and baffle plate holes to the Z brackets on the wing spar.
When I reassembled the tank assembly and tried to cleco all the rib flange holes back to the skin, the forward most hole on the top and bottom rib flanges of the outboard fuel tank rib would not align with the holes in the skin. With the tank completely closed up it was impossible to get those small tab holes in the rib to line up with the skin holes for some reason. Usually this is a sign that more rib straightening and fluting may be necessary, but I was pretty sure 3+ years ago that all the tank ribs had been straightened adequately.Then again, with these leading edge, stressed skins, anything is possible. I did not want to start match drilling any holes in this rib until that forward-most set of holes was lined up and clecoed in place again.
Anyway, to solve this little problem, before I removed the rear baffle plate, I wanted to see if I could realign the holes in those tabs in the rib flanges without removing the rib, since I still needed it to remain in place so I could match drill all the rib flange holes. I decided to leave the baffle plate in place, but to remove the clecoes that were holding it in place in that outboard bay along the flanges of the baffle plate, and then I removed all the clecoes from the rib flanges for that outboard rib. This meant that the tank was still closed up, but only loosely "closed" in that bay. So I could not just easily reach down from the rear and move the front of the rib around, but things were now lose enough that could manipulate the rib a bit to try to line up those forward holes with the skin.
How did I do this? Well, I thought my solution was quite ingenious. I took the largest and longest allen wrench that I own - about 3/8s of an inch as I recall, and 6 inches long. Then I realized that the rib in question was right next to the hole in the skin for the fuel tank fill port. So I was able to take that allen wrench and slip it inside the fuel port hole in the skin, and turn it so that the small "L" portion of the wrench was parallel to the rib web, and positioned it as low toward the front the rib as possible, and lightly tapped on the rib web. I'll be darned if that did not align the holes right up. SO I immediately clecoed all the rib flange holes, starting with those and working my way toward the rear.
Then I was able to match drill all the rib flange holes in that rib - FINALLY! After that the rear baffle plate was able to come off for deburring. So ends another fun-filled day of airplane building.
KPR.
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