402.5 hours on the hobbs - fabricated 3 riblets for trim tab and elevator

After a ton of research on Steve Riffe's and several others builder sites and logs, and a break in our super chilly weather here in Denver, I was able to fabricate the two end riblets for the trim tab, as well as the end riblet for the left elevator cutout which sits adjacent to the outboard edge of the trim tab. I also have to say that I did get a little distracted listening to our Denver Broncos pull out another miracle finish against the Chicago Bears this afternoon, to take sole possession of first place in the western division. Go Broncos!

This weekend was slow in terms of airplane building. Had to do the annual Xmas shopping yesterday, and got a new Smart phone as an early present, which I of course I just had to mess around with this morning. So the weekend airplane work did not actually commence untlil about noon today.

As a preface to the coming photos, let me just say this: Did I save any time on my build by choosing to make riblets instead of bending the dreaded tabs - NO! Did I end up with more piece of mind using the riblet solution without ruining any parts, or having to build a second or even a third trim tab in the process -  YES! So, if you are builder who seeks info about bending the tabs, do not waste any time hunting my blog for that. However, if you choose to cut the tabs off and make the riblets, then read on.

During the process of making the riblets, I encountered many twists in the road that most other builders don't seem to comment about, and I have tried to mention them in this post for the benefit of future builders. If you read my blog, you know by now that I like the details, and I also like to dispell as much of the doggone mystery about some of this stuff that I can.

Here is what I learned and how I made my riblets:

I had already trimmed the edges of the trim tab skin very close to their final state, but I needed to trim the edges of the elevator cutout where the trim tab resides just a bit more to allow enough clearance between the trim tab and the elevator. In this pic I have the skin laid out on my table with the 2x4s slid underneath. I then clamped everything down, and performed a bit more "dremel surgery" with the cutoff wheel to carefully trim away about another 1/8 inch of material from the top and bottom outboard trim tab cutout edges of the elevator skin. My measurements for the long edge of the trim tab cutout were about 17 and 22/32 inches, so this is the minimum amount needed to allow the trim tab to just fit inside the cutout in the elevator so that the edges of the trim tab will line up with the edges of the elevator.

This setup provided enough stiffness and separation of the edges of the elevator to allow me to keep two hands on the dremel tool to keep from making a costly mistake. One slip up here and you will order a new skin, so take your time, secure the work, and move slowly with the dremel tool, and it works out fine. I cut just outside the reference line I drew to leave a bit more material than desired, and finish trimming by using a file to trim away the remaining material up to the reference line.

Next is something I am a bit concerned about, and I will need to talk to Vans tomorrow, before removing any more material on the edge. Vans has you draw a line on the elevator that is perpendicular to the long trailing edge to determine the bend/cut line for the tabs. I expected that the corresponding matching edge of the trim tab would also be perpendicular to the LE of the trim  tab so that both edges would line up evenly. Unfortunately, I found this not to be the case. Upon trial fitting the trim tab in the cutout of the elevator, I found the outboard edges were not aligned as expected, and the trim tab edges are anything but perpendicular.

You are supposed to end up with a minimum gap between the elevator edge and the outboard trim tab edge of at least 3/32 inches. To correct the problem,  I think I will be able to trim the extreme trailing edges of either the elevator or the trim tab to even out this line, and still have the appropriate gap. SO much for cutting straight lines on everything. The next pic shows the additional amount I originally marked that needed to be trimmed from the elevator. Advice to future builders is to avoid trimming anything additional from this area until you actually start fitting the trim tab and hinge assembly in place.

And here it is after cutting and filing the excess down to the new line:

Next, the riblet fabrications begins. What do you need?

2 Vans practice Kit ribs (I don't know the part number but there is one for them - call Van's to find out what it is. thanks again to Mike Rettig for providing me some brand new untarnished ones so I would not have to tear apart my completed practice kit like Steve did!

The riblets fabricated from the ends from these two ribs will go in the OUTBOARD edge of the trim tab and in the edge of the elevator that sits next to it.

1 E703 elevator tip rib. Order one from Vans, or use a discarded one if you messed one up during elevator construction.

The riblet fabricated from this rib will go in the INBOARD edge of the trim tab, or the edge closet to the rudder when mounted on the fuselage.

Here is a pic of the remnant from all three ribs to give you some idea of where I made my initial cuts.

Now to describe the process I went through. This was a bit painful, and involved a lot of measurements of the gaps between the skins, and length measurements from leading to trailing edge, followed by transfers of all those measurements onto the rib stock, followed by more measurements, and more trimming, etc. I must have measured everything about 20 times before deciding where to make the first cut to separate the ends of each rib from the original part.

I essentially used a "more is better" approach, meaning that I took my original measurements, and added a bit to them just to be sure I did not cut anything too short. The elevator riblet pretty much gets cut symetrically off the end of the practice kit rib, while the other one for the outboard edge of the trim tab tends to have a bit of an angle on the leading edge due to the angled nature of the trim tab forward spar. The web on that spar, which has a Z bend on both ends for the flanges that attach to the top and botttom of the trim tab skin,  is not vertical, but sits at an angle.

Next I will go ahead and provide some "finished" photos of each riblet. First is the OUTBOARD or smaller end riblet for the trim tab. On the bottom of the forward part of the riblet you see a small cutout for clearance of the trim tab spar flange. You have to make this cutout to clear the edge of the trim tab spar flange. I suggest measuring to obtain about a 1/8 inch clearance, which is a standard clearance for most other non-attached rib-to-spar clearances. The hole that you see is a tooling hole from the original rib - I consider it a lightening hole (haha). Just debur the hole, and that is all you need to do with that.

Also notice the clearance from the end of the riblet to the trailing edge of the trim tab, and a slight rise in the forward flange of the trim tab skin where it joins the top flange of the trim tab spar. I was not very happy about this. It seems that the angle of the prefabricated practice ribs does not quite perfectly match the angle of the trim tab skin after attaching it to the forward spar. I will need to decide how to manage this, but for now some scuffing for primer and trying to work the edge of the flange of the riblet a bit more to reduce the width are all I can think of. The trailing edge of each riblet will sit just a bit forward of the trailing edge of the trim tab and the elevator to achieve the correct angle to fill the gap between the skins. Of all three riblets, this one does the worst job of mating correctly to the trim tab skin. Options are to make a wood form, take some of your spare metal, and form your own, as many other builders do. I'll have to ponder that this week to decide what I will do - leave it as is or form my own.

You should also know that I did not trim anything off of the trailing edge of this riblet - I used the original trailing edge and only trimmed the forward portion to fit it. Lastly, and this is a personal choice - you can face the web of the riblets inward or outward. For the trim tab I chose to face the web of the OUTBOARD riblet toward the outside to create a difinitive edge that will have the same effect as bending the tabs.

Next is the other side of the trim tab, or the INBOARD side. This riblet is made from the E703 Elevator tip rib, and is much longer and a bit wider than the one on the outboard edge.It will be placed as shown with the web facing inward, to match the edge of the E705 root rib, and allow solid rivets to be used on the flanges instead of pop rivets.

Oh, I guess I should have mentioned something about the rivets. Some holes will be drilled in the flanges of the riblets, and in some cases existing holes will be used. Then they will be dimpled for flush rivets. On this one I can set the rivets with a squeezer, but on the other two, with webs facing outward and flanges facing inward, I will need to use flush pop rivets for those, since the web will close off the access to the flanges. This is all by design.

Again, notice the slight cutout on the bottom forward portion of the riblet, and the clearance from both the web of the forward trim tab spar as well as the bottom flange. Also notice where the riblet trailing edge ends, forward of the actual TE of the trim tab. For this rib, I actually had to trim off about 1/4 inch or so of the end to preserve the correct angle of the trim tab skin without bulging it. This one actually sat much better inside the skin without bulging the leading or the trailing edge too much.

One other very important thing about making this riblet is that you end up utilizing one of the existing holes in the original part without needing to drill a different one. this is the hole on the bottom where one of the two halves of the trim tab control horn is mounted to the bottom of the trim tab. In other words, You will be setting a rivet through the control horn, then the skin, and then the riblet flange which is directly underneath. You can use this existing hole as a reference mark to determine how much to trim off of the front an rear portions of the riblet. Just keep lining up the existing hole in the bottom flange of the riblet with the existing hole in the skin, and put a cleco in there once you get it lined up and trimmed up enough. Then you can fine tune the LE and TE of the riblet accordingly.

One other note - - The rivet holes for the OTHER half of the trim tab control horn assembly end up being very close to the web of this riblet. I will need to decide if I am going to cut a recess on the webof the riblet in order to clear that area, or if I will simply put some RTV over that rivet to prevent any potential cracking from vibration, etc. It appears as though it will sit just on the edge of the dimple in the skin, so there is just enough clearance for the shop head of the rivet, but it is VERY close to the web of the rib.

You may need to trim the flanges a bit to line them up with the edges of the trim tab skin. All rivets that attach the control horn, skin, and this riblet can be set with a squeezer using solid rivets. Just be sure to increase the rivet length where necessary to account fo the additional depth of the flange of the riblet.

Lastly is the riblet that goes into the end of the elevator. This one was fairly easy to fabricate from the other practice kit rib. You do NOT have to cut a fancy recess in the bottom of this riblet like you do with the other ones, but you do need to ensure that there is sufficient clearance from the edges of the spar flanges on the front of the riblet. Again, notice the gap in the trailing edge of the riblet. This one also used the original trailing edge from the original part. I did not have to trim any of the trailing edge off of this rib.

So here are a few more pics to point out specific areas of interest in this process. Here is a blurry pic (sorry) of the cleco inserted into the INBOARD root riblet hole of the trim tab riblet I mentioned earlier.

Next is a close up of the forward portion of the same riblet to show the clearance from the spar web and the bottom flange of the spar of the trim tab. This gap is only 1/8 inch or less, so don't let the close up fool you into thinking that it is bigger than that.

Next are the two trim tab riblets by themselves. The pic on the top is the outboard riblet, and the one on the bottom is the inboard riblet.You can see the original hole in the bottom of the flange of the inboard riblet. You can also see more detail of the recesses I cut in each forward portion to clear the bottom trim tab flange, and the two original holes in the outboard riblet. Not sure if I will be using these or not, but will let you know what I decide. The upper flange holes in the inboard riblet (bottom) are a different story. I may use the most forward hole, and then make new holes and space them evenly along the flange accordingly. It is OK to leave existing holes and make new ones as long as you maintain proper clearance of each hole.

Next are the same two parts flipped on the other side, again for better clarity.

I was able to rough cut the recesses in each flange using the dremel cutoff wheel, and cleaned up each cut and trimmed it to final size with the Scotch Brite wheel. I ensured that each part was securely clamped, and that I could keep both hands on the dremel tool at all times. Had to keep a close eye on each cut, so safety glasses were a must. Also wore ear muffs.
Next is the elevator riblet. This one ends up with three rivet holes that I will most likely use, but if I need to space them out differenty I will do that.

And here is a shot of the trailing edges of each riblet so you see the difference between the ones created from the practice kit ribs and the one from the E703 elevator tip rib.

And finally a pic of the inboard riblet that shows both the top and bottom original holes in each flange.

I ended up doing a lot of cutting and trimming and cutting and trimming. I wish I could spew out exact measurements for everything I did, but you really end up doing most of the fitting on a trial and error basis to get the exact fit that you desire. I ran out of steam after getting them to fit where I wanted them, so I will finish fitting everything tomorrow. The hard part is done. The only other intense activity is the measuring of the other half of the hinge that attaches the trim tab to the elevator, and positioning the trim tab servo mounting brackets. Then I can drill and dimple holes for all the riblets, prime everything, and finally get around to riveting this bad boy together.

389 hours on the hobbs - left elevator and trim tab progress today

Picked up my tools from the chapter 301 auction held recently. Short story about this is that a member of the chapter passed away recently after a losing bout with cancer, and he essentially donated his hangar and it's contents at KFTG to the chapter. After resolving some legal issues, including the sale of his almost completed T-51 kit to a bloke in Australia, a large assortment of tools remained, and these were auctioned off to chapter members by email. This was the first time I had ever done an auction via email, but it was rather fun.

I ended up with a set of nut drivers, 3 impact wrenches, one air drill, and an assortment if impact sockets and other odds and ends. They basically sorted the tools in the drawers of an absolutely humungous tool chest, took photos, sent them to the bidders, and started the auction which ran for about 2 weeks. The tool chest was also auctioned off to the tune of about $450.00.

Thanks Jack for the opportunity to take care of your tools - rest in peace and I won't let ya down. I almost bit on buying the T-51, which is a kit version of a P-51 fighter, but I was already into my own project and did not want to derail that effort. Sad thing is, he was almost finished with it - even had a Corvette engine ready to put in it. Whole thing went for about $35,000.00.

As for the build - I spent time on the trim tab today. Got the skin bent and primed up, and drilled the holes for the hinge on the trim tab side. Also put the lead counterweight back on the drill press after verifying that the drill bit chuck and my work table were at prefect 90 degree angles to each other. Funny thing about that is that one of the lead plugs I had poured into one of the holes the other day was completely pushed out during the drilling, and the other came out as I was final drilling the hole in the E713 counterbalance skin. Oh well, that means my original holes were close enough I guess.The good news is that everything came out OK this time, but I still need to finish match drilling all the holes in the new E704 part. I also had to rebend the flanges to 90 degrees, and flute it just a bit to straighten it out.

All primed up

We pause this trim tab episode momentarily for a trip back to the tip rib assembly. Here is the problem I spoke of in previous posts. The hole on the right is much too close to the bend in the flange. This is the 704 counter balance rib that I had to replace with a new one.

Next is a side view of the trim tab after the bend, with the forward TT spar clecoed in place. As far as I can tell from doing some preliminary fitting to the elevator, everything should line up perfect if I get the hinge placement correct:

Next are the rivet lines I drew on the piano hinge that will attach the trim tab to the elevator. After much research over the past few days, I resolved that the solution to the rivet hole location problem where there would not be enough edge distance if you follow the 1/4 inch measurement in the plans, was to keep the 6/32 edge distance by measuring from the outside edge of the hinge. As it turned out, when I drew the lines per the measurements I just mentioned, the rivet line is pretty much centered in the main part of the hinge flange, just as it should be, and there is also sufficient edge distance for the rivets. Pics are of lines drawn on both sides:

My research on other builder sites regarding the hinge issues revealed so many little tips and tricks to ensure that this gets done correctly, that I will list most of them here to hopefully benefit future builders.

1. Van's drawings showing the hinge assembly are confusing. One drawing seems to show the eyes of the hinges facing upward toward the top of the skin, while others show the hinge eyes facing downward. DOWNWARD is the correct placement. This allows you to adjust the placement of the hinge flange on the elevator side to ensure proper alignment of the trim tab with the elevator, without the eyes getting in the way of the edges of the skin. It also keeps the hinge line flush with the skin and not sticking up into the slip stream, thereby reducing drag.

2. When drilling the holes in the hinge, you have to mark a line, clamp the hinge to the skin and spar under the prepunched holes, and drill complete holes in the hinge flange - they are NOT prepunched. Also make certain that you DO NOT dimple or countersink the holes in the hinge. The dimples and countersinks are in the spar and the skin - NOT in the hinge. Upper skin gets dimples, the top of the spar gets countersunk, and the hinge just gets drilled with a hole to accept the remaining rivet shank.

3. After drawing your reference lines in the hinge flange, remove the piano hinge pin and separate the hinge halves. I use a 3/32 " punch pin for this.Then clamp the hinge half in place lining up the previously drawn reference line and prepunched holes in the skin as a guide.

4. When riveting the hinge flange, remember to put the piano hinge back onto the eyelets (just the pin and not the other half of the hinge). This helps keep the eyelets from bending or distorting during riveting, which may cause binding when you insert the pin and attach the other half of the hinge.

5. Another tip during riveting is to install the other half of the hinge with the hinge pin, and place the other half of the hinge at 90 degrees to the half that you are riveting to provide even more rigidity during riveting.

6. When trimming the end of the hinge on the inboard side of the trim tab, do NOT trim the hinge pin - only the flanges. Leave the pin at it's original length so you can form the bend or at least have something additional to grab on to to remove and insert the pin easily.

Here is the drilled hinge on the trim tab side in progress and almost complete. Use as many cleco clamps as necessary to keep the hinge from moving while drilling the holes. Start at one end of the hinge and drill each hole in sequence until you reach the other end, to ensure that there are no sags in the hinge line. Van's wants the hinge to be placed laterally so that the outboard edge of the hinge is 3/8" from the nearest hole on that side:

And here is the view from the front side of the trim tab after the hinge line has been drilled. All my holes came out right were I expected - centered on each line - both top and bottom. Be sure to keep your drill straight. You have to be patient and have a steady hand because it takes several seconds for the hole to be drilled through the hinge material - even with a sharp drill bit and my super duper and super expensive Sioux air drill running at full speed. Use the mirror technique by aligning the drill bit with its reflection in the alclad trim tab skin - works like a charm every time for drilling straight holes. Let the drill bit do the cutting and don't force it.

And here is the lead counterweight installed in the tip rib assembly. The bolt has been inserted on both sides (only one side showing in this pic). Boy am I glad that is almost over. I say almost because I still need to the following things before it is ready for the next step:
- match drill the 703 to 704 attach holes
- Match drill the 704 flange attach holes to the E702 forward spar
- Dimple the E713 counterbalance skin holes after making sure that they are sized properly and deburred well to prevent cracking when the huge number 10 dimple die is used to make the dimples.
- Countersink the E714 lead counterweight to accept the dimples from the E713 skin

Then I can finally attach everyting to the foward spar so I can final drill the remaining holes in the elevator skin.

Remember - this counterweight does NOT get trimmed like the one on the right side due to the weight differences with the added spar, trim reinforcement brackets, and trim tab assembly all aft of the elevator hinge line. This requires more weight to counter everything added to the left elevator, so you do NOT trim anything from this counterweight.

This shows a much better placement of the screw on the E704 rib side. Still not centered in the flange, but good enough to accept the washer and the nut that will snug it down tight.

Just to recap what I did to fix the problem:
- Filled the holes in the lead counterweight so I could re-drill them after getting a new E704 rib from Van's.
- Attached the new E704 rib to the existing E703 tip rib. I kept the same tip rib since everything seemed to be Ok on that side.
- Attached the counterbalance skin and the counterweight to the tip rib assembly, marked the lead counterweight using the holes on the front side of the E713 with a sharpee, disassembled everything, and step drilled the counterweight on the drill press  - just as I had done before.
- reassembled the counterweight and tip rib/counterbalance skin, and drilled the holes in E713 to size to match the holes in the counterweight. (Drill to Number 12 initially, but will end up being number 10 for the dimple die.) Used my hand held air drill for this part.Tried my best to keep a straight line....
- Verified the hole on the forward flange of the tip rib side aligned with the hole in the counterweight and the counterbalance skin - it did (Whew! was worried about that one)
- Took my number 12 drill bit on the E704 side, slid it through the E713 skin, through the lead counterweight until I felt is stop against the forward flange of the E704 rib. I did not run the drill while doing this - just inserted the bit to verify it would travel all the way up to the point of hitting the solid flange of the new rib.
 - Then I carefully aligned the drill bit - hedging a bit more with pressure toward the outer edge of the rib flange, and HAND TURNED the drill bit to start a reference hole in the flange, being careful NOT to drill all the way through the metal
- Disassembled the counterweight adn ribs one more time, found the mark on the E704 rib, verified that it appeared to be in the correct place to provide a hole with sufficient clearance for the screw, washer,and nut, and finished drill the hole in the rib flange.
- Reassembled everything again to verify that the screws, washers, and nuts on both sides will attach correctly.
 - Now I just ahve to take it all apart again to countersink the holes in the counterweight for the E713 dimples, which also have to be done. Then I put it all back together again, minus the counterweight, so I can attach it to the E702 spar and the skin.

WHAT A PAIN IN THE ASS THIS IS!

Lastly, back to the trim tab. Started measuring for the riblets using the practice kit ribs I got from Mike Rettig a while back.

Here is the outboard or smaller end of the trim tab - will have to fill the areas with the chipped primer - interesting. A very small riblet goes in this end.

Next is a pic of the practice kit rib. I will use 2 of these and the end of a 703 tip rib to make all the necessary riblets.

Next is a pic of some dimesions that I had ruffed out. I will be changing these slightly after reviewing the pics on Steve Riffe's log. The forward spar of the trim tab is a Z shape, and what you end up doing is trimming these riblets so that the rib web coveras as much of the tip area as possible, while making recesses in the flanges of the riblets to ensure clearance from the trim tab spar flanges.

Steves riblet seems to be a bit longer than the dimension I drew up. It is very close to a tooling hole, so I need to be careful about where to cut the tip off.

Next steps for tomorrow, which will finish up my vacation and holiday time off from work - dimple and countersink the spars, fabricate the riblets and drill the rivet holes, and maybe prime all the parts since the weather will finally be somewhat warm again tomorrow. The last part of the left elevator assembly involves aligning the trim tab, drilling the elevator side of the hinge, and then working on the trim servo mounting brackings and nut plates. Then I still have to roll the leading edges....UGHHHH. It just goes on and on and on.......

Have to stay focused on this to get it done, but I really, really, really want to get started on my Wings.

Feb 19and 20 2011 - Attended EAA Sport Air RV Assembly class

John Brecker was the instructor for this class which was held at the RedStone college of Aviation up near Rocky Mountain Metropolitan Airport in Broomfield. Several members of the RV List Yahoo group that I belong to were in attendance. My main goal for this class was to gain some experience with rolling the leading edge of the practice kit, which basically resembled an airfoil section of a control surface such as an elevator or an aileron. Had a lot of fun meeting new folks just getting their feet wet with the whole process, adn some that are still dreaming of the day. I'll have some more pics and info about the class in later posts. It has been a fairly eventful week for the build, so I want to get that updated for now.

Here are some pics of the completed practice kit:

A couple of aluminum sheets, two ribs, 4 stiffeners, and a forward spar. Leading edge is rolled using a 1 inch broom handle adn duct tape.

This is a pic of a back riveting technique that is used on the trailing edges of some control surfaces that use a separate top and bottom sheet, and a wedge that is sandwiched in between the two sheets. Since the rivet gets inserted at an angle, it is not possible to get a typical shop head out of the other end of th rivet when it is set. Instead, the factory or flush head gets taped to the skin, and the skin goes on top of the back rivet plate, and then you take the flush rivet set in the rivet gun and attempt to set the shop head. The result is show below - the shop head only partially fills the dimple in the skin. This is normal, but a bit unseetling to those of us that have been setting rivets for a while, that know what a good shop head is supposed to look like.

Class Partner Gets to Keep the Prize

This was my partner in the class. He had started working on his private license many years ago, but like many others, he ran out of money after soloing. He told me that the next time he starts to work on it he is going to finish it all the way. It was very interesting to see that several people in the class were not even rated pilots (yet)!
As much as I wanted to take home the completed project, I felt that it would be better off remaining in the possession of someone that is still trying to realize the dream of aviation, even if it means having a bunch of riveted metal parts stuffed out of sight in the corner of a garage for a while. Perhaps one day it might just be responsible for the creation of one more pilot, or even better yet, another airplane builder! I wish him well in his pursuit of flight.

EAA Sheet Metal Sport Air Class Practice Kit

Here is the project that we built in the workshop. The inspection panel on the right has 3 screws that are secured with 3 nutplates that are riveted to the underside of the skin. The trim tab on the bottom is hinged with piano wire.

...and more toolbox kit pics

A few more pics

More Toolbox kit photos

Can you tell where the bad rivet is?

Toolbox kit from Vans

OK - here is the infamous toolbox that I riveted together with my own two hands.