Making a Rotisserie for the Fuselage - Part 3

As part of my effort to re-engage in building my wings, I needed to order some new Primer. My old AKZO Nobel 2 part epoxy primer, although proven by me to work well enough enough at 7 years plus older than the shelf life date on the cans, is now so old and unused that I have decided not to continue to try to work with it. So I ordered a new can of catalyst and primer - expensive stuff. Picked up a tip from a fellow builder to get 8 empty quart sized paint cans from HD airplane supply and pour the contents into each of these smaller cans to make it easier to pour, store, and prepare. Having had real experience with this in the past by spilling it on the floor while trying to pour in in the small mixing cups,  and knowing precisely how bad smelling and toxic the catalyst is, I think this is a very good idea.

In addition to the primer, I decided I also needed some additional AN bolt hardware to finish the  rotisserie. Each spider leg has two holes in either end of it, and each of those are between 7/16 to 1/2 inch wide on average. With the hole on one end being addressed by the AN3 hardware and wood spacers, etc., I needed to figure out how to attach the other end to the angle. This other hole would normally contain the metric bolts that came with the engine stand. I need to use this other predrilled hole and drill an additional hole somewhere near the middle of each spider to provide the necessary holes to attach the angle iron to the spider.  You need to drill the extra hole in the middle to ensure that the angle is secured in at least two places on the spider arm, so that it cannot rotate out of position.

The next problem is figuring out what length bolts I should use for the remaining holes, to ensure they are short enough so that they do not come into contact with the firewall after attaching each angle to the spider on one end and the center mounting plate on the other. Each of the lugs on the spiders allows for about 1 and 1/2 inches clearance from the firewall. Unfortunately, the metric bolts that come with the engine stand are about 1 1/4 inches long after being inserted into the hole in the spider, so that leaves a very uncomfortable 1/4 inch of free space between the firewall and the angle iron adn spider bar - This is NOT good enough for me. 

SO I need to get shorter length bolts and corresponding hardware. That means I needed to go back to the suppliers and the conversion/identification charts to figure out which AN hardware I should get. My decision, based on measuring hole diameters and lengths and grip requirements and such, was the following:

For the other big hole in the spider and the 1/8 inch thick angle iron that will be attached to it, I decided on either AN7-11A or AN8-11A, since the holes sizes seem to hover somewhere in the vicinity of either one. I order both, and I will see which one gives the better. tighter fit. After I figure that out, I will know what size hole I have to drill in the angle iron.

For the second hole in the middle of each spider to lock the angle iron in place like others seem to have done, I decided to use AN3-7A bolts. Both of these bolt choices should leave at least a half inch or more of clearance from the firewall after being bolted together. That I think I can live with. I also ordered the required nuts and washers for all bolts. The AN7 and AN8 bolts get AN960-716, 726L, 816, and 816L washers, and AN365-720A and AN365-820A, or MS21044N8 lock nuts. The AN3 bolts use the same nuts I already received from Straight Flight, so I think I already have enough of those to use on the shorter AN3 bolts as well.  

I also ordered some hardware that I mentioned long ago in my blog when working on the fuel tanks. I ordered about 50 NAS1352-08-8P cad-plated socket head cap screws to replace the fuel tank access plate screws provided by Vans - AN515-8R8. I have seen too many posts from builders stating how difficult it is to remove Phillips head screws from the access plates of the fuel tanks when you need to service or replace the fuel senders or the fuel line or return attachment hardware or connections. There are 17 of these screws for each fuel tank, so you only need 34, but I always need extras, so I ordered a few extras. Somebody on VAF also asked if a washer would be needed for these cap screws, since their grip width of the head is not as wide as the AN515 screw heads. I am glad he asked that question, as I would never even thought about that. The washer for the cap screw is AN960-8 or AN960-8L for the thin version. I ordered 50 of each of those as well.

My order was shipped from Spruce's Georgia location, and at first I found this to be strange, since most western-based orders are processed by the Southern California location. But on second thought, with southern California's horrible pandemic situation, I am actually relieved that my order came from somewhere else. It also wised me up a bit about hardware orders or any orders for that matter that I will be needing for supplies, parts etc., as I re-engage. I need to be careful about where these are coming from, and develop a process to clean them carefully when I receive them - just to be safe. It is supposed to be here in a couple of days, and then I will resume the work on the rotisserie.

Coming - up - I need to degrease/remove the oil coating from my QB fuse, which now has a layer of fine abrasive forest fire ash particles on it from all the fires in the state this past summer and fall. I have stupidly left this unattended ever since it was delivered to me in 2018. This stuff even penetrated inside the house, so everything is covered with it, inside and out. So this is long overdue, and needs some serious attention. Also coming soon is the upgraded electrical service and heat into my garage. Enough is enough, and I really need to address my hostile building environment this year if I ever want to finish this project. I will also need to order more Proseal and some special formulated sealant for the fuel tank access plates. More on that later.

Making a Rotisserie for the Fuselage - Part 1

 While I continue to review my parts situation for the wings to prepare to place a new order with Vans and other vendors, I caught an ad from Harbor Freight a couple of weeks ago for a 1,000 pound capacity Engine Stand that many builders have used as a rotating rotisserie for the RV-8 fuselage. The rotisserie is mainly used as a back-saving tool while assembling many of the parts and components of the cockpit interior and floor panels. It may also come in very handy if I decide to paint my own airplane, which I am once again heavily considering. I have a new idea for a paint job for this airplane that so far seems to be pretty unique. That's all that I am willing to share about that for now, in the interest of keeping it as unique as possible. :)

 I have reviewed numerous other build logs from other builders, but I still rely most heavily on the log from Steve Riffe, who has been flying his airplane now for about 3.5 years or so. He used the same engine stand for his fuselage, and he also learned about this from other builders. While looking at pics of his engine stand, I noticed that the frame design is different, because I think they change designs every so often for the same product. Changes are mainly with how the wheels are attached to the base, and how the support bracket that attaches to the vertical bar and the horizontal bar to add support to that critical area is constructed. I purchased the stand brand new from HF for under $70.00. It requires minor assembly, but the parts are heavy, so be prepared.

Since the QB fuse as delivered by VANs only weights between 150-200 pounds max (if that), this 1,000 lb. stand is more than sufficient for the job. the main issue is the length of the fuse, which creates a long moment (Remember your weight and balance training - WxA=M). This means that if the tail is unsupported while the front is suspended by the engine stand, all of that weight along the entire length of the fuselage has to be supported by the stand and its attach points to the firewall. The idea is to use the stand in the front, and lay the tail down on a small saw horse, milk carton, or custom-built wood stand as needed, so the weight that must be supported by the stand itself is minimized as much as possible. I also wanted this particular stand instead of other available models because it has the additional lateral wheel bracket in the front, which helps provide some additional lateral stability to the fuselage when mounted on the stand. 

The main problem I encountered when considering this, is a lack of  a detailed information about the hardware used. So I will attempt to solve that problem. As always, keep in mind that I make no claim of suitability or guarantee that your results will match mine, so you are responsible for determining if thi will work for you or not. YMMV. 

Here is a pic of the assembled HF Engine stand, ready to be converted to a fuselage stand:

I used my yellow angle finder tool to determine the angle of the vertical post and the base support leg, since the angle is not 90 degrees. Most folks remove the front wheels of the stand to bring the vertical post closer to 90 degrees, so that it aligns vertically with the firewall when mounted to the stand. This needs to be done so that it does not put any undo stress on the firewall when mounted to the stand, which would be very bad. 

Since the wheel brackets on mine seem to be a little higher than others, I may need to compensate for that a little by raising the front up a little more with wood shims, but time will tell on that. The angle I measured is almost exactly 5 degrees, although in the above pic it  appears to be much greater than that. 

The rotating bracket that comes with the stand that the firewall will be mounted to comes with 4 "spider leg" attachments that are normally used for running heavy bolts through the spacers or lugs at one end of each arm that then screw into the back of a car engine. 2 of the arms are shown in the pic below.

The mounting plate has slotted holes to allow the location of the spiders to be positioned so that they match the mounting holes on the engine. Unfortunately we have to change this up a bit to modify this assembly for use with the fuselage, but it is not too difficult to do. I will still use the spider arms, but they will be attached to the ends of some angle iron that is cut to the correct length to act as an extension, so that the mounting plate remains near the center of the firewall, while the spiders will be bolted to the 4 holes in each corner of the engine mount holes and brackets behind the firewall, AND to the angle iron extensions. 

Similar to Steve, I decided to use AN hardware for most of the attach points for the spiders to the firewall/engine mount brackets, which have a minimum 125,000 lbs. of tensile strength, to ensure that the bracket has enough strength to stay attached to the firewall the entire time. The immediate problem that has to be overcome is that the stand comes with very large metric bolts. 

Unfortunately, when Vans builds the QB fuselage, all the engine mount holes are only pre-drilled to 3/16ths of  an inch, which is the smallest AN bolt diameter you can obtain before having to revert to screws. Furthermore, if you read ahead in the VAF forums and the Vans instructions for the Fuselage assembly, you will find that they say NOT to drill out those engine mount holes until you have the actual engine mount in your possession, so you can use it as a drill guide. 

This is necessary because the weldments for every engine mount vary a bit from one to the other, so you are not supposed to up-size the bolt holes without the engine mount to ensure the holes are drilled out correctly. The engine mount bolts are 3/8 inches thick, or AN-6 I  think, so they are substantially larger than 3/16 inches. Since I do not have my engine mount yet, I did not want to upsize the holes, but I was also concerned that this would mean that only AN3 sized-hardware would be attached to each existing hole. 

Steve informed me that he did exactly that - used the AN3 bolts in each corner, and he had no issues with anything while using the rotisserie. I also contacted Vans about this, and they said it would probably be OK to upsize the holes about half way in between the current size and the final size, since most engine mount holes may only vary by a max of 1/8 of an inch or less from each other. They also thought that AN 3 bolts would be "a little light. 

Other builders decided to drill up to AN 4 bolt holes, and I think I saw others yet again that drilled them out the final AN 6 size. At the end of the day, I decided to stay with the AN3 bolts to avoid upsizing the bolt holes without the engine mount. Steve said he had no issues, and the reality is that all the other bolts used in the assembly are the same beefy ones provided with the engine mount. So I think his will be fine.

With that decided, there is another  problem that I felt I needed to solve. While the AN 3 bolts will precisely fit in the predrilled holes in the firewall, the predrilled holes in each spider leg are extremely large, I was concerned about running such a small sized bolt through the large hole in the spacer lug in the spider leg, without having some kind of additional support for the bolt shank. So, similar to another builder (I am sorry I did not capture his build log) I decided to cut a wood dowel to the correct length to fit inside the lug or extension, and insert it into the larger hole in each spider. It turns out that a 5/8 inch dowel from HD aircraft supply works very nicely here, at least as far as the fit into the spider lug is concerned. I measured and then cut the 5/8 inch dowel into 4 separate 1 1/2 inch long inserts using my bandsaw, as shown below.

After you have cut the spacers, the next step is to take a rubber mallet and tap them into "submission" into each lug hole:

IT turns out to be a very nice "press" fit. Each dowel is only long enough to reach the base of the lug where it is welded to the spider arm. The dowel will not fit all the way to the bottom of the arm because the holes from the lug that they welded to the top of the bar are not the same size. The holes in the bar are a little smaller, so they will stop at that point.

Now for the hard part. The next step was to drill out  a 3/16 inch hole in the center of each dowel.  I won't lie, for me this turned out to be a bit of a nightmare, because I found out that dowels do not like to allow a drill bit to follow a straight path from one end to the other. All of initial holes I drilled ended up being misaligned, and I ended up having to continue "custom" drilling each hole in the dowels to "force" them to run more or less from center to center. Basically that means I had to enlarge the hole a bit by using a drill bit to gouge out the holes. 

I also needed to create a few replacement dowels, because the hole drilling went so badly that I could not salvage the insert. I tried using my massive large drill press first. It vibrates badly, and I cannot figure out how to secure things very well to the stupid drill table. After a few attempts with the drill press, I gave up and decided to try it free hand.

First I tried to put it in my table vise vertically - same result. the drill bit would meet the wood and instantly take its own undesirable path to the other end of the dowel.

 Then I tried putting them flat on a drill board and clamping then down with bar clamps:

I originally started with a #40 drill bit, then followed with a #30, followed by a 3/16th inch drill bit for final drilling. This also did not work very well for me. The hole on one end starts out centered, and the hole in the opposite end is completely uncentered and off to one side. I even used my center punch to try to start the hole in the exact center of each dowel, and this did not help much either.

Here are the results of several attempts. This side looks OK:

But not this side:

Example of extra gouging:

About as badly aligned as it can get:

At the end of it all I decided to put my 3/16 inch drill bit into my cordless drill, and after drilling the initial hole, I manually "corrected" any offset in each hole by gouging it out with the drill as best I could.  Then I ran each bolt through the holes to check for centering. it does not need to be absolutely perfect, but I wanted it as close as possible to avoid and excess stress on any of the bolts, or the points where they are attached.  Here are the end results:

Here is an example, taken before I made and drilled the dowel inserts, of the upper left corner of the firewall/engine mount hole, and how the spiders are attached to it. The lower end will be attached to the angle iron:

And here is pic that l also do not see in anyone's build log - how the bolt attachment appears on the inside of the engine mount hole, taken from the rear of the firewall, where the bolt protrudes through the predrilled hole from the factory:

More on the remaining assembly in the next post..

Fixing My RIGID 14 inch Bandsaw

 these pics are year a year and half old, but the pics of the mods I performed may still help somebody else along the way, especially if  the quality of any substantial products starts to go way down due to COVID impacts, as I have already witnessed many times. The simple fact is that even for those companies that are still in operation, many of them are working with reduced staff or have experienced reductions in their labor force, and so the number and quality of those products may suffer as  result. Unfortunately, The RIGID 14 inch band saw suffered from many quality problems long before COVID. Thankfully there were some things you could do to help solve many of the problems and make it a almost first-rate tool.

First was replacing the stock black rubber  tires, which required removing both wheels from the saw. You have to completely disassemble the table, guides, and saw blade, but it wasn't too difficult to do: I found and ordered some orange colored neoprene replacement tires. removing the old tires was easy because they were horribly cracked and deteriorated. These needed to go away because they are hard rubber that develops uneven ridges over time, and this contributes to the vibration of the saw. The new tires are softer so they absorb vibration better, and the blade also tracks better. The hard part was getting them on  each wheel. When done, they looked like this:

In the last pic you can see that the width is slightly less than the entire width of the track. This was the result of my over-aggressive sanding of the edges of the tires. This was necessary because the width of the metal track of each wheel is about 7/8 inches, but the tires only come in a 1 inch width. I spent quite a bit of time reading others posts about this. Some tried fitting it "as is" but it does not sit properly in the tire track, and others tried cutting the width with a utility knife. Neither of these methods worked very well, if at all. 

Finally somebody came up with a way to fairly accurately reduce the width of the tires by sanding them down. However, this method still required some careful preparation. Basically you had to fashion a piece of wood long enough to support the tire, and with a 7/8 inch width. then you had to put the tire over the wood, clamp it down tight so that the remaining portion of the tire extended beyond the wood width, and then you carefully run it on your belt sander. Here are the pics and the number of tools involved:

the tricky part about this was not being too aggressive with the sanding and checking your progress often. The sander only reached so far, so you had to do 2/3 of it on one side and then turn it around to do the remaining portion. The idea was to keep sanding until the width of the tire was reduced to the correct depth, and stop sanding before you started to sand away the wood. The above pic does not show the tire all clamped up, which was the other difficulty. but when you hit the sander the tire is wrapped around the wood and clamped in numerous pace to keep it from moving. The hardest thing about the the clamping was being able to clamp it securely but leave enough clearance to allow the tire material to be removed by the sander without also removing material from your bar clamps. The assembly became quite heavy and unbalanced after all the clamps were applied, so this part was a bit challenging. As I stated previously, mine were a little over done, but they still seem to serve their purpose well and do not cause the saw blade or tire to move as long as proper tension is maintained on the blade.

The next big task was disassembling the saw from the stand so that a 3/4 inch piece of plywood could be fashioned that the motor and the saw would both rest on. One of the biggest causes of vibration of this saw was the hard rubber feet that the motor mounts sat on. The fix was to completely remove the rubber feet and mount the motor on the plywood. This fix also required some longer mounting bolts, and there were several vent holes in the metal stand that also had to be transferred and re-created in the plywood base. Cutting the board to size was easy. Cutting those vent slots mounting bolt slots - not so much.

Next was to reassemble the saw and motor with the new plywood stand, re-install the wheels and balance them. The wheels on this saw were notoriously unbalanced. I followed the procedures to determine the unbalanced areas, and used self sticking pinewood derby lead weights with epoxy glue to mount them to the correct locations on each wheel. 

Then came the replacement link belt from Harbor Freight, which replaces the hard rubber belt that came with the saw. This further reduces vibration because the rubber belt develops a memory as it wraps around the pullies of the motor and the bottom wheel. This causes a bump in certain locations in the belt that adds to the vibration.

The links are removeable to get the correct belt length, but it is quite the jigsaw puzzle to figure out how to do this. The other problem was not clearly understanding which way the links needed to be oriented on the pullies. After a while I found pics that clarified this. Operation of the saw confirmed that I had them positioned correctly.

The last mod was to replace the stock, metal saw blade guides with a composite product called Cool BLocks. These keep the temp of the blade down. which results in more efficient cutting and longer life of the saw blade.

And finally my math to figure out the width of the wheels and the new tires and how much I needed to remove, using a digital caliper:

And finally the packaging for the replacement tires I purchased. Once all these changes were completed I put the saw back together, did the nickel test, and the difference was like night and day. No this saw runs much more smoothly, and I can trust it with finer cuts for the airplane parts that it will be making. I also bought a rolling stand set from HF that I have not installed on it yet. Once I put my new shed together the saw will go in there, and I will be able to move it around easily on this new stand. 

This was the last thing I worked on that had anything to do with the plane over a year and half ago.

Next up, went back to HF to purchase the 1000 lb engine stand that many other RV 8 builders have used to fabricate a rotissorrie for the QB fuselage to aid in  numerous tasks with assembling parts, panting, and mounting the landing gear, etc. And yes, you have to fabricate more parts to complete this project, but it is not ear as difficult as fixing the bandsaw was. 

KPR

Restarting yet again - a year and half later

 Hard to figure out exactly where to start this Blog again. Recap - I screwed up the inner and outer skin of my left wing LE Mode in April of 2019. Tech Counselor came out and we discussed using a planishing hammer and dolly to reform the damage to the outer LE skin and inner subskin. I bought the hammer and the dolly, and was about to attempt the task of re-forming the skin, when I had yet another epiphany. 

1. I realized that positioning the dolly had to be done exactly right in a very tight spot inside the LE, and I determined that this would just be next to impossible for me.

2. After having a very honest conversation with myself, I also realized that even if I managed to reform the skins correctly, this mod went wrong almost from the start where I did not create the wood form blocks for the sub skin properly. This meant that curve of the LE of the subskin has NEVER been formed exactly as it should, and leaves a gap between the outer Le skin and the subskin that then causes issues with how the removeable plate would sit when screwed onto the subskin. It also puts additional stress on the rib flanges underneath. IOW, the removable plate will NEVER sit flush the outer skin because of the subskin deformity, and the added stress in the rib might lead to other structural problems later. I should have taken much more care and ensured that the wood form blocks I used to bend the subskin EXACTLY matched from the curvature of the LE Rib so that the radius would have mated with the LE skin correctly.

3. The final straw for me was the realization that, after seeing it all come together, there was a much easier way to approach this whole thing, without the need to use the massive subskin and all the forming, measuring, bending, cutting, laying up, and riveting that was involved. I also realized that I could still attempt this mod AFTER the plane was built per the plans that would take very little time, and could be done using much simpler techniques than my original design.

As a result of this, I decided to abandon the entire mod and order the necessary new parts, including a new left wing LE skin and some ribs to build a stock LE. The only thing I will still do differently is order a left wing LE skin from Vans WITHOUT the cutout for the stall warning vane service access plate. 

It is sad to have spent so much time and effort on this, only to reach the conclusion that I need to abandon it. It is even more sad to come to this decision only after assembling and almost completing it.  However, I am not sad about having made the attempt, as I learned tons about airplane design in the process, and I now have a very deep appreciation for those that undertake the challenge of designing airplanes from scratch. So my only regret is the time I have lost, but nothing else. Basically it was not until seeing entire mod coming together to figure out that there was a much easier, simpler, less invasive and less time-consuming way to do this. I'll keep the details of that to myself for now.

So what happened after all that?

Instead of working on the fuel tank as I previously stated in my last post, I spent the next couple of months working on some mods for my 14 inch RIGID bandsaw.  This saw became notorious for not being very well built to the point that it vibrated so badly that it was difficult to make fine, accurate cuts. With the forming of the forward Fuel tank mounting brackets looming in the distant future that would require the use of my bandsaw, I decided to spend the time to perform several well-documented mods to reduce the vibration and turn it into the tool that it should be. There are numerous You Tube videos on the subject and I watched all of them.  

I needed to purchase some new Neoprene tires for both wheels, some longer mounting bolts for the motor as well as the saw base itself, a custom cut piece of 3/4 inch plywood to fit over the top of the mounting stand, and some new composite saw guides. After much work on this, I ended up with a good saw that passes the "nickel" test, where you place a nickel on the saw table on its skinny edge, then turn the saw on. If the saw is balanced properly, the nickel will stay on its edge without falling over. I was able to achieve this to my satisfaction. 

The end result was that I could now cut the 1/4 inch thick Fuel Tank Angle Mounting brackets with reasonable accuracy on the bandsaw to reduce the amount of forming work to do after the initial cuts. One of the most challenging parts of the saw mod was the need to trim the 1 inch wide neoprene tires down to about 7/8 inches so that they fit in the wheel tracks properly. This required making a special wood frame and using my belt sander to trim the edges accordingly. That, balancing the wheels, and adding the 3/4 inch plywood base and a new composite "link" belt all contributed to solving the vibration problems with the saw. Unfortunately this was yet another delay in the build.

Then, my wife and I needed to take a much needed vacation together, so spent the next couple of months focusing on a multi-faceted trip the New York for the first time. We spent one week in New York City and did all the NYC things a newbie would want to do - Statue of Liberty/Ellis Island, 9-11 Memorial and Museum visit, which I highly recommend to any red-blooded American, went to a Broadway show, Times Square, Stood outside during a Today Show airing, had a real New York Pizza slice, learned how to ride the subway, went to Grand Central Station, Went to Battery Park, the Fashion district, visited the famous toy store FAO Schwartz, and much more.

Then we flew off to Buffalo and took a shuttle to Niagra Falls, Ontario to see the falls for the first time. We had so much fun there, and the falls were so beautiful, that we both want to go back someday. this all happened in early September of 2019. As the whole world now knows, only a few short months later all of New York and the rest of the world would be shut down and fighting for its life due to the COVID pandemic. I have not been back on the build ever since May of 2019 as the the wind just went out my sails after coming to decision about the mod, and too many other things got in the way. After  our vacation, winter and the cold set in yet again, and I still had no heat in my garage. 

Then COVID showed up in the spring of 2020, and the massive wild fires in Colorado soon followed, and it was a struggle to stay alive and to breathe through smoke and ash all at the same time. I almost lost relatives in the Troublesome Fire in Grand County - very scary. So airplane building was not on my list of things to do throughout that entire period.

I endured multiple furloughs and layoffs at work last year, only to find myself working 15 hours days, 7 days a week, for at least a couple of months. So you could say that yes, I kept my job, which was a good thing, but at great personal cost to my overall health and well-being.  Now we are in 2021, where winter is once again upon me, and still with no heat in my garage. What a wildly exhausting time it has been over the past year and a half. 

Is there a plus side to any this? Well, in the interest of counting my blessings, both kids have graduated college, have jobs, and are out of the house and successfully on their own. Several major financial burdens have ended, I have not contracted COVID nor have any of my family members, and COVID vaccinations have begun. Aside from politics and some extremely idiotic people in this world, it seems like the sun may be trying to shine on the world again. So I decided it is also time for me to re-engage with the plane project again. I need to order parts from Vans and finish the wings.

More to come..... Sorry for the long hiatus. Stay safe, respectful, and peaceful everyone. Life is too short. I'll have pics of the bandsaw mod, planishing hammer and dolly, and some other stuff in the next post.

Busy Preparing for the Fuel Tanks and Tech Counselor Checks out my LE

My Technical Counselor and former long time EAA Chapter 301 President Jim Elliot has been mentoring me through all this LE mod fiasco. I had to wait a couple of weeks for him to become available to come and visit the "almost" finished LE work, and he was finally able to come out last Saturday and take a look. He is a Mooney aircraft owner and has helped several people build different makes and models of experimental airplanes. He definitely knows his way around an airplane, and with evaluating potential affects of modifications such as mine. More on that in a bit.

Since I knew I had to wait for a bit for him to be able to come over, I started preparing (for about the third time now) to get back to work on the fuel tanks. So although I have not posted in while, I have still been very busy thinking, reviewing, and planning for re-engaging on the fuel tanks to get those behind me as soon as possible. his started with a review of many previous posts where I actually started on the left fuel tank because you needed to match it up with the LE to check alignment and drill some holes in the T-712 mounting brackets for the wing spar and the rear tank baffle. This little journey took me clear back to posts from the Fall of 2017. About the last thing I remember about the tanks was fabricating the tank stiffeners for the bottom of the fuel tank skin, and countersinking skin-to-rear baffle holes per the plans.

After reviewing the stuff from the past, I ended up coming up with a list of new additional questions that required answers from Vans. As a side note, to date I have order at least 2 proseal tubes, a small sized can of proseal, and a full sized quart of proseal - ALL of which have shelf lives that have long since expired, so they will not be used to seal any part of my fuel tanks, and I will need to put in an order for more proseal yet again. Sucks to be me I guess - that's about the only way I can sum that up.

Many of these additional questions are questions that you do not see either asked or answered by others, but I find it quite strange that others are not asking the same questions. Anyway, to make sure that I don't lose the content, I am posting them here for myself and anyone else following my blog that might also appreciate the info:

385b and c SW fuel senders - for left and right - is it correct that the potentiometer scale/meter on c version for the right tank will be reversed (facing forward instead of to the rear, when installed on the side of the tank, or should the scale for both still appear toward the rear of the tank when installed correctly.

Vans says this backwards orientation is normal - important thing is that they both point down when installed either on the end rib or the rear baffle plate.

Am I supposed to scuff the back side of the sender flange of each sender if I am going to proseal it directly to the tank rib (NOT use the rubber gasket or cork as recommended by many who have been there before.)

Vans says not needed.

The left sender seems to have a dead spot at the end of travel of the arm (empty indication) - either no ohms reading at all or much higher (300 ohms or more - much higher than expected 240 ohms per the plans.) The right sender seems to be indicating correctly per the palns info. Ordered both SW senders from Vans on 4-16-18 order # 74191. SW says has a 2 year limited warranty - how do I proceed with a replacement. Go through Vans or direct with SW?

vans - Contact SW directly to replace it

Left tank will be flop tubed, so sender will be in bay #2 in rear of baffle.
1. Did I do a lot of extra unnecessary work by cutting the big hole in the aft of the end rib, when I found out that the sender needed to be placed in the second bay via the baffle in the first place.

Vans   -still good to have access t that bay due to the trap door and the flop tube/anti hangup bracket attachments.

2. With the sender in the secnod bay of the rear baffle, that means that the only way I can service that sender if necessary is to pull the entire tank, correct?

Vans - correct - you will have to pull the tank to service the sender that is mounted this way

3. For tank baffle mounted sender, do I need to cut another big round hole in the second bay AND use a reinforcement ring (T-407) as well, or just the hole big enough for the sender to fit in?

Vans says nope - no reinforcement ring or big hole needed - just a hope big enough for the sender to be inserted/mounted directly onto the rear baffle plate web. No reinforcement ring needed because the baffle plate is thicker/stiffer than the rib web.

4. Do I need to use another reinforcement stiffener ring for the T-411 cover plate on rib T-703 if no sender is being mounted in that hole, or can I just mount the cover plate, with nut plates mounted on the rib web itself instead of the combo of the rib web and the reinforcement ring?

Vans - would still use the stiffener ring here as the rib is not very thick and alot of strngth is removed by cutting that big hole.

5. Depth of tank for SW sender specs to determine what size to cut the rod - what dimension should I use for that (tank depth so I cut the rod to the correct length?

Vans - just clamp the sender in place and measure to determine based on the area where the float will be traveling.

6. Since the left tank sender will go in the rear tank baffle, do the dimensions of the float wire change from original plans for mounting in the rib on the side? Any issues with clearance of the bottom stiffeners when mounting the sending in the rear tank baffle?

Vans - measure to be sure, but should not be a change or a problem as far as they are aware.

7. Do you know a part number for a more malleable proseal for access plates that is not as hard as normal proseal to remove??

Vans - they do not use it and did not know the part number of hand - said to check Spruce and others.

8. Grounding the sender - how is this grounded to the airframe if you have the tank baffle or rib web, proseal, and the flange of the sender on the thin later of proseal. Are we supposed to run an additional ground wire from one of the sender mounting screw holes to one of the tank attach bolts or something similar?

Vans - Use a lock nut with the cut flanges that bites into the metal on the underside of the screw head and on the sender flange as it gets mashed down during screw tightening to establish contact for a good ground - so additional wire should be needed, even if screws are prosealed. Do it on all screws or just one or something in between?

As far as the tech counselor visit is concerned, Jim took a look at my unfortunate demise on the LE. Said that it is a dent and not a crease, but that it did deform the outer skin and the subskin. Then we had a conversation about acquiring an autobody or planishing hammer and a dolly that may have to be customized to try to pound (actually TAPPED) out to try to reform the skin back to the shape that it was in before. Unfortunately I can see where my unbelieveably STUPID idea t just keep pounding on the skin with the rivet gun when the rivet was not setting properly has indeed flattened it out a bit. So as a result, if I want to continue with the LE mod using what I have done thus far, I now get to learn a new skill that involves removing dents and reshaping metal, and I probably have to custom-make yet another tool = more wasted time.

So I went to local NAPA store, found a planishing hammer with a rounded head (NOT the kit you find at Harbor Freight, that only has flat headed hammers), and a Toe dolly that, when I fitted it up against the curvature of one of my LE ribs that I took with me to the store, looks like it will almost perfectly conform to the curvature of the LE skin/subskin/rib as long as it is held in the correct position. This is probably going to require a helper to hold the dolly in position while I tap the outer skin and hope like hell that I don't just deform everything beyond reasonable repair.

The last part of our visit was spent having a heart to heart about the possible structural impacts of what I am trying to do, and if I should go ahead and contact a DER (Designated Engineering Representative) to come and look at my invention and provide some further experienced insight on what I am doing. I wanted to go ahead and finish this mod regardless of the ultimate decision about its feasibility, just to see what it would take. At the end of the day I am not certain that this is a safe thing to do, and may still decide to abandon it all together. But I'm not throwing in the towel on the mod just yet.

I've got some parts to order from a number o different vendors so I am also putting that list together. I'll have some pics on the next post that show the damage from the F'd up riveting job  more clearly, and the tools I am going to attempt to use to fix it.

Slamming LE rivets, Cont'd.

Pounded a crap load of rivets on the LE over the past two days. Felt good after getting the hang of it again, but I get real sore from all the strange body positions required to accomplish that. I'm not quite done yet, but I only have a few forward-most holes on the top and bottom side of each rib, and the holes surrounding the area where the outer skin that surrounds the perimeter of the removeable section must be riveted to the subskin. Then I figure I need to drill out and replace about 20% of them, mostly due to over setting them (Shop heads bucked a little too far). Here is a shot at the end of yesterday's session with most of the rib flange rivets in place:

Unfortunately after finishing the rib flanges I decided to get "started" on the business end of the mod - the inboard section that I affectionately call the swiss cheese section, since it has so many rivet holes and cut outs in it. What I forgot t take into account was how much flex exists in that area between the two ribs. you don't realize how much stiffness is provided by each rib until you try to buck a couple of rivets in the middle of the skin between them. What follows is the result - yet another rivet that needs to be drilled out and replaced. So I hung it up for the day to regroup, rest, and attack it again today.

To address this, I came up with an idea. I needed to somehow add some stiffness to that area just as I have had to do at other times. I remembered that I still have several of the form blocks that I used to shape the subskin so many years ago. SO I took one of them and a bar clamp, set it down inside the LE where I thought it would provide sufficient stiffness, and clamped it down just enough to hold it in place. With all the nutplates and shop heads of other rivets it did not sit down inside the skin totally flush, but it was good enough to provide the required stiffness in the areas where I needed to rivet the outer skin to the subskin.

This worked out REALLY well. Even if the outer skin was pressed into the wood a bit awkward due to nutplates being in the way, it was good enough to hold it there temporarily without distorting or bending anything out of whack while I set the rivets. Yet another tip for future builders. 

Here is shot after I was able to use the form block by moving it as necessary to allow room to hold the bucking bar while I set the perimeter rivets around each access hole. These would be the rivets that would normally secure the mounting or backing plate that allows a flange to mount the cover plate onto it with screws. In my case the subskin serves as that mounting plate, but I used the same rivet pattern as called for in each actual mounting plate:

Once these perimeter rivets were set it was time to mount the original cover plate from Vans permanently to the subskin. Here it is clecoed into position for the final time:

And here it is after all the rivets were set:

It still fit just like a glove. I was really pleased with how that went together. I was concerned about some of the edges curling up, but that never happened. It fit just like it was supposed to - to cover up the old Vans hole so I could use the SafeAir access panel hole instead. 

And finally the back side with all the shop heads after this was all done:

Like I said - Swiss Cheese.

 But slowly all the holes are getting filled.  Next steps are to set the cradle on its side and secure the back side of the LE so I can push on the forward tip rivets to set them. The problem is that I still need to be able to reach deep inside with the bucking bar to set those most forward rivets - and these are the most critical to do correctly the first time. I can't afford to have to drill any of those out. So the next session will be spent doing a lot of prep and ensuring that everything is exactly right so that setting these last rivets is as easy s possible.

KPR

Final Assembly of the Left Wing LE Begins

After evaluating the nutplate situation a bit more I decided that the nut plate is fine for now. I can still replace it later if I want to.

SO the next step was check the instructions again. They basically take you through the entire process to finish the fuel tanks, but because of the mod to the LE I really needed to finish that first. After the tanks are all but finished, the instructions tell you to rivet the LE together with it in the LE cradle. So the reality is that the LE can be assembled while in the cradle at any time. It cannot be riveted to the Wing spar, however, until the fuel tanks are done, because the screw holes in the tank skin that slide over the top of the joiner plate attached to the LE need to be final drilled, deburred, and dimpled for the #8 screws, and the assembly fit-checked with the LE again to make sure everything is AOK. One of the things that also gets in the way of this is excess proseal on the end rib of the fuel tank that may interfere with the joiner plate flange. Sometimes this has to be trimmed away to prevent this interference, which can cause the screw hole alignment to get messed up if this is not resolved. SO this is all interlinked,  but for now I can go ahead and rivet the LE together, shich also means that the subskin is finally going to become a permament part of the LE.

The instructions say to cleco it all together and then "ensure that the rear holes are perfectly aligned with each other, which I guess means the holes on the rear flanges of each LE rib. SO to reverify this I think I clecoed it all to the wing spar one last time to reset all the ribs after tugging and pulling on all that vinyl, then I carefully removed the LE again, making sure that I did not twist or bend it so that the hole alignment would not be disturbed. Then I carefully placed it back in the cradle.

Next, there were some scratches on some of the rear rib flanges and the area of the joiner plate where the tank skin edges dug into the primer and the metal a little bit, so I sanded those areas out to remove the stress risers. Then the instructions say to start with the rear-most rivet hole with a squeezer on the top and bottom of each LE rib to secure them into place. I was able to do this easily with the pneumatic squeezer and a flange yoke. As part of the mod, the two inboard-most LE ribs also have two additional holes that I needed to add to the skin and each rib and the subskin. These "second" to the last rivet holes are relatively close to the rearmost holes, so I thought I could set those rivets with the air squeezer as well. The thing that I forgot was that the #2 inboard rib, which is a modified 408-1 rib, has the shop heads of the AN470 rivets protruding a bit from the rib web, and when I tried to set these with the air squeezer the rivet set hit the edge of those shop heads and caused the set to jump, which resulted in a badly set rivet, which I had to drill out and replace. After drilling out the bad one, I decided that in this situation I needed to use the hand squeezer to maintain positive control of setting the rivet so that I could ensure that both the yoke AND the rivet set would clear the shop heads of those AN470 rivets holding the rear rib flange extensions onto the rib web. I put the 3 inch yoke on the hand sqeezer and got those rivets set as well.

Now that the rear-most rivets were set on the top and bottom sides of each LE rib, it was time to get out the rivet gun and the bucking bar. More decisions to make and prep to do. For example:

I had to decide the pattern I would use to set the rivets on each rib
I had to get towels and place them inside the LE skin to prevent accidental dings in case the bucking bar slips out of my hand
I had to tape up the edges of each rib web to help prevent gouges from the bucking bar if it slides off the rivet shaft
I had to figure out how to clamp down the table/cradle assembly to ensure that NOTHING would move or slip during the riveting process
I had to check the air pressures on the compressor and at the adjustable pressure regulator on the gun with the new slightly heavier rivet set.
I had to determine all the rivet sizes I would need to attach various parts together.

ON the last, the plans call for AN426AD3-3.5 for he main rib flanges, and AN426AD3-4 for the rivets that attach the skin, rib flange, and joiner plate assembly. However, I found that the 3.5s are OK for the main rib flanges on the main ribs, but on the two ribs that are involved with the subskin assembly, I found that the 3-4s were good for the skin-to-subskin rivets with no rib flange involved, but I found that a 3-4.5 was the correct length for the rib flange, subskin, and outer skin assemblies. A 3-4 just is not quite long enough for some reason.

SO the plan was to start on the center ribs and then work outward toward each end rib. I also started on the bottom side of each rib because it is flatter than the top - this is something that many builder advise to do when building the fuel tanks because you can set the tank down on the bottom afterward to make work on the top a bit easier. I worked from the rear-most hole to the front, as stated in the instructions.

When I started, the one thing I forgot to do was check and reset the pressure on the air compressor, which had been tuned down to 75 psi for the air squeezer. Since the pressure on the rivet gun is controlled by  separate regulator attached to the air inlet of the gun, the pressure at the compressor needs to be at 90 psi. Since I forgot to do that, the first several rivets I set seemed to take forever, and the shop head was not being formed as quickly as I was expecting. A quick check and reset of the pressure at the compressor basically fixed that problem.

Time for the pics. Here are some of the new "rubber boot" flush mushroom rivet set showing the before pic, the disassembled pic before trimming down the rubber, and the "after" pic showing the trimmed down rubber on the reassembled tool:

I took the rubber boot and ran it by hand across some aluminum oxide 220 grit sandpaper after marking it with a sharpee line. I did not want to sand too much of it away because it is still supposed to be a little proud of the set to provide some gripping ability on the skin. Then I put the tape on the rivet set - another important little trick to prevent damaging the metal with this pesky tool:

Here are some pics of the tape prep and towel prep to minimize or prevent other possible damage:

And finally some pics of te rivet gun in place and ready to set a rivet, and another pic of the bucking bar, using the angled side of the bar, showing how all this has to be positioned to set each rivet:

And here are some pics showing the progress - basically not more clecoes and a clean looking skin. the reality is that I have several rivets to drill out, mostly because they were overset, but a few are badly set rivets that need to come out. Overall I was pleased with the rivet process, and the rubber mushroom seems to do well at preventing skin damage. But the one thing that it does NOT do is ensure that the set cannot "walk" across the skin. I had numerous events where this set decided to have a mind of its own and start walking up, down, and to either side. Luckily it did not seem to damage the skin at all, thanks to the rubber edges I guess. It is designed to allow it to swivel a small amount so that you can presumably hold the gun not quite perpendicular to the skin and still get a good set. Personally I found that I still had to figure out what angles to use both up and down and side to side and how much pressure to apply to hold the rivet gun in place. 

You will notice that I left the bottom/forward-most rivets for later. These are too low to be bucked - both from a position standpoint of the gun and bucking bar, and a gravity standpoint where the rivet cannot stay in the hole at the curved angles of the these holes - it falls out. SO these will be set with the cradle turned on its side after all other rivets have been set. These forward rivets are the ones I dread the most, because the potential for skin damage due to a slipping rivet gin or bucking bar is extreme, and I already have enough bad experiences with that to prove it. The trick, once again, is securing the work so that it cannot move, and so that you can easily position the gun and the bar to set those rivets. it usually also means that you have to set these "blind", meaning that if you do this solo, you will either be able to view the bucking bar on the rivet, or the rivet gun, but you will not be able to see both at the same time. I hate setting those rivets. Curved surface riveting sucks big time.

Anyway, this was the longest work session I have had on the place for a very long time several hours today. I only have about 3 more ribs and the final forward rivets to go, as well as the swiss cheese rib, subskin, and outer skin assembly for the LE mod, so there are still a large number of rivets to set. Hopefully I will get most, if not all of them done tomorrow.

Pounding rivets again using every method on the planet and lots of tricks you learn along the way - so far so good...….