THE FORWARD FUSELAGE PAGE 2
(Continued from, "The Forward Fuselage Page 1")
I decided to drill pilot holes in the cowling half of the hinges now. Dan Checkoway (www.rvproject.com) had some manageable problems trying to hold the hinge half in place while he drilled. I intend to drill from the inside out. I wont know until later if that is going to work. In the photo at left you can see a rivet fan in use to drill the cowling side of the hinge. In the photo at right is another Vans surprise. This part re-enforces the F-902 bulkheads for the fuel tank bracket. Where do you think I found this little guy on a drawing? On drawing 38 is where. It would have been nice if drawing 23 referenced #38 for this part but it doesn’t. Anyway, there is one of these on each side and each one gets two shims. The title of drawing 38 is "Wing Attach and Control System Detail."
The picture at lower left shows where the tank bracket re-enforcement lives. On the right, I am busy drilling the left bracket. I can’t imagine the frustration that one might feel when he gets ready to mate his wings and at the last minute he has to make these 6 time consuming parts (2 brackets and 4 shims. It would be especially frustrating at that point because the fuselage would be right side up and you would have to have 2 people to drill these parts. Notice I am standing in the photo and I can drill the parts by myself since the bottom skin is removed at this point.
Are there any other surprises? Why yes of course. This didn’t surprise me as much as it surprised others like Dan Checkoway. By the way, I have to put in a good word about Dan here. He has a very informative web site at www.rvproject.com. It is also very entertaining. I think he may have missed his calling. He should have been a writer. Back to the plane. These two brackets help hold the forward spar covers in place. They get riveted to the F-7101 re-enforcement plates. They are found on drawing 34 which as I said earlier has the title, “Center Cabin Cover.” That would seem like the right name for the drawing that contains these two parts. Problem is, you theoretically installed the F-7101 landing gear re-enforcements back on drawing 23 which you should have completed long ago. No problem. You’ll just install them with blind fasteners. No you won’t, at least not easily. There is exactly .125” of clearance between F-7101 and the F-770 skin. These parts need solid rivets. They should be on drawing 23. Anyway, I knew about them (Thanks again Dan) and I made them and drilled them prior to installing F-7101 (left photo below). Right photo below shows both angle brackets cleco’d in place.
The only detail that I left out of the pictures above is the fact that I dimpled the F-772 skin at this time. The F-770 skins were previously dimpled. I counter sunk all of the stiffeners and longerons where the rivets attach the skin to them. I also countersunk the rivet holes in the cowling hinges. Then I prepared for prime. The photos below show parts etched and alodined (LH photo) and primed (RH photo). I primed a total of 57 individual parts. Some of the parts were for the rear fuselage (2 skins, 4 gussets and 2 longerons). I am now ready for installation of the forward fuselage detail parts. The left photo was taken in my office at the airport in Ft Lauderdale.
At this point I installed the Aft Fuselage Top Skin. After the aft fuselage top skin was installed I returned to the forward fuselage. What can I say? I like to skip around I guess.
What do you think was the first thing I riveted together after returning from the aft fuselage top skin? Why it was the F-782D-L &-R center cabin cover brackets to the F-7101-L & -R gear re-enforcement brackets. (left photo below) (I wonder why these are called gear re-enforcement brackets when the RV7 gear is attached to the firewall?). I did not get back to these parts until 2 weeks later. The next item that went together were the F-684-L & -R lower engine attach re-enforcement gussets (-R shown installed right lower photo below). It would be very difficult to install the rivets that attach these brackets to the vertical angle of the firewall on each side with the firewall in place. I installed these gussets and every other aluminum part that gets riveted to steel or stainless steel with a thin coat of PR 870 A2 sealer in between for protection from dissimilar metal corrosion. (As Dan Checkoway would say.. 8^) I also installed the nutplates on these parts at this time. I installed the firewall wet with a thin coat of PR 870 A2 sealer.
Remember my friend Mario Viteri from Ecuador (Photo is in “Firewall and Bulkhead” section). Below left is his 16 year old son Ritchie. He is very enthusiastic about aviation and may take it up as a career. I am teaching him a little about riveting. He is holding a bucking bar. We riveted the F-719’s on together. The lower right photo shows the F-719-L installed. Don’t forget the F-719B (arrow). It gets riveted to the angle before the angle gets riveted on.
In the left photo below, I have cleco’d the RH lower side cowling hinge bracket in place for riveting. Ritchie is in the background putting on his rubber gloves. This aluminum hinge with its aluminum shim got riveted to a stainless steel firewall. This gave me an opportunity to explain dissimilar metal corrosion to Ritchie. He starts college next year and I think he just may take some aeronautical engineering courses. Mario would like him to attend school in the U.S. but I don’t think he can afford it. Besides, going by the fact that Ritchie speaks perfect English which he learned in Ecuador, the schools in Ecuador are probably just fine. The right photo is a picture that I had Ritchie pose for. He really had a good time and he learned a little about airplane construction.
In the photo at left below you can see me riveting the F-695-R upper engine mount attach fitting re-enforcement to the upper longeron. In the photo at right below you can see me riveting the F-695-L upper engine mount fitting re-enforcement to the left upper longeron after I remembered that I have tools that make certain riveting jobs easier. The shop heads on the left gusset were more consistent than the right one. If you have a rivet squeezer and you have easy access to both sides of part use the squeezer. By the way, if it seems that I am describing left hand parts as right hand and vice-a-versa, don’t forget, the fuselage is still upside down.
Remember earlier when I said that I was going to have trouble with the outboard rivet in the F-695 gussets on each side. I used standard practice 4D minimum rivet spacing on the part. The drawing called for 3D which is legal per AC43.13 but not used as a rule. I drilled the holes on the bench and then put the part up to the airplane. I immediately understood why the drawing called out for 3D (3 times the diameter or 3/8”) spacing. One rivet came out right under a part of the fitting that had an attach flange welded to it. If you look at the photos below you will see what I mean. The photo at left below shows the open hole I had to leave while shooting solid rivets. The insert shows the problem. The solution was a CR3213-4-5 Cherry Max rivet at $.65 each. Aircraft quality blind rivets are expensive but I don’t like the idea of using hardware store “pop” rivets.
Next, I installed the F-713-L &-R aux longerons. I had very little trouble riveting these on by myself. I installed all of the parts of the forward fuselage that touched the outer skins or firewall wet with PR870 A2 sealer. Photo at left below shows the F-713-L riveted on. Notice that the first 5 rivets from the front also go through the lower engine mount attach fitting and the F-684-L re-enforcement gusset. Picture at right below shows the F-713-R cleco’d in place waiting for rivets.
The next thing I did was to rivet the F-7101 assemblies to the F-902 “bulkheads” (below left). These 8 rivets looked like they would be a lot easier to install now. I then installed the inboard lower skin stiffeners, F-772B-L & -R. There are 6 rivets, 3 on each end, in each one of these. I could squeeze 2 of the 3 rivets in each end. The ones closest to the firewall and the F-704 had to be shot with rivet gun and bucking bar.
After the above was accomplished, I took a day off. On Thursday morning at about 5:00 AM, I started preparing to install the rest of the forward fuselage details. You can see the masking tape on the lower skin. I put PR 870 A2 sealer over the rivet holes where the skin meets the firewall and where it overlaps the center fuselage lower skin. I did not take a picture of the sealer on the skin (darn it). I put sealer on the F-902/F-7101 assembly but only on the flange of the F-902’s where they touch the side skin. The picture below right shows one of these assemblies with wet sealer ready to be installed. If you are reading the text and not just looking at the pictures, I want you to know that you do not need to put sealer on these parts. It is something that we do to the jets and I just felt like doing it to this little airplane. (Recreation don't you know.)
I bolted the F-717’s to the lower engine mount attach fitting with 2 bolts. If you look closely (lower left) you can see that the bolts will block some of the rivets. Once riveting began on the longeron, I removed the bolts. They were installed to keep the holes in alignment. I installed all of the rivets in the F-902’s (F-902-R shown) and I installed the rivets through the upper edge (lower edge in the photo) of the F-7101’s where they go through the F-713’s. I put the F-713’s on 2 days prior. Since they went on wet with a thin layer of sealer, I had a cleco in every hole after their installation until today (not shown).
In the photo at lower left you can see the F-902-R is riveted in except where the F-768B-R and its 2 shims go. The F-7101-R is riveted in also. In the photo at lower right you can see that I have riveted nutplates on the F-782D- R. In fact, to this point, I have installed all nutplates that go on any bracket, flange, gusset or other parts prior to installing the part if I can. What makes these parts special? Note that the screw hole itself is dimpled. I am going to put countersunk fasteners in all of the interior cover panels. I also intend to have the baggage floor panels be removable.
Time for the lower skin now. The photo at lower left shows the F-722 skin in place. I put sealer on the skin where it attaches to the firewall, the side skin and where it overlaps the F-776 center skin. I put sealer on the 4 lower stringers because that was easier than masking of the skin to apply sealer there. Why am I doing this? I am not going to keep this airplane for 30 years. So why try so hard to corrosion proof everything. There are 2 reasons. First is that we usually do this when we make any repairs to the jets. This is to keep condensation from between ribs and skins. Second is that I will sell this machine which will be based in Florida someday and I really don’t want to explain away surface corrosion near rivet holes if possible. That leads right in to the photo at right. I mixed some epoxy primer and with a cotton swab I put a little primer in each hole. After the rivets were shot, I cleaned the excess with MEK. Come and see the airplane in 10 years. We will both know whether or not all the trouble I went through was worth it. (Actually, I just like doing this. Taking corrosion preventative steps makes me feel better, even if they are not needed.)
This rivet (arrow) in the photo below left, goes through the side skin, the bottom skin, the lower longeron and the F-7101 on each side. It has to be double flush because that rivet ends up beneath the F-7114 wing attach gusset on each side. The right photo shows the rivet location with the gusset in. It is the same on both sides. It is also a pain to put a shop head in a counter sunk hole in this location.
Notice the green tint of the primer in the photos above. My camera flash is too bright for a close up and with the lower skin on I am using the light from a fluorescent drop light. The same is true in the photos below. The left one is a picture of the fuel tank re-enforcement bracket. There is a counter sunk screw, #10 I might add, that goes through the side skin and the lower skin. It then goes through the lower longeron and finally through the F-796B. The plans tell you to countersink this hole. That is a bad idea. Countersink the hole in the longeron and dimple the holes in the 2 skins. Of course you have to do that prior to installing the bottom skin and the longeron. Notice the limited clearance for installing the nut. That was a real pain. Most of my sockets wouldn’t fit in there. I finally found one that did. If you haven't installed these screws yet, get 2 each MS21042-L3 nuts instead of the AN365-1032. The parts department at any FBO should have them or you can order them from Aircraft Spruce. The RH photo below shows the four bolts in the left engine mount attach fitting.
Below left is a shot of the completed forward fuselage from below. Below right is a shot of the forward fuselage looking aft from the right side.
Above is a picture of the completed forward fuselage with the engine mount bolted in place. Notice anything missing? In the Firewall and Bulkhead section I had put a shim between the mount and the firewall at the two lower inboard bolt holes. After everything was riveted together, I had to remove them because they held the outboard bolt flanges away from the firewall. I have no explanation. (Education?). The forward fuselage is completed. The Fuselage Top Skins are next.