Fitting Cowling

[jrevens]

I'm sure others have had this issue too, Jim. Maybe someone else has a good idea. I bonded (Hysol 9460) and riveted ("soft" aluminum AN rivets) thin strips of aluminum to the lower cowl along the inside of the flanges just to give them a little more stiffness when engaging and disengaging the Camlocs. If you were able to bend a small flange on an aluminum strip, or even just use a flat strip, you could bond something like that to the upper cowl also, on the inside surfaces of both sides just above the actual mating surfaces, and that might help keep them flat and from "scalloping". Ideally, those mating surfaces could probably be a little thicker. That is kind of a common problem with fiberglass cowls in general. I really like the cowls being made by (for?) Van's & others that are fabricated as a double wall honeycomb structure. Still very light but much more stable and stiffer.

[Flybyjim]

I have had several local folks ask me how I like the Kitfox kit and I tell them for most of the build it is good. It is the small details like the cowl that I have to tell them there could be improvements. Same with the manual, there have been updates since I started my build or even before my build and there have not been any updates sent out to previous customers. It is very frustrating when one calls the factory to find out, we changed that or we do not do that like that anymore. I know this also happens with other companies, I have a buddy who built a Challenger, same problems. I don't understand why a company is not keeping customers up to date with changes, mods and such, all it takes is a click of a mouse these days to keep your customers informed. In any case, I like the Kitfox kit and the way the plane handled when I flew with John a couple of years back I will support them when I'm asked about the kit. Their staff has always been helpful when I see them at airshows or call them on the phone. As for support for builders of Kitfox planes, this group is a great resource for both builders and the Kitfox company, most times I can find the answers I'm needing before calling the factory.

I can see why Vans customers are so satisfied, every one of them I have talked to say the parts fit perfectly with very little adjustments. For me fit and finish is important.

Thanks once again John, hope to see you at Oshkosh

[jiott]

A few folks have ditched the camlocs and used a long piano hinge to attach upper and lower cowl, probably for the reasons you are experiencing.

[efwd]

I whish I had done that. Mine worked out along the sides but I lost the close fit between two camlocks along the aft, top edge along the top of the boot cowl. Piano hinge is the way to go. (IMHO)

[jiott]

Its interesting about some folks getting bulging between camlocks when attaching upper, lower and boot cowls. Others, including myself, have none of this problem. I don't know if its luck, careful craftsmanship, or what. I do know that fitting the 3 cowl pieces together is probably the most challenging part of the build. I would encourage new builders to take your time, don't do too much at once, try to end up not having to push anything into position; it should all lay together smoothly with a minimum number of clecos to hold it together before camlock installation. It is also possible that there are enough inconsistencies in the fiberglass moldings that no matter how hard you try, some may end up with less than ideal results.

[efwd]

I believe I know how my top cowl ended up with a warped spot. I had my cowl looking perfect while fitting however, I believe when I drilled holes into the firewall flange, my firewall flexed a bit aft. The flange then sits a tad deeper in the boot cowl which is tapered. It only needed a 1/4 inch maybe and now my top cowl, which was fitted while the firewall was sitting a bit more forward, has to attach to a slightly smaller profile. If that makes sense.

[Flybyjim]

Thank you for all the replies on the cowl issues. This is how I am going to work this out, I did this same thing on a project back in 2011 and it worked out very well. The aluminum channel is 3/4 by 1/4 from aircraft Lowes and was bent using fluting pliers. I'll post again when it is finished. Working all week so it may not be finished for a couple of weeks.

[Flybyjim]

I changed the spacing of the cam-locks from the listed 5.5 inch to 4 inch spacing.

[jrevens]

That looks very nice, Jim... similar to what I did, only better!

[Michaels kitfox]

That is great work, but i would like to hear more about the piano hinge idea. Or even see some photos of such.

[Cherrybark]

The cowling is the most painful part of the project. The initial pieces had such a ridiculous fit that I called the factory to see if something was wrong with my kit. I don't have the proper tool for setting solid rivets and the channel lock method really didn't work well for me. There are multiple "cocked" rivets, really a mess. I need to drill out the rivets, buy a proper rivet setting tool, and start over. Counter sinking the thin metal firewall was also difficult. I was nervous about taking away too much material and not leaving anything for the rivet to hang on. Of course, taking away too little leaves high or cocked rivets again.

Any recommendations for an affordable riveting tool?

[Shadowrider]

I hear you on the cowlings. The cowlings fit and finish was very lacking. Curious if the carbon ones fit any better or I am guessing they use the same molds?

Have you considered vise grips? I ground the vise grips down flat. The trick is to grind them so when the rivet is squeezed the two surfaces are flush or the rivet will bend to the side. I borrowed a rivet squeezer from an AP at the airport to do flapperons. I found if you tell them what your doing most mechanics are very helpful and willing to borrow you stuff. But for the camlocs I decided to try the vise grip trick and it worked good.

[Cherrybark]

Whoops, I meant to say "vise grips". I have them ground down but maybe should check to see that the faces are completely flush. Haven't figured out how to use the vise grips on the oil door.

[Shadowrider]

Yea the oil door was a little more tricky. I didn't use the vise grips on the oil door. I used two punches and a hammer. You just need something solid pressing against the rivet and on the other side hit it with a punch and a hammer. Best with two people but I was able to do it by myself. Basically I just watched some videos on how a solid rivet is set and tried to come up with something similar. I used a piece of scrap fiberglass and countersink and practice setting some flush solid rivets. Then I tried the oil door and they came out good. The cam locs I had a few rivets bend to the side slightly but as long as you squeeze them good they will not go anywhere. When I set the camlocs in the boot cowl that attach to the footwell I just used pull rivets there.

[DesertFox4]

This thread was moved from “ muffler exhaust pipe length” thread.
From Flybyjim:
“ I have the cowl installed and have drilled the side of the cowl as noted in the manual of a spacing 5.5 inches from back to front. I have this in place with clecos and I am getting a bulge on the top cowl between the attached areas along the seam, any suggestions to this? My last plane had a straighter profile from front to back and I riveted an L channel along the top of the bottom cowl to keep it in alignment. This Kitfox cowl has a bit of a curved profile from the front to the rear so I'm not sure I can do the same with it.”

[jiott]

One thing I learned about setting solid rivets with vice-grips; it is very important that the rivet is not too long, otherwise there is too much tendency for it to tilt sideways during the squeeze-pay attention to the rules for proper grip length of the rivets. If you only need a few rivets a tad shorter than what you have, you can carefully sand/grind them down a little keeping the ends square.

[Cherrybark]

I was feeling guilty about hijacking Jim's thread. Thanks for moving it.

Nice tip on paying attention to rivet length. I made a few phone calls and am borrowing a pneumatic gun and bucking bar. YouTube videos show the technique. I'll put a few rivets in some spare material and will surely do a better job the second time around.

[Hawkertech]

The cowling is the most painful part of the project. The initial pieces had such a ridiculous fit that I called the factory to see if something was wrong with my kit. I don't have the proper tool for setting solid rivets and the channel lock method really didn't work well for me. There are multiple "cocked" rivets, really a mess. I need to drill out the rivets, buy a proper rivet setting tool, and start over. Counter sinking the thin metal firewall was also difficult. I was nervous about taking away too much material and not leaving anything for the rivet to hang on. Of course, taking away too little leaves high or cocked rivets again.

Any recommendations for an affordable riveting tool?
Depending on how thin the material is, thin material shouldn't be counter sunk it should be dimpled with a thicker sub material counter sunk for the dimples.
https://www.youtube.com/watch?v=IDbTUt3OG9s&t=127s

[jrevens]

Depending on how thin the material is, thin material shouldn't be counter sunk it should be dimpled with a thicker sub material counter sunk for the dimples.
https://www.youtube.com/watch?v=IDbTUt3OG9s&t=127s


Or, if the "sub material" is also thin enough it should be dimpled also. For 3/32" AN426 rivets, the very minimum thickness for countersinking is 0.032" if I recall correctly. For 1/8" rivets it's 0.040". I would usually prefer
dimpling over countersinking when you have a choice either way.

Carl - if you can borrow one, a rivet squeezing tool would be much easier for all of the rivets that are close enough to the edge of material and accessible. You can use it for the dimpling operation also. Having built a metal airplane I have 2 of them... if we were closer I lend one to you.

[Hawkertech]

And now that I know about the dimpling issue, I will have to dig through my aircraft tolls and see if I saved any from my brother. When he started cleaning out my dads house, he just through a lot of my dads tool away, He was a 51 year sheetmetal man at Lockheed. So we had every imaginable rivet set, rivet gun, rivet squeezer, etc.

[Cherrybark]

With all of this information, I can't stand looking at the mess my rivets are in. I'll get back on the phone and see if someone local has a hand took with dimpling dies.

[Hawkertech]

I can look but Iam the opposite side DFW from you.

Sent from my SM-N960U using Tapatalk

[jrevens]

You can install your Camlocs and nut plates with 3/32" pulled rivets also. Additionally, if you dimple all of the material that a Camloc or nut plate are installed on, you have to have countersunk or dimpled mounting ears on them.

[rv9ralph]

I have to comment on using vice grip pliers for squeezing rivets... don’t do it. Even if you grind the jaws to be flat and parallel, they do not move parallel. If you don’t have proper rivet tools to set a 3/32 solid rivet, get a pair of Knipix pliers. The jaws are smooth, parallel and move parallel. EAA hints for home builders just did a video on this versatile tool, you should have a pair in your toolbox.

Ralph

[efwd]

Nice Ralph, Thanks

[Cherrybark]

Thanks for mentioning that tool Ralph. I have two or three pieces of equipment with large nuts and hate using channel locks. These will work great. I almost expected the EAA guy to squeeze a small, solid rivet in his demo.

[Flybyjim]

I was able to get much of the cowl top finished today and I am much happier with this result. The last cam-locks on the side are not in place, the same with the top cam-locks, perhaps tomorrow. There will still need to be some sanding and super-fill work to get the cowl ready for painting. I have yet to decide if I am going to rivet the boot cowl in place or use nut plates.

[Shadowrider]

I just used some aluminum rivets to attach the boot cowl as they take about 2 seconds to drill out if I need to remove.

[rv9ralph]

I suggest nut plates. Reasons... easier to remove to work on behind panel items and, rivets into composite have a tendency to loosen (the composite tends to migrate away from the pressure of the rivet with time). Resulting in loose rivets and enlarged holes that need bigger rivets to hold.
Ralph

[jrevens]

I used SS machine screws & AN 365 nuts w/ washers on the rear edges of the boot cowl - those nuts are accessible & easily reached inside the airplane while using a screwdriver outside. I used machine screws & Tinnerman locking clip-nuts on the 2 forward attach points on each side.

23988

[Cherrybark]

Nut plates riveted to the convenient tabs on the frame and SS machine screws / nylon lock nuts along the arch of the firewall. I'm certain easy access to this area will be important down the road.

John, your suggestion to use pop rivets on the firewall clecos worked nicely.

[Flybyjim]

I just got back the water pump housing from Kitfox, anyone know the torque value of the housing screws?

[jrevens]

Those are M6 screws. I believe that the Rotax recommended torque for 6 mm screws is 90 in. lbs. I know that this is the torque value listed for the bottom SS drain screw.

[Flybyjim]

Thanks John.

[HighWing]

Piano Hinge - For those interested.

I helped finish a Lancair IV a while ago and learned the technique from that build. This is the method I remember. For maximum strength at the joint it is suggested that the aluminum hinge be the extruded type rather than the rolled type. The closed hinge loops in the extruded type cannot be pulled apart.

First, follow the manual to get the cowl sections centered and every other fitting procedure as recommended. Then with everything in position rivet top and bottom together through the joggle with soft aluminum flat head pull rivets (counter sunk). Begin at one end of the joint and proceed to the other to prevent “bubbles”. Rivet spacing suggested about 4 inches. This is[L1] (https://teamkitfox.com/Forums/#_msocom_1) done to maintain positioning for the next step that will enable a precise repositioning after the joggle on the lower cowl is removed and modified for the final assembly.

Lay a strip of aluminum that spans the riveted joint so that holes can be drilled outside of the joggle area for the placement of clekos that will secure the top and bottom sections together in the established position. Again, work from one end to the other. Once drilled and clekoed, remove and mark the aluminum strips, for position. Drill out the aluminum rivets and separate upper and lower cowls. Cut off the joggle on the lower cowl and thin the glass there so it is similar in thickness to the top cowl. For the trimming I have used the diamond disk cut off wheels by Dremel. For the thinning I have used flap wheels.

Once everything is prepped, re-fit top and bottom cowls together using the aluminum strips secured with clekos and fit the piano hinge. Verify positioning. Pre drilling the piano hinge will simplify final assembly. For strength and longitudinal smoothness, it might be wise to drill for solid rivets at the center of every hinge pivot extension. Fit, drill and cleko the hinge with the holes drilled (every other hinge hole) - through the aluminum strip also. (Using every other hole is to accommodate any possibility of a redo if alignment is not satisfactory. Remove all clekos to remove the aluminum strip and the hinges. Reposition the hinges and again, place the cowl top and bottom onto the airframe for a position evaluation. If everything is OK, remove, pull hinge pins and drill remaining holes. Mark each of the hinge halves for position identification. If there has been error introduced, the undrilled holes can be used to reposition as necessary.

Counter sink the rivet holes at the outside surface keeping in mind that the rivet heads should be at the glass surface to help in preparation for final finishing. Apply a thin bead of structural epoxy between glass and hinge. Re-cleko the hinge halves temporarily (4 or 5 holes) for final positioning. Rivet the hinge in position using soft-aluminum solid rivets dipped in micro.

A note on Micro. It is a very versatile filler. It can be mixed with epoxy to any consistency. From a runny glue to a stiff putty like consistency. Best here is a stiffness so that if drawn up to a peak in the mixing cup, the peak may bend over slightly, but not collapse.

After final riveting, prepare all unused holes by lightly drilling with a counter sink to give a more angled edge to the holes and wipe a bit of micro into the holes. After curing sand everything smooth.

Optional
If, after final curing, the junction between top and bottom is not to your satisfaction, You might consider this next step. With the cowl mounted to the front of the fuselage sand the cowl surfaces adjacent to the joint to prep the surface. With a plastic squeegee (without a lot of pressure) squeegee a bit of micro into the hinge-line between top and bottom cowls and onto the adjoining surfaces as needed. Then using something like the rounded end of a table knife. Run the tip down the joint (knife 90 degrees to the surface) with the flat against the straightest of the two edges and the tip against the hinge. After curing, sand the joint and if necessary, add more micro to the surface areas and sand. With fiberglass aircraft – Lancair, Glasair, Varieze - this last “step” can become several steps depending of the level of perfection desired. Remove the hinge pins and separate the two sections. This can improve the surface flatness and gives a very nice thin joint line for final finishing and paint.

A note on pictures: The second and third show a tab made from a bit of retained joggle to keep the sharper angled forward edges in alignment. It was sanded smooth, wrapped in two layers of clear packing tape, waxed and coated with separator, then a layer of glass laid up over it on the inside of the cowl. The fourth and fifth show a metal tab bent and Hysoled to the forward door post to keep the aft portion of the cowl snug against the post. Model IVs tended to flair out there a bit. The first and sixth are self explanatory.
[L1] (https://teamkitfox.com/Forums/#_msoanchor_1)

[Flybyjim]

I do not seem to have the 2-camlock receptacles #92000.000 or the winged stud # 92002.000 for the oil door. Has there been a change to use a different attachment such as the skytain camlocks used on the cowl top? If so I still do not have any with wing tops.