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Old 01-14-2020, 01:07 PM
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CA models extra300l 24%

got bored one afternoon and picked up a bunch of old kits from a guy in town. one I started building kind of interested me. its a CA models extra 300l. its 1/4 scale, 74" wing and comes pre assembled and ready to cover. uses really strange construction to me. it has foam core balsa sheeted wings and stabs. even the hatch cover uses foam sheeted in balsa. seems pretty strong but nothing like anything I've seen in recent years. instructions are horrible.. the fuse was lacking any structural integrity for a gas engine. I reinforced the firewall with solid 1/4" ply and re glued all joints. I then stuffed a dle35ra in the front and will have 645 hitecs throughout. no hardware came with this kit so I'm using my best judgement on finishing it. ill post a pictures of the fuse. more as I progress. getting ready to fit the tail and cover it. id like to know if anyone has had experience with these models in the past? maybe some key areas to support? firewall and landing gear should be satisfactory now. good resources on foam core building?

I see the 31% model they produced was more popular in the community. I cant find much info on complete finished builds of the 24 or 27% kits.

maybe someone still has one flying out there!?
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Old 01-14-2020, 02:30 PM
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Foam wings and hatch are actually very common.
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Old 01-14-2020, 04:07 PM
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Foam wings and hatch are actually very common.
My biggest concern to date is the foam core wing. the wings are located to the fuse using dowels and obviously the wing tube. the mounting of the wing is accomplished by putting a bolt through the middle of the wing and into the tube. I for see this procedure becoming a problem for transport and field setup. not to mention keeping the wing tight against the fuse while drilling this location will get frustrating quickly.

like my other planes I prefer to mount through the fuse into the root. quick and easy, and always keeps the wing tight to the fuse. Being foam core there really is no support at the root to mount too with it being backed with foam. I decided to drill and insert a 1/2" diameter wood dowel 1 inch into the root face, sandwiched between the middle of the wing tube and top sheeting. filling the cavity with glue and inserting the dowel. once dried, I drilled and inserted a 4-40 brass anchor flush into the center of the dowel. gives me a pretty solid location to pull the wings in as the only fastener. keeping as close to the wing tube should give me all the strength I can get out it I would think also.

just a different animal I suppose. but I still hope it doesn't come apart mid flight due to a structural issue like that.
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Old 01-14-2020, 04:22 PM
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Bolts into the wing tube were very common years ago and worked well ..... though as you state this system didn't pull the wing tight against the fuselage.

Pretty much standard today, most planes (wood or foam wing) use one or two bolts into each wing panel. These bolt through the fuselage sides into bling nuts in a wing root plywood cap. This is pretty common and I've never seen any issues with this system. Usually something like a 6-32 or 4mm bolt is common. 4-40 seems a bit small. I've updated some older foam wing planes I have with this same system simply by cutting a small hole in the bottom of the wing sheeting near the root so I could insert a bling nut(s). Sometimes I have to double the ply in a local area to support the nut but plenty of strength to retain the wing. I just cover the small hole with a bit of covering.
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Old 01-15-2020, 07:19 AM
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Originally Posted by Truckracer View Post
Bolts into the wing tube were very common years ago and worked well ..... though as you state this system didn't pull the wing tight against the fuselage.

Pretty much standard today, most planes (wood or foam wing) use one or two bolts into each wing panel. These bolt through the fuselage sides into bling nuts in a wing root plywood cap. This is pretty common and I've never seen any issues with this system. Usually something like a 6-32 or 4mm bolt is common. 4-40 seems a bit small. I've updated some older foam wing planes I have with this same system simply by cutting a small hole in the bottom of the wing sheeting near the root so I could insert a bling nut(s). Sometimes I have to double the ply in a local area to support the nut but plenty of strength to retain the wing. I just cover the small hole with a bit of covering.
I figured 4-40 hardware would be ok for a wing bolt application. I cant imagine too much force actually acting on pulling the wing away from the plane. my only real threat is if the wing somehow flexes on the tube and shears the bolt. but everything seems to fit pretty snug and if it behaves like any other built up wing ill have confidence there.

starting to wonder what I can get away with for push rods? elevator rods look like they are going to be quite unusually long. twin servos are in front of the tail assembly.. I was hoping to use some locking metal 4-40 rod ends to the surfaces since that's my main rod end i keep in stock. surfaces are built for posts so I scrounged around eBay and picked up some aluminum ones (pictured below). if I could use 4-40 threaded rods it would probably be advisable to at least epoxy the spans of them into carbon tube or similar for support? I'm not intending to do much of any 3d with this plane more just general sport club flying
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Old 01-15-2020, 02:24 PM
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The main problem I see with 4-40 hardware retaining the wings are the blind nuts if thats what you use. 4-40 blind nuts are tiny and have very little bearing surface to bed against the wood. Repeated tightening of the bolts every time you install the wings can pull them right through the wood they are installed in. Screw in brass pocket nuts are not secure enough in my opinion, especially if installed in end grain wood.
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Old 01-15-2020, 02:52 PM
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The main problem I see with 4-40 hardware retaining the wings are the blind nuts if thats what you use. 4-40 blind nuts are tiny and have very little bearing surface to bed against the wood. Repeated tightening of the bolts every time you install the wings can pull them right through the wood they are installed in. Screw in brass pocket nuts are not secure enough in my opinion, especially if installed in end grain wood.
yea I do see your point there. I did try to combat the issue, used quite a bit of epoxy to set all this stuff up. I really would be shocked if I could pull these brass nuts out before I rip either the bolt head off strip the brass or pull it all through the fuse. will need to look into this more though, maybe do some testing for actual strength.
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Old 01-15-2020, 05:36 PM
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I built one back in probably the late 90's or possibly early 2000's? Seems like this was about the end of the AW builders kits era. I thought AW actually tried selling these for a short while right before CA disappeared from the scene. I did the single 1/4" nylon bolt into the wing root right behind the wing tube. Very likely tapped into a 1/2" dowel buried in the foam. There were some quality issues including bowed wing panels and very hard to get the issue rectified. I think I received 3 sets of wings, including one trip to Toledo OH trade show to get a decent set. Seems like a long time ago and my recollection of how it flew is fuzzy.
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Old 01-15-2020, 07:07 PM
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I built one back in probably the late 90's or possibly early 2000's? Seems like this was about the end of the AW builders kits era. I thought AW actually tried selling these for a short while right before CA disappeared from the scene. I did the single 1/4" nylon bolt into the wing root right behind the wing tube. Very likely tapped into a 1/2" dowel buried in the foam. There were some quality issues including bowed wing panels and very hard to get the issue rectified. I think I received 3 sets of wings, including one trip to Toledo OH trade show to get a decent set. Seems like a long time ago and my recollection of how it flew is fuzzy.
I like the trim scheme. I was never that patient to pull off a covering job that neat. I also read there were problems with twisted wings. Ones in this kit were very nice. The fuse on the other hand was a mess. Must have been mostly assembled with ca glue. I could dissasemble every glued part off of it without trying.
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Old 01-15-2020, 08:34 PM
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Thanks. I just remembered I still have a spare Gator wing tube they gave me at Toledo to go with my wings.
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Old 01-24-2020, 11:19 AM
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a couple pictures, almost covered
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Old 01-25-2020, 06:18 PM
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Had a 31% I built some years back. Was a great flying plane.
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