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Old Sep 23, 2006, 09:46 AM
I'm a pilot... 100 yrs to late
Thermalin's Avatar
USA, FL, Palm Harbor
Joined Jan 2005
3,510 Posts
Question
Bolt and dowel wing attachment

I'm interested in replacing the rubber bands / dowels to hold the wing on my Tower 40 Trainer.

Question:
Two bolts - one fore and one aft or one or two dowels protruding up front with one or two bolts in the rear.

If dowels I understand I need to add add'l thickness to the front bulkhead and would run the dowel(s) through leading edge back into main joiner area.

If two bolts in rear, I was thinking of attaching to the fuse sides (after beefing up a bit) rather than putting on the rear bulkhead to get more seperation... adds just over an inch. Also replacing the balsa center sheeting in the last section of the rear with lite ply for support. Or if bolts go through trailing edge, etc.

I have always used rubber bands so am not familiar with how to proceed.

Pic shows what I have for a nylon bolt attachment assembly x 2.

Appreciate your input,
Mike
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Old Sep 23, 2006, 11:19 AM
Registered User
United States, KS, Andover
Joined Oct 2005
539 Posts
Two dowels and two bolts will work well. Make sure your wing structure at the LE can handle the 1/4" dowels. Beef up the wing structure there. I'd probably glass it, but I'm not familiar with the construction of your plane. On the back end of the plane, I'd just take some 1/16" ply and glue that to the top of the wing where the bolts will go. Make the ply patch big enough to spread the load. Most of the wing load is really being handled by the dowels.

On the fuselage, I'd use some 1/4" ply, preferably one piece going to each side of the fuse. If you can also tie this in to a bulkhead, so much the better. Use some triangle stock to reinforce these joints. Use quality epoxy, not the 5-minute stuff. I used to pin these joints with 1/8th inch dowels through the fuselage sides, too. Remember, you want the bolts to break before the glue joints.

I'd put the dowels in the LE of the wing first. Then drill the corresponding holes in the bulkhead on the fuselage. I'd usually make these bigger than needed, then make some 1/8" ply (not lite ply) squares with 1/4" holes. Put the wing on the fuse, line it up, then slide the ply squares on the wing dowels on the other side of the front bulkhead. Hit it with just enough CA to hold the squares on, carefully remove the wing, and finishe CAing the squares. Once this is done and you are sure the CA is set, put the wing back on, line everything up, and drill the rear bolt holes for the wing and the fuse at the same time. Remember that this hole is smaller, as it has to be tapped at the fuse. Now tap the fuse holes, hit with CA, let dry, Repeat a few times. Drill out the wing holes for the bolts and you are done.

Mark
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Old Sep 23, 2006, 03:12 PM
I'm a pilot... 100 yrs to late
Thermalin's Avatar
USA, FL, Palm Harbor
Joined Jan 2005
3,510 Posts
Quote:
Originally Posted by markschaffin
Two dowels and two bolts will work well. Make sure your wing structure at the LE can handle the 1/4" dowels. Beef up the wing structure there. I'd probably glass it, but I'm not familiar with the construction of your plane. On the back end of the plane, I'd just take some 1/16" ply and glue that to the top of the wing where the bolts will go. Make the ply patch big enough to spread the load. Most of the wing load is really being handled by the dowels.

On the fuselage, I'd use some 1/4" ply, preferably one piece going to each side of the fuse. If you can also tie this in to a bulkhead, so much the better. Use some triangle stock to reinforce these joints. Use quality epoxy, not the 5-minute stuff. I used to pin these joints with 1/8th inch dowels through the fuselage sides, too. Remember, you want the bolts to break before the glue joints.

I'd put the dowels in the LE of the wing first. Then drill the corresponding holes in the bulkhead on the fuselage. I'd usually make these bigger than needed, then make some 1/8" ply (not lite ply) squares with 1/4" holes. Put the wing on the fuse, line it up, then slide the ply squares on the wing dowels on the other side of the front bulkhead. Hit it with just enough CA to hold the squares on, carefully remove the wing, and finishe CAing the squares. Once this is done and you are sure the CA is set, put the wing back on, line everything up, and drill the rear bolt holes for the wing and the fuse at the same time. Remember that this hole is smaller, as it has to be tapped at the fuse. Now tap the fuse holes, hit with CA, let dry, Repeat a few times. Drill out the wing holes for the bolts and you are done.

Mark

Ok.. that was pretty descriptvie...thing is .. the bolts I have come with mating pieces as in the pic... so that will simplify it somewhat... I just need to attache them to the fuse via the small bolts provided.
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Old Sep 23, 2006, 05:04 PM
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United States, KS, Andover
Joined Oct 2005
539 Posts
The most important thing when building any airplane is to build it straight and square. The fixture you have looks pretty nice, but I know that I would have a very very very hard time knowing that I would be able to line everything up. If you attach it to the fuse, how do you know where to drill the wing.

I like my method because it allows you to get everything lined up before you commit to drilling holes. Same with the holes in the forward bulkhead. I've never been able to get those to line up properly, but by overdrilling them, then glueing on the ply squares, you make it easier to get the desired precision.

I may have misunderstood your question. If you do use your fixture, make sure you reinforce the area that you are bolting to. Shame to see bolts coming out of the side of your plane, though.

Good luck,
Mark
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