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wood for fuselage

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Old 08-08-2013, 08:37 PM
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ameyam
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Default wood for fuselage

Hi,

I am building a 3d airplane similar to a ucd & another similar to funtana60 from free plans. I am custimising them to use materials available locally. The fuselage & bulkheads call for 3mm wood but doesnot specify which type. I am building in cad first so I can work out the bugs. Since i have access to laser cutting, I am going for interlocking construction. The other kit i have so far built (GP US40) had this part in light ply. The LHS has poplar ply in that thickness. They also have model grade ply but its much thicker. What should I use?

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Old 08-09-2013, 03:27 AM
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Use the thinner stuff because 3mm is way overkill as it is and you want to keep it light if you want a great 3D capable airframe. I only use 3/32" thick plywood on my motor boxes with the exception of a 1/4" thick firewall, and fuselage hard points, otherwise I mainly use 3/8" X 3/8" balsa sticks and tri stock as illustrated in these pictures.

Bob
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Old 08-09-2013, 06:40 PM
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ameyam
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well, there is no thin ply available. So I M going for 3mm balsa. Finishing the cad build with interlocking formers. Lets see..

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Old 08-09-2013, 06:56 PM
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It's important to use the correct wood for the job at hand. 3mm balsa is not a replacement for 1mm ply in most cases. If you look at Bob's fuse structure you will see that the strength is engineered into the structure and that the motor box, firewall and wing attachments are all ply. Thicker balsa would not be a substitute in these areas. I know that not all materials are redily available everywhere but I know you have been able to order stuff from the states. Take the time to get the proper materials needed.
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Old 08-09-2013, 07:13 PM
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ameyam
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Actually, not 100% balsa. the firewall and come critical points will be additional layer of birch inside the balsa former but the rest of the fuse and ribs will be ply. I just dont have enough material to build in ply and its madly expensive to import right now


Instead of balsa sticks, I am getting the wood laser cut

Ameyam
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Old 08-09-2013, 07:30 PM
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Still, If I do decide to use ply, what thickness should it be- 1/8" birch ply or 1/8" poplar? I am asking because I have some 1/16" birch ply lying around, I could use that

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Old 08-09-2013, 08:36 PM
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Looking at the plan I don't see much where 1/16 ply could be used. if I were to build that airplane, I would use 1/8" balsa for the fuse sides and 1/8" poplar ply for all the formers and use the 1/16 birch as a doubler front and back of the former at the wing LE but only half way up. I would use 3/16 birch for the firewall.
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Old 08-10-2013, 12:47 AM
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Speedracer, if you look at all the debris I have left through the modelling procedure, I am planning the fuse sides laser cut as well. All the stuff is 3mm or 1/8" but I need to decide what will be balsa and what ply. If I make the fuse sides of balsa and the bulkhead formers of ply, will that do?

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Old 08-10-2013, 07:40 AM
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Quote:
Originally Posted by ameyam View Post
Still, If I do decide to use ply, what thickness should it be- 1/8" birch ply or 1/8" poplar? I am asking because I have some 1/16" birch ply lying around, I could use that

Ameyam
You could laser cut the 1/16" birch plywood fuselage sides and attach a medium density 3/8" X 3/8" balsa stick frame work to those sides giving you a very strong and lightweight fuselage, but you will need to change your way of thinking and the current model design you posted.

Bob

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Old 08-10-2013, 08:43 PM
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Hi,
I finiashed the cad build yeaterday. I also investiated wood & found a sheet of 1/8" poplar ply I had. Its 12"x36" & weighs 600 odd grams. I think all my fuse could come out from it & since its mostly holes, it should weigh no more with the firewall. I will also use it for the frame in the ailerons, rudder & elevators & sheet over with balsa. For the wings I still need 1/8" balsa. Just the spars are unsourced

I noted the idea to use 1/16" birch with stringers. Only prob, still looking for stringers. Need them for the turtle deck as well

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Old 08-29-2013, 06:38 AM
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Bob,
On a side note, sorry to get off topic but,,
I am glad to see that people are building large plane and from scratch..
I have seen several of your projects here on RCU, very impressive.
I too build but mostly from plans.
Question Bob,
What type of sticks are you using for your fuse as you have shown above??
I have been using poplar I ripped up into 1/4 sq etc, have you used pine b4?
Thanks,
Chip
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Old 08-29-2013, 10:41 AM
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Hello Chip,

Thanks for the kind words, I use 3/8" X 3/8" X 48" long medium density balsa I purchase from Specialized Balsa LLC. I then glue it all together with thin and medium CA.

Bob
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