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Author Topic: Scratch build 3.9m F5J glider  (Read 239 times)
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egejce
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« on: June 09, 2021, 04:36:10 PM »

Hi,

Last few months F5J category couth my eye. Basically you can enter a competition with almost any powered RC sailplane. The competitions look interesting. So I decided to build a plane that will be at least close to the competitors so I can try to enter some contest.

The plan is to build a 3.9m sailplane from scratch. I plan to make 3-part carbon D-box wings. For the rest I will decide on the go. Wink
So far I cut the foam cores for the d-box and I’m now working on the carbon spars. I made a flat 1mm carbon sheet from witch I cut strips for the spars.

I post update as the build progresses.
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Scratch build 3.9m F5J glider
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dosco
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« Reply #1 on: June 09, 2021, 04:47:00 PM »

Neat! Watching with interest!
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USch
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« Reply #2 on: June 09, 2021, 05:09:32 PM »

leaning back and watching   Tongue Roll Eyes

Urs
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egejce
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« Reply #3 on: June 12, 2021, 03:32:40 PM »

The spars are ready, complate with tubes for the wing joiners.
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Re: Scratch build 3.9m F5J glider
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egejce
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« Reply #4 on: June 14, 2021, 06:12:55 PM »

Hi,

Just t share the progress. It's ready for the d-boxing.
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Re: Scratch build 3.9m F5J glider
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egejce
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« Reply #5 on: June 17, 2021, 03:09:11 AM »

The first D-box for the wing tips are ready.
I have made armored fiber D-box some 22-23 years ago for F1B models in this way, but this is the first time I'm making carbon fiber d-box, and they look ok.
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Re: Scratch build 3.9m F5J glider
Re: Scratch build 3.9m F5J glider
Re: Scratch build 3.9m F5J glider
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SP250
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« Reply #6 on: June 17, 2021, 03:50:28 AM »

I'm interested in what you did years ago for the F1B d-boxes - what do you mean by /use for "armoured fibre" ?
Might be able to use it for F3RES now that carbon is banned in the d-box construction.
John M
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egejce
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« Reply #7 on: June 17, 2021, 04:11:34 AM »

Hi,

Back than the only cloth that we had available in the club was armored fiber cloth (Kevlar). The process is the same, you wet the cloth with epoxy on some thin plastic sheet and than wrap it on the foam core and press everything with the negatives from the foam core.
If you have balsa ribs under the d-box. Working with armored cloth is easier. You can mold the d-box on 90 degrees L shape and than glue it with epoxy over the ribs. The armored D-box can be folded to the airfoil shape easily without braking it. This is the way we did it.
The stiffness is lower than the carbon but the kevlar is more crack resistant on impact.

I don't know if kevlar is allowed or not for F3RES but I'm sure you can make a good D-box from it.

Best regards,
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egejce
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« Reply #8 on: June 17, 2021, 04:23:08 AM »

I'm interested in what you did years ago for the F1B d-boxes - what do you mean by /use for "armoured fibre" ?
Might be able to use it for F3RES now that carbon is banned in the d-box construction.
John M

I just read the rules for F3REs and it say any composite d-box. Sorry, the kevlar is a composite material.
But it say that you are allowed to use composite for the spars. Maybe you can use carbon tubes as spars. This way you can increase the torsional stiffness.

Best regards,
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SP250
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« Reply #9 on: June 17, 2021, 06:32:43 AM »

Thanks for your reply - Kevlar is not allowed and many people are using carbon tubes as spars. 
I am looking for a substitute material to make the D box with and will always use a carbon I beam as a main spar.
John M

 
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Tapio Linkosalo
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« Reply #10 on: June 17, 2021, 07:14:19 AM »

But it say that you are allowed to use composite for the spars. Maybe you can use carbon tubes as spars. This way you can increase the torsional stiffness.

Carbon tubes, especially full-depth, make excellent spars that give plenty of torsional stiffness. You may want to laminate them with (part of the) fibres at 45 degrees to give the torsional stiffness, though.
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dosco
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« Reply #11 on: June 17, 2021, 08:41:14 AM »

I'm interested in what you did years ago for the F1B d-boxes - what do you mean by /use for "armoured fibre" ?
Might be able to use it for F3RES now that carbon is banned in the d-box construction.
John M

I'm late to the party.

Hopefully it's clear he was trying to say "Aramid fiber."

Best-
Dave
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egejce
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« Reply #12 on: June 17, 2021, 09:00:49 AM »

You are right Dave. Thank you.
Sorry for the confusion that I made.

Best regards,
Vasil
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egejce
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« Reply #13 on: June 18, 2021, 06:39:32 AM »

The d-boxes are ready. I am not sure but I hope that I will stay under 800 grams for the wings.
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Re: Scratch build 3.9m F5J glider
Re: Scratch build 3.9m F5J glider
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dosco
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« Reply #14 on: June 18, 2021, 09:01:35 AM »


Nice progress!

-Dave
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