I disagree. When doing it properly, the carbon will not pop off and
wrapping with kevlar thread only adds weight. In F1B, the spars I make
never use wrapping and they have never come loose. Only around the wing
joiner wrapping is necessary since the wing joiner introduces a peeling
force inside the spar. For the rest of the spar, wrapping does not add
anything but weight.
Co-curing 19 gsm UD prepreg with balsa might be an option for indoor spars
as well. Although I think boron is much stronger on the compression side
due to the higher buckling strength compared to the 20 micro meter thick UD
prepreg.
Best wishes,
Kevin
2015-01-12 18:38 GMT+01:00 Chuck Etherington chuck.etherington_at_jeppesen.com
[Indoor_Construction] <Indoor_Construction_at_yahoogroups.com>:
>
>
> The carbon spar cap that is in compression will pop off the balsa
> regardless of adhesive or technique. Wrapping the spar with Kevlar thread,
> however, will increase its strength exponentially.
>
>
>
> *- Chuck *
>
>
>
> *From:* Indoor_Construction_at_yahoogroups.com [mailto:
> Indoor_Construction_at_yahoogroups.com]
> *Sent:* Monday, January 12, 2015 10:09 AM
> *To:* Indoor_Construction_at_yahoogroups.com
> *Subject:* RE: [Indoor_Construction] Carbon capped spars
>
>
>
>
>
> Vladimir,
>
> I dabbled a little in making laminated spars for Coupe d’Hiver so it may
> not be in your league. I think it was probably in the early 1990s that
> some carbon sheet, 0.003/0.004 thick became available on the English
> market. The carbon appeared to be very thin strips joined side by side and
> mounted on a brown paper backing. I cut a strip of carbon about 0.5” wide,
> leaving the paper backing in place, cleaned the other side and then glued
> it, with contact adhesive (‘Evostick’), to the balsa sheet, which was about
> 0.1” thick. This was stripped with a normal, home-made, balsa stripper and
> the backing paper was then removed.
>
>
>
> The big trouble was that if the spars flexed the carbon would ‘pop off’
> the balsa and the popped off pimples would need reattaching with cyano.
> The problem could have been wrong glue or poor technique but I realised
> that it was good for the wing spars to flex upwards under load and the
> spruce spars that I was already using were better than carbon capped balsa
> for a Coupe. I hope this is of some help if only in a negative way.
>
>
>
> John Barker - England
>
>
>
>
>
> *From:* Indoor_Construction_at_yahoogroups.com [
> mailto:Indoor_Construction_at_yahoogroups.com
> <Indoor_Construction_at_yahoogroups.com>]
> *Sent:* 11 January 2015 23:11
> *To:* Indoor_Construction_at_yahoogroups.com
> *Subject:* [Indoor_Construction] Carbon capped spars
>
>
>
>
>
> Dear All
> Has anyoneaminated unidirectional carbon on sheet and then sliced wing
> spars producing capped spars top and bottom with carbon? If so please share
> details.
> Vladimir Linardic
>
>
>
Received on Wed Jan 14 2015 - 03:26:20 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:48 CET