You’re right Kevin. I should have prefaced my comments by saying that it depends on the loads that the wing will see. If the F1B and F1G loads are within the capability of the spar without the thread, it would certainly be wasted weight that could otherwise be used elsewhere. In the case of events like F1A and F1C, an unwrapped spar will suffer catastrophic failure.
- Chuck
From: Indoor_Construction_at_yahoogroups.com [mailto:Indoor_Construction_at_yahoogroups.com]
Sent: Wednesday, January 14, 2015 4:19 AM
To: Indoor_Construction_at_yahoogroups.com
Subject: Re: [Indoor_Construction] Carbon capped spars
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<mailto:chuck.etherington_at_jeppesen.com> [Indoor_Construction] <Indoor_Construction_at_yahoogroups.com<mailto: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> [mailto: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<mailto: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> [mailto:Indoor_Construction_at_yahoogroups.com]
Sent: 11 January 2015 23:11
To: Indoor_Construction_at_yahoogroups.com<mailto: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 Thu Jan 15 2015 - 09:20:18 CET
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:48 CET