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Nov 16, 2020, 07:55 AM
Boo
Boo
Registered User
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Discussion

Solid CF Wing Joiners - howto ?


Hi,

I did a quick search but maybe someone here can do better and point me out a thread (with videos and pix, ideally) that shows how to make the humungous CF wing joiners that eg competition slope gliders use ? Or else post in this one...

Thanks,

Boo
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Nov 22, 2020, 04:57 AM
Entropy is happening!
Jim.Thompson's Avatar
Boo,

I just spent some time scrolling through the pages of my Entropy build thread, hoping to find some pictures.
However, I could not find any. From memory (I will confirm later), the joiner is around 40 x 12/14 mm.
I cheated and did not build a plug and mould, which is the proper way to start.
I used a small sheet of plate glass with two strips of 16 x 16 mm RHS aluminium glued on this with CA at the 40 mm spacing.
Then I welded up two steel fixed "clamps" that slide over the ali strips to limit spreading when the layup is compressed.
Cleaned and waxed up in the usual way.
Cut strips of Uni-carbon (200 gsm will make approx 200 microns in thickness) and lay in the mould one by one wetting out each layer thoroughly.
Mop out with paper towel as you go to de-bulk.
When slightly over full (some guess work required here!), clamp with another strip of 3 mm aluminium flat bar (waxed before use).
Clamp up and fit anti-spread "clamps", then apply full pressure with weights, clamps or whatever you have.

Break off one of the ail strips to de-mould. Wet sand on a firm flat wet and dry sanding board to accurate dimensions. Sand off the arris to assist fitting of the box.
Post cure.

Make your receiver boxes around this.

Let me know if you need more details.

Jim.
Nov 24, 2020, 05:09 PM
Boo
Boo
Registered User
Thread OP
Thanks Jim for your reply,

would I be right in saying that your wing joiner at 12mm thick would comprise upwards of 60 laminations of 40mm wide C/F tape/cloth ? Is it possible to infuse the resin in preference to laying up layer by lauer ? If so what vacuum level is used ?

Thanks again,

Boo
Nov 24, 2020, 06:04 PM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by Boo
......................... Is it possible to infuse the resin in preference to laying up layer by lauer ?................
Very possible.

Quote:
....................... If so what vacuum level is used ?
.........................................
As near to absolute vacuum as you can achieve.
There are infusion threads on these forums somewhere, I'm pretty sure. Also, there are youtube instructional videos.
Do some reading I suggest. It is a whole new chapter in composite work, and requires some special setting up and experience etc.

I would do the hand layup any day, but that is only because I don't stock infusion resin and the associated air bleed materials etc. etc. And I am set up and very familiar with hand layups.
What is your composite experience?

Jim.
Dec 02, 2020, 05:02 PM
Barney Fife, Vigilante
tom43004's Avatar
https://www.rcgroups.com/forums/show...le-build/page8

Not tons of detail here but it's how I created the molds to make my F5J joiners. Mine have foam cores but could have easily had vertical balsa or even solid.

Process is pretty simple... my tooling is bolt-together, meaning that even if not a ton of release is used, the molds come apart to demold the part... reducing the pain associated with removing joiners with no draft angle etc...

I searched a lot of threads and came up with a "hybrid" method that worked for me.
Dec 09, 2020, 12:56 AM
Diesel Danny
danny mz's Avatar
Has anybody tried moulding 'I beam' spars and wing joiners?

I ask because an 'I beam' is structually a very efficient use of materials and sound engineering practice.

Look at a building, not many circular or solid beam roof supports but plenty of 'I beams' and looking at full size aircraft the same appears to be prevelant in the wing structures.

Is it just the moulding hassles that prevent this structure from being used in our models?
Dec 09, 2020, 07:09 AM
San Antonio TX.
sensei's Avatar
Quote:
Originally Posted by danny mz
Has anybody tried moulding 'I beam' spars and wing joiners?

I ask because an 'I beam' is structually a very efficient use of materials and sound engineering practice.

Look at a building, not many circular or solid beam roof supports but plenty of 'I beams' and looking at full size aircraft the same appears to be prevelant in the wing structures.

Is it just the moulding hassles that prevent this structure from being used in our models?
I manufactured a set of carbon fiber and glass I-beam spars for my Staudacher back in 1999 and it is a very simple process to do. I did my I-beam spars from high temperature pre pregs, but have also done it in room temp wet layups, the only real difference is the tooling to manufacture with. The Staudacher was high temp I-beam spars and the biplane was an all carbon fiber and Nomex honeycomb biplane with wet layup I-beam spars I built in in 1996.

Bob
Last edited by sensei; Dec 09, 2020 at 08:07 AM.
Dec 09, 2020, 09:53 AM
Barney Fife, Vigilante
tom43004's Avatar
I beam manufacturing isn't hard with silicone molding... actually it's pretty easy. Google around and you'll find examples.
Dec 09, 2020, 10:34 AM
San Antonio TX.
sensei's Avatar
Quote:
Originally Posted by tom43004
I beam manufacturing isn't hard with silicone molding... actually it's pretty easy. Google around and you'll find examples.
Heck, you don’t even need silicone molds to manufacture them, just a plain old vacuum bag, some Mylar tape, a couple of home made caul plates and a couple of simple home made plugs made from wood for the wet layup process. The wood plugs can actually be made from lumber from Lowe’s or Home Depot. For the pre preg I-beams molds, I folded up . 040” 6061-T6 on a break press, laid up parts, vacuum bagged and oven processed, that’s it.


Bob
Last edited by sensei; Dec 09, 2020 at 11:02 AM.
Dec 09, 2020, 11:42 AM
Scott
Pylonracr's Avatar
What is that biplane Bob? That thing is cool as heck.

Scott
Dec 09, 2020, 12:12 PM
San Antonio TX.
sensei's Avatar
Quote:
Originally Posted by Pylonracr
What is that biplane Bob? That thing is cool as heck.

Scott
Hey Scott,

It is a slightly modified version of the Cobra X wing racer. Believe it or not I still have the fuselage molds, a fuselage, and a set of wings and wing tips. The wing molds I bumped rolled out of sheet steel on the break press but I donít know what has happens to them now, canít find them...

Bob
Dec 10, 2020, 06:25 PM
Entropy is happening!
Jim.Thompson's Avatar
Where have you gone Boo?
Dec 18, 2020, 04:48 PM
Boo
Boo
Registered User
Thread OP
Quote:
Originally Posted by Jim.Thompson
Where have you gone Boo?
Hi Jim, still here. I read the threads you referred to and am having a think. My plans are to make some free flight F1A gliders and wondered how to go about joiningbthecwings without needing bent wire dowels as joiners.

Very interesting thread, thanks to all who posted,

Boo2
Dec 18, 2020, 05:16 PM
Entropy is happening!
Jim.Thompson's Avatar
Deleted Post.
Last edited by Jim.Thompson; Dec 18, 2020 at 05:21 PM.
Dec 18, 2020, 05:21 PM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by Boo
............................ My plans are to make some free flight F1A gliders and wondered how to go about joiningbthecwings without needing bent wire dowels as joiners. ......................................
Ok, some details might assist the reader to contribute to the "wondering".
How about sharing some of the basic parameters like size, weight, span. Two part wing or one or three part?
The more info the better the result, usually!....................
Besides, your post above is distinctly at variance with your opening post below!

Quote:
Originally Posted by Boo
......................... humungous CF wing joiners that eg competition slope gliders use ? ......................
Free Flight gliders do not use "humungous CF wing joiners"!....................


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