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May 15, 2019, 07:13 AM
Entropy is happening!
Jim.Thompson's Avatar
Holding the knife vertically would be the only challenge doing it that way. Less of a problem with thin wings.
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May 15, 2019, 05:50 PM
supreme being of leisure
ZAGNUT's Avatar
i is confused...are you guys talking about just cutting shallow channels for carbon spars or cutting all the way through the core to add in a wrapped spar?
May 15, 2019, 06:01 PM
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Thread OP
Cutting core full depth to add shearweb connecting top bottom skins. Currently I'm using a tapering layer of 80gsm uni carbon. Starting from up to 50mm wide at root to 30mm at first panel break. I want to spread 'spar' loads as broadly into XPS core and skin as possible.
May 15, 2019, 06:33 PM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by RaceMag
Cutting core full depth to add shearweb connecting top bottom skins. Currently I'm using a tapering layer of 80gsm uni carbon. Starting from up to 50mm wide at root to 30mm at first panel break. I want to spread 'spar' loads as broadly into XPS core and skin as possible.
I am also a bit confused. What are the full details RM?
Are you cutting out a wedge shaped slice of the core full depth 50 mm wide to 30 mm wide? Then thinning it a bit and constructing a spar out of that.
Then gluing back in with a 1 mm soft balsa sanding caps like Mark Drela has designed?

I suspect we have multiple lines of thought running; all will have there applications, but all vary a bit.
May 15, 2019, 09:34 PM
Registered User
Thread OP
Ok.
I'm using a solid XPS hot wire cut core skinned with FG and some CF. Currently I'm covering cores with 50gsm or 100gsm glass on the bias. The beam strength is provided in part by the single layer of 80gsm unidirectional running spanwise, under the skins. I want to increase the beam strength of the wing by using a thin shearweb between the skins and/or potentially inserting a spar if this is insufficient. A spar would be a 3mm wide spar consisting of 3mm diameter CF rod top/bottom. The core would need to have material removed to allow insertion of the shearweb/spar. I hope this helps clear it up?
May 15, 2019, 10:10 PM
Registered User
Maybe either use weblets as you mentioned, or attach your material with 924 tape or light spray adhesive. After attaching, if bagging, install a glass hinge on one side using light spray adhesive, like at the hinge line. This should let you open the area, wet the shear web out then after closing, hold the two together when bagging. And with light spray adhesive, the epoxy would still penetrate through it. This would be similar to the hinge line, just no foam insert in between and glass or carbon instead of kevlar.
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May 16, 2019, 12:39 AM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by RaceMag
............................. A spar would be a 3mm wide spar consisting of 3mm diameter CF rod top/bottom. ................
They become the spar caps component of a full "spar". The combination of spar caps and shear webs are what constitute a "spar".

Quote:
I hope this helps clear it up?.................
Pretty well. Thanks.
May 16, 2019, 05:22 AM
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Thread OP
Quote:
Originally Posted by Bchirrick
Maybe either use weblets as you mentioned, or attach your material with 924 tape or light spray adhesive. After attaching, if bagging, install a glass hinge on one side using light spray adhesive, like at the hinge line. This should let you open the area, wet the shear web out then after closing, hold the two together when bagging. And with light spray adhesive, the epoxy would still penetrate through it. This would be similar to the hinge line, just no foam insert in between and glass or carbon instead of kevlar.
OK, the photo was excellent and I've got pretty much all of this apart from the last sentence - would you mind expanding on it a bit?
May 16, 2019, 11:00 AM
Registered User
Quote:
Originally Posted by RaceMag
OK, the photo was excellent and I've got pretty much all of this apart from the last sentence - would you mind expanding on it a bit?
If bagging and going to face both sides of the hinge line, you need a strip of foam between both faces. This foam strip would be mostly removed when hinging. If you're only facing the front of the aileron, you wouldn't need the foam strip. On my hinges, i deflect the hinge, wet out with a roller, then close it back up in the layup.
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May 19, 2019, 06:31 PM
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Thread OP
Thanks, that was a very clear explanation. I've noticed that many f5j planes don't face their control surfaces and I was planning to follow their practice. Your method looks good however.
May 19, 2019, 10:34 PM
Entropy is happening!
Jim.Thompson's Avatar
Quote:
Originally Posted by Bchirrick
If bagging and going to face both sides of the hinge line, you need a strip of foam between both faces. This foam strip would be mostly removed when hinging. ...........................
Something like Mark Drelas method here?

https://www.charlesriverrc.org/artic...DFs/hinges.pdf
May 21, 2019, 09:04 AM
Barney Fife, Vigilante
tom43004's Avatar
There was a lengthy discussion of different versions here:

https://www.rcgroups.com/forums/show...t=zone%20clone

I adapted the MD method a little.... simplified it for my use. I do this to this day and think it's one of the easiest improvements you can make to a molded or bagged airframe.

Post #14 on the first page was the beginning of discussions....
May 28, 2019, 04:25 AM
Registered User
Thread OP
I have some trial panels with a slightly different method, I'll report on this soon whether it works or not.


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