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Author Topic: Laminated Spars  (Read 2477 times)

Offline Motorman

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Laminated Spars
« on: October 02, 2016, 10:54:38 AM »
Plans say to laminate 2 balsa sticks 3/16th x 3/32 with .007" carbon fiber laminate in between to make the spar. Last time I did this I used epoxy and it was a difficult mess.

This time I want to lay down some parchment paper on my glass table, hold the lamination between two long aluminum angles then zap the center line with thin CA. I was wondering if thin CA glue would hold the carbon and balsa parts together.

Thanks,
MM
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Offline Brett Buck

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Re: Laminated Spars
« Reply #1 on: October 02, 2016, 04:50:06 PM »
Quote from: Motorman on October 02, 2016, 10:54:38 AM
Plans say to laminate 2 balsa sticks 3/16th x 3/32 with .007" carbon fiber laminate in between to make the spar. Last time I did this I used epoxy and it was a difficult mess.

This time I want to lay down some parchment paper on my glass table, hold the lamination between two long aluminum angles then zap the center line with thin CA. I was wondering if thin CA glue would hold the carbon and balsa parts together.

    I think I know where that spar arrangement originated! Harry O'Shortal's "restaurant" that was closed by the Napa County board of health a while back.

    CA will be fine and probably superior to most consumer-grade epoxy. I saw some test data from RC guys who tested various adhesives with graphite laminate adn various forms of CyA came out on top. In any case, it only has to be stronger that the balsa, and at least as tough.

       Brett
     
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Offline Motorman

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Re: Laminated Spars
« Reply #2 on: October 02, 2016, 08:56:44 PM »
Thanks Brett. I made a little 3" test piece and it's stiff as a nail. I roughed up the CF with 220 paper. I had to be careful to glue it right down the middle and not get any extra glue on the aluminum bars. I wanted to wax the bars but I was afraid the wax might transfer to the balsa. It looks like the glue went all the way through but I put a little glue on the other side after I broke down the jig. Much easier straighter and stronger than my last spar, very happy.

MM
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Offline Gerald Arana

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Re: Laminated Spars
« Reply #3 on: October 03, 2016, 10:02:02 AM »
Quote from: Motorman on October 02, 2016, 10:54:38 AM
Plans say to laminate 2 balsa sticks 3/16th x 3/32 with .007" carbon fiber laminate in between to make the spar. Last time I did this I used epoxy and it was a difficult mess.

This time I want to lay down some parchment paper on my glass table, hold the lamination between two long aluminum angles then zap the center line with thin CA. I was wondering if thin CA glue would hold the carbon and balsa parts together.

Thanks,



MM; SBSS (South Bay Soaring Society) of which I used to be a member, made tests with CA and the best was thick slow curing CA. It gives you some time to work.

So Brett, you're absolutely correct as usual!  y1

Carry on, Jerry
MM
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Offline Tim Wescott

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Re: Laminated Spars
« Reply #4 on: October 03, 2016, 10:17:03 AM »
Are you using plain carbon tow, or are you using pre-laminated stuff?  If you're using pre-laminated stuff is it woven, or unidirectional?  If it's unidirectional, where in heck can I get some?
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Offline Motorman

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Re: Laminated Spars
« Reply #5 on: October 03, 2016, 12:06:03 PM »
I use the Dave Brown laminate that comes rolled in a coil. You have to cut it to width but it cuts easy with a #11 blade. It seem to have most of the strands running lengthwise buy the way it cuts. I make it about 5-10 thou less than the width of the balsa so the glue tube has a slight trough to follow.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXB965&P=ML

I also use it on the sides of profile fuselage, really adds stiffness.


MM
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Offline Tim Wescott

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Re: Laminated Spars
« Reply #6 on: October 03, 2016, 12:15:21 PM »
Quote from: Motorman on October 03, 2016, 12:06:03 PM
I use the Dave Brown laminate that comes rolled in a coil. You have to cut it to width but it cuts easy with a #11 blade. I also use it on the sides of profile fuselage, really adds stiffness.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXB965&P=ML


MM

Gawd I'm stupid.  Been looking for that forever, never saw it.  Now I just need to remember it's there.
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AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Geoff Goodworth

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Re: Laminated Spars
« Reply #7 on: October 03, 2016, 05:48:01 PM »
I've found that Cya does not stick to ordinary old clear packaging tape.

I have a couple of popsicle sticks wrapped with packaging tape that I use to support and align small parts before I drop thin Zap on the joint.

The Cya sort of sticks to the support but it takes very little persuading to have it let go.

The spars would not stick to aluminium angles if stick tape on the faces.
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