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Wing spar bonding Hysol amount

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opcod

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Aug 28, 2010
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Hi

I search several place to find out about the Hysol 9430 bonding process. Pretty clear, we add about 1:1 flox and put the mix on the spar, rib and then close out.
But : For a wing of 20feet long , the Hysol can is only 2lbs at Aircraftspruce.

So How many can do we need to bond a complete wing ? Or let say we have a spar of about 1inch large by x feet long : with 1 can of Hysol, how many feet can i cover ? 40ft long by 1inch ...?

Many thanks
 

autoreply

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Molded wing panels? If so, assemble with some clay and measure the final thickness of the clay on a few places. Then use spar cap width*length*clay thickness and double that number for a bit of margin and you know the volume of Hysol you need.
 

BoKu

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Hi

I search several place to find out about the Hysol 9430 bonding process. Pretty clear, we add about 1:1 flox and put the mix on the spar, rib and then close out.
But : For a wing of 20feet long , the Hysol can is only 2lbs at Aircraftspruce.

So How many can do we need to bond a complete wing ? Or let say we have a spar of about 1inch large by x feet long : with 1 can of Hysol, how many feet can i cover ? 40ft long by 1inch ...?

Many thanks
Opcod,

Having used Hysol EA9430 in the assembly of various HP-18 bonded metal sailplane parts (mostly flap sections, but also in some wing repairs), I would be very reluctant to add flox to Hysol EA9430 epoxy unless specifically directed by someone who had done that in the past. The EA9430 epoxy is already so thick that it is quite difficult to mix the hardener into it, and it is every bit as thick as it needs to be for most bondline applications. If I was in your position, I would use it straight out of the cans.

As to how much epoxy you need, that is fairly easy to calculate using a simple volume analysis. The trouble is that the empirical results rarely match the calculations very well. As Autoreply suggests, you can start by taking your volume estimation and doubling it, that will probably put you in the neighborhood. To be really accurate, you will need to do a test section, and just see how much it takes.

Thanks, Bob K.
 

opcod

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Aug 28, 2010
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77
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Canada
Hi Bob

For sure your right about testing a section. Better than being in hurry at the middle of the job and not having enought..
I check futher your site with your fabulous sailplane.. and when you close your wing it look you use flox, cabosil and resin. (you call that ''shmoo'' if i'm right.) hehe

So overall, is using the same epoxy as the wing skin: the bonding will be about as high vs using an Hysol adhesive ?

Of course, one of the main point with the same epoxy system : we don't have to worry about the time too much, like a 2hr pot life for the MGS and just 50min all for the Hysol.

Thanks
 

autoreply

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Two major problems with using the same epoxy is that it's often much stiffer as a good structural glue, resulting in far lower peel strength since failure occurs at a lower elongation.
Not sure whether it's valid for all, but epoxies typically quicker loose shear strength at elevated temperatures as structural glues do.

Afaik, most composite production planes still use mumpe (cotton/epoxy mixture). Peel isn't much of a concern for spar bonding, unless you have a Duo Discus. Glue the top skin/spar first.
 

BoKu

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...when you close your wing it look you use flox, cabosil and resin. (you call that ''shmoo'' if i'm right.) hehe

So overall, is using the same epoxy as the wing skin: the bonding will be about as high vs using an Hysol adhesive ?
I don't really know if the bondlines I'm getting are stronger or weaker than were I using one of the Hysols like EA9430. All I know for sure is that they seem to be every bit as strong as they need to be.

Also, for bonding the big things like wings and fuselages, we aren't using the same resin system as for laminations. For those bondlines we generally use Epon 828 resin and Versamid 140 hardener. That is based on a recommendation from George Applebay; it is what he used in the Zuni sailplanes. And, yes, the filler is mostly flox with a bit of cabocil to make it more thixotropic (less runny).

Thanks again, Bob K.
 
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