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Alu DIY

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revhed
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Re: Alu DIY

Postby revhed » Mon Nov 23, 2015 8:05 pm

faklord wrote:@RH
How is the strut to plate mount joint holding up?
I cant believe the epoxy fillet that you applied adds much mechanical strength
Anyhow i was wondering about potting (Epoxy + chopped strands) the ally strut into a foilbox
(eg http://www.ketos-foil.com/en/kitefoil/2 ... isser.html), still using the 8mm bolts.
Should be cheaper and lighter than TKF part.
Thoughts?
The product used for the STRUT to board connection reinforcement is a "high teck" bonding agent, not epoxy at all, now discontinued (at least here in France) due to saftey issues in using it, made to bond alu and many other materials. We did this as a test but only 3 sessions so far as is getting cold (not for PF :o ) but for us. Great question and only time will tell?
We also considered tig welding a fillet around the STRUT to base plate but as said did this for a test.
I know from years of trying that getting a GOOD bond between alu and even the best epoxys is all but impossible, (even doing meticulous cleaning and roughening up surface, sanding wet, ect...)UNLESS one uses the available (expensive, dangerous) prep treatments that airline makers use.
You can do a search to find these products.
We have never even seen or used these products as they seem to be not user friendly, acid?
The only reason we are testing this specific product is because it was free from a friend in the business.
So far we have bonded alu to carbon, ss, inox to carbon and alu, so far so good, but again only time and stress, temp changes will tell.
I have imbedded inserts and seems to hold strong, even using cheap brass ones.
Maybe (have not seen yet) the Zeeko alu STRUT is stronger because I think it has 3 M8 at the board plate connection?
So I think your idea of "filling" a Ketos STRUT to board box to fit but not bond to a alu strut seems like a GREAT idea!
Just be sure to rough up the inside of the box well, clean perfect and finley chopped carbon mastic mixture should be tightly packed in it around STRUT that has been waxed or other demold prep, seran wrap over grease to prevent bonding, cooked well of course.
Please let us know how it works.
R H

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renaudbarbier
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Re: Alu DIY

Postby renaudbarbier » Fri Nov 27, 2015 6:07 am

faklord wrote:@RH
How is the strut to plate mount joint holding up?
Main reason for asking is i seem the recall Renaud (TKF) posting that bolting to flat surface was ok for strut to fuse but NOT recommended for strut to board....i assume he tried it and developed his plate adapter ( http://www.thekitefoil.com/#!online-sto ... y=12087150 ) because of problems???
I cant believe the epoxy fillet that you applied adds much mechanical strength


Thoughts?
I do confirm...

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Re: Alu DIY

Postby faklord » Fri Nov 27, 2015 2:30 pm

@Ranaud
Thanks for the confirmation.
Can you explain what the problem was with just bolting a plate to the strut. Did this result in a mechanical failure, or was it just a lack of stiffness or something else?

@RH
Actually i was thinking of making the 'potted adapter' part of the strut and removable from the foilbox. This would:
a) Give compatibility of both parts (foil and board) with other foils/boards, assuming they also use the same foilbox interface.
b) Make use of the tapered fitting and thus improve rigidity of the interface.

The build process would be as follows:
1) Prep the foilbox for mold release. This is the part i am most unsure about, as the access is limited for operations like polishing wax.
2) Insert a thin plastic spacer into the bottom of the foilbox. This will be removed after curing and is to ensure a gap is present under the 'potted adapter' so it doesn't bottom out when in use.
3) Line the foilbox with carbon cloth. (1-2 mm thickness?). This is include to ensure that, when in use, the bolts can't just pull the strut through the potted adapter due to poor adhesion of epoxy with anodized ally.
4) Bolt the strut in place. Bolts and female threads well waxed.
5) Pack the the gap between the strut and carbon mat with chopped strand & epoxy. Would it be better to use chopped glass rather than carbon to minimize electrolytic corrosion?
6) Cure and hope it can be disassembled....

3), 4) & 5) would all be done in one go.

This construction has the advantage that the bolts will pull it all together and it doesn't rely on the bonding between any of the parts.

More thoughts?

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renaudbarbier
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Re: Alu DIY

Postby renaudbarbier » Fri Nov 27, 2015 4:41 pm

failure due to the torque on the bolts/ plate assembly and of course resulting lack of stiffness.

not sure how zeeko or other brands do it.

LF does it same as us.


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