Aircraft ski build

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Kevin6q
Posts: 22
Joined: Thu Jun 19, 2008 3:24 am

Aircraft ski build

Post by Kevin6q »

I'm adding a layer of 3/16" UHMWPE to the base of an aluminum ski. There is a compound curve at one end. The ski is approximately 50" long, 8" wide with the center 6" being flat. The outside edge 1" is bent up at approximately a 20 degree angle. Looking for suggestions:

How to pre-bend the plastic along the edges to help add contact area and keep it on the original shape. This is important so the bolts used to hold more in provide more shear than tension and to keep the plastic flat and not scalloped.

Bonding the aluminum and plastic. I have a full vac bag set up and was planning on using it to provide clamping pressure. The idea is to flame treat the plastic to help with the bond. Recommended adhesives?

The edge will also be mechanically attached with bolts and there are 1/8" thick by 1" wide aluminum strips running the length of the ski. These provide some tracking, wear resistance, and help hold the plastic in place. The adhesive is helpful but not critical to keep the piece in place.

It'd be great to add some graphics to the white base. Suggestions on sublimation houses or DIY?

If you need more info please ask.

Thanks in advance, Kevin
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chrismp
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Location: Vienna, Austria

Re: Aircraft ski build

Post by chrismp »

You should definitely sand the UHMWPE with some 80 grit sandpaper and flame treat it right before bonding. To test if the flame treatment worked properly, you can do a water drop test (drop of water on the treated surface should spread out and not form a drop).

For the adhesive, I would probably use some automotive structural adhesive like Sikaflex that stays flexible when cured.

In the US, Miller Studio does sublimation on UHMWPE http://www.millerstudio.net/sublimation
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mattman
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Re: Aircraft ski build

Post by mattman »

Kevin, another option is to laminate a couple plies of tip-fill material. This 2.1mm thick, UHMW, and already treated for bonding on both sides. By laminating a couple thinner layers of UHMW together, its also easier to form more complex shapes.
TimW
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Re: Aircraft ski build

Post by TimW »

For forming the UHMWPE to the shape of the ski I'd suggest first vacuum bagging it dry, and the apply heat to the UHMWPE to form it. Just heating locally along the 20deg bend with a heatgun may already do the trick, better if you have a way to heat to whole thing.

Doing it dry will give you plenty of time to try out what works.

For bonding my experience is mainly with epoxies. THe PE just sand and flame treat. The aluminium may be trickier to get a good bond. I have had good results with wet sanding for metals (so first apply epoxy and then sand in the wet epoxy). This way you get rid of the oxidation layer on the aluminium without a new layer forming immidiately. But that may get messy for such a large part. Maybe the bond will be strong enough with less effort, I have no idea how much abuse it will get.
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