UHMWPE Hull

Moderators: chrstjrn, mje, krudave

Post Reply
Waiheke

UHMWPE Hull

Post by Waiheke »

Does anyone have familiarity with UHMWPE (Ultra High Molecular Weight Polyethylene - google it) and have any thoughts if it would work as a replacement hull material for a standard hypalon hull that has given up the ghost? I am trying to determine if it comes in a sufficiently flexible solid sheet. It is appealing due to its remarkable light weight (floats on water), abrasion resistance and penetration strength.

User avatar
krudave
Site Admin
Posts: 1035
Joined: Sat Apr 16, 2005 9:02 pm
Location: Astoria, OR

Re: UHMWPE Hull

Post by krudave »

You'd need to laminate it with a fabric such as rayon or nylon to get the tear resistance and puncture protection the hypalon had.

LATER EDIT: Belay that. Looked at your other post. Spectra as a woven material such as cloth I know nothing about. How do you bond to it to make a skin? Does it lend itself to sewing?

Others have sought a lighter hull material with adequate abrasion and puncture resistance, and with mixed results. Folbot, for example, put out its early Coopers with a thermoplastic polyurethane hull having some sort of weave to it, and it did not hold up to rough usage, so they dialed back to a hypalon somewhat lighter than their original hypalon, the weight used in their Greenland II double.

I own one of the early Coopers, and if I am careful, the skin is OK. But, a less meticulous user would destroy it.

Feathercraft uses a proprietary skin material which is light and tough. Good luck getiing enough of it from them to do a complete hull.

You might PM Tom Yost of Yostwerks about using a vinyl skin as a replacement. He has a host of experience with skin choices and many designs out which use vinyl for a skin material. EDIT: PVC would be nowhere near as tough as a fabric based on Spectra, but Tom might know of some sources.
Dave Kruger
Astoria, OR
--
Folbot Kodiak, Cooper, and Edisto; three hardshells; Mothership: Surf Scoter the Bartender; dinghy Little Blue Duck.

mje
Site Admin
Posts: 1973
Joined: Thu Apr 14, 2005 12:34 pm
Location: Southeast Michigan

Re: UHMWPE Hull

Post by mje »

UHMWPE by itself is a solid that would be very difficult to fabricate into a flexible hull. You can get it in very thin sheets, but I have no idea how you'd bond it into a hull shape. You can't get it as a liquid coating, and I don't think the tensile strength is very high is sheets thin enough to use for a hull.

A quick Google search indicates it has a tensile strength of 21MPa, which is pretty low and an elongation of 350%. It has great wear and self-lubricating properties, but it doesn't appear to be a very good choice for hull material.
Michael Edelman
FoldingKayaks.org Webmaster

User avatar
krudave
Site Admin
Posts: 1035
Joined: Sat Apr 16, 2005 9:02 pm
Location: Astoria, OR

Re: UHMWPE Hull

Post by krudave »

Mike,

He is thinking of Spectra cloth. See his Intro post, in which he explains what he has in mind:

The hull of my Aerius is no longer seaworthy, and every so often I think about doing something about it... I live on an island 20 km east of Auckland, New Zealand. Recently I have been working with UHMWPE, an amazing form of very light yet strong polyethylene used for bullet proof vests, fishing line and bearings, among other things, and have been trying to see if a form of it can be used to replace hypalon. The only part I can't determine is if I can get it in a form that would be flexible enough. It would greatly reduce the weight, is very resistant to abrasion and is unaffected by most chemicals, including salt water.

In its woven form (brand names Dyneema and Spectra cloth) it would make an excellent deck material at less than 150 grams per square metre (GSM). In contrast 1000 denier Cordura is about 350 gsm.

If anyone knows about this material, I would appreciate hearing from them.
Dave Kruger
Astoria, OR
--
Folbot Kodiak, Cooper, and Edisto; three hardshells; Mothership: Surf Scoter the Bartender; dinghy Little Blue Duck.

Alm

Re: UHMWPE Hull

Post by Alm »

Few people are making their own skins, but it's either PVC or Hypalon. What you are going to achieve by coming up with a new material - weight reduction? Klepper is heavy, and better material will make skin only few kilos lighter, frame remains the same, this doesn't make a difference. And it won''t make the whole package less bulky - which is the main problem of Klepper-type frames when you have to travel with it. You may try and order Feathercraft hull material, it will be lighter and more compact than Hypalon, but this brand is expensive, so their proprietary material won't be cheap either. OTH, Hypalon is more readily available, and so is PVC.

Possible challenges with Polyethylene:

1) Sheets:
to be flexible, it has to be so thin that it won't be good enough without fabric substrate, like Dave mentioned.
2) Woven form: It's not waterproof, is it? Woven polyethylene tarp is "waterproof", but only under conditions of intended use - to hold a puddle of water. If you subject it to stresses in all directions, as any kayak skin when stretched on the frame, loaded with cargo, and paddled - it will leak between the strands.

Both forms 1 and 2: is there any adhesive for Polyethylene? I recall unconfirmed marketing info on Loctite 3030 last year, but don't anything more. Sewing is also questionable, as it depends on whether you will be able to seal the seams.

mje
Site Admin
Posts: 1973
Joined: Thu Apr 14, 2005 12:34 pm
Location: Southeast Michigan

Re: UHMWPE Hull

Post by mje »

Dave: Duh. How'd I miss that? ;-)

Still, the weight of the polyester cloth used in folders isn't the big contributor to the weight- it's the Hypalon laminated to it. Spectra cloth is used in racing sails, where weight it very critical. Of course, this comes at a price.

If you could combine a Spectra cloth with a light abrasion resistant coating, you'd have something.
Michael Edelman
FoldingKayaks.org Webmaster

Rejedejo
recent arrival
Posts: 1
Joined: Fri Sep 10, 2021 6:52 pm

Re: UHMWPE Hull

Post by Rejedejo »

Just found this old post, hope someone is still paying attention.

The UHMWPE fibers may be too inert and slippery to effectively integrate into a impermeable cloth to use in kayaks or whatever. Wondering about that though, I am not sure and am looking. Notice that many posters associate UHMWPE with solid sheet goods I’m thinking about the fibers that are about as strong as Kevlar, much lighter and these days not expensive.

Post Reply

Return to “Klepper”

Who is online

Users browsing this forum: Google [Bot]