View Full Version : Geodesic Airolite boat in Kevlar?
03-27-2006, 07:03 AM
Could you build one of theses boats and cover it in Kevlar (carbon) / epoxy?
Thinking that the Kevlar would be more durable / tuffer than their recommendations of a Dacron fabric. i.e., similar weight.
Would it be "lighter" than a similar standard / equivalent kevlar canoe?
-Keeping in mind that a kevlar canoe is more than a single layer of cloth for rigidity / stiffness.
-The internal wooden frame would give the Geodesic Airolite boat its rigidity / stiffness.
(in quest of responsibly lighter canoes)
This system has been pretty thoroughly researched and tested. If you think that you could improve on it then give it a try. but the heat shrink dacron seems to me a good way to get a nice snug fit.
03-27-2006, 09:47 AM
Aside from the difficulty of working with Kevlar, I would think the main problem is that the whole structure is fairly delicate. Dramatically changing the strength of the skin might save a few holes now and then, but the overall system wouldn't improve much.
Oops--just noticed the mention of epoxy. These are skin boats, depending on the flexibility of the Dacron skin. A thin, rigid shell would simply crack.
[ 03-27-2006, 09:49 AM: Message edited by: Dan McCosh ]
03-27-2006, 12:03 PM
The ones I've seen built are dacron with epoxy impregnation.
I understand that kevlar does not shrink in with heat as well as dacron and that's an important part of the building. After stitching nice and snug, you get with the heat gun. Then you epoxy.
Epoxy in mass is brittle but thin coats take such flexing as these structures have quite nicely.
They are remarkably tear resistant, really no more likely to open up than any other structure - eg ultralight cedar construction - that's more than double the weight anyhow.
03-27-2006, 01:57 PM
If you think the 3.7 oz dacron would be too fragile, you could always cover it with 8 oz. nylon (possibly the most popular fabric for SOF kayaks) from Dyson, Baidarka & Co.
03-27-2006, 04:26 PM
"I understand that kevlar does not shrink in with heat as well as dacron"
I suppose you could say that. When I worked repairing and inspecting hot air ballons, the specs for Kevlar control lines stated that they had to be able to survive an eight second direct blast with a 25,000,000 BTU balloon burner at point blank range. So don't expect it to shrink, melt or do much of anything else when you apply heat. Your heat gun will be worn out and dead long before anything happens to the Kevlar. Unlike most synthetics, it's so heat resistant that they can't melt it with heat in order to spin yarn from it. Instead, they have to "melt" it with acid, which is one primary reason that Kevlar fabric is so expensive.
Geodesic Aerolite construction is a means of adapting aircraft construction methods to make a very light, light-duty boat with a very lightweight skin supported by a very lightweight frame. They do that quite successfully, but will never be what they aren't. If those parameters suit your needs, by all means build one. It should be a great little boat that you will enjoy. On the other hand, trying to swap out part of the construction with heavier, or heavier-duty materials is most likely a waste of money and time. There are proven ways to make a Kevlar boat and proven ways to build a sturdy skin boat. They are quite different and neither really have very much in common with G.A. boatbuilding.
03-27-2006, 06:18 PM
To put this more succintly.
Anybody who builds a Kevlar hull with the Kevlar exposed to abrasion deserves what he gets. Once the Kevlar yarns are pulled loose they are a mess to repair. The stuff is very hard to cut and doesn't accept sanding at all.
The late Platt Monfort had a sterling idea when he conceived Geodesics. Follow his lead and get the lightest boat possible.
Trying to put a resin/cloth composite layer over an Aerolite frame is a bad idea. Every place the cloth isn't firmly supported will sag and the hull will have the texture of an oversized golf ball.
This idea comes up very often on the kayak building sites. The mere mention of "Kevlar" makes some hearts go pitty-pat. Anyone who has seen an old C-1 or C-2 Kevlar canoe knows how bad they get after too much contact with rocky bottoms and immovable boulders.
03-27-2006, 07:22 PM
I'll second that motion. The heat-shrink dacron is much stronger than you probably think it is. It will take all sorts of abuse. Plus, the wrinkles shrink out of the dacron like magic when you hit it with the hair dryer. In use, the remaining stretch in the fabric saves it from tearing. You can double up the fabric over the stem and under the keel.
03-27-2006, 07:31 PM
I built 2 SOF canoes ala Morris/Cinningham and a friend has built 2 GA boats right to Monforts plans. The GA's are sweet and amazingly strong. Yes they are puncture sensative but duct tape is a nearly permanent repair. My SOF's are 12 and 15 0z nylon respectively and are like tanks from both a durability and weight standpoint. The 14' SOF with the 15 oz fabric weighs exactly the same as my 14' Royalex solo canoe. There is a reason to follow Monforts directions if light weight is high on the priority list.
03-28-2006, 09:57 AM
You might like to make a test section. Just knock up a canoe cross section and experiment.
I did this before building my own GA canoe. Then I tested it to destruction and was very impressed by its strength.
I would take a stock GA canoe in the bush. I'd use it with the same degree of care I would with a wood-canvas.
03-28-2006, 08:37 PM
You will add weight using Kevlar, and it is not as good as using Carbon. I race marathon canoes. Started with kevlar canoes. They CAN be repaired but it is not easy. Hint: epoxy and shipping dept stretch film makes for a nice finish. The canoes I use are carbon and the 18ft6in boat I race weighs in at about 20lbs. This gets scuffed and gouged and occasionally holed. But they are pretty rugged. Just keep the kevlar out of the sun. Carbon holds up much better. Kevlar boats are about 20% heavier. Carbon is more expensive and recently, VERY hard to get. You can even get a combination weave of carbon/kevlar. With epoxy and kevlar, you will triple the weight since you won't be vaccuum bagging it (right?) and you ultimately defeat Platt Monfort's concept of ultralight. Take care of it and that dacron will hold up just fine.
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