Boat Building

P

Paul Charron

New member
Guys, I am a new member, but a long time reader of the website. I have a boat building question. What do you think of using Kevlar cloth and tape in place of Fiberglass cloth and tape when building a boat? I deal with lots of rocky shores and icy conditions here in the New England and was thinking of using Kevlar for the added durability.
Has anybody ever used it? Any special techniques required or precautions needed?

Paul
 
Since Paul opened the door on kevlar ... I would like to expand on his question and in addition to kevlar use and techniques inquire about ceconite as an alternative to glass and / or kevlar.

Anyone, with experience with ceconite application technique and durability I would like to hear about that too! Glass seems to be the go too fabric for skin over wood, but, at the expence of substancial weight increase. Where as kevlar is strong and lighter, but, very expensive.

Ceconite is an aircraft fabric that seems to be very light strong and priced in between glass and kevlar. The application seems to be more intensive with the primary tool being of all things a hot iron. My research also suggests that painting entails several more steps.

My dad ceconited a 16' oldtown canoe and it is definitely lighter then canvas over wood and looks great. Unfortunely, it has not seen much use since it was done ,as Dad, is medically disabled now. Thusly, I'm not certain it would stand up to the abrasion of repeated beached landings on various coastal terrain. Rocky shorelines I'm thinking would be harsh to a ceconite skin.
 
I have seen a lot of people ask about using kevlar fabric for its durablity over the years and it has always left me wondering.

Look at the mechanics of a boat rubbing on a rock step by step.

First layer is paint/primer.
Second layer is epoxy.
Third layer is the cloth embedded in the epoxy.
Forth layer is epoxy saturated wood.
Fifth layer is the raw wood.

Kevlar is durable, but it is the third layer to be affected by the boat rubbing on a rock. The only time this would matter is if the boat owner never maintained the boat or never made seasonal repairs to any rubbed areas.

Having a very hard durable paint allows for some serious rubbing to take place without the epoxy becoming jeapordized. Using quality epoxy resin under that hard paint also helps out. Not letting your boat rub on rocks all day is even better. If you are going at speed and hit a rock ledge kevlar won't really help since the epoxy and wood bond will more than likely fail anyway.

This leaves the only real value of kevlar in wooden boat building its strength when used to reinforce a resin and its light weight. If you are building a boat that you are planning on car topping or carrying on your back then kevlar makes a lot more sense.

Consider that Ed Askew skips his boat over oyster beds each year and it does not have a kevlar bottom and is not damaged.
 
My hunting partner and I both hunt rocky shores in New England as well... have been for 5 seasons... I don't know what kind of boat you are building but in my experience the best hull abrasion resistant tool is the sacrificial runners or keelsons on the bottom of the boat. Those suckers take a lot of abuse... My boat bottom has seen a lot of sand and coarse rock and not once has the hull fiberglass (2 layers) been breached. I have a heavy duck boat, with gear, me, dog and motor, about 950 lbs.

I have a friend who used Kevlar successfully, but I hear that it's a pain to sand, i.e. the product gets "fuzzy" instead of shaped smooth if that makes sense. And, of course, it's more expensive.

Whatever you do, good luck.

Andrew
 
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Guys, I am a new member, but a long time reader of the website. I have a boat building question. What do you think of using Kevlar cloth and tape in place of Fiberglass cloth and tape when building a boat? I deal with lots of rocky shores and icy conditions here in the New England and was thinking of using Kevlar for the added durability.
Has anybody ever used it? Any special techniques required or precautions needed?

Paul
Click to expand...


I will diverge from Ray's advice a bit and say that Kevlar is worth it in some situations. I have Kevlar under 6 ounce glass on the hull bottom and several inches up the edges. I hunt, clam, and fish in a lot of rocky areas where I am trying to anchor and leave the boat amongst barnacle covered boulders a lot (to hunt, leave the boat to clam or pick crabs for bait, etc...).

I have on a number of occaisions: 1) struck rocks at very low speed that did not hit the strakes, 2) swung at anchor into rocks on windy days, 3) had the tide drop me on a rock or 4) have a rogue swell deposit my boat on a rock outcrop (actually that only happened once). I spend a lot of time "tighter" to the shore than most people, but I like to hunt that way. I have a dozens and dozens of scratches in my hull that went down to yellow (the kevlar) on the first try - so to use Ray's example, layers 1-2-3 were breached in one incident, but the kevlar held. As Andrew says, he has 2 layers of glass, the second layer may have stopped the insult there, but I think the kevlar is what does the trick. I use my boat a lot, I'm on the water at least once every week most of the year and under conditions that are worse than most.

Kevlar is more expensive (for my boat it was in the neighborhood of $200 bucks) and a tiny bit tougher than glass to apply (it needs to be under glass, because it doesn't sand well, so you are stuck with 2 layers). From what I have seen in my conditions it is worth it. I have lots of scratches that go through the glass and to the kevlar, but none go to wood.
 
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Ive got kevlar on the underside of my scaup, and it has taken serious abuse over the years. But like Andrew mentioned, keel guards are an important addition. My hull has oak stringers and bronze half rounds to guard against abrasion.

Kevlar is nice, but again, a pain to work with. It is very difficult to cut cleanly, and hard to sand. The best way my dad found of cutting it was with a pair of quality shears. If you use some type of keel guard, fiberglass should be fine. Its all just a trade off, with kevlar being more expensive (but lighter and hopefully stronger), and glass being heavier (but cheaper and easier to work with). Estimating the quantity of cloth needed would allow you to compare prices, which might help you gauge whether it is worth it or not.
Good luck,
Neil

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It seems as thought forum members have experience with both glass and kevlar. That having been said does anyone have any experience with ceconite?
 
I had to look this stuff up. It is a 100% polyester fabric for covering aircraft frames replacing the old cotton coverings. In my brief search it does not appear to come in a wide variety of weights. Three were listed on one site and all those weights were fairly light compared to regular FG materials for powered boat building. The weight of the cloth is what provides the strength once it is fixed in the resin matrix.

It appears to be more expensive than FG cloth, but half the cost of kevlar.

There are polyester materials that are specifically made for epoxy work on boats. Xynole and Dynel. They are both cheaper than ceconite and are engineered for the purpose of boat building. RAKA sells both of these materials in 4oz up to 68 inches wide.
http://www.raka.com/
 
Guys,
Thanks for the thoughts.
Tod, the situations you talked about are exactly the situations I encounter. Wind blowing, birds flying, a falling tide, hunting tight to the shore on a shale bottom, with intermediate size rocks thrown in. I don't want to have to reposition the boat every five minutes. I was just thinking that the kevlar might save you some future problems, but didn't know if there are draw backs to working with it that might out weigh the benifits.
Sounds like there is some additonal pain involved, but additional value also.

Thanks Again

Paul
 
Paul,

I'll get a rash of shit for this, but... these boats are relatively fragile in some conditions. For example, you would never want to intentionally ground one out on anything but sand or mud. They are plywood (fairly soft) with a hard shell of glass and epoxy. You could do a lot of damage if you grounded one out on a rock that didn't hit one of the keelsons. For most situations they are indestructible, but you are going to make a mess of one if you aren't careful if the conditions you describe are the same as I hunt in.

As for the kevlar, it is only tougher in that you need to apply two layers wet-on-wet. Glassing is super easy and I can't imagine that anyone but the least handy would have trouble doing at.

Any other questions holler.

Fill in your proflie, so we know where you are from.

T
 
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I will stick my neck out here and take the flak if it comes as well.
I have many hours logged in boats with just raw AC ply and paint. Have struck rocks at full speed with same. Amazed at the ability of the material (Ply Wood) to take a hit.
BUT not indestructable. I know Dynel has better abrasion resistance than glass(and can move with the epoxy and wood way better) and Kevlar has better resistance than Dynel.
Glass is cheaper and more commonly avail.. Kevlar is a less easily workable material than glass. If you have to grind it it frays instead of cutting. Try to cut it with your wife's scissors.
But if you are talking about the scrapping type wear like a beach landing where the keelson does not take the brunt of the land then you have to use some care and also keep an eye out for a maintainence item. If you wrap wood up in epoxy and (Glass,Dynel,Kevlar) you have to keep it that way.
This is where the market for heavy AL welded hulls comes from. BUT they are not resistant to sharp type puncture impacts either and care is required,(IE good sense with the speed)
The beauty of the wood hulls is that a guy can get out a great hull shape and finish it off with a little care and time. I think good welding in AL is not a first time out thing, and for most, Epoxy and some type of cloth is easier.
 
Actually, I don't think that YOU are sticking your neck out Bob... I think most of us first time boat builders are sticking OUR necks out... i.e. I happen to know your background and you know more about boat construction than 95% of us on this site... so, therefore, your advice and perspective should be counted on more than us weekend guys.


Come to think of it, I believe I put a layer of Xynel first, then a layer of good old glass down as a second. Either way, if you hit a rock at speed and your boat is made of aluminum, wood, etc... you may have some problems depending on conditions. I for one, didn't trust wood when I first got into this hobby of ours. After 5 years of running a wooden boat in shallow ducky waters around New England's coastline and Vermont's rocky lakes I can attest to wood's toughness.

So... the best piece of advice to come out of all of this... is BE CAREFUL.

Thanks Bob, we're fortunate to have someone of your experience actively post.
 
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Bob,

I seem to recall a story of yours about gashing a wood hull while breaking ice. I can't remember if the wood was glassed or not. It may be a good time to repeat the story since a number of us are breaking ice to get out.

Hope your getting out!

Scott
 
Andrew,
I am blown away by the construction and detailing that get put up on this site on a weekly basis and I would never feel comfortable being looked at as anything more than just one more guy who has used a boat, sometimes way to hard.
I do get to see some cool stuff thru work but I find things here regularly that I even show coworkers.
Scott,
I was just reminded of that faitfull trip last weekend when I drilled the ice at the Patchaug Ramp to check for ice fishing.
Long Story /short
We had a rapid deep freeze in one nights time that set fresh water black ice 5/8 thick by 4:40 launch time. We were sure the big pond would be open somewhere and we would limit in 5 min with birds looking for open water.
Pressed on thru it at hull speed. By the time we got to the big water we realized two things. It was frozen due to 0mph of wind and we were floating decoys at our feet.
The hull sides were cut thru just like you would think. A line at the WL about 3 inches wide and a good long 1 inch gash fully thru. No Glass on the ply hull, but I will say that this stuff would make a mess of most boats. The AL boat we used to make a hasty salvage of my boat/motor was in danger of a hull tear as we forced it thru the first cut path which was now the only breakable ice on the lake by 8:00am.
I am sure a well covered glass over wood hull would have lasted longer but I am equally sure it would take some abrasion damage.
Here is how I know. Once every 3 years or so we get a heck of a deep freeze and the salt in the river here locks up. Since it only happens every 3 years some guy forgets and tries to get his lobster boat out to check his traps. Solid glass hull(No core) maine built lobster boats get trashed by this soft salt ice. We have done the insurance repairs. (Ice breakers are made of steel plate for a reason)
Just remember. Ice is serious and demands good planning and a triple backup plan. EMS does not like getting into the stuff to save you and your broken stuff.
Build well, start off small (1/4 inch for practice) and dont go if you dont feel right. First time ice missions are not the place to try to make your longest run of the year. If you really want to do it, drill in the daylight without your hunting stuff to get a feel for it first.
I will also say that I think the coast guard is right to equip their boat guys in dry suits for cold exposure work where a dunking is a possibility. I dont own one but would sure feel better about my fav winter hunting trips in one. I have much less confidence in my waders than I used to.
This is the Link for any one who goes ice breakingDr Geisbrecht Ice ManWatch all 3 video clips.
 
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