Kevler keel strip
Posted by: underhills on Sep-02-13 11:29 AM (EST) Category: unassigned
In a Binadryl haze I thought it a good idea to load my boat on top of my truck by myself in the Wind River range. When the wind caught my boat and it came off the top of my truck it hit a rock and cracked it. I did a repair to the glass inside the haul to keep paddling but now it is time to repair the gel coat. Since it is not a huge area and right on the keel I'm thinking of adding a keel strip since I have more gel coat then I need.
I've found some tutorials on using gel coat as the bonding agent for the keel strip but what I was wondering, would Kevlar be a good cloth to use instead of glass? I have the gel coat so it would cost me the price of the Kevlar tape, around $40, which would be half the price of something like Easy Keel.
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- Kevler keel strip - underhills - Sep-02-13 11:29 AM
In a word I would say 'no'.|
Posted by: wetzool on Sep-02-13 1:20 PM (EST)
S-glass is more abrasion resistant and doesn't fuzz when damaged. I would opt for that, but many do you Kevlar.
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Not as planned|
Posted by: CEWilson on Sep-02-13 2:03 PM (EST)
To instal a keel strip you'll need remove all gel down to the outer composite layer in a longitudinal strip wider than your tape. This is true whether using glass or kev tape. Mask the area off.
As as cross linking is not going to happen at this date you'll need an epoxy resin to wet out the tape and peel ply to tack the edges down. After the first wet-out, remove the peel ply and brush on another coat of epoxy, feathering the edges. When set, scuff sand it, masking tape still in place.
The chances your gelcoat will adhere to the epoxy keel tape are close to zero. You will need an epoxy gel coat matching the original.
Much easier to mask the center off, scuff sand it, clean w/ acetone and brush on catalyzed gel.
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dont' complicate this|
Posted by: suiram on Sep-02-13 3:52 PM (EST)
Keel strip is a sacrificial structure. Since it has no intrinsic structural value, requirements for good quality laminate are not valid.
Kevlar/Aramid is an awesome material, but money is wasted in using it as a keel strip.
For OP - just do a quick search for keel strip on kayaks, quite a few walkthroughs will come up. Even Sea Kayaker Magazine did a write-up some time ago.
KeelEasy - well, folks opinions will differ, but, based on my personal experiences, you should consider something else. That vinyl tape works really great for heel protection on the inside of the boat, though.
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I'm kinda with Charlie on this. |
Posted by: ezwater on Sep-02-13 4:58 PM (EST)
If you're going to add glass and weight, you should do so in a way that adds strength, rather than just adding breakaway and wearaway properties. Charlie's method will result in a low, smooth keel strip that has minimal effect on drag.
Of course, Kevlar, for all its wondrous properties and mysterious reputation, is almost always a rotten cloth to add to the outside of a hull. It has less compression strength than S-glass or even E-glass, and it fuzzes badly when it wears.
I have used outside Kevlar patches over breaks in the chines, which occur when a boat thumps down on a ledge so that the center of the hull is pushed upward. In that situation, Kevlar outside makes a similar break less likely.
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Posted by: havekayakwillpaddle on Sep-03-13 9:26 AM (EST)
Not sure where this fits, but take it FWIW...
In my experience of applying keel strips/ re-enforcements on hulls in the Lake Superior region, I have found kevlar to be, well superior. We've reinforced several hulls of fleet boats for sea kayak rentals and I've helped guides with hooking their boats up.
It seems that using a glass tape, is just a temporary solution, even whilst being careful, people wear through that within a season. I need to do a little research on the S -Glass vs. E -glass, but I have to think its not as abrasion resistant as the kevlar. You will have to note though, kevlar is thicker and can be a bit of a PITA (pain in the ash) to hold around extremely peaked areas (see Nordkapp hull).
Perhaps one thing that I've done differently, is the bonding method. Just solely using kevlar and a resin may warrant to a 'fuzzing' when excessive abrasion is experienced. Generally I will use a mixture of resin and gelcoat (say a 1:1 ratio) - this creates a viscous bonding structure that cures thick and can be quite BOMBER if applied in several coats. (Numerous guides have done this and haven't come close to wearing through the cloth.) I have seen bits of the coating break off, but that seems to be in cases where people used a 1:2 ratio of resin to gelcoat (e.g. 1 oz resin 2 oz gelcoat - as the gelcoat is a touch more brittle than the resin). Also, depending on how wide of kevlar tape you use, it seems to stiffen the hull up a bit. (However, if that is what you are really after you can throw 1/8" foam under some carbon cloth on the inside of the boat ;-)
In a dream world, I'd use Diolen glass, (have, a few times and that product is BOMBER!), however its tough to get state side and when I asked about getting some from P&H, they recommended me to just use kevlar, as it is easier to get and just as tough. (That's probably a subjective statement).
Hope that sheds a little light for yah!
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It depends on what you mean by |
Posted by: ezwater on Sep-03-13 2:47 PM (EST)
resistance to frictional wear. In Wallbridge's Boatbuilder Manual, a table comparing performance of various cloths shows S-glass only a little below Diolen in standing up to wear. But I think that those cloths deal with wear quite differently. S-glass is the hardest commonly available fiber one can use on a boat. It resists wear by pure hardness. Diolen is a "trick" substance that seems to duck back out of the way of sharp, wearing stuff, though Diolen is not very hard or strong by itself.
Kevlar resists frictional wear in a third way. The fibers may be caught by sharp stuff, but they are very hard to tear, so they tend to slip loose and snap back into place. But if they do get torn, the ends are going to hang loose as fuzz rather than getting sheared off to provide a new smooth surface. But I have one epoxy canoe that came with thin Kevlar drape skid plates, and they have worn smooth. Probably because we're careful.
The problem with Kevlar is not just the fuzzing, but the lack of compression strength, which is what is needed in an exterior cloth. That's why some Kevlar felt skid plates simply crack and break off of Royalex whitewater canoes. Layered, bias-cut S-glass skid plates are thinner, lighter, less likely to break off, and easier to repair.
I don't understand mixing "resin" and gelcoat. Epoxy is the very best resin for repair, and that is it. You should get some Raka, West, System 3, whatever, and try it.
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Posted by: underhills on Sep-04-13 8:41 AM (EST)
Thanks for all the input. I think I'm going with glass even though I found a place that has Kevlar tape on sale. I have a strong boat (WS Arctic Hawk Pro) so I don't need the added strength.
If anyone else is thinking about a project like this here is the link to the tutorial.
I figure a company that runs a fleet of boats may be a good place to start.
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