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Your new canoe will weigh 38 lbs natural, or 44 lbs painted, what do you prefer?
Natural all the way, baby, I like the look! 33%  33%  [ 9 ]
I don't really prefer natural, but I want a lighter canoe! 30%  30%  [ 8 ]
Give me paint, a nice traditional colour! 19%  19%  [ 5 ]
Might as well make her real pretty, two tone please! 19%  19%  [ 5 ]
Total votes : 27
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PostPosted: December 12th, 2009, 12:28 pm 
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thanks for that info.

one big advantage of gelcoat is the fact that it's surface finish is going to be as perfect as the mold it is sprayed into, and never will one have an issue with problems that might occur when paining a boat after it has been removed from the mold

so then the question is, can two part lightweight poly paint finishes be sprayed into the mold just like gelcoat is now applied? that would possibly be an ideal solution to the problem.

Interestingly, before I worked for H20 I had no idea at all that any kind of 'paint surfcace' (read gelcoat) could be applied as the first layer in a mold of a boat being built, I just assumed they would be sprayed when out of the mold.

one advantage also of gelcoating in the mold is it actually prolongs the life of the mold, as most catalyzed resins used in infusion (of the fabric layers) eat away at the mold, so having a gelcoat layer there increases the life of the mold significantly


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PostPosted: December 12th, 2009, 1:37 pm 
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I think that the issue of what gets sprayed into a mold has more to do with how it bonds to the subsequent laminations, and resins. The trick is to find the right material match so that strength and flexibility complement the overall skin of the boat.


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PostPosted: December 12th, 2009, 4:10 pm 
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davidchiles wrote:
so then the question is, can two part lightweight poly paint finishes be sprayed into the mold just like gelcoat is now applied? that would possibly be an ideal solution to the problem.


I've never done anything like that, nor have I heard of it being attempted, but I'm going to go out on a limb and say, "Most emphatically... no". I doubt mold release waxes are formulated to work with two-part poly. Also, I'd think that the adhesive qualities of poly applied wet are totally different from trying to get resin to adhere to it once is has cured.

The gel coats I've seen seem to be still slightly tacky when the cloth is laid in. I don't believe it fully hardens until the resin contacts it. That leads me to think there is a strong chemical reaction taking place between the gel coat and the resin.

Adhesion is not the strongest suit of urethane paints (many need some sort of primer) and the finish would be a very fragile few thou in thickness. I suspect what you'd get would be a real mess, with large areas releasing from the mold and others releasing from the hull. This would probably ruin both.

I'd love it if someone more experienced would dispute this, however. It would then seem to be the best way to build a boat without adding weight.

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one advantage also of gelcoating in the mold is it actually prolongs the life of the mold, as most catalyzed resins used in infusion (of the fabric layers) eat away at the mold, so having a gelcoat layer there increases the life of the mold significantly



Interesting. Didn't know that.

I wonder why, then, so many big companies are going to skin-coat construction? Seems that amortizing the costs of the mold over "X" number of boats would be pretty critical to them given the high tooling costs to replaced damaged/worn out molds.

How significant are you talking about? 600 boats vs. 1000 (not good at all) or a 5% difference (not pleasant but livable)? Can the molds be repaired/refurbished or must they be rebuilt from scratch?

BTW... very good thread, I think.

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PostPosted: December 12th, 2009, 4:38 pm 
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If catalyzed resins eat away at mold material, it must be with resins other than polyester. With the latter, the resins and gelcoat use the same polyester base, though there is the addition with gelcoat of colorant. Epoxies are supposed to use a different colorant, though I have successfully used colorant meant for polyesters with epoxies successfully. I don't have any experience with vinylester resins so I can't comment on those.


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PostPosted: December 12th, 2009, 9:24 pm 
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just to clarify, there are catalysed resins that do not affect the mold paint, but are (at least to my knowledge) significantly more expensive than those that can damage the mold over time if applied directly against it.

so two part gelcoats do not damage the mold, and protect it when using the less expensive resins.

but if you want to go with a resin designed for use directly against the mold, it is a fair bit more expensive.

I have long forgotten whether or which is an epoxy resin, or vinylester resin, or polyester resin, etc, but that simply is one of the coincidental benefits of gelcoating a boat before infusion, you get to save money on resin.

good question as to durability of molds, I will go out on a limb and say a mold treated well (release agent wiped on initially, then waxed every second boat, then retreated with release agent every 50 boats or so should last 500 + before having to be repainted with mold paint and refinished, whereas a mold subjected to the improper resins might only make up to 100 boats before needing to be completely refinished.


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PostPosted: December 12th, 2009, 10:11 pm 
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I think you've answered my question by mentioning the use of inexpensive resins. As far as I know, all of the top quality boat builders are using epoxy vinylester resin and not polyester resin, especially on the skin coat (without gel coat) boats.

I know the vacuum infusion builders like to use it because of its lower viscosity, which helps the vacuum draw the resin through the cloth. Still, in spite of using superior (and apparently less damaging) resins, the infusion process itself is harder on molds than wet bagging is, so they have to figure that into the final cost of the boat since they get fewer boats out of a mold before repairs are necessary.

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PostPosted: December 12th, 2009, 10:19 pm 
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I think we're all playing for the same team, different positions though!

I have a feeling that gelcoated boats regardless of manufacturer will use less expensive resins, though many who have gone to clear boats will simply use the more expensive resin on all boats so as not to confuse anyone, don't know for sure though.

but back to the poll, a large number of respondents want an unpainted/unfinished looking kevlar boat, a large number might not like the appearance but will appreciate the weight savings, and a whole whack still like pretty painted boats!

so does that mean certain Canadian canoe manufacturers will be introducing a 'natural finish/unpainted' kevlar composite boat for '2010'? who knows for sure!


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PostPosted: December 13th, 2009, 6:21 am 
Battenkiller wrote:
davidchiles wrote:
so then the question is, can two part lightweight poly paint finishes be sprayed into the mold just like gelcoat is now applied? that would possibly be an ideal solution to the problem.

I've never done anything like that, nor have I heard of it being attempted, but I'm going to go out on a limb and say, "Most emphatically... no". [...]

According to John Winters it can be done, but costs too much:
viewtopic.php?f=20&t=10694&p=101931

Quote:
Adhesion is not the strongest suit of urethane paints (many need some sort of primer) [...]

Someone more knowledgeable than me should answer this,
because (AFAIK) PU in itself has very good adhesion,
so that may not be the reason why primers are sometimes used.

Dirk Barends


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PostPosted: December 13th, 2009, 10:44 am 
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Just to keep things real for those of us who can't afford 200 bucks to paint our canoes.....I use a Plain Jane Marine paint I get from the local hardware store for 18 bucks a litre, on both the inside and the outside hull. Works real good. I've used it on four canoes now, on top of system three stuff.


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PostPosted: December 13th, 2009, 12:36 pm 
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Dirk-Barends wrote:
Battenkiller wrote:
davidchiles wrote:
so then the question is, can two part lightweight poly paint finishes be sprayed into the mold just like gelcoat is now applied? that would possibly be an ideal solution to the problem.

I've never done anything like that, nor have I heard of it being attempted, but I'm going to go out on a limb and say, "Most emphatically... no". [...]

According to John Winters it can be done, but costs too much:
viewtopic.php?f=20&t=10694&p=101931

Quote:
Adhesion is not the strongest suit of urethane paints (many need some sort of primer) [...]

Someone more knowledgeable than me should answer this,
because (AFAIK) PU in itself has very good adhesion,
so that may not be the reason why primers are sometimes used.

Dirk Barends


Gee, DB, if you read through the whole thread, you'll see that I've been advocating the use of cross-linked linear polyurethanes as a canoe finish from the beginning of this thread... and have been for quite some time elsewhere. Don't forget, I actually ran an imaginary canoe company for a short time, and that's all we ever pretended to use.

:rofl:

If you check out the DS thread, Mr. Winters wisely recommended it there as well, and with good reason. It is basically automobile paint, and we all know how tough that is (have you ever seen a gel coated car?). Auto paint is sprayed on the outside of the auto bodies themselves (after they are primed), but David Chiles was asking if the paint could be used to spray the inside of the mold in the way gel coat is applied. John Winters says nothing about applying it in that manner. It just will not work, trust me. You'd have to wait until the boat is out of the mold to spray it on the hull surface.

Adhesion is a relative term. Surely, PU will stick to stuff - so will epoxy resin - but the bond of both materials is increased immensely by creating a mechanical bond (prep sanding) first when using it on smooth, shiny things... like canoes hulls. The highly polished surface of the hull after it pops out of the mold is not a good surface for anything to adhere to. Some light sanding (maybe 800 grit) is necessary to get the PU to adhere in a way that it wouldn't lift off over time.

This poses a problem for makers of straight Kevlar layups since, even though there is a very thin layer of resin at the interface of mold and hull, it is on the order of a few thousandths of an inch. If you sand through that and hit the Kevlar itself (extremely likely), a smooth and glossy finish will be impossible to achieve since Kevlar fuzzes up when sanded.

A layer of fiberglass (S-glass is best) on the outside of the hull (first blanket laid inside the mold) would not only eliminate this problem, it would put a compression resistant material on the outside of the hull and the material with the stronger tensile strength (Kevlar) on the inside where it belongs.

RHaslam wrote:
Just to keep things real for those of us who can't afford 200 bucks to paint our canoes.....I use a Plain Jane Marine paint I get from the local hardware store for 18 bucks a litre, on both the inside and the outside hull. Works real good. I've used it on four canoes now, on top of system three stuff.


That would be keeping it real for me as well. The problem is that the maker of my canoe never put anything on the outside at all and the Kevlar is starting to degrade. I have to get on top of it because I paid $2000 (sale price) for the canoe and having someone spray it for $200 is a great way to keep it looking original and to protect my investment. Otherwise, in 10-15 years all I'll have left is an ugly brown and very fragile hull. Who knows, I may want to sell it in the future. Doubt I'd get much for it at all if I just overpainted it with marine paint. Two coats of automotive clear coat with UV inhibitor added would protect it from the sun and make it look great again. When it came time to sell it, I wouldn't have to drop the price way down in order to move it.

BTW, the $200 price I mentioned was to prep and spray it at a professional auto body shop. That includes them using their equipment, spray booth, labor and knowledge, plus a small surcharge I'm sure for doing something they aren't geared to do on a regular basis. The actual costs of the paint itself is much less than that (although still higher than marine enamel I'll admit).

You can't compare the price of someone else doing the job against the cost of the materials alone when you are doing it yourself. As for me, I already have all of the proper equipment (compressor, HVLP spray gun, respirators, Tyvek suits, and other safety equipment), so in reality, I'll probably do it myself this spring. I figure about $60-80 total for top coat and several sheets of 800 grit sandpaper (which I already buy quite cheaply by the 100 sheet pack). Room for a 16 1/2' canoe is a bit of a problem, but I can move stuff around a bit just to spray.

Personally, though, if the issue of resale/trade-in was not there, I'd paint it with marine paint in a heartbeat.

Fire Engine Red. :wink:

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PostPosted: December 13th, 2009, 1:24 pm 
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I haven't paid full attention to this thread, because I've been studying for the 3-hour exam on the Dragonslayer discussion.
:o
What do people think of the approach Millbrook uses for their vinylester boats? Kaz the builder says:

"I use a pigmented skin layer (first fiberglass layer) for color, rather than a gel coat, to keep weight down."

The colors are nice and bright, and there is a bit of depth so that the color doesn't scrape off like paint. If the surface is scratched, however, you're immediately into the outer layer of S-glass. There is no ablation layer as with gelcoat. One has to keep some quality yacht wax on the hull to intercept UV. Patching is easier, because one does not have to remove gelcoat to get the patch cloth flush against the structural layers.


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PostPosted: December 13th, 2009, 1:40 pm 
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A buddy of mine bought a used Souris River duralite canoe. It had been used hard, to the point that the glass was actually fraying. We took the Marine paint to it (green), came out very nice. He touches it up every year or two.

I can't stand the look of those kevlar, duralite and other mixes that let the sun shine right through. Something about it rubs me the wrong way.....there is more to canoeing than how much weight you can peel off your hull...there is also the aesthetics of canoeing.....seeing one of those thin skinned monsters under the best of conditions disturbs me....put some clothes on the damn thing, even if it cost you 2 or 3000 bucks doesn't mean everyone wants to see it naked!


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PostPosted: December 13th, 2009, 1:54 pm 
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RHaslam wrote:
I can't stand the look of those kevlar, duralite and other mixes that let the sun shine right through. Something about it rubs me the wrong way.....there is more to canoeing than how much weight you can peel off your hull...there is also the aesthetics of canoeing.....seeing one of those thin skinned monsters under the best of conditions disturbs me....put some clothes on the damn thing, even if it cost you 2 or 3000 bucks doesn't mean everyone wants to see it naked!


I agree. Those canoes with opaque sidewalls do not seem right. I like a good solid color.

dave

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PostPosted: December 13th, 2009, 3:27 pm 
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You boys should try putting lipstick on your boats too... :D That'll make 'em look real pretty! :rofl:

Another drawback of ultralights are the volunteers that want to pack that thin skinned monster for you just to see how light it is!

Seriously though, to me canoeing is more about how you feel not what you paddle. If that hand made baby makes you feel great than more power to ya. If that poly pig makes you feel great than more power to ya.

I go for function not fashion.

Oh yah... I vote no paint!


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PostPosted: December 13th, 2009, 4:01 pm 
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One of the issues that this thread is covering, is the reduction of weight. The ultralite revolution hit backpacking and climbing 15 or more years ago, and cycling as well. In some cases, it came at the cost of durability, particularly in the climbing and backpacking area.
A number of manufacturers are eschewing ultralite now in an effort to produce products that last. The cycling analogy may also be appropriate. Years ago, I remember guys showing up with the latest technology, super light cranks, etc. and sporting more than a few pounds on their middles. While "super light" bragged about how his crank sets, etc. were 5.2 grams lighter than ours, my buddies and I would quietly say that if "super light" stayed away from the all you can eat buffets he would have to spend x less dollars for that super light gear and still be light. I have gel coated kevlar canoes(Novacraft and Hemlock). I could reduce weight by using aluminum gunnels instead of wood, kneeling thwarts instead of seats, but light weight is not my only consideration. Durability is certainly a factor, but as well, let's not forget the aesthetics. Wood gunnels just feel better and IMHO, look better than aluminum. Is it worth a couple of extra pounds to have wood gunnels? IMO, "Yes".


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