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 Post subject: Paint a stripper???
PostPosted: September 27th, 2007, 10:42 am 
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Location: Vermont
In a serious effort to minimize weight in a solo tripping canoe to be built this winter, I'm considering paint. Specifically, I'm considering the following:
1. Exterior, below the load waterline, filling the weave of the fabric in the normal way but adding either graphite or aluminum powder to the resin and filling only sufficiently to get a smooth, minimal resistance, surface. The fillers are to block UV when cartopping and to increase abrasion resistance. I've been happy with this schedule in the past.
2. Exterior, above the load waterline and interior, after a carefully applied wet-out and clean-up, skipping fill coats and going directly to an opaque marine paint. I would aim at only enough paint for UV opacity, leaving the fabric pattern showing.

I understand the feeling of those who consider it an outrage to paint over the beauty of the natural wood. Having been an enthusiastic woodworker since my dad caught me messing with his chisels in the late '40's, I feel the same way. But at my current age I simply have to minimize weight any way I can or give up portaging. Fill coats and UV blocking varnish with sufficient depth to be effective seem like an extravagance--when canoeing I can't see the exterior, the interior is largely covered with stuff, and where I go I hope there's no one else to see it.

Questions:
1. Will this departure from convention seriously reduce hull strength?
2. What kind of paint will give the best UV protection with minimum film thickness?
3. How many coats will I need to apply?

Comments and suggestions will be greatly appreciated. Just keep in mind that the goal is minimal weight.

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PostPosted: September 27th, 2007, 10:47 am 
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How much weight are you looking to save by going this route?

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 Post subject:
PostPosted: September 27th, 2007, 10:52 am 
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Paint a stripper? Sure if she'll let you. Go for it... :tsk:

I think it's a reasonable idea... I've never heard it done, but it's probably because everyone is trying to make a museum piece as opposed to a functional canoe. I presonally like the idea.

I don't see how that would matter strengthwise. the fabric gains little strength from "filling the weave"... As with skincoat boats, it's the minimum resin to wet out the fabric.

As to paint, I suspect a simple auto enamel would be the lightest, you could spray on a marine poly if you wanted. Obviously spraying will reduce weight over brushing on, so I'd opt for that.

As to coats, I guess it depends how long you want it to last. If you are only using the paint to protect from UV, I'd say the least to cover everything, if you want it to look good for a number of years, put on another.

PK


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PostPosted: September 27th, 2007, 10:53 am 
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I think it's a great idea. I have painted some of my older strippers...... used just regular marine paint (red of course)on sanded fiberglass, but I think it might need to be thinned if used on just the wetted out weave. I would think you would only need one or two coats on that area of the canoe...in terms of weight saved...I think it will probably be minimal, but I also think that any strength loss would be minimal as well.


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PostPosted: September 27th, 2007, 11:11 am 
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alscool wrote
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How much weight are you looking to save by going this route?

Several pounds. How much is saved depends on where you're starting from. Some advise filling to a smooth surface and then adding "several" coats of Captain's 1015. If that's the starting point then "several" is a higher number than if the starting point is the single coat of 1015 I used on my first stripper.
I've had trouble finding ways of estimating weight added by fill coats and weight added by coats of varnish. Both obviously depend on who's applying it. The current state of the design, which is nearing final, has 30 to 31 square feet of hull surface. (More on the hull at viewtopic.php?t=24683)
What would your guesstimate be?

bob[/quote]

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PostPosted: September 27th, 2007, 12:06 pm 
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My Bear Mountain Huron now has a cream enamel exterior - I painted over the varnish because I thought the contrast between the interior wood tones and enamel outside would make for a better-looking boat, like the look of brightwork is improved with enamel on larger boats. IMO, it looks great, and the enamel is more durable and shows abrasion marks less than varnish.

The added weight of three coats of Interlux Schooner varnish on the exterior was about a pound, while two coats of Interlux Brightside enamel added on less than a pound, maybe only a half-pound (the scales were only marked off in half-pound increments).

An even lighter and more durable paint is Endura, a two-part polyurethane, dries very thin and light, and is more abrasion-resistant. Expensive, a liter can cost from $60 - $100, depending on color. I've used it on another canoe but did not weigh before and after.

Since using the expensive Interlux varnish and enamel, at about $50 a liter, I've switched to Rona's floor and porch paint, reinforced with some kind of epoxy additive, less than $20. It's durable, although not as durable as Endura, and adds on about the same amount of weight as the Interlux enamel.

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PostPosted: September 27th, 2007, 12:33 pm 
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frozentripper,
Thanks for the good info and experiences. I'll check the huron and estimate it's square footage for a good comparison. With the positive feedback so far, I see no reason to back off from this idea. I'll probably go with a single spray-on coat of whatever product I settle on and add a second coat only when the need becomes apparant.
b

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PostPosted: September 27th, 2007, 12:33 pm 
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Paint can look good. I'm not certain about the amount of weight saved but you may be correct.

An article was published in Wavelength Magazine, the wooden kayak issue a while back by Adam Bolonsky where he discusses the various methods of finishing a kayak, including the pros of a painted hull rahter than varnish. The same applies to canoes. Find the article here.

Cheers,
Bryan

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 Post subject:
PostPosted: September 27th, 2007, 12:53 pm 
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pawistik,
Thanks for the link. Good advice from someone who obviously knows what he's doing.
b

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PostPosted: September 27th, 2007, 9:19 pm 
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Fill coats help with pinholes, which is something to consider. Peel ply is an option that will leave a rough surface that will need to be sanded, but in my experience it tends to fill the weave in one go when you apply the peel ply over the glass after squeegeeing.

Here's an interesting article that Jay Morrison (lightjay) allowed me to post on my site: http://www.nessmuking.com/lightjaycanoe.htm It has some great weight saving advice for building.


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 Post subject:
PostPosted: September 27th, 2007, 10:02 pm 
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Bryan,

Thanks for reminding me about pinholes. Now I have to ask myself whether a coat of paint will deal with them satisfactorily. In fact, I intend to begin with a seal-coat of epoxy before the glass and that should help too.

Jay's article on your website is a gem. I just discovered your site and Jay's article a couple days ago and immediately bookmarked your site.

Jay's comment that the tiny boats built by Rushton and used by Nessmuk are not for him is as it should be; Nessmuk weighed 105 on his first trip and even less on later ones. My own discovery was that at 135 the Wee Lassie is a wee bit small for me. I'm holding to 11' 6" but filling out the underbody a bit for greater displacement. As I see it the important lesson from from Rushton and Nessmuk is not that any of their designs is perfect but rather that fitting the boat to the user is important. If someone who weighs 180 and canoes with a keg on tap in the bow tells me not to even consider a canoe of less than 18 feet then I will probably smile and ignore the advice. His shoes wouldn't fit me, why should his canoe?

b

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 Post subject:
PostPosted: September 28th, 2007, 7:08 am 
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Painting is a good and viable option... But for even lighter load consider not even doing that.

Just leave bare epoxy... Unless you're planning on spending a LOT of time in the sun the UV breakdown will be minimal... There are some resources showing testing of epoxy UV resistance, and most only show surface chalking and some milkiness even after a full year of exposure. For instance http://oneoceankayaks.com/Epoxtest.htm here.

This is something I've thought about quite a bit... As Bryan mentioned, pin holes may be a concern so a second very light epoxy coat might be adviseable no matter what route you take. Alternatively consider using vacuum bagging and then leave the bare finish. It'll give you a smoother finish with less chance of voids/pin holes and a reduced epoxy weight.

I like the filled bottom with the combination of graphite and silica, as this is something I'm considering for mine.

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 Post subject:
PostPosted: September 28th, 2007, 7:46 am 
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Rapt wrote:
Painting is a good and viable option... But for even lighter load consider not even doing that.



Good thought. If I had access to a really precise scale I'd make up a sample and weigh the glued-up and sanded strips, then weigh after a seal coat of epoxy, then after fabric and wet-out epoxy, then after a spray coat of paint. To paraphrase one of the more imaginative contributors to this thread, "So many options, So little data."

b

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