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PostPosted: February 11th, 2008, 5:23 pm 
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Graybeard wrote:
Sundown,

You are obviously doing your level best to be as helpful as you can, and I certainly appreciate that. It's also becoming fairly obvious that you're not the only one who doesn't quite understand what I'm looking for, and that means that I haven't explained it well enough--which makes it my problem and not yours or the others. And it's entirely possible or even probable that I'm trying to do something that in the real world is just plain impractical. I'll give it one more shot---and don't feel bad if it just makes no sense to you.

Experience over the last few decades has shown that 6-oz glass, doubled on the bottom, is overkill for most tripping with a stripper. Many builders are coming to the conclusion that 4.oz glass, doubled on the bottom, may well be overkill. Michael Storer from Down Under built a pack canoe with balsa strips and 0.75 oz. glass and found it satisfactory for his purposes but dented easily. That's only a fifth of today's 4-oz standard.

I'd like to build as lightly as I can and still have a reasonably good chance of coming home alive. That does NOT mean I can't tolerate scuffs and scratches. NOR does it mean I'll consider myself a failure if I get killed by lightening, or if my canoe gets wiped out by a falling tree in the middle of the night.

If I go ONLY by my own close calls, I'm limited by the one experience described above of running into a just-below-the-surface boulder. That experience suggests that the forward area below the waterline needs more "armor" than other areas. I'd like to hear from others who have had potentially life-threatening experiences that suggest other areas that need extra "armor."

Maybe you haven't had experiences where you paddled away thanking your lucky stars that the boat held, or where it DIDN'T hold and you got away anyway. But if you HAVE had such experiences then I'd like to hear what part of the boat would have benefited from greater strength. I do realize that we can't go out with canoes that will withstand any possible threat. But if many of those incidents form a pattern then it's worth anticipating them by beefing up, or not thinning out, the areas most likely to come to grief.

b


Graybeard

Yeah, I hear that... like I said: Front Thwart to Midships.

I, and most folks here, aren't too familiar with 16 lb 6 Ounce Craft, though.

I indicated your query was a tough one, especially since I am completely
unfamiliar with your Paddling Style, or Risk-Reward Decisions.

And, you are absolutely right. I've never had a Life-Threatening Incident.
Don't plan to allow one either...

I do have to say, and with respect to BK and You, both...
I dont think I'd ever look at Someone Else's Boat Damage to determine
how my Unique Decisions and Methodologies would dictate how those
of Others ought dictate how I ought Design My Boat?

Good Luck, Graybeard. It's a Tricky One, like I said.

Regards

Sundown


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PostPosted: February 11th, 2008, 5:41 pm 
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Greybeard; my sugestion would be to run some CF on the bias (tape) from the bow stem to about 1/3 down the keel line. Most damage I've seen is in that area (split stems, cracked keels from deadheads, or submerged logs or rocks) I hope this answers your question

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PostPosted: February 11th, 2008, 6:12 pm 
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Have you considered some of the more exotic fibres, weaves and resin techniques?

I am going out on a limb to say that the bulk of the weight will be in resin not glass.

If you use a tighter weave than you can usually get away with less weight and less resin. You will need to use a vacuum bagging system though, especially if you are going to layer the tighter weaves.

If you are serious about it, you can contact Andy at composite creations. He will talk for hours about fancy techniques for reduced weight.

He teaches classes on composite fabrication, and does contract work making custom parts for F16s an Stealth Bombers. So he knows a thing or two about high strength to weight ratios.


he posts as CC on this board

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PostPosted: February 11th, 2008, 7:12 pm 
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Location: Vermont
Dan. wrote:
Have you considered some of the more exotic fibres, weaves and resin techniques?

I am going out on a limb to say that the bulk of the weight will be in resin not glass.

If you use a tighter weave than you can usually get away with less weight and less resin. You will need to use a vacuum bagging system though, especially if you are going to layer the tighter weaves......


Yes, I'm considering many possibilities but have actual experience only with E-glass. The Pack boat I'm readying for this Spring uses 2.25-oz E-glass. I'm told that three layers of 0.75-oz glass will have the same strength but will be lighter if well applied because it will achieve a higher fiber to resin ratio. In fact, it was thinking about using 0.75-oz fabric in multiple layers that got me thinking about varying the number of layers in different parts of the boat based on locally anticipated stresses.

Unfortunately a vacuum bagging system is not within my retirement budget. I'm hoping that by wetting out individual layers and squeegeeing them well and then going on to the next layer while still green, will give me a lighter total than a single layer of equivalent fabric weight, though without hope of closely approaching the high ratios that are possible with vacuum bagging.

b

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PostPosted: February 11th, 2008, 7:46 pm 
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Graybeard wrote:
Michael Storer from Down Under built a pack canoe with balsa strips and 0.75 oz. glass and found it satisfactory for his purposes but dented easily. That's only a fifth of today's 4-oz standard.


GB,

I think you may be mistaken here. This list of scantlings for that boat comes from his web site:

Quote:
Scantlings:
(25.4mm to the inch)
Balsa Strips - 7mm (just over 1/4 inch)
Fibreglass cloth - 75gsm (2.25oz) - which looked more like tissue paper - doubled on bottom as per adjacent picture inside and outside
Gunwales - 8 x 14mm
Inwale Spacers - 10 x 6mm
Inwales - 10 x 5mm
Stems inner and outer - laminated to 22mm thick
Keelson - 6 x 8mm hardwood.
Spreader bar - 25 x 25mm

System Three Clear Coat should be good for wetting out those tight-weaved cloths. It is very thin bodied. Lots of guys are using it for the first two coats then switching to the regular resin for the fairing coat. I've use Clear Coat as a finish on fretless bass fingerboards and it is very tough, abrasion resistant and as hard as a rock.

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PostPosted: February 11th, 2008, 8:11 pm 
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Location: Vermont
BK,

You're right about what Mike's website says but I noticed a different spec in another online source and emailed him to find out which was correct. He responded:

Quote:
I got mixed up in the conversion between gsm and oz

I did use 0.75 oz which is OK with careful handling. (0.75 oz comes to around 220gsm - so you can see my mistake)


Good to hear a testimonial from someone I know about System Three resin. I've also given thought to RAKA. Just about anything is likely to be better than the two-decade :o old WEST 105 I used on the current boat. That's not a criticism of WEST. They do say in their literature that it may thicken with age, and two decades certainly qualifies as "age."

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PostPosted: February 11th, 2008, 8:45 pm 
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Location: Geraldton, Ontario Can
Howdy Graybeard!

I've built about a dozen strippers now, and have lots of damage. We use them for our school club, and I have personally used them very hard. I used to build with only a single layer of six ounce cloth. For flatwater tripping and careful use, it was more than adequate. I'm sure a single four ounce cloth would be fine too. However, I always use a double layer of six now, I put a generous football down first before i drape the whole canoe. Most of my damage has occurred on the mid to aft bottom, but especially on about the first few inches of the chine. I found the six ounce just wasn't enough for all around tripping, with rocky take-outs and bouncy rapids. I fetched up once on a submerged log just aft of center, cruising at a good speed with the canoe loaded with weight, and the inner layer of glass actually split for about 18 inches. The outer layer held up, but once the water starts penetrating the inner core, problems occur. Running rapids, a have put pretty good gashes, right through to the wood, in the chine area. And one day, cruising down the middle of a lake, I found a sharp rock with the canoe..it sliced cleanly through the bottom to the wood, but was servicable with duct tape. Anyway, i have damaged these boats lots, and the good theing is they are easy to repair...

And system three is the best, in my opinion, and I have used quite a few different kinds. Clear Coat is so good for wetting out, and also seems to be the strongest and clearest of all the epoxies and resins I have used.

However, on a boat the size of yours, and if you use it carefully, a single layer of four ounce should be just fine. Most places only carry narrow rolls of four ounce, so on a larger boat, it is neccessary to overlap, but that mightnot be a concern for you.


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PostPosted: February 11th, 2008, 9:51 pm 
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RHaslam wrote:
.....Most of my damage has occurred on the mid to aft bottom, but especially on about the first few inches of the chine. ....... Running rapids, a have put pretty good gashes, right through to the wood, in the chine area.


Many thanks for a very helpful response!!!

I need a bit of clarification, though, about word usage that may be different between Canada and the US, or may be that usage has changed over the last thirty years or so, or may be that I am far more familiar with usage pertaining to ocean cruising sailboats than to canoes. To me, "chine" refers to a structural member where a transversly flat bottom meets transversly flat sides, as in a hull built of plywood. Am I guessing correctly that for you "chine" refers to the area of transition between bottom and sides? That seems to make the most sense as the area most likely to be damaged. It's an area that I'm accustomed to referring to as "the turn of the bilge."

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PostPosted: February 11th, 2008, 10:55 pm 
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Location: Geraldton, Ontario Can
Yes, turn of the bilge, that's a good description...that's the area where most of my repairs have been.


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PostPosted: May 9th, 2008, 8:36 am 
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Location: Belleville, ON
My experience is that the kinds of damage you are talking about depends somewhat on the design of the canoe and how it is routinely trimmed in use.

Level trim on a boat with little rocker will have bow stem/transition point impacts moving forward.

Boats with more forward rocker or trimmed bow high will tend to ride up over the front impact and carry the point of most damage to somewhere amidships.

Dan raises some very good points about most of the canoes I've ever seen or used with damage. 95% or more is "wear".

The other 5% is often turn of bilge or the other hard point (bow stem), because anything else is likely going to be a relatively shallow scrape (even if it cuts glass) rather than a potentially serious impact causing failure.

Canoe "liveries" may give a poorer set of data than you think, since there will be a higher proportion of "unskilled" users.

Sorry this isn't likely as specific as you'd like.

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PostPosted: May 9th, 2008, 8:51 am 
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Location: Kanata, Ontario Canada
Graybeard,

our boats see the most wear damage where the paddle is most likely to contact the boat (chine or midline...from the knee to the hip area) if you miss a move and take a rock on, the most abrasive damage occurs if you hit here, otherwise likely a slide off glancing blow.
Hubby's boats always get thin here.....oh and the bow. If it's a less rockered boat another spot is about two feet in from the stern on the bottom where you might hit on a boof coming off a ledge

If you check with ABS canoe manufacture they don't order a uniform sheet of ABS.....it is custom thickness in specific spots for wear.

Esquif canoes does this as i bet do others. Might be a place to look

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PostPosted: May 9th, 2008, 10:25 am 
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Thanks to the posts here and several private communications, a picture is beginning to form for my next build, probably next winter. Overall, I want adequate strength where needed but without adding extra weight where I'm unlikely to benefit from it.

A consideration that I had not given a lot of thought to before, now seems important; that is the shape of the stem. I prefer a boat with minimal rocker but a stem that enters the water at a high angle (approaching plumb) will take a much harder impact than a stem that sweeps into the water at a lower angle. I'm therefore now considering a keel line with my preferred low rocker but that begins a sweep up in the forward 10% to 15% of boat length, transitioning to the stem curve at or slightly above the load waterline. That should lessen the damage from a surprise head-on encounter with a barely submerged obstacle.

For the layup, I'm now considering three layers on the outside. The first, about 4" wide, running right down the keel from the top of the fore stem to the top of the aft stem. The second, the "bottom" layer, would begin about halfway up the fore stem. From there the upper edge would slope down to an inch or two above the load waterline amidships and stay at that level to the stern. The third would be a full layer.

On the inside, two layers; a full layer and a "paddler's floor" layer.
Fabric weight will depend on boat size and target weight overall, but unlikely to be heavier than 2 oz.

Thanks to all who have posted, and don't hesitate to critique or add further experiences and advice

b

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PostPosted: May 9th, 2008, 12:13 pm 
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The layup sort that you describe has the added advantage of increasing rigidity in the hull floor. The sides are best mead rigid with gunwales rather than more cloth.

At least that's my view... Another way to increase the strength with less weight is consider S-glass.

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