BWCA Fiberglass...6 oz & 4 oz combo??? Boundary Waters Group Forum: Boat Builders and Repair
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      Fiberglass...6 oz & 4 oz combo???     

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amhacker22@hotmail.com
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08/17/2009 01:31PM  
Hello everyone.

I am wondering if anyone has tried using 6oz glass on the hull exterior and 4oz for the interior. It seems like a great way to cut some weight, but I'm wondering if it leaves the hull overly susceptible to oil-canning. The boat I'm building is pretty wide with a 36in maximum beam.

Any thoughts or experiences to share?

-Nick
 
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Cedarboy
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08/17/2009 04:06PM  
4 oa vs 6 oz in a 17 footer will only save you about 10-12 oz, not much. More important is resin lay down to save wt. Yes oil canning can be issue with wider boats. Stay with 6 IMO. CB
 
Woodbender
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08/18/2009 09:24AM  
Yup - I gotta agree with CB.

I was told by Al at NorthWest Canoe Co. that handling 4oz w/ epoxy is like handling wet nylons. Handling nylons on occasion does not bother me but I wouldn't use only one layer of 4oz inside.

Some kayak builders do this but for a canoe your size go with CB's recommendation.
 
amhacker22@hotmail.com
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08/24/2009 09:59AM  
Thanks for the replies.

I'm still on the fence. I got a pretty good deal on some 4oz and I'd like to use it if I can. I may give it a shot and risk adding another reinforcement layer if it does end up being a problem. I'm also thinking of reinforcing it with a few strategically paced extra pieces or layers. I still have to fair out the inside of the hull, so I've got some time to think about it.

I'll let you know how it goes.

-Nick
 
08/24/2009 11:23AM  
Can't remember which book I read, but it suggested an extra 'football' shaped piece of glass. I'm really struggling here, but I think he put it on the outside of the hull first and then covered it with a full layer.
 
amhacker22@hotmail.com
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08/24/2009 01:24PM  
jdevries, I think the Gil Gilpatrick book suggests that method.

The 6oz/4oz combo approach was suggested to me by the guys at Ketter Canoeing. They thought the reduced amount of expoxy necessary to fill in the 4oz glass would cut about 5lbs off of the finished boat. We discussed the dimensions of the boat, and they didn't seem to think I would have an oil canning problem. I wasn't really concerned about it until I took the hull off the forms and saw how easily I could press it down without any glass/epoxy on the interior. I realize it will stiffen up quite a bit when I add it, but it was still surprising.
 
amhacker22@hotmail.com
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09/13/2009 09:53AM  
Well I glassed the inside yesterday and I did use the 4 oz. I didn't find that the 4oz was that much more difficult to work with than the 6 oz. When I initially set it down it was a struggle to get it down neatly, but once the glass itself was wetted out it was not bad to work with. SInce I was working solo I did cut the glass into several strips (illustrated in the NW Canoe build book) so that may have minimized the difficulty of working w/the 4 oz. To avoid oil canning I overlapped the pieces by a few inches to create several ribs, and I also doubled up the cloth strips at the bottom of the middle 3rd of the boat to make kind of a default football. Overall I'm pretty happy with it, although I'm hoping I'll be able to sand down the seam of the cloth to minimize the appearance of the cloth edges. Some of them got kind of sloppy with stray fabric threads. I'll put some pictures up one of these days when I can get the boat out of the garage and into the light.

Thanks for all your input. I'm guessing you'll probably se some posts over the next week asking for help on gunwales, seats, decks, etc.
 
TOAD
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05/05/2010 12:10PM  
Ever thought about using Kevlar? It's excactly like fiberglass but alot stronger, so you are able to use a lighter weight. You could probably use a 2 oz and be stronger then a 4 oz. Try contacting expresscomposits.com I think that's how you spell it. They would know the best way to do it and save weight.
 
amhacker22@hotmail.com
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05/06/2010 06:00AM  
It never occurred to me, but I'm certainly open to it. Would Kevlar be able to go on clear?
 
TOAD
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05/09/2010 02:41PM  
The Kevlar won't be perfectly clear, I guess I never thought of that. Everything I have used Kevlar on always gets topcoated with a color so I have never had a chance to sand and polish it to see how it looked. I imagine it would look like a new Winohna light canoe. Hey where did you get the plans for the conoe. I'm looking to build a solo for myself. My checkbook says I can't buy a new one.
 
Cedarboy
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05/09/2010 08:35PM  
Kevlar cloth on a stripper will look like shiney kevlar cloth after it is wetted out. It does not go clear like fiberglass. Stop by NWC somtime and look at the inside of one of their NorthBoats. They are using kevlar and diamonds of carbon vacumn bagged over foam cores on the inside of these 24 footers. It makes for a very,very stiff boat. So much that they dont have to use thwarts. These are high tech strippers to say the least.
CB
 
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