Fibreglass weight inside vs outside

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kent
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Type of boat I like: Trapper 15-38

Fibreglass weight inside vs outside

Post by kent » Wed Sep 24, 2014 9:06 am

Hi there.

Just ordered the plans for the trapper 15-38 and waiting for them to arrive.
Whilst planning out my materials I'm wondering what weight fibreglass cloth to use.
Ideally I would like quite a heavy duty boat. On the rivers here in New Zealand where I will be using it there are occasional rapids which arent too big (most the time). But they are quite remote and isolated, so if I broke the canoe its a really long walk out.
I was thinking about using either 10oz or 2 layers of 6oz glass on the outside for strength and abrasion resistance, but is it still necessary to use something that thick on the inside too? or just stick to 6oz?

Lookin forward to it arriving!

Regards, Kent

makenmend
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Re: Fibreglass weight inside vs outside

Post by makenmend » Wed Sep 24, 2014 10:29 am

Kent I do pretty much the same with my boats and 6oz cloth has worked well for me, I also like to epoxy/graphite coat the bottom of my boats,I feel this helps and after a river trip it's easy to see if a touch up is required or not. if it is it only takes minutes and a small amount of epoxy/graphite plus some drying time and your as good as new (maybe better).

MM

LesForgue
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Re: Fibreglass weight inside vs outside

Post by LesForgue » Wed Sep 24, 2014 11:36 am

Kent
from what I've read on this forum, seems like the extra layer would better protect from smashes if it were on the inside rather than the outside. Are you more concerned with smashing into rocks, etc, or with abrasion damage?

Looking forward to future post from you on your build, as I myself am (painfully slowly) building Matt's Jem Trapper 15-38.
Got the plans and plywood and drew the cut out lines for 3/4 of the panels over 2 years ago, and just now about ready to put the saw to the cut out lines. haven't even ordered the epoxy and fiberglass yet. (had major issues with my work space).

Take care.
Les (Chicago, North America)

tx river rat
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Re: Fibreglass weight inside vs outside

Post by tx river rat » Wed Sep 24, 2014 12:06 pm

I agree with Makinmends 6 ounce inside and out ,I also double the cloth on the outside front and rear for about a ft to be a wear strip.
Ron

kent
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Re: Fibreglass weight inside vs outside

Post by kent » Wed Sep 24, 2014 1:06 pm

Thanks for the advise, it would mainly be for smashing against rocks more than abraision.
I find it counter intuitive that you would double the inside glass to make it stronger but you lot are the experts.
Would be interested to hear from anyone who has done this.

I'm planning on doing a build log with lots of photos, seeing others builds helped inspire me so might as well do the same.

Regards, Kent

LesForgue
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Re: Fibreglass weight inside vs outside

Post by LesForgue » Wed Sep 24, 2014 1:21 pm

kent wrote:Thanks for the advise, it would mainly be for smashing against rocks more than abraision.
I find it counter intuitive that you would double the inside glass to make it stronger but you lot are the experts.
Would be interested to hear from anyone who has done this.

I'm planning on doing a build log with lots of photos, seeing others builds helped inspire me so might as well do the same.

Regards, Kent

Kent, Yes there are experts on this forum, but me I am not one of them. Nevertheless, when a rock and the hull do not agree, it has to do with the hull's outside suffering compression (less likely to break it), while the hull's inner side suffers from forces trying to expand it (more likely to break it).

tx river rat
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Re: Fibreglass weight inside vs outside

Post by tx river rat » Fri Sep 26, 2014 12:14 am

Somewhere there is a long discussion on this.
The outside compresses when you hit something , which isnt very strong the inside has tension the more pressure you put on it very strong.
The outside is for wear the inside is for strength.
Take a steel wire and try to bend it then tie both ends and see how hard it will bend ,same principle. You can take a 1/4 rod and pick up a car with it but you cant push 20 lbs with it.
Ron

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jem
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Re: Fibreglass weight inside vs outside

Post by jem » Sat Sep 27, 2014 6:46 am

If you're using good quality marine ply, then smashing a hole is less likely.

Graphite the exterior abrasion areas helps. You could also add an additional layer of cloth on the inside.

Better yet, avoid those rocks! :lol:
-Matt. Designer.

kent
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Re: Fibreglass weight inside vs outside

Post by kent » Mon Sep 29, 2014 2:17 am

Thanks for the help guys.

I think I will go with 6mm Gaboon.

Also here in New Zealand I cant seem to find any fibreglass cloth that is 1.5m wide, all the stuff here seems to be 1m instead.

But I think this will actually work better.

I will do a layer of 200gm per side with a very generous overlap in the middle both inside and out.

Cant wait till the plans arrive...

Regards Kent

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