It is currently November 20th, 2019, 9:00 pm

All times are UTC - 5 hours




Post new topic Reply to topic  [ 10 posts ] 
Author Message
PostPosted: May 10th, 2006, 12:04 pm 
Offline

Joined: May 7th, 2006, 6:57 pm
Posts: 3
I have acquired a fiberglass canoe (home built) based on the Osprey design. It is underbuilt i.e. weighs only 26.6 lbs w/o gunwales and seat. The sides appear to be only one layer of fiberglass thick. There are ribs glassed in on the interior and what appears to be a core on the bottom. Generally the canoe is fairly stiff with the exception of the sides. I am sanding the primer/paint from the exterior of the hull with 80 grit and plan on adding a layer of 6 oz fiberglass over the entire hull to strengthen it. Am I on the right track? Should I use polyester or epoxy to wet out the fiberglass? What system is best to use? I have moderate fiberglass experience with car parts. Any and all advice is appreciated. I want to do this as well as I can.

Thanks in advance.

p.s I see that this design was created by John Winters, nice job, beautiful lines. I can't wait to get it into the water.


Top
 Profile  
 
 Post subject:
PostPosted: May 10th, 2006, 2:44 pm 
Offline
User avatar

Joined: June 22nd, 2001, 7:00 pm
Posts: 1268
My advise is to use epoxyy. Epoxy will stick to anything, polyester only sticks to itsself.

Why do you want to add another layer? Is the canoe not useable in it's current form? How flexible are the sides? Have there been any delamination?

_________________
Solo canoes and single blades, with a sail for those windy days...

...........O
......(___|/____)
.........../


Top
 Profile  
 
 Post subject:
PostPosted: May 11th, 2006, 5:24 am 
Offline

Joined: May 9th, 2006, 5:28 am
Posts: 4
My only experience is with woodstrip\epoxy construction, so bear with my limited knowlege.
The hull is made entirely of fiberglass? Not glass over some other material? The inside of the hull is glassed, too? I'm just attempting to get this straight. The only canoes I've ever seen up close have been plastic or wood strip\epoxy.
Anyway, if you want to toss a layer on the outside I would suggest using 4Oz cloth and West System epoxy. Other boat builders use MAS epoxy. I've used the WS in both my boats and it's easy to work with. You will want to make sure that whatever you're bonding to will "key" with the fiberglass\epoxy, otherwise you will have a very hard mess.
A picture might help.


Top
 Profile  
 
 Post subject:
PostPosted: May 11th, 2006, 11:45 am 
Offline

Joined: May 7th, 2006, 6:57 pm
Posts: 3
jjoven: the canoe is usable but I think that if I came up aginst something hard that the sides would crack. It is only one layer thick. I am only using it in calmer water. There isn't any delamination.

Farmpunk: the canoe is made entirely of fiberglass. Without the gunwales the sides are extremely flexible.


Top
 Profile  
 
 Post subject:
PostPosted: May 11th, 2006, 12:45 pm 
Offline
User avatar

Joined: June 22nd, 2001, 7:00 pm
Posts: 1268
Well then, you may find 4 oz glass isn't enough to strengthen the sides. You need to build the mils to obtain stiffness.

Wonder what the filler is in the bottom? Foam sheet?Balsa?

Knowing more I now agree with your original idea of another full sheathing of 6 oz., BUT you can get a stronger and lighter laminate if you make it 2 layers of 3 oz with one laid on the diagonal.

Or why not use carbon cloth? Stiffer and lightert han glass. It is getting hard to buy though.

_________________
Solo canoes and single blades, with a sail for those windy days...

...........O
......(___|/____)
.........../


Top
 Profile  
 
 Post subject:
PostPosted: May 11th, 2006, 2:27 pm 
Offline
User avatar

Joined: June 9th, 2005, 2:27 pm
Posts: 1640
Location: Saskatoon
jjoven wrote:
.... Or why not use carbon cloth? Stiffer and lightert than glass. It is getting hard to buy though.


Though it is stiff, CF cloth is pretty expensive isn't it? Also, it's my understanding that unless you are able to use vacuum bagging techniques to remove all excess epoxy, the weight difference is not that substantial. I've never worked with carbon fibre so what I said above is strictly based on my impressions from what others have written. Another factor, is low impact & abrasion resistance according to some info posted at One Ocean Kayaks website.
Quote:
Carbon has the highest Modulus of Elasticity (stiffness) of all boatbuilding fibers. The fibers are very strong in both tension (three times that of steel) and compression. It has about 60% of the density of fiberglass but is slightly heavier than Kevlar. Carbon fabric is very easy to work with and in many respects, it handles like plain fiberglass. The disadvantages are poor sheer strength ( low impact and abrasion resistance). Graphite fabrics are best included in protected areas where strength and stiffness are very important.


By the way, without gunnels, most fiberglass canoes would be pretty flimsy. In woodstrip boat building, we normally fill the weave with epoxy (it's clear so the wood shows through). Since you're familiar with auto parts and will probably be painting afterwards, maybe bondo type filler would be more appropriate.

Just my thoughts.
Bryan

_________________
Bryan's website - http://pawistik.net
ColdspringPaddling.com
Image


Top
 Profile  
 
 Post subject:
PostPosted: May 11th, 2006, 2:38 pm 
Offline
User avatar

Joined: June 22nd, 2001, 7:00 pm
Posts: 1268
Yes carbon isn't cheap, and thx to Bushs' War it's harder to obtain. But it is the lightest and most stiff fabric for laminations.

Vacumn bagging would be nice, but probably beyond this project. Judicious use of epoxy resin is called for no matter what is used.

I would place it inside to alleviate your abrasion fears(and in accordance with Ocean Ones recommendation above).

" Graphite fabrics are best included in protected areas where strength and stiffness are very important."

_________________
Solo canoes and single blades, with a sail for those windy days...

...........O
......(___|/____)
.........../


Top
 Profile  
 
 Post subject:
PostPosted: May 17th, 2006, 5:33 pm 
Offline

Joined: August 11th, 2005, 9:30 am
Posts: 24
Location: Barrie, Ontario
Carbon would certainly be stiffer, but is getting quite expensive again. Another suggestion is S-glass, which is as easily worked as ordinary e-glass, but significantly stronger and stiffer. Shouldn't cost a fortune, either. It will have the optical properties of regular glass when laminated (ie, it turns clear) so that you could verify a good, void free wet out. Keep in mind that epoxies will have to be painted (poor UV reistance). It's true that a single layer of glass is not very stiff by itself but you only need to increase thickness a fraction to double stiffness (in oversimplified terms, the stiffness of a laminate is proportional to it's thickness cubed).


Top
 Profile  
 
 Post subject:
PostPosted: May 18th, 2006, 6:48 am 
Offline

Joined: September 28th, 2004, 6:52 am
Posts: 442
If the inside of the boat has not been painted it makes more sense to add extra glass inside. That way you won't have to do a lot of finishing to get things smooth. If the boat was painted inside you might try removing the paint with one of the environmentally friendly paint removers being careful to flush teh boat out well with water afterwards. Do not use the methylene chloride based removers as they eat fiberglass like kids eat hamburgers.

The nice thing about doing it on the inside (besides being less work) is that you can add some glass, check the stiffness and then add more if you need it. Also you can add it in local patches. For example you could run a 6" strip down the sides only if you thought the bottom was stiff enough or maybe just stiffen the middle half of the boat. Lots of flexibility (sorry about that) in what you do that way and yuo can keep the weight down.

Hope you enjoy the boat after you get it stiffened up.

_________________
Cheers,

John Winters


Top
 Profile  
 
 Post subject:
PostPosted: July 14th, 2006, 8:54 pm 
Offline

Joined: May 7th, 2006, 6:57 pm
Posts: 3
Great advice, thanks all!
I'm. still working on it, hard to find time must make it or it will be a winter project.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 10 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 11 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group