poly or epoxy - SailNet Community

   Search Sailnet:

 forums  store  

Quick Menu
Boat Reviews  
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Hatches and Portlights
Interior And Galley
Marine Electronics
Other Items
Plumbing and Pumps
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here

Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 
Old 10-06-2010
Junior Member
Join Date: Mar 2009
Location: Saskatchewan Can.
Posts: 12
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 0
Hunterdon31 is on a distinguished road
poly or epoxy

I'm repairing my rudder that has several cracks in it. After i've filled all the cracks I would like to wrap it with fiberglass. Now the question is does it matter if I use poly resin or epoxy resin? What kind of fiberglass should I use? Mat or weave? What weight? Any help would be great. After I finish with the fiberglass should I use a epoxy barrier coat. If so how many coats do I need. This is a fresh water boat.

Reply With Quote Share with Facebook
Old 10-07-2010
sailingdog's Avatar
Telstar 28
Join Date: Mar 2006
Location: New England
Posts: 43,291
Thanks: 0
Thanked 10 Times in 10 Posts
Rep Power: 13
sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice sailingdog is just really nice
In general, structural repairs should be done with epoxy, especially if you're not proficient or familiar with polyester and vinylester resins and their use. This is for several reasons.

First, epoxy resins are generally easier to mix and more forgiving of small errors in measurement than polyester/vinylester resins. Most epoxy resins are a 1:1, 1:2, 1:3, or 1:4 ratio and are not dependent on temperature or other variables for changing the mixture ratio, which can be the case with polyester/vinylester resins and their catalysts.

Second, epoxy resins have far greater secondary (adhesive) bonding characteristics than do polyester or vinylester resins. This means that the bond between the repair and the original material will generally be stronger when using an epoxy resin.

Third, epoxy resin is more resistant to water or moisture intrusion, since it is generally less permeable to water than vinylester or polyester resins are. Polyester resins are generally the worst with regards to osmosis or water permeation. Vinylester resins are better than polyester resins.

I would use 6 oz. or 10 oz. cloth, since you're really not trying to build a lot of thickness or strength here. Ideally, you should use a layer or two of kevlar under a couple layers fiberglass, then fair the fiberglass with thickened epoxy. The reason for this is simple—kevlar cloth has very good abrasion resistance and it will make the rudder far more damage resistant than just fiberglass cloth alone. However, kevlar cloth has a nasty tendency to float in most resins and is impossible to sand fair, so putting a couple layers of fiberglass over it is usually necessary.

You shouldn't need a barrier coat, since the epoxy layup is pretty good at resisting osmosis.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Telstar 28
New England

You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

If you're new to the Sailnet Forums... please read this
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Reply With Quote Share with Facebook
Old 10-07-2010
mitiempo's Avatar
Senior Member
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,110
Thanks: 0
Thanked 71 Times in 62 Posts
Rep Power: 8
mitiempo will become famous soon enough mitiempo will become famous soon enough
Use epoxy because it has much better adhesion than polyester. The cracks can be filled with thickened epoxy. Mat by itself has no great strength and most mat is not epoxy compatible. If additional strength is desired use biaxial which is stitched roving with epoxy compatible mat on one side. It is available in different weights. If additional strength is not needed a light to medium weight cloth is all that is necessary. Epoxy is its own barrier coat and after glassing a few coats of straight epoxy is all that is required before bottom painting. Here's a link to West's fiberglass repair manual which is downloadable. Excepting for mixing proportions of the brand you are using it will apply to any brand of epoxy. Fiberglass Boat Repair and Restoration
Living aboard in Victoria Harbour
Reply With Quote Share with Facebook
Old 10-07-2010
pedcab's Avatar
Senior Member
Join Date: Dec 2008
Posts: 192
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 6
pedcab is on a distinguished road
I'd quote both previous fellows.

Whenever your wallet allows for it, go for epoxy...


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Similar Threads
Thread Thread Starter Forum Replies Last Post
High Density Poly davidpm Gear & Maintenance 7 02-24-2009 12:56 PM
Mold west epoxy with poly vinyl sandwich wrap? GBurton Gear & Maintenance 6 03-17-2008 11:39 PM
Varnish, Poly or Epoxy for interior woodworking? scurvy Gear & Maintenance 14 09-17-2007 05:55 PM
1 Party poly over Awlgrip? VIEXILE Gear & Maintenance 3 07-18-2003 09:44 AM
Poly-Propolene, Canvas, or Fiberglass akin_alan Gear & Maintenance 1 01-18-2002 07:04 AM

All times are GMT -4. The time now is 04:46 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.