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View Full Version : OT Whats a good epoxy for fiberglass repairs?



tattoomike68
08-18-2008, 01:36 AM
I looked around some of the sailing forums but they are dead or they never send you an e mail after you register. I figure some of you folks know about boats and fiberglass.

I am going to rebuild the tillers for a catamaran sail boat so everything made of metal is tight with no slop but some of the fiberglass has damage.

this one is not to far gone.

http://i44.photobucket.com/albums/f24/snoopdog6502/repair1.jpg

This one needs lots more work.

http://i44.photobucket.com/albums/f24/snoopdog6502/repair2.jpg

I figure I can epoxy in a sleeve like nylatron and add a plastic thrust washer to stop the top side wear.

Whats good stuff to use on a boat? Its a Hobie cat 16.

http://i44.photobucket.com/albums/f24/snoopdog6502/Hobie16.jpg

BobWarfield
08-18-2008, 01:55 AM
West Marine has a resin system I'll bet. I use their epoxy, but not for fiberglass. I mix it with sand and gravel and pour it into my machine bases.

Cheers,

BW

HTRN
08-18-2008, 01:59 AM
Uhm, Bob? That West Marine Resin you use IS for Fiberglass.

West Marine has a whole slew of Resins and catalysts, so you can precisely tune the application(IE slow setting, etc).


HTRN

tattoomike68
08-18-2008, 02:15 AM
West Marine has a resin system I'll bet. I use their epoxy, but not for fiberglass. I mix it with sand and gravel and pour it into my machine bases.

Cheers,

BW


Thanks.
Yea a search finds it. I may have to order some out of spokane unless some auto body guys or local boat yards have some. I can get next day freight from there cheap.

Thats the only part of the whole boat that looks shabby and I promised the kid I would take him sailing before school starts so I have to get it done ASAP.

bollie7
08-18-2008, 03:32 AM
Mate
After having spent 5 years rebuilding a fibreglass bodied sports car which included intensive glass work, my suggestion is try and grab book on fibreglass repairs. A good one is called "repairing fibreglass bodied cars" (or something like that) by Miles Wilkins (I think, It'll come to me later.) Im in a hurry now but will try and dig it out a bit later tonight.
With glass repairs if it's not done correctly you may as well not bother at all. Especially in a high load area like the rudder post on your cat.
I have to go now but will try and post a longer reply later. Pics of my car rebuild at this site

www.users.bigpond.com/bollie7/

regards
bollie7

rantbot
08-18-2008, 03:41 AM
For fiberglass-to-fiberglass joints I usually just use fiberglass resin (polyester) as the glue.

Epoxies are good for attaching fiberglass to metal - the polyester resin is not too good for that, as it isn't really an adhesive.

bollie7
08-18-2008, 05:18 AM
I haven't been able to find the book I mentioned earlier but I'm pretty sure of the title and author and also I think it is published by "Osprey Books or Publications"
Also most fibreglass supply places (at least here in Aus) usually have "how to" sheets on various glassing & repair methods. A fibreglass material supply place will almost certainly be a lot cheaper than buying from a boat or hardware place. I haven't done a net search recently but there might also be info there.

When buying materials don't forget to buy some styrene. This is very important to re -activate the old resin so that the new will adhere properly.

regards

bollie7

bob ward
08-18-2008, 06:49 AM
Tattoo, I don't know how much you know about the 2 main fibreglass systems, so forgive me if I'm telling you stuff you know already.

99% of pleasure boats are made from polyester resin, so its odds on that's what you have there, plus the fracture looks like a typical polyester resin laminate fracture. Polyester resin is the resin that has a strong smell and uses hardener at the rate of 1 to 2 parts per 100.

Epoxy resins are 2 to 3 times the price of polyester, which is why most boats are made from polyester resins, but the epoxies do have several advantages. They are stronger, bond to metals and timber better than polyesters, and even bond to polyester better than polyester. (Polyester won't stick to epoxy) Epoxy resin to hardener ratios are typically 3 to 1, 4 to 1, 5 to 1, it just depends on the brand.

For the repair you need to do, being a high stress point, I would be thinking of epoxy resin epecially if you need to bond a bush of some type in there. Any of the woven fibreglass reinforcements are OK with epoxy. Chopped strand mat comes in 2 flavours, emulsion bound and powder bound, make sure you use the powder bound if you go with epoxy. Ask for laminating epoxy for this job.

Resins tend to be sold by weight, I imagine a 1 or 2lb kit would be enough for your job. Avoid chandleries and some boat shops they tend to charge like wounded bulls. Best bet is to find a boat repairer or fibreglasser and take some clean jars for him (or her) to fill.

It will be hard to do that repair and make it look like it hasn't been repaired but if its just a 'muckabout' type boat that won't be important.

oldtiffie
08-18-2008, 07:02 AM
Mate
After having spent 5 years rebuilding a fibreglass bodied sports car which included intensive glass work, my suggestion is try and grab book on fibreglass repairs. A good one is called "repairing fibreglass bodied cars" (or something like that) by Miles Wilkins (I think, It'll come to me later.) Im in a hurry now but will try and dig it out a bit later tonight.
With glass repairs if it's not done correctly you may as well not bother at all. Especially in a high load area like the rudder post on your cat.
I have to go now but will try and post a longer reply later. Pics of my car rebuild at this site

www.users.bigpond.com/bollie7/

regards
bollie7

Hi Bollie7.

I caught the "bigpond.com" and realised that it was an OZ address.

I took the opportunity to read your web-site as I pass the Bolwell factory at Mordialloc (VIC) on my way toward the city and have followed its sinking and resurrection.

I sure am glad I read your site and was - to put it mildly - blown away!! A fabulous effort on the parts of you and your wife.

That sure was (is?) one helluva project - congratulations.

bollie7
08-18-2008, 07:15 AM
oldtiffie
thanks for that. It is now a "was" project for me as I sold it a couple of months ago. Still have the Nagari, which I will do a bit to when I feel like it. Nothing like the other one though. The trouble with having a car that you have put so much effort and time into, is once its done you don't like leaving it anywhere. You are always worried about it. "is someone going to scratch it" etc etc. I'm a bit past the whole car resto thing at the moment, which is why my interest in doing a bit of machining has been rekindled. I really should update my website but there always seems to be something else to do. (like reading forums. LOL)

regards
bollie7

Circlip
08-18-2008, 07:24 AM
Looking at the application Mike, I wouldn't even think of trying to bond a bush into the glass. I'd be inclined to make some propper bearing blocks and brackets to hold the rudders onto the vertical face of the transoms, cut the top parts of the deck back and re model/flare the parts where the glass has broken away. If the existing glass smells like cat pea it's polyester, and watch out for osmosis.
Regards Ian

Swarf&Sparks
08-18-2008, 07:42 AM
Not to forget the Bolwell Ikara Mick ;)
VW engine, IIRC

winchman
08-18-2008, 08:25 AM
The Hobie hulls are made with polyester resin, and that's what should be used for repairs.

In this case the repair is mainly cosmetic. The hinges attached to the lower hull are meant to take the load. Worn hinge pins will cause the type damage seen on your boat.

The 16's are great fun. I used to sail mine all year 'round in SC. I used a 14' mainsail (instead of reefing the 16's main) and a rag jib made from a Windsurfer sail, so I could safely solo it in just about any wind conditions without fear of turtling.

Roger

oldtiffie
08-18-2008, 09:54 AM
Not to forget the Bolwell Ikara Mick ;)
VW engine, IIRC

Well Lin, you really are a well of knowledge of "bl**dy good stuff" and so you are not just a pretty face - or a "Bimbo" - after all!!

I followed that info up - and its NOT OT as it IS about fibre-glass!! - and here it is - good read too - thanks.

http://en.wikipedia.org/wiki/Bolwell_Nagari

For what its worth, as Lin is well aware and alluded to, I had some things to do with another OZ "Ikara" (which had fibre-glass parts too.
http://en.wikipedia.org/wiki/Ikara_(missile)

Swarf&Sparks
08-18-2008, 10:19 AM
Welcome Mick
Though I must admit to some doubts re my failing memory.
After opening my big mouth, I did google, and found confirmation (and consolation) in wikipedia.

To stay on topic, I'm no composite builder but I've worked with a lot of em (top end stuff) and I've been told NOT to use epoxy on run of the mill "fibreglass" repairs (IE, acrylic and mat).

Stick with the acrylic resins and "engineer a solution" to prevent recurring damage.

Again, I'm no composite builder, but I've done the stainless for 'em, and that's pretty well universal among the cognoscenti.

kendall
08-18-2008, 11:28 AM
I normally use MAS flag (brand name) resin, slightly thinner than the 'west system' and slightly cheaper. Normally keep a supply around for everything, I use it for glue, filler etc.
even used as my home brewed 'bondo' when I need something stronger than real bondo.
Also works well for molding odd-ball brackets and other parts, make up a mold with plaster or putty, shred some fiberglass cloth pack it into the mold then fill with the resin, work out the bubbles and instant part. Most are ready to use, some need machining before use.

Epoxy is best for repairs, it gives a much stronger secondary bond, pretty much just needs a clean surface.
Polyester gives it's strongest bond if it's assembled before it's fully cured. Poly finish resin has a wax so it cures (keeps air away) layup resin doesn't have the wax so it doesn't fully cure and additional layers can be applied and maintain full strength. It will still glue things, but the patches can sometimes be pried off with surprising ease.

Ken.

Swarf&Sparks
08-18-2008, 11:42 AM
Sorry if I wasn't quite clear there Ken.
The sort of damage on that hobie (frinstance) would be where I came in.

The composite guys would have already ground that completely away. I would weld and/or machine something in 316 and maybe nylon or acetal, which they would mount, then complete cosmetic repairs to the hull with acrylic.

I don't wish to mislead anyone re hull repairs, as opposed to cosmetic surgery to hide the engineering.

oldtiffie
08-23-2008, 01:47 AM
As there was so much interest in boating and fibre-glass(ing), I thought I'd post this web site about a boat-building enterprise in the Philippines.

The factory manager is a friend of mine who had been sailing almost for-ever. He is a very competent Engineer as well.

He saw the opportunity and took it and has never looked back (ain't coming back either).

The main interest might be how they go about the construction and fibre-glassing.

Its well worth a look.

http://www.melvestmarine.com/home.html

firbikrhd1
08-24-2008, 01:38 AM
I don't claim to be an expert, but I have done some of this type of work on boats. There are a few ground rules, but epoxy will work great. The epoxy I use is made by a company here in Florida called Fasco. They have all kinds of epoxy products and can help with good tech info. Other epoxies should work well too. The fellow that started the company may be retired now but he is a chemist and knows more than most people forgot about his products.

Rule #1: Epoxy will stick to polyester resin but polyester won't stick to epoxy. This means that future repairs in that area will either require the use of epoxy or removal of the epoxy repair made last time. In fact epoxies stick better to more materials than polyesters.

Rule #2: Grind before making the repair. Any resin needs a good clean surface and sticks better to one roughed up with a grinder. Some polyesters actually harden with a wax left on their surface. That must be removed before any repair is undertaken.

Rule #3: Use the correct fabric for the repair and the area to be repaired/ built. This isn't too complicated. Remember that the strength comes from the combination of the resin and the fabric. Air bubbles have no strength. If you use woven roven or cloth in a corner where three surfaces meet or a compound curve, it won't lay flat in that area without making relief cuts and overlapping them. Mat will conform to almost any shape because of it's multidirectional structure, i.e., it isn't woven. It will take more of layers of mat to obtain the strength of the heavier cloth or woven roven. Some say many layers of mat are stronger than either cloth or woven because of the mulitdirectional construction. There are fabrics with rip stops woven into them to be had as well.

Rule # 4: Lots of extra resin doesn't make extra strength. This sort of dovetails to #3 above, but the point is to roll out any extra resin that isn't needed to wet out the fabric. With it will come the air bubbles. Special rollers are available for this work and a cheap chip brush can also be used but not with as good effect. Use a roller if you can find one, they are cheap and work well in most areas.

Rule #5: If possible add additional layers while the epoxy is still tacky from the previous layer. Not too tacky or it will move the previous layer around some, but it's better not to let it fully cure. If it does, grind lightly before beginning again.

Rule # 6: Pretty obvious, butt joint have little strength, Be sure you have ample overlap at joints.

MEK makes a good solvent and evaporates slower than acetone. Don't use it to "thin" resins that have begun to harden before they were used. Weakness will result.

Epoxy can be used on polystyrene foam without melting it, polyester can't.

There are structural foams available today that take the place of wood. They don't rot, are much lighter than wood and are available in various densities and designs for different uses. Some trade names are Divinicel, Clegicel, Corex. There are probably many others today, it's been a while since I've used any. They don't melt with the application of either polyester or epoxy.

Epoxy nor polyester will stick to polyethylene plastic. Don't try to use it to repair that poly gas tank. There are "primers" that will allow it to stick but I can't speak to their longevity as I haven't used them. I believe polyethylene is better repaired by welding. That goes for other plastics too. Check compatability before making the repair.

Epoxies can have different rates of hardning just as polyesters can. Some can be varied by changing ratios of the two parts, within limits. Talk to the manufacturer about that before you try it.

Don't be afraid to work with the stuff, it's really very forgiving. Even if you make a mistake you just grind it away and start again. I have used it to repair the rusted out steel bottom of an A/C unit in an old van I owned. The original had areas rusted away so I used it, waxpaper and cardboard for a form and made the repair. When cured the cardboard and wax paper were removed, the part painted black & it couldn't be differentiated from the original steel part, but never did rust again, and never will. That old 1977 van is still going! Remove the rust before applying the epoxy though, Rust will continue underneath it if you don't, albeit at a slower rate. Eventually it will "grow" and break the epoxy bond.

The things that can be done with this material and system are endless. Just use your imagination and you'll be amazed at what you can do.

Itch: All that grinding will make you itch something awful, particularly if you support yourself in the dust on your elbows or knees or apply pressure to any body part against the dust. If you use a shaving cream with lanolin and smear it all over yourself, rubbing it in before beginning and wear long sleeves and other protective clothing, a lot of that itching will be prevented. Notice, I said a lot, not all. Duct tape rolled backwards over a hand and blotted sticky side to the skin in itchy areas will also help. Cold showers followed by hot also help wash it away. In the worst case scenarios you just itch for a couple of days.

You can use the same fabric with epoxy that is used with polyester resin. You can also use fabric made of Kevlar with epoxy but it doesn't like to be used with polyester. The caveat with Kevlar is cutting it. You would be amazed at how difficult it is to cut with conventional tools.

I was given a demonstration of the strength of Kevlar once that was pretty amazing. One thread of Kevlar and one of polyester cloth were taken from pieces of scrap. A single knot was tied in each and I was told to pull on the ends of each thread until it broke. The polyester had virtually no strength at all and easily parted, I was unable to break the Kevlar. It's amazing stuff when used in the right place with the proper resin.

That about covers what I know. Good luck!