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Fri Sep 12, 2014 4:49 am

Planning on doing some fiberglass repair,what type of resin should I use,epoxy resin or polyester?I understand that poly don't set as quickly as epoxy,but epoxy sticks better.

Fri Sep 12, 2014 5:11 am

Cure time is not really an issue as it depends on quantity of catalyst and ambient temperature. These can be adjusted easily.

For car body repairs just use polyester resin as it is much cheaper and works just as well. If you feel you need a little more strength just add a few more layers of matting. Pre cut all the matting before mixing the resin to give you maximum time to work. Switching between layup and cutting is bad and you can get in a real mess.

Epoxy resin is generally used for more specialised structural designs where strength / lower weight is more important. Epoxy is generally considered stronger, but in fibreglassing strength is mainly dependant on the shape of the design and how well the fibreglassing is done as it often fails across air voids/ around holes or delaminates due to bad layup.

Fri Sep 12, 2014 5:26 am

I've always used a pre-mixed filler for regular repairs, saves a lot of messy mixing and laminating...

Fri Sep 12, 2014 6:23 am

I have always used poly resin from my local Home Depot...and I have done some extensive repairs.

If you are doing aything other than light patching a great investement is a fiberglass roller. I have used the old paintbrush method but a roller makes it stronger (less trapped resin) and easier to finish.

Fri Sep 12, 2014 7:17 am

I have always followed the philosophy of making repairs with same or like materials as original build.... Since body is most likely a resin cloth/mat layup, my preference would be resin...

Also with many repairs be sure you grind away old oxidized resin /cloth materials at crack or holes and create a wide feather edge , giving a new clean wide surface for repair to bond to..... Be aware that some body fillers will shrink over time on fiberglass... It's really disheartening to find a year or two after paint job the filler has shrunk and you have a divot or dimple where repair was made....I generally like to have repair stand proud of surrounding surface and grind/sand it down to same level as surrounding surface using as little fillers (or no filler) as possible... The is also filler materials you can add to your resins to make a filler "paste" the can be used to fill small voids and what ever without having to resort to "body putty" fillers...

Dale

Fri Sep 12, 2014 9:56 am

Polyester resin is ideal and easy to work with. I love epoxy for it's strength, but it's expensive, cures slowly and is more difficult to sand. You also have to be careful to remove amine blush from many epoxies and that adds an additional labor intensive step. Hardware store or boatyard resin will work, but the materials used for surfboard repair are more specialized and will make the job easier and finish nicer. Use laminating resin for big lamination jobs, and sanding resin for finish work that you will be sanding. It has a wax additive, and it allows easy sanding. Laminating resin will not cure hard and quickly gum up your sandpaper. Most of these resins are also available in UV cure formulations, which give you plenty of working time (out of direct sunlight) and cure with UV (sunshine). Do your lams in the garage, then roll it out in the sun and watch it cure to a sandable state in 15-20 minutes. A great source for laminating supplies of all types is http://fiberglasssupply.com/
Good prices, great telephone customer service and fast shipping. I live in a surfing town, but I get all my glassing supplies from these guys.

Fri Sep 12, 2014 2:10 pm

Thanks gents.I'll go with the polyester with fiber strand cloth.Here are a few pic of what I'm into.
Thanks again.

Fri Sep 12, 2014 2:15 pm

I have cut out around some of the cracks with a box knife,now to sand it down to a long taper and get the hole filled.body has a LOT of stress cracks in the gel coat which I will be sanding down to the fibers and recovering with poly resin.

Fri Sep 12, 2014 2:28 pm

I wouldn't just use resin. It is really not a good thing to just use as a "skim coat" material.

Fri Sep 12, 2014 2:38 pm

What would you recomend,a fiberglass based filler?

Fri Sep 12, 2014 4:26 pm

For large repair areas you may want to start from inside and work out.. Specially if big rip or chunk missing..... I have taken to grinding (feather edge) both inside and outside of a break... Put a heavy layup of masking tape across break (on front side) so wet resin/cloth has a form to shape to for first layup.... Have used a board screwed to (through) body panels to hold panels in alignment (on front side) and do first layup from inside, most likely two or three layers of mat.... Once first layup cures remove screws and board and tape, and you have the repair area "bridged" and a solid surface to do final layup from front side... Be sure to wash new glass area with acetone to remove an sticky residue from tape before continuing ... For smaller repair areas you may not need to use the board (support ) method and just tape method for support for initial layup... If body or hood had some large nasty gaps to repair, you may want to have it upside down so "inside" is more accessible... Remember inside repair is first step... Rest of repair (outside) should be second step as it is the one that will be presented to the world.... Also strength is in cloth/mat, not resin, resin just makes it rigid... Excessive resin where mat/cloth "floats" is not best repair... Use minimal resin to just wet the glass material...

Anyway this is method the works for me...

As mentioned also above resin and catalyst mixture is temperature sensitive, so only mix amount you can use (in disposable container) according to ambient temperature ... catalyst and resin contain should have chart with drops per oz of catalyst per specific temperature , follow instructions...

And once mixed resin/catalyst start to get thick and like jello, STOP, you are DONE....

Also helps to have you materials (mat or cloth) precut for shape of repair, if you have any resins on your hands and try to pick up scissors to cut material you will have a unbelievable mess on your hands...

Also consider all tools and containers and brushes and clothing as disposable, once resin cures on whatever its there forever.... Use drop cloths on shop floor if you do not little bead of hard resin on floor... Have can or open container with some acetone in it available so any brushes or tools you use can be cleaned (washed) BEFORE resin sets up...

Didn't meant to be so long winded, but want you to know what you re getting into.... It's not hard materials to work with if you follow ITS rules (instructions)... BUT it can get messy...

Also until you understand how it works, try small repair areas first, trying to do to much (many areas) at one time can cause you to just waste materials...

IF you do you layups to where the repair stand above surrounding areas you should not need any filler (yeah right) once you sand it off.... Many different fillers materials available that can be mixed in resin to create a filler... Even "Bondo" (type products) can be used for final surface, I would just keep it to a minimum as possible...

Dale

Fri Sep 12, 2014 5:12 pm

Good advice above, follow it. Also, note that cloth is strongest but thinnest in terms of filling gaps, then woven roving and finally strand mat. I like cloth for initial layers, with roving or mat under for extra strength and thickness. For cloth, if you can make a wet out table (something smooth covered with sheet plastic) so that you can cut your cloth, wet it out, then squeege out excess resin. You will minimize resin waste, have fewer drips and runs and get a stronger bond. Get a box of chip brushes, and pull loose bristles out with tape before using. Also get a few rubber (not plastic) squeegees from Fiberglass Supply for wetting out material. The less air you entrain in the lam, the less sand and fill you will do on the next layer. Also, when feathering out patch area, use 80 grit to give host area some teeth. Lots of good resources and videos out there, and the surfboard repair and build guys have glass and resin down to a science. It all translates, and there are some good techniques that will make you job easier. Do a search here for more specifics http://www.swaylocks.com/forum/1000005

For final smoothing and filling of chips and scratches, use polyester based automotive body filler (like bondo) and red lead for the fine stuff before primer.

Another good resource for cloth, resin and laminating supplies is a specialty plasctic outfit like Tap Plastics or Plasticraft. Do a google search for one in your area. The Home Depot stuff is crap and the West Marine stuff is good but grossly overpriced. Surf shops that cater to home shapers have good stuff and reasonable prices.

Fri Sep 12, 2014 6:41 pm

Most big box stores do not stock laminating or sanding resins, they stock something inbetween..... I was able to find local fiber class repair specialist who would sell me small volume (quarts) from his bulk drum .... If you want sucess be sure to get "laminating resin" (verify lable on can) for your major work..... You only need one application of "finishing resin" (verify label on can) as final coat to cause proper hardening of glass layup.....

Dale

Fri Sep 12, 2014 7:38 pm

Hoping to start my fiberglass repairs soon so I will be watching this thread. I did pick up the West Marine product guide and one of their boat repair books.

Sat Sep 13, 2014 8:04 am

A repair made with big box store resin and matt. Done by me in my garage

Simple fiberglass dunebuggy repairs can be as simple, or as complicated, as you choose to make them. As with anything else they can be over thought and over executed.

Todays quality fillers are nothing like the past. They are extremely flexible (they can be used on bumper covers), have almost no shrinkage, and sand very easily.

I said it once before, but I think its worth mentioning again....a simple fiberglass roller is far superior to the disposable brush method for finishing your work. It virtually eliminate air pockets, resin blobs and also provide superior adhesion. Invest in one before you consider investing in expensive epoxies.

Sat Sep 13, 2014 11:40 am

I use the kitty hair on small repairs and on the larger stuff Polyester and mat
Buy the stuff from E bay and Home depot both seem to work for me