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Author Topic:   Fiberglass Repair

DavidBrent posted 05-10-2010 09:32 PM ET (US)
After reading several threads on fiberglass repair, I have a question about repair of fiberglass damage resulting from tire rub due to a broken axle. The tire rubbed through the plastic fender onto the hull. The tire rub removed an arc of up to 1/4 to 5/16-inch fiberglass on the chine. The length of damage is about 10 inches. After inspection, it appears that the fiberglass was not breached as I did not see or feel any foam. (I poked the area with a screwdriver.)
What is the best method to repair this damage?
Is the area of damage too large for this polyester gel or gel coat method described here:
http://continuouswave.com/ubb/Forum3/HTML/016540.html

Thanks!
Peter
jimh posted 05-10-2010 10:39 PM ET (US)
If the damaged area is right at the chine line, you may find that the thickness of the gel coat layer is greater there than in most areas of the hull. This is from a tendency for the gel coat layer to build up in that area as it is sprayed into the mold. Usually the gel coat layer is quite thin, perhaps only 0.020-inch thick. When the gel coat layer gets built up to greater thickness, it tends to get brittle, and pieces can crack off.
Repairs techniques are described in two excellent articles in the REFERENCE section:
Repairing Hull Damage the Whaler Way
http://continuouswave.com/whaler/reference/whalerRepair.html
Instructions--Hull Patch Kits
http://continuouswave.com/whaler/reference/repairInstructions.html
In making a repair, you should try to avoid applying gel coat resin in a thickness that will be too great. If the repair needs to be filled in to any depth at all, it is best to fill the damage with other material than pure gel coat resin. Making a thick repair with pure gel coat resin may result in the repair being brittle and cracking later.
tjxtreme posted 05-10-2010 10:41 PM ET (US)
That appears to be a method for improving the shelf life of matched gelcoat, and not its application. You can of course make as much as you need, so that area won't be too large.
Its hard to say what method to use to apply the gelcoat without seeing pictures, but generally speaking if the fiberglass is still in good shape you can just gelcoat following the standard method and be all set.
burning_hXc_soul posted 05-11-2010 08:48 AM ET (US)
If the area isn't that large and you don't feel that the fiberglass was damaged underneath the surrounding gel coat. You could just sand it down to roughen the edges, and use fiberglass strand Bondo to build it up, then sand it down below the surrounding gel coat and then gel coat the damaged area. If the structural integrity of the fiberglass was not compromised, I personally wouldn't make it into a major repair. Some people are a little bit more [deleted--unclear] than I am though.
jimh posted 05-11-2010 08:49 PM ET (US)
To put the concept more simply, use gel coat resin like a paint. Do not use it as a structural filler or adhesive.
Jeff posted 05-12-2010 12:42 AM ET (US)
Well since you are referring to my post on gelcoat material mixing options, I will say I have used the mixed combination outlined in the linked thread along with fiberglass mat to repair a large area. Actually on a larger area than what you seem to have outlined.
The addition of the polyester gel allows you to use the mixture in a larger repair situation. Adding some fiberglass mat or Cab-o-sil (for smaller fixes) will provide the mixture with the added structure to create solid repair. Of course could just use epoxy and mat as well. Either way once you fill and sand the area smooth you will want to recoat with gelcoat. I have used the same mixture as above and applied it by using a high quality brush or even a very fine foam roller. If you are going to use straight liquid gelcoat I would spray it on. Once the new gel coat is applied you will wet sand the area smooth and polish it out.
Remember to prep the damaged area well by sanding the chipped area and some area just around with with heavy 80 - 100 grit sand paper. Once sanded I clean the area with acetone or Lacquer thinner. This will provide a quality surface for the repair to bond to.
DavidBrent posted 06-23-2010 11:35 PM ET (US)
(Late) thanks for your replies...I finally got down to business 2 weekends ago. I'm using West System epoxy. My first application went well and sanded out well, but I did not build out the repair far enough, there was still roughly 3/16" depression in a part of the repair. So I went back in last weekend to lay in more fiberglass and hope to sand it sometime this week. I will check in when I am done. I have some reservations about gelcoating in regards to purchasing a large quantity for a relatively small repaiir (~1-1.5 sq. ft) and color matching. I'm going to research this more now. I appreciate any advice.
modenacart posted 06-24-2010 07:03 PM ET (US)
It is usually not advised to use epoxy when you are going to gelcoat over it.
Plotman posted 06-25-2010 01:06 AM ET (US)
Gelcoat over epoxy works fine, you just have to clean it first. Soap and water, rinse, dry, then wipe with acetone.

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Author	Topic: Fiberglass Repair
DavidBrent	posted 05-10-2010 09:32 PM ET (US) After reading several threads on fiberglass repair, I have a question about repair of fiberglass damage resulting from tire rub due to a broken axle. The tire rubbed through the plastic fender onto the hull. The tire rub removed an arc of up to 1/4 to 5/16-inch fiberglass on the chine. The length of damage is about 10 inches. After inspection, it appears that the fiberglass was not breached as I did not see or feel any foam. (I poked the area with a screwdriver.) What is the best method to repair this damage? Is the area of damage too large for this polyester gel or gel coat method described here: http://continuouswave.com/ubb/Forum3/HTML/016540.html Thanks! Peter
jimh	posted 05-10-2010 10:39 PM ET (US) If the damaged area is right at the chine line, you may find that the thickness of the gel coat layer is greater there than in most areas of the hull. This is from a tendency for the gel coat layer to build up in that area as it is sprayed into the mold. Usually the gel coat layer is quite thin, perhaps only 0.020-inch thick. When the gel coat layer gets built up to greater thickness, it tends to get brittle, and pieces can crack off. Repairs techniques are described in two excellent articles in the REFERENCE section: Repairing Hull Damage the Whaler Way http://continuouswave.com/whaler/reference/whalerRepair.html Instructions--Hull Patch Kits http://continuouswave.com/whaler/reference/repairInstructions.html In making a repair, you should try to avoid applying gel coat resin in a thickness that will be too great. If the repair needs to be filled in to any depth at all, it is best to fill the damage with other material than pure gel coat resin. Making a thick repair with pure gel coat resin may result in the repair being brittle and cracking later.
tjxtreme	posted 05-10-2010 10:41 PM ET (US) That appears to be a method for improving the shelf life of matched gelcoat, and not its application. You can of course make as much as you need, so that area won't be too large. Its hard to say what method to use to apply the gelcoat without seeing pictures, but generally speaking if the fiberglass is still in good shape you can just gelcoat following the standard method and be all set.
burning_hXc_soul	posted 05-11-2010 08:48 AM ET (US) If the area isn't that large and you don't feel that the fiberglass was damaged underneath the surrounding gel coat. You could just sand it down to roughen the edges, and use fiberglass strand Bondo to build it up, then sand it down below the surrounding gel coat and then gel coat the damaged area. If the structural integrity of the fiberglass was not compromised, I personally wouldn't make it into a major repair. Some people are a little bit more [deleted--unclear] than I am though.
jimh	posted 05-11-2010 08:49 PM ET (US) To put the concept more simply, use gel coat resin like a paint. Do not use it as a structural filler or adhesive.
Jeff	posted 05-12-2010 12:42 AM ET (US) Well since you are referring to my post on gelcoat material mixing options, I will say I have used the mixed combination outlined in the linked thread along with fiberglass mat to repair a large area. Actually on a larger area than what you seem to have outlined. The addition of the polyester gel allows you to use the mixture in a larger repair situation. Adding some fiberglass mat or Cab-o-sil (for smaller fixes) will provide the mixture with the added structure to create solid repair. Of course could just use epoxy and mat as well. Either way once you fill and sand the area smooth you will want to recoat with gelcoat. I have used the same mixture as above and applied it by using a high quality brush or even a very fine foam roller. If you are going to use straight liquid gelcoat I would spray it on. Once the new gel coat is applied you will wet sand the area smooth and polish it out. Remember to prep the damaged area well by sanding the chipped area and some area just around with with heavy 80 - 100 grit sand paper. Once sanded I clean the area with acetone or Lacquer thinner. This will provide a quality surface for the repair to bond to.
DavidBrent	posted 06-23-2010 11:35 PM ET (US) (Late) thanks for your replies...I finally got down to business 2 weekends ago. I'm using West System epoxy. My first application went well and sanded out well, but I did not build out the repair far enough, there was still roughly 3/16" depression in a part of the repair. So I went back in last weekend to lay in more fiberglass and hope to sand it sometime this week. I will check in when I am done. I have some reservations about gelcoating in regards to purchasing a large quantity for a relatively small repaiir (~1-1.5 sq. ft) and color matching. I'm going to research this more now. I appreciate any advice.
modenacart	posted 06-24-2010 07:03 PM ET (US) It is usually not advised to use epoxy when you are going to gelcoat over it.
Plotman	posted 06-25-2010 01:06 AM ET (US) Gelcoat over epoxy works fine, you just have to clean it first. Soap and water, rinse, dry, then wipe with acetone.