Hand laid part blog post to read before asking a question.

Vumad

Vumad

Super Hero, with a cape!
Location
St. Pete, FL
Great blog post by fiberglass coatings inc. they are local to me an have taught me most of what I know. This is great info if you plan to make a mold and part, use my on-the-part method of repair or even if you are making a repair without a mold (can just skip a few steps).

This is one of their best blog posts. You can follow them on Facebook as Fiberglass Coatings Inc and can also be used as a supplier.

https://blog-fgci.com/2016/11/03/how-to-guide-hand-lay-up-on-fiberglass-molds/


How-to Guide – Hand Lay-up on Fiberglass Molds
November 3, 2016FGCI


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1. PREPARING THE MOLD

Remove dust and dirt from mold.

a. If mold is of plaster, wood, or new fiberglass, apply soft wax (Wax #2) and buff with soft towel. Then spray or brush with PVA parting compound and allow to dry.

b. If mold material is glass, metal, ceramic, or well-cured fiberglass, apply three coats of hard wax, carnauba type, buffing between each coat.

2. APPLYING THE GELCOAT

a. If gelcoat is to be brushed on, allow the first coat to cure and then apply second coat to make sure there are no light spots.

b. If gelcoat is to be sprayed on with a gelcoat gun, spray up to a thickness of .015” to .020”. When gelcoat has cured long enough that your fingernail cannot easily scrape it free (test at edge of mold where damage will not show on part) then proceed with next step.

3. LAY-UP SKIN COAT

Cut ¾ or 1 oz. mat to cover your part. Brush catalyzed resin over the cured gelcoat and then apply the mat. Work with the roller, adding more resin where necessary until all white areas in the mat fibers have disappeared and all air bubbles have escaped. A mohair roller is ideal for rolling in the resin, and a ribbed plastic or aluminum roller assists greatly in popping any remaining bubbles. Avoid leaving excess resin standing in puddles. Resin-rich areas weaken the part. Where rollers will not reach, brushes must be used. When this step is complete, clean all your tools in acetone. Allow skin coat to cure before next step.

  1. LAYING FIBERGLASS REINFORCEMENT
For a 12 ft. boat, two layers of 1½ oz. or 2 oz. mat and one layer of roving may be adequate, depending upon design. For a 14 ft. boat, an additional layer of mat and roving will add additional strength. Apply each layer as in step 3, but it will not be necessary to wait for curing between these layers. Be sure to shake all acetone out of brushes and rollers before applying resin. Acetone drips can result in uncured spots in the lay-up.

  1. TRIM
On a small lay-up, the fiberglass laminate which hangs over the edge of the mold can be trimmed off easily with a razor knife if you catch the “trim stage,” of the period after the lay-up has gelled but before it has hardened. On a larger lay-up, it can be trimmed with a saw or diamond blade.

  1. CURE
The cure may take from two hours to overnight, depending upon turnover desired, temperature, catalyzation, and nature of the part. If laid up in a female mold, longer cure will affect shrinkage and easier parting. In the case of the male mold, the part comes off more easily before it shrinks appreciably. If the part is subject to warping, a longer cure may be necessary. In any case, when the part is removed, it should be supported in its desired shape until fully cured.

  1. REMOVE PART FROM MOLD
First, examine the trim edge all the way around the mold and make sure there is no resin bridging the line between the mold and the part. Sand this edge where necessary. Then wooden or plastic wedges can be pushed into the edges to start the separation. Continue separation by pulling and flexing. In some cases, it is necessary to drill a small hole in the mold and apply air or water pressure.

  1. FINISH
Trim edges and back of part may need to be sanded and coated with surfacing resin or interior gelcoat.

  1. GELCOAT PROBLEMS
“Alligatoring,” or wrinkling of the gelcoat may be due to the following reasons:

  1. Gelcoat is too thin in spots; consequently it does not completely cure.
  2. Insufficient hardener added, or hardener not mixed well enough. In general, it is best to use about twice as much hardener in gelcoat as in lay-up resin at the same room temperature, since the gelcoat goes on thinner than a mat lay-up.
  3. Gelcoat has not cured long enough before mat lay-up.
  4. Acetone from tools drips onto gelcoat or into skin lay-up.
Click to expand...
 
tom21

tom21

havin fun
Location
clearwater FL
this is a lot of good info, this is how I started and here are some the issues I have had and what I did to fix them.

1. PREPARING THE MOLD

Remove dust and dirt from mold.

a. If mold is of plaster, wood, or new fiberglass, apply soft wax (Wax #2) and buff with soft towel. Then spray or brush with PVA parting compound and allow to dry. pva when brushed on can have runs, these will show up in your gelcoat and you will have to sand that out. spraying can be done perfectly where the surface is very smooth, I have always had a hard time setting the gun up, could be the gun IDK. If you are like me you will end up with a matte surface and that will need to be sanded out of the gelcoat. the finer the mist, a very fine mist will over many coats, drying each coat will give you the flat surface you want. THE most important thing is that which ever method you use you need to have a slightly green surface. this means you have enough pva on to ensure you wont have resins to surface contact with your plug.

b. If mold material is glass, metal, ceramic, or well-cured fiberglass, apply three coats of hard wax, carnauba type, buffing between each coat. you can test that you have enough wax by using masking tape. if it sticks you need more coats. also after multiple waxing and pulls you can build up enough wax to get multiple pulls. the best is the semi permanent release. you apply it and its good for many pulls. the first bottom I laid up came out with just one hand and no prying around the edges first. it was amazing. expensive but worth it for production level building. for the one off part is not worth it, wax still works great. the smoother your plug the smoother the mold. sand and polish the mold to a high gloss and all your parts will come out glossy.

2. APPLYING THE GELCOAT

a. If gelcoat is to be brushed on, allow the first coat to cure and then apply second coat to make sure there are no light spots.
I never had good results. it was a streaky surface, not uniform and smooth. I also had a tough time making it uniformly thick. plus it takes a long time to brush large parts.
b. If gelcoat is to be sprayed on with a gelcoat gun, spray up to a thickness of .015” to .020”. When gelcoat has cured long enough that your fingernail cannot easily scrape it free (test at edge of mold where damage will not show on part) then proceed with next step. I had issues with applying the gel to proper thickness, it seemed like it would pull away from the mold if applied too heavy and the part would have dips in it. I found the thickness I can spray to not have that or you have to wait for the first coat to set up and spray a second coat. You really need the depth gauge when you start out so you can get it right.
 
tom21

tom21

havin fun
Location
clearwater FL
3. LAY-UP SKIN COAT

Cut ¾ or 1 oz. mat to cover your part. Brush catalyzed resin over the cured gelcoat and then apply the mat. Work with the roller, adding more resin where necessary until all white areas in the mat fibers have disappeared and all air bubbles have escaped. A mohair roller is ideal for rolling in the resin, and a ribbed plastic or aluminum roller assists greatly in popping any remaining bubbles. Avoid leaving excess resin standing in puddles. Resin-rich areas weaken the part. Where rollers will not reach, brushes must be used. When this step is complete, clean all your tools in acetone. Allow skin coat to cure before next step.
I never liked doing the skin coat. when cured the chop leaves bumps and hairs and you have to sand it but it never really is smooth. then you have little air pockets that you cant roll out cause there is a stupid bump there. plus I prefer to have the resin wet out thru all the layers instead of laying wet to dry. sure sometimes the layup has to cure before the next set of layers can be applied. You cant lay 10 layers deep without kicking off a lot of heat and risking warping.

I never had good luck with cleaning rollers. at best I got the very outside of the roller clean and the center has a sticky gluey snot like resin in it. took too long to get to that point and I just don't have time or patience. I know someone who swears they use the same roller for months. its dumped in 5 gallon of acetone. whatever. I found the white cigar rollers at the box stores and then even cheaper at harbor freight. use it and throw it away. waaaaay cheaper than remaking a part. 2 to 2-5 inch chip brushes. same thing, use it and toss it.


  1. LAYING FIBERGLASS REINFORCEMENT
For a 12 ft. boat, two layers of 1½ oz. or 2 oz. mat and one layer of roving may be adequate, depending upon design. For a 14 ft. boat, an additional layer of mat and roving will add additional strength. Apply each layer as in step 3, but it will not be necessary to wait for curing between these layers. Be sure to shake all acetone out of brushes and rollers before applying resin. Acetone drips can result in uncured spots in the lay-up.

  1. TRIM
On a small lay-up, the fiberglass laminate which hangs over the edge of the mold can be trimmed off easily with a razor knife if you catch the “trim stage,” of the period after the lay-up has gelled but before it has hardened. On a larger lay-up, it can be trimmed with a saw or diamond blade. Again I have no patience to sit around waiting for the exact moment to trim a part. the times I did try it, the material pulled away from gel or it cut so jagged I fig what is the point? I'm not will to risk the part just to trim the excess. trim it when you lay, its still wet you can still get it down again and make sure there are no gaps between the gel and material. plus my molds are slightly larger than the part in the beginning so I have to cut it later anyway. Now I make everything with a 6-8inch flange so I can bag it if I want to. infusion is the best. you can take your time setting the layup and there is no time standing over the part slopping resin. cleaner, nicer, lighter, stronger.

  1. CURE
The cure may take from two hours to overnight, depending upon turnover desired, temperature, catalyzation, and nature of the part. If laid up in a female mold, longer cure will affect shrinkage and easier parting. In the case of the male mold, the part comes off more easily before it shrinks appreciably. If the part is subject to warping, a longer cure may be necessary. In any case, when the part is removed, it should be supported in its desired shape until fully cured. cheaper resins will shrink more. like boatyard is 5% vinylester is 2 or 3 I think and epoxy is not at all.

  1. REMOVE PART FROM MOLD
First, examine the trim edge all the way around the mold and make sure there is no resin bridging the line between the mold and the part. Sand this edge where necessary. shouldn't be if you did it right. Then wooden or plastic wedges can be pushed into the edges to start the separation. Continue separation by pulling and flexing. In some cases, it is necessary to drill a small hole in the mold and apply air or water pressure. this is better done BEFORE you lay the part, or how do you not damage the part?

  1. FINISH
Trim edges and back of part may need to be sanded and coated with surfacing resin or interior gelcoat.

  1. GELCOAT PROBLEMS
“Alligatoring,” or wrinkling of the gelcoat may be due to the following reasons:

  1. Gelcoat is too thin in spots; consequently it does not completely cure. not sure this is what happens, I notice that when brushing resin on the gelcoat that color comes off on the brush so I feel like it is dissolving it a little and if its very thin it will wrinkle up. that's why you need that gauge and have the proper uniform thickeness
  2. Insufficient hardener added, or hardener not mixed well enough. In general, it is best to use about twice as much hardener in gelcoat as in lay-up resin at the same room temperature, since the gelcoat goes on thinner than a mat lay-up.
  3. Gelcoat has not cured long enough before mat lay-up.
  4. Acetone from tools drips onto gelcoat or into skin lay-up. not a problem if you use fresh clean tools.
this is just my experience with what I have done. Its very possible I'm doing something wrong or whatever but I have to try things out and fix my process when things don't work. I work in Florida and some days its humid, hot, cold or raining and the resins react to that. they work better with some materials than others, they work best when fresh and of course when mixed properly. I have been so scared to lose or damage a mold for so long that I only used wax and pva to make sure it never happened. Then I worked on a project in a shop where they only waxed the part. I saw it and did it and was so happy to never spray pva again. saved tons of time and made the parts surface so much nicer. Then I got the opportunity to use the TR semi permanent release. it is a lot of prep applications to get it done initially but after that you just reapply the sealer and its good for multiple pulls. so now the prep stage is zero steps. just spray gelcoat set up and lay the glass. where in the beginning it was 2 coats of wax, waiting for each to flash, then multiple coats of pva with each coat drying and the last one drying a lot. that could be an hour!!!!! or more if the part is a hull.

Best advice is to read, read and read some more. eventually you will see where the similarities are with every authors experiences and that is probably about as close to an actual education in fiberglass as you can get. we all bend or break "the rules" for one reason or another. and I am sure there are more ways to do things properly than just one. the right way is still right and wrong is wrong but there is always some grey area. Take metton for instance, nothing is supposed to stick to it, which means technically you cant repair it. But I have several times. I'm sure other have also. but I took steps to try to make sure that I got the best repair I could make and so far they are holding years later.

Be safe wear ear ear and breathing protection, Tyvek sleeves, shirts or suits work great or talc or baby powder will help fill in your pores to keep the glass out.

I shop at basically only 2 places.
Aim supply for well supplies www.aimsupply.com
www.fiberglassdiscountstore.com is where I get all my fiberglass and resin. The owner, Jesus (pronounced hey soos) is friendly and knowledgeable. He has been working in composites most of his life and knows everybody in the biz. If he doesn't have it he can get it or at least tell you where to find it. He has been a huge help to me and is always willing to help me with whatever I need. I cant speak highly enough of him. There of course have been others over the years, but I eventually got to a point where costs or knowledge caused me to look for a new source. Pat at fiberglass coatings as well as Jenny at Fiberlay both were very knowledgeable and also helped me when I was getting started.

Hope this helps someone, and again don't take anything I say as an absolute. This is just what works for me.
 
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