Fiberglass fabrication

D

drfeno

Member
Joined
Jun 19, 2008
RO Number
30284
Messages
133
Hi,

I realize this is a huge subject with many facets, but I'm just looking to begin the process of learning. My eventual goal is to fabricate a fiberglass hardtop for my boat (a 31' silverton convertible). I've been looking online for books and videos and I've learned a little, perhaps enough to try building something small. Most of the stuff I find online is choppy and filled with lingo for someone who already knows fiberglassing. There is very little "from the ground up" stuff. I've also seen some book titles that sound promising, but I'd like to hear some feeback before buying a book. Does anyone have any suggestions on where to look for information?

Thanks
 
You can check out youtube. There are a lot of videos there...just enter "fiberglass" or something similar to that and check out some of those. Fibreglast dot com sells books and videos. They are not the cheapest around, but helpful. Buy some gelcoat, glass, and polyesther resin and play with it a bit. make some flat panels or make simple molds from MDF and get used to handling the stuff. Stick with polyesther resins for now...epoxy is somewhat more fickle and I wouldn't use it for a hard top anyway as its not very UV resistant. BTW, I think you'll need a core material such as balsa or foam for that hardtop to make it stiff enough, yet light enough. Post any questions you have here. Myself or someone else will be sure to respond.
 
Get a copy of The Fiberglass boat repair manual, by Vaitses.
 
Thanks for the input. I already learned something, use polyester resin.

Ghost- Does the book you're referencing cover fabrication, or is it all about repair?

I also have another basic question. I've seen the fabrication of one-sided finished pieces on Youtube. for instance the building of a fiberglass hood scoop for a car. They create a mold, wax it, spray in Gelcoat. Once set they wet it out with resin and lay in and wet and roll out the glass mats whether they be chopped strand or fabric. My question is can this "rough" side of the project be finished and smoothed and gelcoated to create a piece thats finished on both sides (like I'd want my hardtop to be). If possible I'd imagine you'd spray in several coats of resin (once you were happy with the structure using the glass and/or core material) until it was smooth and then top it off with Gelcoat. Is this done? I have not seen it in any video on youtube or elsewhere.
 
yes, the inside or rough side can be finished and gelcoated, although its a lot of work as its not a mold surface. You would have to sand and use filler to get a nice smooth surface on the fiberglass and then spray the gelcoat. You will have to add wax to the last layer of gelcoat as it will not cure completely unless its sealed off from the air. You will also probably need to wet sand and compound this gelcoat to get a nice finish. The alternative is to make a second mold. You make the second mold a male mold that is smaller than the first female mold (smaller by the thickness of the laminate and core material) and layup up this laminate, remove it, then bond it into the female mold laminate. Not sure if my explanation is clear, but you will need 2 molds to get a true "mold" surface on the inside of the hard top. Probably not worth it for a one piece fabrication. Use the time it would take to make the 2nd mold and wet sand and polish the gel coat using the one mold method.
 
Thanks,

Since my initial question, I looked up Polyester resin, and I came across the Fibre Glast website. I've been reading the material on their website. It's pretty informative on resin types, fabrics, mold and plug construction (even a glossary so I now know what a plug is). I also read a few pages of the book by Vaitses (as much as amazon would let me) and it was also informative. I will probably buy it as it is pretty cheap. Before today I didn't know there were different types of resin and that "gelcoat" is for polyester resin construction. Most if not all the resins I've seen for sale at boating supply places have been epoxys and I thought that was all there was. In reality if I do build this project, it won't be until probably next fall, I'm just trying to build the knowledge and skills that may let me attmept it in the future.
 
if you do go ahead with the project, for the bottom finish, white spray on bedliner would look nice and hide alot... just a thought.
 
"white spray on bedliner would look nice and hide alot..." -- Mike Ryan

I agree, but I thought that bedliner was heavy. Is is actually light?
 
Thanks for the Ideas,

I'm probably going to buy some gelcoat, polyester resin and some cloth and try out a couple of small projects to get a feel for it. I think I will also buy a cup gun. I've seen them for sale online for about $120.00. I have some experience with spray painting with a compressor, so this shouldn't be too much of a stretch.
 
Not trying to rain on the parade, but...

You will want to invest in a quality respirator and face shield, and also very likely protective clothing. The respirator is essential ( I know. Many people do not use them. You truly should, especially if you intend to spray the resin/epoxy. This stuff does terrible things to your lungs and eyes ). They protective clothing is less critical, but highly desirable. The small fiberglass bits are very irritating to the skin ( some folks get all macho and say it is beneath their concern ) and the epoxy/resin is always a beast to deal with on skin, and will, over time cause a contact dermatitis and/or sensitivity. What you actually do is up to you, but I strongly suggest that you pay strict attention to the safety measures.

That said, playing with fiberglass can be fun. Especially if you like sanding... ( you will understand the sanding part after the project is done... ;) )
 
Thanks Radioactive,

I did plan to use a respirator, but its kind of old. Maybe I'll buy a new one. I had not thought of the face shield, but I think I own one for grinding that fits on a hardhat. As far as protective clothing goes, I may try to get some hospital scrubs from my wife (she's a nurse). I have another couple basic questions which may seem dumb. Once you have a suitable mold, and have applied the release agent to it. You then spray on the gelcoat. I assume you let this coat set up before applying the structual fiberglass and resins. One comment I read somewhere said to watch out to not scratch the gelcoat layer when applying the structural stuff which might cause the mold to not release properly. I would think if you let it set up it would be pretty tough and hard to scratch. Another question is would you apply more than one layer of cloth in one batch of resin. In other words, should you just apply one layer of matt, roll it out, wait for it to cure and repeat? Or can you apply multiple layers of glass, as long as your batch of resin is still not setting up. I would assume you could do multiple layers, but this is not expressly stated in anything I've read. Also, when applying strutural layers, is it OK to wet out the surface with a spray gun, add the fiberglass, and then wet the top with the gun again and then roll it out. Again, I'd think so. but you don't see that done in the videos on Youtube. They all use brushes for that. Perhaps its just the scale of what they are building. For a large square foot project (like a hardtop), I'd think spraying would be better.
 
My experience is with epoxy, not polyester or polyvinyl. And you don't spray epoxy. I think that you will find that one layer at t time is the way to do it. You -must- entirely wet the fabric, and you must do it in a timely schedule. Your working time, at best, is short.

You might try out the Glen-L boatbuilding site. They are "epoxy-centric" and they are covering a plywood boat vs building fiberglass objects, but there is a lot of good info available that will translate easily to what you are doing. Here is one example.

Two things worth keeping at the top of the list: The hardeners are toxic. Using a spray gun spreads a toxic cloud around the work area. The working life of the mixed product will be SHORT. Even with the poly- resins, it is usually around 30 min to: mix resin and hardener completely, set up applicator, spread liquid, work liquid into the fabric. This is a short working time. Plan ahead, set up all materials/tools. Rehearse before doing...

-edit-

I forgot. OOps.

Yes, let the resin harden between layers. Read the manual, but it will show that timing is everything, and in some cases you can proceed with the next layer before full cure, but after a certain period of time. In other cases you will wait overnight, and it may be necessary to do some surface prep before applying the next layer ( ie: waxed resins and/or epoxy w/ amine blush ).
 
dfreno,

I am no expert or even a novice on building your own hardtop, but had one built for me so I have a tiny bit of knowledge to share.
First off, someone mentioned using balsa as a coring product to stiffen the top, that sounds good, but if you look at the picture below of my hardtop, they used aluminum ribs to stiffen the top. With that in mind you will need some experience in tig welding, as well as a tig welder.
Before you do this, maybe you should take a ride to Atlantic Towers in NJ, and see how they make their tops. Also, when I was looking and goggling “Boat Hard Tops” I ran across a manufacture that touts a special light weight material they use.

If you have any questions about my hardtop please ask, hopefully I will be able to answer them. AT had a Hi Line version of my top, basically the difference was the underside was finished (fiber glassed) and you did not see the ribs, I passed on this version due to the weight (weighed twice as much).

Weight is a serious consideration, you don’t want to make your boat top heavy.

Best of luck, and please post lots of pictures of the entire process.

Walter

Go here to look at my hardtop and to see the ribs I am talking about
http://www.boatered.com/forum/topic.asp?TOPIC_ID=120220
 
dfreno, you are getting a lot of info here and it must be confusing for you. I can only give you the info from my 8 years of experience in the composites field. I worked for several companies that built advanced composite structures for military, industrial and aerospace applications. So here are a few guidelines I learned for designing and fabricating with composites: epoxy is stronger and a better adhesive than polyesther or vinylesther, but much more fickle and doesn't stand up to UV (you must paint it)so stay with polyesther but use epoxy as an adhesive to bond the core material; epoxies bond to polyether but polyesther doesn't bond to epoxy; chemical bonds are stronger than physical bonds--i.e. in a perfect world you want all the resins to cure at the same time (a physical bond is when you sand a previously cured laminate and layup more resin and glass on top); sandwich structures provide the strongest and lightest parts (using balsa, foam, honeycomb cores); the strength of the fiberglass is in the direction of the fibers--woven fabrics are much stronger than fiberglass mat and unidirectinal tapes are the strongest; don't thin your gelcoat with acetone,use styrene; if you're going to spray gelcoat you need at least a 2.0 tip on your gun; I would spray the gelcoat but brush and roll the polyesther resin to push out all the air voids. This is all I can think of at the moment. Your best bet is to get some materials and play with them.
 
Thank you everyone so much.

You can never have too much info. I'm an engineer by education and I love to build things. I do a lot of woodworking, and I have a MIG welder (may buy a TIG). I wouldn't go into this project lightly, which is why I'm trying to get all the info I can to try and not make dumb mistakes. I certainly will build some small projects and experiment with different techniques before attempting something this large. I know how to use AutoCad, and I'm pretty proficient at it (from a previous job). I would use it to get the final design correct before attempting any fabrication. Walter - That hardtop looks awesome, and thank you for the photos from many angles. Your boat is beautiful. I have some initial thoughts on a design. I would think lightness and torsional stiffness would be important, as well as simplicity of design due to the large mold I would need. I've learned more in a couple days here about resins, fabrics, and material compatibility than I did in a month of research on my own. If I do go ahead with the fabrication, I will take lots of pictures of it, but it won't be too soon.
 
You must log in or register to reply here.
Back
Top