Hi Andy I’ve been working specifically with polyester based resin for 15 years and have tried many different approaches as to your question with laying up with gelcoat the bigest setbacks are weight and ability to take movement or impact due to gelcoats viscosity the space between layers is grater than resin this causes micro fractures to happen quite quickly when the product is finished you can use in at either the first layer or two or the final layer or too if your looking for a crisp colour contrast ie no thin spots As for mixing resin and gelcoat this is most commonly called flowcoat it’s mainly used for sealing the layup tends to have extra styrene or (wax) in it at so fully cure as you mention you do with pva hope this helps if anyone wants to know more I’m happy to help Also great work on the channel

Hi Andy, wanted to say thanks for your videos. It has given me the confidence to restore a recently purchased 6m keelboat used on the Norfolk Broads in U.K. I stripped the boat hull back to gel and treated below waterline in Coppercoat and the rest in Alexseal and applied all by roller and no tipping. The finish is superb. Thanks for your help you really are a master of your profession. Marine Industrial are the distributors in U.K. and provided great service. Thanks again and best wishes for holiday season.

Hi Andy. I first learned how to fiberglass in the mid 60s, although I haven't done much in the past 30 years. I was taught that you could use gelcoat to in the lamination process, adjacent to the gelcoat in the mold to give it more of a scratch proof effect. The rub is air bubbles are hard to see and work out. Also when fiberglass chairs were/are made (again back in the 60s) fibaerglass roving was run through a chop gun and sprayed with a polystyrene binder over a perforated steel mold to form the rough shape of the chair. That piece was then placed in a heated matched metal mold where it was injected with gelcoat and cured in the mold. So basically the strength of the chair was chopped strand and gelcoat. Love your work!

I am rot repairing an old fiberglass Hourston Glasscraft and found some matting in the motor-well installed with gelcoat used as the resin.There were lots of cheap-out tricks used at the factory. Viewing from westcoast Canada. Cheers

Excellent content. It's always good to address what "What-if" elements of any subject and this is a great example. Thanks for exploring this issue.

I love you man because you've already told everybody what you don't think you know. Consider this idea please when you post these just say if you're stuck on a sandbar in the Bahamas this might work that way you're not on the hook for somebody going out and spending big time but if somebody's in a bad jam you can say with what's in your heart how they might be able to come home for the materials they have. One thing I appreciate is you coming back in and saying what it looked like 24 hours later. In the fiberglass game too fast too slow I don't know. If you did patch something together like that and it sat for a week instead of a day it might have changed a lot. Past that you're just not going to get the results very often. From from my broad experience in misery and trying to solve problems, that one week number is a rule of thumb on most consumer chemical reactions.

In my experience there are a couple of reasons not to use gel coat for laminating. 1) Gel coat costs quite a bit more expensive than laminating resin, so cost argues against its use. 2) because gel coat is thickened and pigmented it will be more difficult to wet the glass out and see any bubbles in the laminate. Also you are are likely going to end up with a higher resin (treating gel coat as resin) to glass ratio which is bad from the standpoints of weight, strength and cost. 3) Gel coat is quite a bit more brittle than laminating resin. The result will be that a piece laminated with gel coat that is subject to flexing is more likely to crack than a piece laminated with normal laminating resin. 4) the amount of actual resin by volume in gel coat is lower than in the same volume of laminating resin due to the added fillers and pigment in gel coat. That is likely to create a part that is not as strong. Just my opinions.

Excellent experiment. Thanks!

Thanks for the instruction Andy.

Thanks! A fun and interesting experiment. Seems like not being able to see the trapped air bubbles would tend to make a gel coat laminate lower quality due to the the difficulty in making a bubble free laminate...which several other folks have said...

Very much needed info. Thanks for testing theis things out ;)

Thanks for the video, more knowledge and understanding is no burden ,

Very helpful. Restoring a 73 Glastron Carlson. Plan on using epoxy resin with 1708 for the stringers over the sea cast stringers

As always, great video and awesome presentation, thanks

Came to watcj after your channel was mentioned on Sailing Doodles. Love learning the techniques.

Thanks for another video. Always good. I was wondering why I have never seen you snip a chip brush down about 1/8-1/4 inch. The better surface really helps push air out more easily.

Hi Andy regarding the gel coat being used to bond I do on occasion use it with a layer of tissue to assist in filling dimples in the chopped stranded prior to finishing. I have found that works well then I use gelcoat to paint over once the gelcoat and tissue coat have set up. Saves a bit of sanding but also gives the gelcoat integral strength so helps avoid fish eyes from gel coat that's to thick as a surface coat. The supplier I use also does coloured resin so has the same viscosity as general purpose or laminating resin so is good when working on a project you want to avoid transparency and light bleed. For example a boat cabin. Also the powder bond does work very well I've never tried 1708 as never found that here but would also be interested to see how it compares with powder bond. Maybe we should do a post swap of a sqm piece and see the results for ourselves. 👍👍

Great info there thanks

You should try staggering the two layers to see if you could pull them apart. We did that with two layers of kevlar and vinylester resin and were able to pull them apart.

Chopped strain mat works with epoxy strength wise but it makes the glass very springy, so unless it is flat or so, it’s not going to stay down while setting up. And it doesn’t look good as you said. Gets cloudy. I’ve found 3/4 oz mat looks as good, not the case with 1.5 oz. , but still springy. I just use multiple layers of 3/4 oz if I want it thicker and can get it clear.

In production work we would use gelcoat to install forgotten “NON structural” things such as bilge pump pads, battery boards, etc... all this was with foam cores and only if something was missed during production. It saved time and worked fine. I don’t believe I’d use gelcoat for a structural lay up though as the thixotropic and other properties have been altered and it is a bit more brittle than laminating polyester.

Interesting content, really enjoyed this...

It would be great if you could get someone from totalboat on the line to discuss the results with,

Just found your channel, love it. Questions for the group, back in the late 70's there was a one man operation near me, that made fiberglass canoes. I helped him on a few weekends and was paid with a canoe. His process was to spray two layers of gel coat the first one was a color and the second was white. Then while the gel coat was still sticky, he would coat, pre cut glass with VE resin and lay it in. Next before he would put in another layer of glass that was coated with PE resin. All of the layers where tacky to touch, and he did not roll the glass in. Then he would bag the top side of the mold with plastic and pull a vacuum and let it set overnight before pulling it out of the mold. What was the purpose of mixing the two types of resin? And why two layers of gel coat?? Was this all a cost saving measure to mix the resin and to use white as the second gel coat layer?

I have heard of people putting poly resin into flow coat or gel coat with wax to thin it out a bit when its cold

can you do a test strip with the gel coat and the other one that is like it please.

I wish you would have done one other and that is a user thinned epoxy, but thanks for this information

Sailing doodles plugged you today.

I always used 17oz bi-ax (no chopped-strand) with epoxy. I always bought from US Composites, and their 3-1 seems to be about midway between your 2-1 and penetrating epoxy. Wets easily, and even penetrates fair, though I thinned with acetone to give Doug-fir or Hem-fir a penetrating coat before layup or tabbing.

Hi Andy. I always find your videos very interesting and informative, but regarding the use of polyester resin. I regularly use polyester resin out of a 45 gallon drum, so shaking is not an option for me. Do it make much of a difference to the resin to shake it?

Really enjoyed this video, thanks. By the way, Bobby White mentioned you in his latest video on Sailing doodles.

Curing in the absence of air is called: anaerobic. Just FYI. I love this channel.

What about using fiberglass to repair gelcoat stress cracks with only fiberglass and gelcoat? Is that something worth experimenting with?

Interesting!

I wonder if temperature (coefficient of expansion) will affect mixed layups.

Iv seen a 70 foot wood shrimp boat that was glassed with chop stran gun and they used poly resin and mixed gel coat pigment into it and then shot the boat I was a kid and was around the boat 20 years are so and it held up great only boat I ever seen that was done that way and we glassed alot of old wood shrimp boats

Here's a question that I've never heard answered: Are stress cracks that are visible in gel coat, structural or purely cosmetic? Or (another way of asking), are "stress cracks" cracks in the actual fiberglass fibers or simply cracks in the hard gel coat cosmetic layer? Asking because my boat has stress cracks in places that I wouldn't believe there is ever much actual stress (non-structural components).

Hi Andy, just subbed the other day,, great video's. Haven't messed with epoxy resins much, Im patching a fiberglass tank on the side towards the top, I need good adhesion. Bought some Tap plastic 4 in 1 epoxy, and Knytex X-Mat DBM 1708 woven and 1708 stiched together. I mixed 6 oz resin and 1.1/2 oz of epoxy hardner. 4 to 1 ratio, I mixed it thoroughly for at least 4 min. it really didn't seem to start hardening to quick, after 2 hrs its slowly starting to harden. It was 78° when I started. Is there a better epoxy resin option, or is this normal? Any thoughts Thanks so much!

I made experiment for fiber glass and PVA wood glue. With paper I succeeded made tube for make model for machine support part. Next with fibers.

Hi Andy can I use gel coat for help to cure the epoxy resins..???? Thank you for you videos I learned a lot

So, what would you use for the whole cabin top over replaced balsa core or other than balsa?

Resins are formulated for specific applications... strength, flexibility, adhesion, etc. Gelcoat can be buffed, so it is hard & brittle, not to be used in structural applications. Remember when covering the deck with cotton duck, then varnishing or painting it was the “industry standard? That wasn’t for strength, it cracked (like gelcoat) & needed constant touch-ups. It depends on what you are asking it to do!

How about curing laminating resin with epoxy? Seems it would work since its just starving the resin beneath of air. Perhaps the epoxy softens the resin and you get a weird mix inbetween the two. ????

I’m restoring an ‘81 hobie 16 and just found a soft spot. Because it has a plywood/glass laminated hull, would penetrating resin be a good choice for injecting into the soft spot in order to seal the laminate back together? Thanks again!

I saw one time a KZfaq professional say that you have to get fresh resin or you will have problems with it. And as an example referenced the 3M bondo brand from Walmart as being normally old resin. Do you have any information on that? It kinda makes sense. He said that it would look cloudy and be extra thick (and I assume as well needs to be shaken in the container before mixing part A and B) too.

I got a question. Can you use gelcoat over fiberglass that has been laid up with epoxy? Thanks

thanks to your videos, i only use slow epoxy. so far so good!

Just remember not everyone is a business who can justify buying one more epoxy. Us DIYers try to cut materials down so we don’t let 10 different cans of epoxy go bad because we needed 8oz of each one for its “particular use”. Where you can probably save it for a couple months and use it on another job. Most of us only have one boat or one repair

Hi there! I've never tried fiberglassing. Is the epoxy resin that you were talking about also use in casting using silicone mold? Or mainly used with fiberglass? Thanks!

I’m wanting to do a fiberglass over plywood boat. Do you or will you do a dos and don’ts with this???

I a not a hundred percent positive, but the white textured commercial bathroom wall panels the sell in Lowe's and home Depot, are either vinyl ester or polyester gell coat, of you should p up and burn a scrap of it there is a layer of Matt within the white. Also when cutting it, it does s seem to smell like hell coat to me

Was watching an old video of yours about using epoxy to do your varnish base coats. What products would you use today?

How much does wood expand and contract when it’s fully encapsulated in resin? I thought that occurred due to moisture changes.

Maybe a trivial question, but one I have. A lot of my friends are adamant about using epoxy resin, but since gelcoat is poly based and as I have been told poly WILL NOT bond to epoxy, can you use gelcoat on an epoxy repair?

Which resin is best for fiberglass car body kit?

I am not a chemist but it is in essence the same thing, because it is still resin but it just has other stuff added to it, paint pigments and maybe some other stuff to thicken it, and to get UV protection, and possibly something to make it a harder more dense surface, etc... If you can saturate cloth then it could probably work in a pinch, it is still resin. But the base coat resin is more pure resin, but according to your test using top coat for the base shown it probably don't have to be that pure to be strong. I suspect, based on how we humans do things, that they made the top coat out the base coat but added stuff to it, so in reality it probably cost more to make, and buy.

I am wondering if you ever post anything on the iboats forum. Your "I wonder what would happen if" videos would draw a lot of attention from that forum. Just a thought.

There is a big difference between stifness and strength for materials. Briefly, Stiffness is the resistance to flexibility or the amount of deflection for a given load, which is what was being tested in the video. Strength is what is the max load it can carry with out permanently deforming the material. Eg aluminium alloys can be very strong, as strong as some steels but are not stiff materials. Where as steels of the same strength can be 3-4 stiffer than high strength aluminium alloys.

Andy, here in NC, we have hurricane damage to deal with. I have a small tri-hull boat which was lifted up off of its trailer and one of the guide boards came off. When the water levels deminished, a hole was punched through the bottom of the hill. It is about 2 inches in diameter. What do you recommend using to patch this hole?

Por 15 rust preventative works great with fiberglass

So if the Penetrating Epoxy was almost as stiff as the 2:1 after another 24 hours, you could use it in light weight applications where a little flexibility was ok. I say light weight applications because it would go on a lot thinner than 2:1 and possibly not require vacuum bagging to squeeze out the excess? I once used Flow Coat (it was all I had on hand at the time) to repair my Nacra 5.8 after it kissed some rocks at speed, it held up really well.

what about mixing polyester and epoxy together?

I built a LongEZ experimental aircraft with techniques taught by the man himself (Burt Rutan) and I can tell you, you can't use polyester resin on foam. It had to be structural resin epoxy. I used MGS epoxy. pricey but the only one certified for commercial aircraft use. I'm not building an aircraft this time, but a recumbent trike frame, by covering a foam form with 5-6 layers of bi-directional e-glass. What epoxy do you recommend that doesn't cost an arm and a leg like MGS or West system? I can't use table top or polyester /casting resins.

Hey Andy. Here's another one for you- Since penetrating epoxy is thinner and designed to soak into wood, what about using it for the first layer of 1708 when glassing over plywood? You'd get the benefit of deeper penetration on the wood and still use epoxy, then put second, third etc coat with regular epoxy....Just thinking...

So, if gelcoat is used for lamination, how are you going to see any voids or trapped air bubbles? I'd certainly be worried if I purchased a boat layed up totally with gelcoat that there would be unseen voids everywhere.

I have a carolina skiff that I'm going to fiberglass over the original floor I sanded it down. I want to get something like bondo but for boat and than gel coat with color tint and a non slip. Whether liquid or sand. Is that a bad idea? And with gel coat if why I use with or without wax? I'm also in florida

good video, very helpfull ,, ply no mask?

I believe that TAP Fiberglass has powder based CSM

Will polyester bond to vinyl-ester resin?

Laminating gelcoat?

I have a question... I’m putting new stringers in my 17ft fiberglass boat. It’s an 1989 should I be using epoxy or polyester to tab in and cover my new stringers. The previous stringers and bottom of the boat fled more than I’m used to and I’d like to use epoxy to make sure it’s stiff. Please help

Andy, powder bound CSM is available in the US, although it is tough to find. If you search on Amazon for 'chopped strand powder' you will get at least one place that sells it. I will try and include a link here for the product, but KZfaq may strip it off. www.amazon.com/Fiberglass-Chopped-Strand-Premium-Powder-Bound/dp/B01FPI8WQ0/ref=sr_1_1?keywords=chopped+strand+powder&qid=1574028687&sr=8-1

What about that 3m polyester resin that they sell at the Walmart?

You use 1708 a lot both with polyester and epoxi. I have a similar glasfiber cloth that wight 600 grams per sqm (you will have to translate it to your familiar metrics :) ) . It is good in certain applications, like a backer. For curved applications it is just to thick. Therefore, after having watch your videos a lot, I thought 1708 300 grams per sqm would be a nice cloth to have home. However, I cannot find it here in Europe. All sites is in the US. Most likely (almost) the same cloth have a different name. Someone has any knowledge?

I'm pretty intrigued with the results, but I wish you would have given the test a full 24 hours to cure.

Concrete knowledge is for concrete. :-)

I have a Devils Advocate question of my own , if Epoxy is so great and I have used it a lot why don’t boat manufacturers use it instead of fiberglass resin on their “plastic” boat hulls ? Here is kind of a funny so to speak a few years ago in my retirement home I met a older gentlemen who was a retired DuPont chemical Engineer his specialty was Polyeurethane Epoxies he unfortunately is no longer with us and he unfortunately spent his career developing Epoxies used primarily for bonding the magnetic particles onto recording video and audio tapes that kind of made him a sort of brilliant but boring person he knew his field but didn’t have a lot of other interests in life ? In his defense he did make a boatload of money in his life I tried discussing my experiences and knowledges of West and TotalBoat Epoxies that I used on boats I’ve owned over the years honestly years ago I began with West Systems because that’s what I could get locally and get some help with in my Marina etc BTW West was available in both my West Marine and Ace Hardware stores although very expensive to purchase it I’ve also found over the years of owning 17 or 18 boats plus cruising internationally that I do prefer to use kind of the more well known brands It was also before the internet got to be what it is like now as a resource

If working with polyester and your boss is on your ass - throw that MEK in and spread it out before it smokes...

See how this 1971 pearson hull cracked in spectacular fashion. No Kevlar reinforcement. kzfaq.info/get/bejne/m5yJdtRlyOCUZo0.html

You're not wearing a mask? Yuck. I had some poly splash into an eye. I was lucky

First