Boat Builder Central - Builder Forums

I would like to use the polyester fabric rather than fiberglass because of the ease of application and draping capabilities of polyester. So, do I use the same resin for polyester fabric as one would use for fiberglass? I know that it drinks up a lot more resin, I am OK with that. That's it. A simple question and hopefully a simple answer.
Thanks
Walter Thom

Walter Thom wrote: ↑Tue Dec 05, 2023 5:28 pm I would like to use the polyester fabric rather than fiberglass because of the ease of application and draping capabilities of polyester. So, do I use the same resin for polyester fabric as one would use for fiberglass? I know that it drinks up a lot more resin, I am OK with that. That's it. A simple question and hopefully a simple answer.
Thanks
Walter Thom

While polyester resin instead of epoxy is common in boatbuilding(but not for the boats built here) I have never heard of using polyester fabric as an alternative to fiberglass in structural applications such as boat building. Can't find anything while searching either, but because polyester resin is so common it's not easy to search for. Can you link to some information about this technique or the particular fabric you want to use? The manufacturer should be telling you what resin to use and giving the mechanical properties of that finished composite.

My gut is that you can't do this in a structural application, but I'm open to learning something new. The closest I've seen is using fabric stretched over a frame and cured with resin to make a hard shell which is then fiberglassed over for strength.

Essentially no you can not use a different fabric. Some people use xynole for sheathing and abrasion resistance in a wood boat but it can in no way replace glass for structural integrity. It has superior performance against abrasion but almost no performance in holding your boat together.

If you were to use a Xynole you would need to completely reengineer the boat. I’d guess at least twice the hull thickness, which then would not bend so you’d need to cold mould. Then there’s the stringers etc, which would still need to be glassed in.

The good news is that you can drape biaxial cloth just fine. It’s woven that wrinkles.

Walter Thom wrote: ↑Tue Dec 05, 2023 5:28 pm I would like to use the polyester fabric rather than fiberglass because of the ease of application and draping capabilities of polyester. So, do I use the same resin for polyester fabric as one would use for fiberglass? I know that it drinks up a lot more resin, I am OK with that. That's it. A simple question and hopefully a simple answer.
Thanks
Walter Thom

I believe. that if you use polyester cloth you need to use polyester resins neither are sold here. I do not know why you believe that polyester drapes easier than fiberglass but you will need more layers of polyester than one layer of 12oz fiberglass.

Tom

Walter Thom wrote: ↑Tue Dec 05, 2023 5:28 pm I would like to use the polyester fabric rather than fiberglass because of the ease of application and draping capabilities of polyester. So, do I use the same resin for polyester fabric as one would use for fiberglass? I know that it drinks up a lot more resin, I am OK with that. That's it. A simple question and hopefully a simple answer.
Thanks
Walter Thom

Why?

No you can't do this. Resin doesn't stick to polyester fabric. It's also very flexible compared to fiberglass. It has no structural properties.

Evan_Gatehouse wrote: ↑Fri Dec 08, 2023 2:18 am No you can't do this. Resin doesn't stick to polyester fabric. It's also very flexible compared to fiberglass. It has no structural properties.

Xynole is polyester I thought? Do they treat it for resin to bond. I've never used the stuff, though apparently it's good for its purpose, which is not holding a boat together.

OK,
It looks like I am not going to use polyester fabric and will do the fiberglass. This is my first motor boat build after 70 years of floundering my way along. I have built a couple of skin on frame kayaks. It will be a Inlet Runner 18 by Dix design. He recommends a 12oz biaxial fiberglass fabric.

I am putting the items on his material list together so I have an idea how much of an investment this will be. I have priced out most of the items so far but, there is a solvent for cleaning on the list... I don't know what I am to be cleaning with this and/or what type of cleaner is to be used. I would like to avoid pestering him for these types of questions which is why I am seeking answers here on the boat builders forum.

One thing that isn't on the list is gel-coat or paint. So that's another question. Paint or gel-coat, which one is best or are they both just fine? I have seen gel-coat crack with age and I would prefer not to go that route for the ease of future touch ups and maintenance... I'm sure there will be more questions along the way.
Thanks
Wally

If you are using epoxy you need paint.
If poly or vinyl ester then gel or paint.

If you go gel, match it to the base… so vinyl ester gel or poly ester gel. A good ester supply company can help with that.

Cleaner should be alcohol for general wipe down post sanding or surfaces before fully cure is achieved. Acetone for tool clean up or material destruction. Acetone on uncured surfaces is bad.

If you are using ester, styrene for a thinning agent. There is no thinning agent for epoxy.

MEK (not MEKp) can be used for some clean up but I find acetone is easier to obtain and stays usable longer. I keep some mason jars for tool soak and a “lab bottle” for directed spray.

For working with epoxy I find denatured alcohol to be cheaper, less toxic, and just as effective as acetone for almost everything. There are almost no tools I try to save, just buy disposable things from the start in bulk. You'll spend more in solvent trying to reuse something. So alcohol for everything until prep for paint, at which point I use the paint company's expensive cleaning solvent of choice. Buy it by the gallon and if you use it very freely as I do you'll spend a couple hundred on it over the entire project at $20 a gallon. You could be less wasteful with it if desired.

Also buy an entire case of gloves and of towels. I like scott rags in a box, the white ones not the blue shop towels. They are the only disposable ones that don't start to fall apart on me leaving bits behind on the project.

I wouldn't consider gel coat personally. Gel coat is great when applied directly to a mold as you get a chemical bond to composite applied afterwards and a finished surface as soon as you pop it out of the mold. Applying it at the end you don't get any of those benefits, I'd just use paint. Paint can be several hundred to several thousand dollars depending on what direction you choose to go with it.


Things to buy in bulk to save money:
-gloves
-rags
-mixing cups(check for accuracy)
-stir sticks
-chip brushes
-painters tape

To joe's point... most of my post was about ester based build. If you are going ester and gel, spraying gel like a paint is the win, but you spray a lot. And it winds up costing a bit. The acetone is needed there and in the early build stages with ester.

Stick with Alcohol with epoxy. Use the acetone for cleaning your table and floor

Thanks Guys!
This is great information. I am going the epoxy route so, do you guys have a preference for one brand of epoxy over another? It seems some folks like the 2 part epoxy. What about paint brands? My boat will spend most of it's time under cover with maybe a week or so in the water for spring and fall fishing trips. That's about it for now.
Thanks
Wally

I prefer the 2-1 epoxys. They seem to be a little more forgiving of small mixing mistakes.
As for brands I have used 5-6 of the big name brands and do not see much difference in them. I would guess over half of the epoxy I have used is the house brand from here. They can ship it to me cheaper than what I can buy locally and I get to give BBC my business so that is a win-win

All epoxies are two part. I have a preference for 2:1 ratio epoxies like system 3 silvertip over 5:1 epoxies like west system. They have a number of properties that make them easier to work with but are more expensive. Either way you will end up with a great boat just depends on if time or money is your more limiting factor.

For a high end paint I like alexseal, but its expensive and takes meticulous prep. Great option if you want a "yacht finish" and I prefer it to awlgrip. There are many far cheaper options that can still look great that I'm sure others on the forum can recommend.

For primer I like the system 3 epoxy primer. They changed the name recently and I don't know if the formula changed. If it's the same as before its good stuff.

1. I'm a lazy turd
2. refer to #1

Significance: I don't like to do things that will fail or require me to do more work than I need. That said my experience:
* BBC marinepoxy: I know I mix it work, use it incorrectly, bad environment, etc. It just works. that doesn't mean it won't fail on you, but the 2x I was forced to use west... never again.
* EMC/Quatum for paint over the S3 primer. Spray it if you can. Roll it is fine. I did crap for prep (just wash) and it covered nearly all my sins. So hard to get off I have to use 40gr. Which doesn't matter since it seems to repair with just a bit of sanding on the edge.

That's my experience with success product. FG1K had a terrible experience with EMC/Quantum (I think it was him).

That's a lot to ponder but, now you having given me some direction and I appreciate you thoughts. All I have to do now is get on with it and make some choices. What got me going on this polyester thought is a polyester product named "Xynole" by the folks that sell it to make it there own. I have seen studies on Xynole and it is nothing more than Polyester. I have use both Polyester and Nylon for skin on frame kayak and duck skiff builds. The Polyester was a lot easier to work with.

The fundamental difference is how the fabric is used. In the skin method it is just a water barrier and tensioner. In the composite method (what we do here) it is a structural component taking loading forces in multiple directions. The fabric in a composite hull is as critical to the strength of the hull as the frames and core.

Now an interesting option would be to build something less critical… say center console? … with glass tape (structural) but skinned in poly. That might give you the ease of finish in a high vis area.

What about bottom paint?
My boat will only be in the water for a week or so a couple times a year, spring and fall fishing trips. The rest of the time it will kept out of the elements, high and dry.
Should it be bottom painted and if so which paints would you recommend?
I will be purchasing all of the finishing materials from BBC.
Thanks
Wally

No need. Just use a good top coat. At most use the graphite methods but it you are decent at loading and not hitting everything in the water … lots of boats don’t have graphite bottoms.

No bottom paint!
That would be great, I had some folks tell me that if I were to leave it in the water for more than a few days at a time that the paint could start blistering and peeling of. I am guessing that would be if I were to use a low grade paint.
I will be using a quality paint from BBC.
Thanks Wally

Crap paint and/or bad surface prep will get those results. Spend the dollars and the time, do touch up and repairs when needed. Good quality paint will last longer than bottom paint.

I will spend the $$$ and do as you say.
Thanks
Wally

Wally, I sent you an email this morning. Call Reid on Monday to discuss paint. He is off today. Call us at 772.742.8535. Thank you, Jeff

Jaysen

You said you used Quantum and S2 Primer and that you did crap for prep (just wash) and it covered all your sins... does that mean you didn't use micro-balloons to get a fair and smooth hull and just prime over an unsanded hull before priming?

So, which was it that covered all your sins, the S3 Primer, the Quantum or a combination of both? This will be primarily a fishing/hunting and just messing about rig. I'm not worried about getting that show winning finish but, I would like it to look nice enough to prevent me from being heckled by onlookers on a dark, foggy moonless night.

You have to understand that this will be my very first wood/fiberglass boat and absolutely no knowledge of how any of this works so... when I ask a question it's because I have no idea what the answer is.

Do you have to sand the entire area of a fiberglass covered hull if it is applied well and as smooth as possible. I do understand that I will have to knock down the obvious high points but... I see some people use something called peel ply. Does that take care of the need to sand the entire boat? I am a lazy turd too but I will do what is necessary.

I haven't bought the plans or supplies yet but, this is going to happen. I am gathering info and knowledge for the project so I know what I am getting myself into.
Thanks
Wally

You must fair the hull to some degree. Fairing makes the hull efficient-ish in the water (primary) and creates pretty surface for finish (secondary).

The build process is simple (this is small boat)
1. Base construction: cut, tie, glue tape. Here you have a boat shaped thing that is “squared” relative to its lines with even curves but has major surface defects and likely insufficient structural reinforcement.
2. Reinforcement and glass: here you are adding structural ties like frames, bulkheads, stringers as well as adding layers of glass. At the end of this you have a sound hull that has many surface imperfections, is hydrodynamically evil and isnt comfortable.
3. Finish structure and fairing: here you balance the order between putting non structural components on the hull and making the hull “perfect” (where perfect is the enemy of done) from a hydro and paint perspective. This is silica/ballon application and sanding land. The thing is that SOME non structural parts need to be under faring and some over. So you get to figure that out. Fairing isn’t only for the OUTSIDE of the hull. It also can be used inside to help make smooth surfaces (think drywall compound).
4. Finish: painting and pimping the ride time! Get your paint, chrome, electrical, motor etc done.
5. Launch. Self explanatory I hope.

Now the problem is “what if I have a big, heavy hull?” Well, now you start sticking steps 3 and 4 up into 1 and 2. I think most boats in the 16+ range will have you fair and paint the hull before you flip it to install frames. And that’s ok. Big hulls need to reduce the number of flips. Imagine rolling a TW28 6 times like I did with my V12!

To your actual question. You must do some fairing. But you don’t have to be perfect. A short list of my sins… I sanded to 80g and these days rarely past 60g. Since my boat get smashed on oysters and concrete I know it will always have dings (she’s slow too) so I’m not going for perfect smooth. I’ll accept 1/16” gouges in the surface. I didn’t fill the interior glass weave all that well… or at all.

The S3 primer just acts like any other primer. But it is thin enough that crappy surface prep is acceptable. It will flow into all the lines, gouges, etc that you leave behind. It will not bridge pinholes well.

EMC/Quantum is the same. BUT, what I discovered, is that if you can increase the viscosity by reducing the thinning agent you magically get a better finish than you deserve! And this isn’t magic, it’s on the side of my can! “Reducing thinning agent will allow for improved covering of surface imperfections” (or something like that, the can is a couple hundred miles away right now). So I cheated on the fairing/sanding but got a much much better quality finish.

So to recap:
1. You gotta fair and sand.
2. You’ll do a lot more than you planned but plan on 3x what you want to to.
3. Focus on the structural hold accuracy (square) more then perfect fairing.
4. Good paint properly manipulated makes up for some laziness in the fairing/sanding.

Also, Quickfair was an easy product for me as a first time builder to use. I sanded the glass (didn't use peelply) with 80 grit, then smeared Quickfair over it and sanded again with 80 grit. I did start mixing my own fairing mix after a bit, but Quickfair teaches you what works. You'll see when you get there.

Dougster

Super!
Thanks guy this helps a lot. It looks like I am going to open a pretty big can of worms here.
Wally

It’s not that bad. It’s just another building project. Unlike building a house or remodeling, it’s easy to get distracted (funds reallocated, time commitments pop up, spouse/kids, etc) and the “3-4 months” turns into years. I know you’re not building a BBC/Martens-Goosen plan but non of this is hard. The only super technical bit is finishing and dealing with the government to get your numbers. Other than that, idiots like me can do it successfully.

Keys to success:
1. Take your time.
2. Ask questions.
3. Go back to #1.
4. Keep your work space clean.
5. Don’t reuse consumables.
6. Back to #1
7. Slow down and enjoy building a boat.