Fiberglass a boat Hull

[Riotvan88]

Hello 

 

I've been building a billings smit rotterdam kit and have almost finished planking the Hull. 

 

I plan to fiberglass the exterior but this is the 1st time doing this type of work. I'm not sure in what order the next steps are. 

 

My plan was to sand the Hull smooth use wood filler if and where necessary then fiberglass it then prime it and then any last minute sanding/filling before painting the base coat on. 

 

Does this sound right? Should I sand and fill and prime the Hull before or after fiberglassing it? Thanks much appreciated 

[Roger Pellett]

Sand the hull before glassing it.  Sanding should be to give the hull a nice fair smooth shape.  Final sanding with very fine sandpaper is not necessary or desirable as some “tooth” on the sanded surface is a good idea.  Any localized wood filling necessary to produce a fair surface should be done prior to glassing, but do not use sanding sealers, primers or other paint type coatings before glassing.

 

Assuming that the resin that you are using is a two component mix, take care to mix it in the correct proportions.  Adding additional hardener will not make the resin cure faster but it can prevent it from completely curing completely resulting in a sticky mess.

 

Do not try to glue the cloth to the resin coated hull.  Instead drape the dry cloth over the hull and pour the resin on to it.  Then using a plastic squeegee spread out the resin working it into the weave to wet out the cloth.  More than one application of resin will probably be required to completely fill the weave.

 

Some resins produce an “Amine Blush” on the cured surface that can interfere with paint.  This can be removed with detergent and water.  I would then sand the hull to provide a finished surface for painting.

 

Roger

[thibaultron]

Use a marine epoxy type resin, not the polyester (automotive) type resin! The polyester has a tendency to pull away from wood. The marine epoxy type is designed to stick to wood and will stick much better, in the long run. If you find either has trouble setting, heat the hull in a semi sealed container (plastic tub, etc.) in the sun. The resins use chemical heat as part of the setting process, and thin sections may not generate enough heat to do the job. You may have to paint on a second coat of just resin, after sanding.

[thibaultron]

Use very light cloth on the outside, and at least a coat or two of resin on the inside, after the outside is finished.

[allanyed]

Riotvan,

If you want to go the route of actual practice you could build a mold using your hull.  I did this years ago making models of the Islander 36 sailing yacht and a couple Californian 48 motor yachts  for their owners and they  came out beautifully.  I was lucky in that I worked for PPG Industries Coatings and Resin division at that time and had folks in the lab to show me the ropes. 

 

IF you want to give it a try, these are the basic steps as I remember them.

 

After you are satisfied the original hull that you have has a perfect finish and is polished as much as possible, coat the hull with a  mold release and rub and polish it until it gleams.   Any soft rag will work for this.  A rough finish is not desirable based on my own experience as it will show on the final product.  

 

Next  paint on a couple layers of gelcoat onto your hull.   Black is what I used, but any color should do.   I used black to contrast with the final color of the hulls that I would be making.

 

Once the gel coat is cured, apply the fiber glass and resin on top of the gel coat.  I would not use woven glass as the weave can be noticeable no matter how many coats of your final finish that you use apply.  I speak from experience on this.   Unwoven fiberglass cloth is a far better choice and is generally thicker so will make a stronger mold.    While the resin is still wet, you can add some stiffeners that will also allow the  mold to stay upright when it is done.  Glass over these pieces of wood stiffeners and let the entire set up cure.   You will wind up with what looks like a small bath tub in the shape of your vessel hull.

 

Once cured, remove your hull and you will have a finished mold from which you can make as many hulls as you want.   When going to make the glass hull, apply and polish the same mold release onto the gelcoat  inside  the mold.   Once it dries apply  a coat of gel coat that is a contrasting color to the mold.  In my case the hulls were blue or white.   Once this coat of gel coat, which will be the extreme outside of your hull,  is cured, apply nonwoven glass and resin in the mold.   Once cured it can be popped right out and you have a glass hull similar to an actual fiberglass boat.   You can add some wood battens here as well before the resin cures and lay some additional glass on top of these battens/stiffeners and they will be there forever and protected plus stiffen the hull.

 

Sounds like a lot of work, but they were fun projects.  I truly wish I still had those molds.  Foolishly I got rid of them during one of our many moves.   Such is life. 

 

I am sure there are tutorials on line so if you want to investigate further take a look as things may have gotten easier since I took this on back in the late '70s before getting into wooden ship model.  

 

Allan

Edited July 5, 2021 by allanyed

[Riotvan88]

2 hours ago, thibaultron said:

Use very light cloth on the outside, and at least a coat or two of resin on the inside, after the outside is finished.

Thanks for all the info. Can I just varnish the inside? I've already applied varnish to parts that will be inaccessible when planked. Ideally I only wanted to fiberglass the exterior of the Hull. 

 

Also in the past I've used PVA mixed with sawdust to create a thick paste and used it as filler. Will this be OK to fiberglass over? 

[thibaultron]

varnish should work, as you've already varnished parts of the interior. As far as the PVA/sawdust mixture, others will have to chime in. I've never tried it.

[PRS]

For fiber glassing this is how they do it for R/C airplanes.

 

https://www.modelairplanenews.com/workshop-tips-working-with-fiberglass-and-resin/#visitor_pref_pop

 

 

[Bob Cleek]

Why do you want to sheath the hull in a cloth and resin laminate? Just curious.

[mtaylor]

Just an FYI, riotvan88, I deleted your duplicate topic in the other area as this one is in the proper place and got you some answers.

[Riotvan88]

54 minutes ago, Bob Cleek said:

Why do you want to sheath the hull in a cloth and resin laminate? Just curious.

Because I'm wanting to make it RC and I had seen others do it. I've read it makes for a strong hard wearing surface and is easy to sand smooth for painting 

[gjdale]

Riotvan88,

 

I was faced with a “never done this before” situation with my Chris Craft runabout. A detailed explanation of trials and then the actual process can be found in my build log here starting on page 5 at post 145 for the trials and page 6 post 153 for the actual process. I was guided a lot by a tutorial I found on the RC Groups forum.

 

 

 

[Bob Cleek]

7 hours ago, Riotvan88 said:

Because I'm wanting to make it RC and I had seen others do it. I've read it makes for a strong hard wearing surface and is easy to sand smooth for painting 

Fiberglass can be a "strong, hard wearing surface," but it's a real bugger to work with, particularly on small scale pieces and it sure isn't "easy to sand smooth for painting. It will add thickness to your hull and weight, neither are advantageous. It can be tricky to work with and if something goes wrong, it could ruin the model completely. It's about as strong as an eggshell, so until it gets around 3/16ths of an inch thick, it's going to crack like an eggshell if it gets whacked. At least, that's my story and I'm sticking to it.

 

If your hull is properly put together, it should not need any strengthening and if you operate the model prudently, it should not require a "strong hard wearing surface." 

 

If it were me, and I realize is ain't, I would sand the hull fair and apply a liberal coat of Smith and Co,.'s Clear Penetrating Epoxy Sealer. ("CPES")(See:http://www.smithandcompany.org/ for technical information) This will penetrate the wood surface and cure, turning the surface of the wood into rock hard wood impregnated with cured epoxy resin. (CPES is not just "thinned epoxy," it contains special solvents which cause the resin to permeate the wood fibers. Before the CPES cures completely (less than 2 or 3 days... read Smith's instructions... this will create a molecular, rather than just a mechanical bond between the CPES and WEST epoxies,), I would apply a thin coating of WEST System G/flex 650 epoxy resin mixed with WEST System 407 Low-Density or 410 Microlight fairing additive. The additive will make the cured epoxy very easily sand-able to a very finely smooth surface. It will also fill any cracks or divots on the surface. Then sand the surface fair (without sanding the epoxy off down to bare wood. If that happens, apply more CPES to the bare spot(s.)) Then paint with a good quality marine enamel primer and topcoat paint.

 

WEST G/flex epoxy resin cures to a hard, but slightly flexible epoxy that should not crack with slight wood movement. The CPES will provide a decent water barrier and the West G/flex will add to that. A good marine enamel will complete what should be a matrix that isn't going to leak in your lifetime, nor, probably, the lifetimes of your grandchildren. It won't add noticeable thickness to your hull and won't weigh down your model with unnecessary weight.

 

You could also add WEST System 422 Barrier Coat Additive, which will increase the moisture resistance of the G/flex epoxy resin, but it's overkill for this application. You've also got the option of using WEST's kevlar additive if you want your bottom to be bulletproof, but that's a story for another night. Amazingly versatile stuff, epoxy.

 

Fiberglassing small, irregular surfaces is tricky business and the glass cloth or mat is nasty to work with, too. (Tiny bits of glass fibers become airborne and land on your skin, quickly working their way into the skin like fine cactus needles, resulting in painful itching. I don't ever want to begin to think what they do when you inhale them, but I've done my share of fiberglass work on boats in the days before hazmat suits and filtered air-supply masks and I'm still here, so...

 

Anyway, that's how I'd do it. 

 

Edited July 6, 2021 by Bob Cleek

[Nirvana]

I can vouch for the West products as my r/c T37 got an epoxy surface before being primed and painted.

Did not use any fiberglass! 

[Riotvan88]

3 hours ago, Bob Cleek said:

Fiberglass can be a "strong, hard wearing surface," but it's a real bugger to work with, particularly on small scale pieces and it sure isn't "easy to sand smooth for painting. It will add thickness to your hull and weight, neither are advantageous. It can be tricky to work with and if something goes wrong, it could ruin the model completely. It's about as strong as an eggshell, so until it gets around 3/16ths of an inch thick, it's going to crack like an eggshell if it gets whacked. At least, that's my story and I'm sticking to it.

 

If your hull is properly put together, it should not need any strengthening and if you operate the model prudently, it should not require a "strong hard wearing surface." 

 

If it were me, and I realize is ain't, I would sand the hull fair and apply a liberal coat of Smith and Co,.'s Clear Penetrating Epoxy Sealer. ("CPES")(See:http://www.smithandcompany.org/ for technical information) This will penetrate the wood surface and cure, turning the surface of the wood into rock hard wood impregnated with cured epoxy resin. (CPES is not just "thinned epoxy," it contains special solvents which cause the resin to permeate the wood fibers. Before the CPES cures completely (less than 2 or 3 days... read Smith's instructions... this will create a molecular, rather than just a mechanical bond between the CPES and WEST epoxies,), I would apply a thin coating of WEST System G/flex 650 epoxy resin mixed with WEST System 407 Low-Density or 410 Microlight fairing additive. The additive will make the cured epoxy very easily sand-able to a very finely smooth surface. It will also fill any cracks or divots on the surface. Then sand the surface fair (without sanding the epoxy off down to bare wood. If that happens, apply more CPES to the bare spot(s.)) Then paint with a good quality marine enamel primer and topcoat paint.

 

WEST G/flex epoxy resin cures to a hard, but slightly flexible epoxy that should not crack with slight wood movement. The CPES will provide a decent water barrier and the West G/flex will add to that. A good marine enamel will complete what should be a matrix that isn't going to leak in your lifetime, nor, probably, the lifetimes of your grandchildren. It won't add noticeable thickness to your hull and won't weigh down your model with unnecessary weight.

 

You could also add WEST System 422 Barrier Coat Additive, which will increase the moisture resistance of the G/flex epoxy resin, but it's overkill for this application. You've also got the option of using WEST's kevlar additive if you want your bottom to be bulletproof, but that's a story for another night. Amazingly versatile stuff, epoxy.

 

Fiberglassing small, irregular surfaces is tricky business and the glass cloth or mat is nasty to work with, too. (Tiny bits of glass fibers become airborne and land on your skin, quickly working their way into the skin like fine cactus needles, resulting in painful itching. I don't ever want to begin to think what they do when you inhale them, but I've done my share of fiberglass work on boats in the days before hazmat suits and filtered air-supply masks and I'm still here, so...

 

Anyway, that's how I'd do it. 

 

Excellent. Thanks for the information. Although I've made static models this is my first wood RC boat. I think I'll go the epoxy route. 

 

What's the kevlar additive you mentioned for the bottom? I may add this to protect from grounding. I always prefer to over build and over engineer for durability and redundancy, anything that adds strength and longevity peaks my interest. Thanks again 

[Nirvana]

You don't need kevlar.

Kevlar is a very flexible material being used in protective west for enforcement.  Masts on extreme racing sailing yachts are made out of it. Very lightweight. Racing bicycles are entirely made out this material.

You can lift such bike with two fingers without any effort. Try that with a bike from the 80's.

Besides it's nasty stuff to work with, just like fiberglass.  You need really good ventilation and PPE.

Take a look at my T37 build log and you may pick up an idea when it comes to be working with epoxy. 

Good luck.

 

[thibaultron]

Nirvana, could you post a link to your T37 build, a search of the forum did not turn it up.

[No Idea]

I would recommend using 49g fibreglass cloth and a good non blooming epoxy finishing resin. You will need to apply 2 coats of the resin and then spend time sanding it flat. The cloth will take just about any shape and it’s an easier process to do rather than explain. It will give you a glass like base for your paint. Here’s one I made earlier using exactly this process. 

[Nirvana]

3 hours ago, thibaultron said:

Nirvana, could you post a link to your T37 build, a search of the forum did not turn it up.

 

Ron, 

It just dawned on me, my log disappeared when we had the "Big Crash" in 2013, and I don't have saved independent log on my PC. 

[Bob Cleek]

12 hours ago, Riotvan88 said:

What's the kevlar additive you mentioned for the bottom? I may add this to protect from grounding. I always prefer to over build and over engineer for durability and redundancy, anything that adds strength and longevity peaks my interest. Thanks again 

It was basically a joke. Kevlar, added to epoxy, yields an expremely impact-resistant cured resin material used in bullet-proof personnel armor plate vests. U.S Army combat helmets are now made of kevlar and epoxy material. Trust me, you don't need kevlar on your RC boat bottom. The same goes for the spectrum of special additives available, such as carbon fiber, which will yield an epoxy/carbon material which is lightweight and extremely strong. It's used for sophisticated state-of-the-art racing boat masts and bicycle frames, etc. (I've seen carbon fiber epoxy being finish sanded. The dust goes everywhere and is much like graphite powder. You'll look like an old time coal miner at quitting time in the mine if you work with that stuff.)

 

The schedule I recommended above is for as strong a hull sheathing as I can imagine any RC boat would ever need. (Glass cloth or mat will add strength to a sheathed hull, to be sure, but it won't increase the impact resistance much without laying it on thick and IMHO I don't think it's worth fiddling with, although the hull pictured above is done very nicely.) Don't forget that many successful wooden sailing models have been built with nothing but wood, putty, and shellac primer coating, then undercoating and enamel paint and do just fine. They don't spend that much time in the water to begin with and are stored indoors, so they don't need much more. I have a three-masted schooner sailing model that's around a hundred years old now in my shop for a restoration job. (Do not ever let a commercial shipping outfit pack a ship model for shipping! When I get around to starting the job, I'll post pictures of what happens when you put a model in a big box and then fill the dead space with packing peanuts... broken spars and rigging all around.) The plank on frame hull appears to have been painted with a common early 20th Century enamel paint which has held up very well. I won't be repainting because the owner wishes this family heirloom built by a relative Maine Cape Horn sailor to retain its antique patina. There is some minor cracking of the paint along the plank seams, to be expected when an uncased plank on frame model spends that much time on a mantle or window sill, but no light showing between the planks. I expect the model would float today without significant leaking if put to the test. 

 

One more caveat to mention in passing is that glass-reinforced fabric and mat sheathing may exponentially complicate repairs if catastropic hull damage occurs. One can always throw more resin and glass on it and sand (sort of) fair, but deconstruction for "as new" repairs becomes far more complicated if it is to be done right.

Edited July 6, 2021 by Bob Cleek

[mikegr]

a nice step by step action by a modeler which i consider quite advanced even using simple materials

 

http://www.shipmodels.info/mws_forum/viewtopic.php?f=75&t=8912&start=20

[Nirvana]

The only area where I have carbon fiber material is in my mast for the T37.

Good enough for the sailing I am doing, will take a lot of force to break.

[Riotvan88]

On 7/6/2021 at 10:16 PM, Bob Cleek said:

It was basically a joke. Kevlar, added to epoxy, yields an expremely impact-resistant cured resin material used in bullet-proof personnel armor plate vests. U.S Army combat helmets are now made of kevlar and epoxy material. Trust me, you don't need kevlar on your RC boat bottom. The same goes for the spectrum of special additives available, such as carbon fiber, which will yield an epoxy/carbon material which is lightweight and extremely strong. It's used for sophisticated state-of-the-art racing boat masts and bicycle frames, etc. (I've seen carbon fiber epoxy being finish sanded. The dust goes everywhere and is much like graphite powder. You'll look like an old time coal miner at quitting time in the mine if you work with that stuff.)

 

The schedule I recommended above is for as strong a hull sheathing as I can imagine any RC boat would ever need. (Glass cloth or mat will add strength to a sheathed hull, to be sure, but it won't increase the impact resistance much without laying it on thick and IMHO I don't think it's worth fiddling with, although the hull pictured above is done very nicely.) Don't forget that many successful wooden sailing models have been built with nothing but wood, putty, and shellac primer coating, then undercoating and enamel paint and do just fine. They don't spend that much time in the water to begin with and are stored indoors, so they don't need much more. I have a three-masted schooner sailing model that's around a hundred years old now in my shop for a restoration job. (Do not ever let a commercial shipping outfit pack a ship model for shipping! When I get around to starting the job, I'll post pictures of what happens when you put a model in a big box and then fill the dead space with packing peanuts... broken spars and rigging all around.) The plank on frame hull appears to have been painted with a common early 20th Century enamel paint which has held up very well. I won't be repainting because the owner wishes this family heirloom built by a relative Maine Cape Horn sailor to retain its antique patina. There is some minor cracking of the paint along the plank seams, to be expected when an uncased plank on frame model spends that much time on a mantle or window sill, but no light showing between the planks. I expect the model would float today without significant leaking if put to the test. 

 

One more caveat to mention in passing is that glass-reinforced fabric and mat sheathing may exponentially complicate repairs if catastropic hull damage occurs. One can always throw more resin and glass on it and sand (sort of) fair, but deconstruction for "as new" repairs becomes far more complicated if it is to be done right.

I have one more question possibly I have made a big mistake. I drove the planking nails all the way in as I planned to leave them in the hull.  

 

Should I remove these? Is it irrelevant? I guess the potential is for them to rust but they should be completely covered by the epoxy and water barrier sealers you recommended. I could still remove them but would be a pain to do. 

[gjdale]

As long as they are sanded flush, they shouldn’t be a problem as you will be sealing them. If oxygen can’t get to them, they can’t rust.

[Bob Cleek]

6 hours ago, Riotvan88 said:

have one more question possibly I have made a big mistake. I drove the planking nails all the way in as I planned to leave them in the hull.  

 

Should I remove these? Is it irrelevant? I guess the potential is for them to rust but they should be completely covered by the epoxy and water barrier sealers you recommended. I could still remove them but would be a pain to do. 

 

i doubt they will rust if they are sealed as described. The major risk with iron fastenings in a model boat that is going to be used in the water is that any crack, however small, is a way for a wooden hull to soak up moisture, and especially water, like a sponge. Then, the iron nails may well start to rust and the wooden hull can start to rot. That said, if they are only wet occasionally and stored where they can dry out, my guess is the nails will do okay.]

 

It's unfortunate they are there, but we've all done similar things along the may in our modeling journeys. The biggest problem I see is that the nail heads may interfere with your sanding the hull fair. I doubt you can drive them much more with a countersink punch without splitting your frame, either. It's your call, surely, but you wouldn't be the first guy to undo and redo something that didn't work out on the first go-round. BTW, I'm curious. Did the Billings' instructions say that the planks were supposed to be nailed to the frames?

[Don Case]

When I first started making RC sailboats I made a balsa fin keel for one and covered it with 2 oz cloth and epoxy. I guess when I was sanding it I went through the cloth a bit on the leading edge. It was subsequently painted and looked fine. I sailed it numerous times then one day it was sailing along great and then shuddered and almost came to a dead stop. I pulled the boat out and the entire leading edge of the fin looked like popcorn. Somewhere, sometime some water had gotten in and virtually exploded the leading edge. I'm not sure what the moral is other than be very careful, water will find a weak spot.

[Riotvan88]

On 7/7/2021 at 8:56 AM, mikegr said:

a nice step by step action by a modeler which i consider quite advanced even using simple materials

 

http://www.shipmodels.info/mws_forum/viewtopic.php?f=75&t=8912&start=20

 

16 hours ago, Bob Cleek said:

 

i doubt they will rust if they are sealed as described. The major risk with iron fastenings in a model boat that is going to be used in the water is that any crack, however small, is a way for a wooden hull to soak up moisture, and especially water, like a sponge. Then, the iron nails may well start to rust and the wooden hull can start to rot. That said, if they are only wet occasionally and stored where they can dry out, my guess is the nails will do okay.]

 

It's unfortunate they are there, but we've all done similar things along the may in our modeling journeys. The biggest problem I see is that the nail heads may interfere with your sanding the hull fair. I doubt you can drive them much more with a countersink punch without splitting your frame, either. It's your call, surely, but you wouldn't be the first guy to undo and redo something that didn't work out on the first go-round. BTW, I'm curious. Did the Billings' instructions say that the planks were supposed to be nailed to the frames?

 

I've decided to leave them in if water gets in its just as big of a problem to the wood as it is the nails so I don't feel they're an additional liability. I'll just be sure to make it absolutely sealed before painting. 

 

 

[Bob Cleek]

You'll probably be just fine. A good finish on  the exterior should prevent leakage. 

[Riotvan88]

On 7/6/2021 at 5:58 AM, Bob Cleek said:

Fiberglass can be a "strong, hard wearing surface," but it's a real bugger to work with, particularly on small scale pieces and it sure isn't "easy to sand smooth for painting. It will add thickness to your hull and weight, neither are advantageous. It can be tricky to work with and if something goes wrong, it could ruin the model completely. It's about as strong as an eggshell, so until it gets around 3/16ths of an inch thick, it's going to crack like an eggshell if it gets whacked. At least, that's my story and I'm sticking to it.

 

If your hull is properly put together, it should not need any strengthening and if you operate the model prudently, it should not require a "strong hard wearing surface." 

 

If it were me, and I realize is ain't, I would sand the hull fair and apply a liberal coat of Smith and Co,.'s Clear Penetrating Epoxy Sealer. ("CPES")(See:http://www.smithandcompany.org/ for technical information) This will penetrate the wood surface and cure, turning the surface of the wood into rock hard wood impregnated with cured epoxy resin. (CPES is not just "thinned epoxy," it contains special solvents which cause the resin to permeate the wood fibers. Before the CPES cures completely (less than 2 or 3 days... read Smith's instructions... this will create a molecular, rather than just a mechanical bond between the CPES and WEST epoxies,), I would apply a thin coating of WEST System G/flex 650 epoxy resin mixed with WEST System 407 Low-Density or 410 Microlight fairing additive. The additive will make the cured epoxy very easily sand-able to a very finely smooth surface. It will also fill any cracks or divots on the surface. Then sand the surface fair (without sanding the epoxy off down to bare wood. If that happens, apply more CPES to the bare spot(s.)) Then paint with a good quality marine enamel primer and topcoat paint.

 

WEST G/flex epoxy resin cures to a hard, but slightly flexible epoxy that should not crack with slight wood movement. The CPES will provide a decent water barrier and the West G/flex will add to that. A good marine enamel will complete what should be a matrix that isn't going to leak in your lifetime, nor, probably, the lifetimes of your grandchildren. It won't add noticeable thickness to your hull and won't weigh down your model with unnecessary weight.

 

You could also add WEST System 422 Barrier Coat Additive, which will increase the moisture resistance of the G/flex epoxy resin, but it's overkill for this application. You've also got the option of using WEST's kevlar additive if you want your bottom to be bulletproof, but that's a story for another night. Amazingly versatile stuff, epoxy.

 

Fiberglassing small, irregular surfaces is tricky business and the glass cloth or mat is nasty to work with, too. (Tiny bits of glass fibers become airborne and land on your skin, quickly working their way into the skin like fine cactus needles, resulting in painful itching. I don't ever want to begin to think what they do when you inhale them, but I've done my share of fiberglass work on boats in the days before hazmat suits and filtered air-supply masks and I'm still here, so...

 

Anyway, that's how I'd do it. 

 

Thanks again for this advice this is the route I've decided to take. I'm now almost ready to do this part now I just have a few questions. 

 

How much Gflex will be needed I've seen half liter bottles at force 4 but not seen any larger quantities. 

 

And can I mix multiple additives in sucj as the fairing additive and the water barrier in one mix or would these need to be two coats?

 

Lastly would you recommend fitting the korts nozzle before or after the cpes and epoxy coats? 

 

Sorry for the questions this is my first build and Thanks again for the help. 

Edited August 17, 2021 by Riotvan88

[Bob Cleek]

7 hours ago, Riotvan88 said:

Thanks again for this advice this is the route I've decided to take. I'm now almost ready to do this part now I just have a few questions. 

 

How much Gflex will be needed I've seen half liter bottles at force 4 but not seen any larger quantities. 

 

And can I mix multiple additives in sucj as the fairing additive and the water barrier in one mix or would these need to be two coats?

 

Lastly would you recommend fitting the korts nozzle before or after the cpes and epoxy coats? 

 

 

 

 

A half liter Gflex kit should be more than sufficient for a single coat on that model, but perhaps not for two. To be on the safe side, I'd get a liter, although, if you run out, there's no problem applying more to what you didn't have enough to cover, although coats are best connected within a couple of days to ensure a molecular, rather than a simply mechanical bond between the two. (This is especially true of CPES epoxy sealer. Read Smith's instructions.)  The catalyst and resin have very long shelf lives, so you can always put any leftovers to good use. Mix it in small batches and use a flat surface to mix it.  I use a shallow tray lined with tinfoil. When the job is done, I simply discard the tinfoil. Beware of exothermic reactions. These cause a batch of epoxy to "cook off" when the heat generated from the chemical reaction of the mass of mixed catalyst and resin begins to accelerate the curing process and the process runs out of control, getting hotter and hotter until it starts flaming. A flat mixing container spreads out the surface area of the epoxy mixture and permits it to dissipate heat. Fill a paper cup full of the stuff and you can have problems.

 

You can mix some additives together without any problems and not others, but those you can are relatively obvious, like a thickener with a color additive. Always refer to the WEST System instruction manuals which are online. They will provide instructions on everything you could ever want to know about WEST products: Epoxy Instruction Manuals - WEST SYSTEM Epoxy Check to see if there are any contraindications to mixing the additives you are intending to use together. I'd be inclined to apply the two you mention separately, the fairing additive first, and then the barrier coat. Barrier coat goes on fairly smooth and is hard to sand. Fairing additive sands like butter, but if applied in a "peanut butter" consistency, it won't be smooth and will require sanding to fair it. Mixing the two isn't likely to produce a "waterproof easily sanded" surface. I'd be more inclined to expect you'd get a harder-to-sand surface that wasn't waterproof. But, again, check the manuals.

 

I'm not completely familiar with the installation procedures for your kortz nozzle, but I would say it would be best to fair and coat your hull before installing the nozzle because 1. epoxying and sanding is a messy business and working around the nozzle would be a huge pain, if possible at all, and 2) the fairing and coating process will add thickness to the surface of the hull and yield the final dimensions to which the nozzle will have to be fitted.

 

Good luck with it!  And again, consult the WEST System manuals on line! Don't guess. Using epoxy coatings can be mastered by anyone who knows how to follow "cookbook" instructions, but if one ignores the instructions, it can quickly turn you into a "mad scientist" with an out-of-control experiment.

 

I'll also add that you should probably "start small" and get the feel of the stuff as you go along. Mix a small single "pump" batch and apply it on a piece of scrap wood and let it cure, Sand that and apply your barrier coat and see how that works out on the test piece. Don't use your hull to learn on. When you are comfortable, mix no more epoxy than you can use before it starts to cure too much. You can always mix more as you need it, but if you mix a big batch and it "cooks off" before you're done working with it, that epoxy is wasted and the stuff isn't cheap, as you know.

 

 

Edited August 17, 2021 by Bob Cleek