glassing plywood prior to hull installation

[Scout 30]

OK, I'll admit that polyester resin has some sticky properties. So does maple syrup. Personally, when I'm sticking things together I think I'll stick with an actual glue.

[ramblinrod]

Originally Posted by Scout 30

OK, I'll admit that polyester resin has some sticky properties. So does maple syrup. Personally, when I'm sticking things together I think I'll stick with an actual glue.

The design intent of polyester resin is to stick to wood and polyester resin FRP when cured.

It meets design intent very, very, well, as demonstrated by the millions of boats that have plied the water for 50 years that employ it for this purpose.

If you don't wish to use polyester resin, that is your right; I only object to publicly declaring it's use inappropriate for intended purpose, where it is actually an excellent product and solution.

[scott2640]

Originally Posted by UNCIVILIZED

what's the plan to provide clamping power when gluing on the layers. As 10mm plywood (in sheets) will have a lot of spring back. Probably more than staples can contend with, especially well enough to prevent any gaps or voids in between each layer. Which is critical when using resourcinal.

I was going to use resourcinal for the frames, keel lamination, deck beam lamination's, etc. I won't be using that in between the layers of plywood for the reasons you stated. I cant thing of a way to get the clamping pressure necessary. However Aerodux 185 is a resciornol glue that has some gap filling properties, lower required clamping force along with the fact that it can be thickened as well. It also has a much lower acceptable application temperature at around 50 degrees. A real bonus here in upstate NY.

I'm not sure what I'm going to use between the layers yet. I'm leaning towards a slightly thickened epoxy. I've seen others use tar, construction adhesive and one time i saw picture with what looked like a thinset of some kind being troweled on, not really sure what it was. So I'm still searching for the best choice.

[mitiempo]

Originally Posted by ramblinrod

The design intent of polyester resin is to stick to wood and polyester resin FRP when cured.

It meets design intent very, very, well, as demonstrated by the millions of boats that have plied the water for 50 years that employ it for this purpose.

If you don't wish to use polyester resin, that is your right; I only object to publicly declaring it's use inappropriate for intended purpose, where it is actually an excellent product and solution.

The op's boat is a wooden boat - not a fiberglass boat with a core.

Not one respected builder of cold moulded boats uses polyester. Not one.

The key to longevity in a composite wooden structure is keeping the moisture out. Epoxy, in addition to its gap filling properties, does this best.

[Lojanica]

I'm enjoying this discussion. Many good points from all sides are being made.

[Terra Nova]

Polyester resin would not even make it to last choice on my list.

[jimbunyard]

Originally Posted by scott2640

I was going to use resourcinal for the frames, keel lamination, deck beam lamination's, etc. I won't be using that in between the layers of plywood for the reasons you stated. I cant thing of a way to get the clamping pressure necessary. However Aerodux 185 is a resciornol glue that has some gap filling properties, lower required clamping force along with the fact that it can be thickened as well. It also has a much lower acceptable application temperature at around 50 degrees. A real bonus here in upstate NY.

I'm not sure what I'm going to use between the layers yet. I'm leaning towards a slightly thickened epoxy. I've seen others use tar, construction adhesive and one time i saw picture with what looked like a thinset of some kind being troweled on, not really sure what it was. So I'm still searching for the best choice.

This may sound a little facetious at first, but I've heard of and seen 3M 5200 used successfully for this purpose. And it seems hideously expensive, at about 7000.00 for a 50 gallon drum, but when you start comparing it to the Aerodux 185 above, at 120.00 a gallon, pre thickener, it doesn't look quite so bad. Just throwing that out there.

Don't know if you've seen this one, but thought it had at least a little relevance here. Just shows what is possible with wood. And yes, for you epoxy fanatics, that's what they're gluing and laminating with...surprisingly to me, given the level of workmanship, the boat is fairly reasonably priced, as best I could determine at about 700,000.00 sterling...

https://www.youtube.com/watch?v=rDgKIPaW5xY&t=637s

And not to be too agreeable, the following is for those who don't know that epoxy is the do all and end all for fiberglass boat repairs and wood boat construction.

Unless one has a boat that is made of fiber-reinforced epoxy resin, there are times when polyester makes sense, and times when epoxy makes sense.

All the bonds made on repairs, and many of those on new construction, often from necessity, are secondary, or, as may be considered more explanatory, mechanical. I've seen different figures for the 'superiority' of the 'bond strength' of epoxy over polyester, and if memory serves they range over about 10-25 percent 'better'. (Of course, that assumes perfectly mixed resins, properly prepared bonding surfaces, and proper application and cure conditions.) But we'll say they're reasonably accurate.

So why would anyone use an 'inferior' product over one that is 'just a little more expensive'?

Usually it comes down to some form of efficiency; the gains had by using the supposedly superior product are not met by the costs regarding strength, serviceability or functionality.

To cover a couple of these points at once. For the rear deck rebuild described previously, if I remember correctly, 8 gallons of resin were required. At the time, iso was about 70.00/5gal, so 140.00. for resin. Don't know what West epoxy was at the time (about 8 years ago) but gas was sky-high back then, so I assume resin prices were about the same as now, or about 830.00 for 8 (not 10) gallons.

So the cost for resin alone would have been about a third of the cost of the entire job, with virtually no increase in strength. I can assure you the owner wouldn't foot that increase to his bill...

Slogging on...to compatibility. Polyester resin will not set when applied over epoxy. So if you have a polyester resin boat, and repairs have been made with epoxy, any time you need to cover them with polyester, say for gel-coating, a barrier coat must be used. Not the end of the world, but an additional step, cost, and another potential failure vector. And we don't want to leave out the uninitiated who try and re-repair that high-end epoxy repair with polyester...

Of course it can go on and on. The point is that some times polyester is the right choice, and sometimes epoxy is, one has to make an informed decision based on the facts prescribed by the application...should we bring up vinylester resins, which (supposedly) have better water impermeability than either epoxy or poly?

[smj]

The boatbuilder I worked for would lay a hull up in polyester but after that all secondary bonds were done in epoxy. If any resin were to touch wood it would be epoxy. Quite a few of these boats were catamarans used for snorkel trips. They were heavily abused daily in all types of weather. Not one structural failure that I know of. Compare that to the thousands of old boats with polyester tabbed bulkheads that have broken loose. Polyester has its place, but it's not secondary bonds and it is definitely not for use on wood.

[Scout 30]

Originally Posted by ramblinrod

The design intent of polyester resin is to stick to wood and polyester resin FRP when cured.

It meets design intent very, very, well, as demonstrated by the millions of boats that have plied the water for 50 years that employ it for this purpose.

If you don't wish to use polyester resin, that is your right; I only object to publicly declaring it's use inappropriate for intended purpose, where it is actually an excellent product and solution.

I understand that this is the internet & anyone can pretend to be an expert but it takes little research for anyone to realize how little you know about this topic. Unsaturated Polyester Resin was first patented in the 30's & at that time there was no actual intent. It's first use came during WWII when it was used to cast radomes. It then went on to be used to cast thousands of different products including cars, planes, boat hulls, furniture, etc.. Saying that sticking to wood was the designed intent of polyester resin is simply a lie.
Polyester Resin – The Plastics Historical Society

[ramblinrod]

Originally Posted by Scout 30

I understand that this is the internet & anyone can pretend to be an expert but it takes little research for anyone to realize how little you know about this topic. Unsaturated Polyester Resin was first patented in the 30's & at that time there was no actual intent. It's first use came during WWII when it was used to cast radomes. It then went on to be used to cast thousands of different products including cars, planes, boat hulls, furniture, etc.. Saying that sticking to wood was the designed intent of polyester resin is simply a lie.
Polyester Resin – The Plastics Historical Society

So I've stated my background in fibreglass construction.

What's yours?

You seem to be confusing my statement regarding "design intent" with "invented for the sole purpose of"...

These are not the same thing.

The design intent of current formulations, is most certainly to be suitable for application to wood in fibreglass boat construction. This is a huge market for polyester resin manufacturers.

[Scout 30]

Originally Posted by ramblinrod

So I've stated my background in fibreglass construction.

What's yours?

You seem to be confusing my statement regarding "design intent" with "invented for the sole purpose of"...

These are not the same thing.

The design intent of current formulations, is most certainly to be suitable for application to wood in fibreglass boat construction. This is a huge market for polyester resin manufacturers.

Once again you're off the mark. Pretty much no fiberglass boat builders use wood anymore due to the well known problems of water intrusion & rot. In fact that's a big selling point these days. Try again.

[smj]

Originally Posted by ramblinrod

So I've stated my background in fibreglass construction.

What's yours?

You seem to be confusing my statement regarding "design intent" with "invented for the sole purpose of"...

These are not the same thing.

The design intent of current formulations, is most certainly to be suitable for application to wood in fibreglass boat construction. This is a huge market for polyester resin manufacturers.

I doubt if you could find one reputable builder of a wood composite construction that isn't using epoxy. And if you do, then their reputation has gone to sh!t


Sent from my iPhone using Cruisers Sailing Forum

[Scout 30]

Originally Posted by scott2640

I was going to use resourcinal for the frames, keel lamination, deck beam lamination's, etc. I won't be using that in between the layers of plywood for the reasons you stated. I cant thing of a way to get the clamping pressure necessary. However Aerodux 185 is a resciornol glue that has some gap filling properties, lower required clamping force along with the fact that it can be thickened as well. It also has a much lower acceptable application temperature at around 50 degrees. A real bonus here in upstate NY.

I'm not sure what I'm going to use between the layers yet. I'm leaning towards a slightly thickened epoxy. I've seen others use tar, construction adhesive and one time i saw picture with what looked like a thinset of some kind being troweled on, not really sure what it was. So I'm still searching for the best choice.

I've used Fiberglass Coatings Superbond for quite a few years with great results. 1 to 1 mixture that's already thickened & is really easy to use.
https://www.fgci.com/bp_viewproduct....oldItem=135361

[Scout 30]

John cross posted this into the wrong thread so I'm moving it to the correct one:

Dear Friends,

Before this discussion leads to virtual fisticuffs, may I recommend reading "Covering Wooden Boats with Fiberglass" by the late Allan H. Vaitses and published by International Marine/McGraw Hill. It's the bible on this subject and will answer most, if not all, of your questions and concerns. I have used the techniques described by Mr. Vaitses, with complete success. The few custom builders who still use cold molded plywood all use similar techniques, relying on mechanical connections to resist laminar shear, rather than adhesion, which is weak for polyester resin, and stronger than the face of the plywood can tolerate for epoxy resin.
Reading is also relaxing and good for the nerves

Happy New Year and Safe Passages
John Mardall
Vetus Maxwell Group

[Scout 30]

Originally Posted by Scout 30

John cross posted this into the wrong thread so I'm moving it to the correct one:

Dear Friends,

Before this discussion leads to virtual fisticuffs, may I recommend reading "Covering Wooden Boats with Fiberglass" by the late Allan H. Vaitses and published by International Marine/McGraw Hill. It's the bible on this subject and will answer most, if not all, of your questions and concerns. I have used the techniques described by Mr. Vaitses, with complete success. The few custom builders who still use cold molded plywood all use similar techniques, relying on mechanical connections to resist laminar shear, rather than adhesion, which is weak for polyester resin, and stronger than the face of the plywood can tolerate for epoxy resin.
Reading is also relaxing and good for the nerves

Happy New Year and Safe Passages
John Mardall
Vetus Maxwell Group

In response, I bought this book more than 20 years ago & I agree, it is a great book. However, it actually pertains to glassing old wooden plank on frame boats in order to save them. Vaitses theory, which has been proven by time, is that if you use the wooden hull as a mold, mechanically fasten the first layer of glass to the hull & then actually apply a layup thick enough to be a fiberglass hull in an of itself you have the best of both worlds. Although it would seem that the boat would be much heavier they actually ended up lighter because the wood was allowed to dry out. More than one great old boat has been saved this way which is a credit to Vaitses & a boon for the rest of us. One of the unique things about Vaitses process is that he actually lays the boats on their sides to make the glassing easier.