Resin Questions

[bman1985]

hi, I'm working on a transom rebuild on a 17' runabout. I'm going to be using 3 layers of 1/2 inch exterior ply for the core. I was thinking that I'd coat all the wood in polyester resin (no wax), then do my installation and glassing with epoxy.

Does this Sound reasonable? I'd do all epoxy but the poly is so much cheaper.

[robherc]

For as little as you're going to be using, I'd just stick with the epoxy. I might be tempted to "go cheap" if I were building the entire boat, but not just for a transom repair.


...just my $0.02, take it or leave it.

[bman1985]

How much resin do you think I'll end up using? I'm doing transom and stringers. I was going to buy a gallon of poly and half gallon of epoxy

[robherc]

I'm not sure...too much depends on the total area to be laminated & glassed, plus the weight/# of layers of your glass fabric, plus how much soaks into the wood...I just don't have enough experience to tell you for sure. My GUESS would be that you should be ok with a 1.5 gallon kit of something like MAS low-vis or similar (avalable for a VERY competitive price from jamestowndistributors.com).


....just my $0.02, take t or leave it.

[apex1]

Do´nt know, or can imagine the size of the transom, nor the extra work (you are not planning but may envisage), but do NOT use Poly! If it does´nt stick as you need it to, if it delaminates after some time, if you do´nt cover it (with epoxy), you have a issue.
Pay once, buy Epoxy!
And lettuce have some measurements for a rough calc.

Regards
Richard

[bman1985]

Its 6 feet wide, 20" high at motor mount, total height at risers is 33" pictures attached.

[ondarvr]

Stick with one product or the other, it will survive with either one.

[bman1985]

A local glass supplier told me that new glass won't stick to old glass using poly resin...

[apex1]

A local glass supplier told me that new glass won't stick to old glass using poly resin...

GO FOR EPOXY...................................shall I write it in capitals?....... he was´nt so wrong.

[ondarvr]

Secondary bonding isn't as strong as the chemical bond you get when the entire boat is made in a short period of time by the manufacturer, but the difference isn't as dramatic as most people think. The reason people think polyester doesn't bond well is because of how many repairs are done. Someone with little or no instruction buys some resin and cloth and heads for the boat. They're supposed to grind the surface very well with a 36 grit disc on a grinder and clean the surface well, what they do is find an old used piece of 150 grit paper designed for wood, that's been in the garage for 15 years and then make a feeble attempt at sanding the surface. After about two minutes they give up without even breaking the surface of the old laminate or gel coat, they haven't even removed all the old dirt and oil on the surface yet. It gets the once over with a rag and that's all the prep it receives. Now they mix up a quart of resin and pour it over a 6"x6" piece of cloth, I didn't mention mat or catalyst because if any catalyst was added it was most likely no where near the correct amount. Mat needs to be used as the first layer and in between each layer of woven fabric or the bond will be poor and the first timer never uses it.

After about two weeks the resin is sort of hard so they put the part (whatever it is) into service and wouldn't you know it, that cheap polyester resin failed, it must be junk. At that point they go back to where they bought it and complain. This time they get epoxy because its supposed to stick much better (and it does) and head home. The old repair gets ground off and cleaned well, they were also told epoxy needs to be mixed accurately for it to harden, so for a change they measure it. This time multiple layers of cloth are used and the repair holds up, it must be because they used epoxy, its great stuff.

There are many secondary bonds in boats, the bigger the boat, the more there are, if the surface is prepped well these bonds don’t fail and since the prep is the same for epoxy or polyester the same amount of work is involved. Don’t get me wrong epoxy does bond better, it’s a glue, polyester isn’t, but polyester does bond well enough to polyester to make a very good, long lasting, strong repair.

In the end there’ll be no difference in how your boat performs or survives over the years with either product, you’ll never notice the difference. The difference will be in how well you do the job, make sure all wood is covered well and all the holes you drill need to be sealed. Unsealed holes, gaps in the laminate, trim that isn’t applied correctly and lack of attention to detail is where the failure starts.

[c_deezy]

Secondary bonding isn't as strong as the chemical bond you get when the entire boat is made in a short period of time by the manufacturer, but the difference isn't as dramatic as most people think. The reason people think polyester doesn't bond well is because of how many repairs are done. Someone with little or no instruction buys some resin and cloth and heads for the boat. They're supposed to grind the surface very well with a 36 grit disc on a grinder and clean the surface well, what they do is find an old used piece of 150 grit paper designed for wood, that's been in the garage for 15 years and then make a feeble attempt at sanding the surface. After about two minutes they give up without even breaking the surface of the old laminate or gel coat, they haven't even removed all the old dirt and oil on the surface yet. It gets the once over with a rag and that's all the prep it receives. Now they mix up a quart of resin and pour it over a 6"x6" piece of cloth, I didn't mention mat or catalyst because if any catalyst was added it was most likely no where near the correct amount. Mat needs to be used as the first layer and in between each layer of woven fabric or the bond will be poor and the first timer never uses it.

After about two weeks the resin is sort of hard so they put the part (whatever it is) into service and wouldn't you know it, that cheap polyester resin failed, it must be junk. At that point they go back to where they bought it and complain. This time they get epoxy because its supposed to stick much better (and it does) and head home. The old repair gets ground off and cleaned well, they were also told epoxy needs to be mixed accurately for it to harden, so for a change they measure it. This time multiple layers of cloth are used and the repair holds up, it must be because they used epoxy, its great stuff.

There are many secondary bonds in boats, the bigger the boat, the more there are, if the surface is prepped well these bonds don’t fail and since the prep is the same for epoxy or polyester the same amount of work is involved. Don’t get me wrong epoxy does bond better, it’s a glue, polyester isn’t, but polyester does bond well enough to polyester to make a very good, long lasting, strong repair.

In the end there’ll be no difference in how your boat performs or survives over the years with either product, you’ll never notice the difference. The difference will be in how well you do the job, make sure all wood is covered well and all the holes you drill need to be sealed. Unsealed holes, gaps in the laminate, trim that isn’t applied correctly and lack of attention to detail is where the failure starts.


+1, good info. Just like everything else, final product is only as good as the prep.

[apex1]

In the end there’ll be no difference in how your boat performs or survives over the years with either product, you’ll never notice the difference. The difference will be in how well you do the job, make sure all wood is covered well and all the holes you drill need to be sealed. Unsealed holes, gaps in the laminate, trim that isn’t applied correctly and lack of attention to detail is where the failure starts.

Right, and for that reason go for Epoxy............. sticks several times better, no fear about moisture or blistering, and the same hours of labour!

Regards
Richard

[ondarvr]

In this application there is no fear in bonding, nor is moisture and blistering an issue, so we're back to even.

The reason for blistering with polyester (and I'm including VE) is using the wrong resin for skinning the hull, if you use the wrong epoxy for a critical application it will fail also.

Polyesters are so forgiving that they can be abused horribly in production and still build a part that looks good when it goes out the door. Its a few years down the road when these abuses come back to haunt the owner. Don't blame the product for misuse by those using it, epoxies would have the same issues if untrained, careless employees were mass producing products for the lowest price possible.

[apex1]

In this application there is no fear in bonding, nor is moisture and blistering an issue, so we're back to even.
The reason for blistering with polyester (and I'm including VE) is using the wrong resin for skinning the hull, if you use the wrong epoxy for a critical application it will fail also.
Polyesters are so forgiving that they can be abused horribly in production and still build a part that looks good when it goes out the door. Its a few years down the road when these abuses come back to haunt the owner. Don't blame the product for misuse by those using it, epoxies would have same issues if untrained, careless employees were mass producing products for the lowest price possible.

Nothing to argue.......:cool: .....if not misused...

Regards
Richard

[bman1985]

Thanks guys, I just want to do it right the first time so I'm doing lots of research. I've got the book runabout rennovation in the mail, I heard good reviews, gonna read that and then get to work.

I ran through the math on going all epoxy vs a mix, its really not even much more money. If epoxy is more forgiving, then me as a first timer will probably be better off.

I'm thinking I'll order 2 gallons, if I have extra, then I'll find myself another project to work on.

[ondarvr]

You're right, for a job this size the cost difference will be miminal.

Depending on the epoxy you get, it may be a little more difficult to work with than a polyester, but that's about it.

[bman1985]

I was looking at the stuff from uscomposites, 635 thin epoxy with medium hardener.

[ondarvr]

Epoxies tend to drain out of the glass a little more than polyesters do, so you need to keep an eye on it until it starts to harden.

I can't tell you anything about the product your looking at though.

[legendinownmind]

ondarvr, is right about all of it. Polyester is the way to go. It wets out better and does not drain as bad. I just had to write something.

[PAR]

Polyester isn't the product to use and frankly there isn't a debate to argue, the facts speak for themselves. Polyester makes a poor bond to itself and much worse on wood. It's not waterproof, which isn't good for wood and doesn't have the modulus of elasticity to compete with wood's physical properties (the primary reason it fails on wood). This isn't subject to debate, it's fact.

The only way to make polyester work on wood is to make the laminate as strong as the wood, which defeats the reason for using wood in the first place. Even if this thick laminate sheers, the wood is irrelevant as far as strength is concerned.

Epoxy on wood, if you don't want to do this again in the future.

I will agree with Ondarvr in that both products rely heavily on surface prep and sufficient cure times.

Skip the mat, which is a bulking agent in poly lay-ups, but completely unnecessary in epoxy laminates.

Epoxy is far easier to work with then polyester resins and much more forgiving to the novice. It smells a whole lot better too.

Log onto West System's web site and download their user's guide to familiarize yourself with its uses. Also perform a search on this site for transom repairs. It's a subject that's been covered many times with much useful information.

[bman1985]

Yeah this site is great, I've looked at a lot of transom repairs, but the resin was still holding me up.
I had found the west system guide through another post on here a few weeks back. It really tied everything together.

I'm planning to use all 1708 in this repair, and epoxy thanks to all the good info.

[apex1]

I just had to write something.

sometimes the waiver of, is the wisemans comment.:cool:

[mydauphin]

I agree on Epoxy, specially for transom. However, I can make a mean boat out foam core, polyester resin, then epoxy. Polyester is stiffer, epoxy more flexible. Lighter and stronger than either alone. Consider alumimum plate to reinforce area of engine plate.

[bman1985]

I've seen aluminum plate on transoms before, I thought it was just an attempt to fix a weak transom without doing the work of replacing it.

[mydauphin]

In a few boats, I have glued and bolted aluminum plates to transom with Epoxy. Sometimes on both sides It greatly strengths it. Many people put large engines on transom than the design entailed. Alumimum helps distribute forces.

[ondarvr]

PAR

I agree with you on many things and respect your opinion, I know many people on this site are anti-polyester, some for good reasons and some for not so good reasons, just bias.

Epoxy is vastly superior in many ways when compared to polyester, but frequently epoxy is overkill in many applications, and it is in a repair like this is one. We're looking at a very old boat with a small OB and when you look at what failed it wasn't the resin, it was the wood that rotted and the polyester is still there holding the pulp in place. Did the wood rot because the polyester wasn't water proof... no.... water gets in through unsealed holes and other similar shortcomings in construction, not through the laminate unless it was very thin ( and that happens, another shortcoming in construction). On this boat it looks like the trim cap on the transom is a good place to start looking for water intrusion and there are most likely other holes that leak also. These areas would leak whether the resin was epoxy or polyester and rot would be the result, with no difference between the two.

This boat looks to be from the late 60’s or early 70’s, so we’re looking at around 40 years of service out of the original construction, which may have been less than ideal. If he repairs it with similar products and probably more care than when first built, it will probably last that long again, not bad for a terrible product like polyester.

When bonding to wood there is no comparison, epoxy is far better and when building a wooden boat there is no question, epoxy is the product to use. But in this type of repair rarely is the bond stressed to the point of failure with polyester, the transoms on small power boats are thru-bolted in many places so the skins are secured in place.

The bonding, or should I say lack of bonding, of polyester to polyester is blown far out of proportion, while the bond isn’t as strong as when using epoxy, it’s more than strong enough to be reliable and durable.

I think the big difference is in the care and experience of those using the two products, plus the intended market of the finished craft.
Craftsmen using epoxy are taking extreme care to have the part engineered and well thought-out before starting the project and then proceed with great attention to detail, this includes original construction and repairs. These finished products are also valued for their design, workmanship and function over cost.
Until recent years it was rare to have an engineer working on production boats and even now many have no education in marine related composites. Production boats were built as needed to speed the build and lower the cost, these were the goals, “best practices” were rarely a concern. Resin choices were based on price and how fast they could build a boat with them, not strength or water resistance. Even to this day we make many resins that are far superior to what gets used in production. Now figure in low paid, poorly trained workers only looking forward to getting drunk on the weekend and the result is a mess. It was only the illusion of the supposed very forgiving chemistry of polyesters that made all of this possible. These shortcuts and/or bad decisions didn’t show up until a few years down the road, the boats more or less looked good going out the door.
The customer was buying based on style and price, not the quality of the finished product.


For the type of craft and customer base you have, epoxy is the product to use.
These small project boats are purchased for a couple hundred bucks and the budget for repairs is even less. Typically it’s a new boater that will only keep the boat for a few years at most before it’s sold at a loss, or is forgotten in the side yard. If the repair is small, as in this case, then the cost difference between the two products is marginal, if the project is larger, then the cost difference can be a deal breaker. 99% of people that finish a project like this, and many don’t finish them, will never see any difference in the final product with either resin, so I can’t see a reason for an “epoxy only” view point.

For decades I traveled around North America repairing, modifying, building, refinishing and installing just about anything you can imagine made from fiberglass. 95% of time it was some type of polyester or VE that was used, when needed I used epoxy. After doing it for that many years the numbers of call backs and/or failures were so few that I can’t really recall any (there must have been some minor ones though).

What it comes down to is that sometimes good enough, is, well, good enough.

OK, blast away.

[ondarvr]

Had to add one more thing.

One reason epoxies haven't been used more in production boats is because they are more difficult to use, it would be much harder to make 25+ boats a day using epoxy. I wish all my boats were made of epoxy, but if they were I don't think I could afford them.

[PAR]

I agree for the most part with you Ondarvr, in that well done repairs with poly work fine. The results will be heavier, more brittle and more effort for the novice. Epoxy is easier for the novice to work with then poly. It's strength can over come lamination mistakes made under the shade tree.

My experience has shown that back yard users, routinely screw up poly batches or laminate procedures more readily then when using epoxy.

Manufactures don't use it simply as a business decision based on end product cost and having to change a shop over to epoxy.

I'm like you in that I've done many poly repairs, with few difficulties, but this isn't our first picnic either.

On home brew transom jobs, I prefer epoxies repairs just to insure good tabbing and bonding to the substrate. One of the difficult things with these home grown repairs is getting sufficient bonding area, from old to new work and a good bond between the layers of plywood. I've seen shade tree jobs where the feathered back area was 1" wide and the tabbing overlap the same. To insure a limited access area stays stuck and the small amount of materials and work involved in these types of repairs, I tell folks epoxy. It's an easy way to get extra insurance the transom's not going to pop off when they gun the engine the first time.

You are also correct in that these era boats were poorly engineered, usually way heavier then necessary with pretty crappy resins and poor lay up procedures. I've repaired a lot of them and wondered why they used wood at all some times. I remember a particular sailboat, built in 1970 as a 22' centerboard cruiser. It had a 1" thick laminate near the keel and was about 3/8" at the rail, on a one ton boat! You could set a grenade off under this thing and it would have hurt it. Of course it sailed like a pig too.

Many of these boat survive purely by the ridiculousness of their laminate schedules. Then came the "dark years" and you know what era I'm talking about. They started fooling around with resins, fabrics, techniques, etc. and boy did they save money in manufacturing costs. These are showing up with more frequency in recent years. Some love the cool styling, other the prospect of a free or cheap boat.

I'm sure you and I could go on all day about the good, bad and ugly of it all, but I'll stick with telling amateurs to use epoxy, if for no other reason then it smells better and puts a pretty shine in your hair if you get some on you.

[bman1985]

Well I got my runabout rennovation book, read up to the transom section. (not sure if any of you are familar with the book) He uses poly resin. Also he says he puts aluminum plate on the outside.
Not sure which resin I'm going to use still, epoxy really isn't much more money so I'll probably use it.

ondarvr, you are correct in the years, its a 1964 Crestliner, I'm supprised I didn't put that in my post originally.
The rating plate says its rated for 120 hp. Motor on the back when I got it is a chrysler 140, which by no means is putting out 140 hp but I'd still like any extra support I can add in.