More Transom Questions

[TripleBBB]

New to all this and maybe taking on more then I can chew here but I been reading what I can on the subject and have a few questions.


1. Is Epoxy and Fiberglass Resin the same thing? .... What i Picked up at the store is "3M bondo brand" Fiberglass Resin with hardener. Is this suitable for the job or not?

2. The lumber yard dealer here in Canada (Windsor Plywood) is telling me that the good one side Fir plywood they have, is made with the same glue as the marine grade plywood only difference is its good both sides, and of course the price $122 for marine. $42 for good one side Fir. This project needs to last only about 5 years. Is the one side good Fir suitable, and if so should I put good good sides of plywood to the inside or outside.

3. The old Transom I ripped out had a sandwich of fiberglass mat between them (factory). this is the way I planned to do it also. Please correct me if I'm wrong ... Two coats of epoxy to both layers of my cut out Plywood a layer of soaked fiberglass mat between the two and screw together using 1 and a 1/4 inch screws. (should I remove the screws after it drys and fill in the holes with another coat of epoxy?)

4. What is Tabbing? "tab the plywood into the hull"

I will see if I can get this far ok with out asking the next batch of questions .... :D

Thanks for all replys

[ondarvr]

1. The resin you're looking at is a polyester, not an epoxy, but it will work. The problem with this particular brand is that it gets hard very fast and can be difficult for a rookie to work with, especially in the summer.

2. Marine plywood is a better product and there are various grades of marine ply for different applications. But if all you want is 5 years out the repair, most any exterior product will last that long. Are you sure you only want it to last 5 years?

3. Yes you can bond them together in this fashion.

4. When the transom is in place it needs to be tied into the rest of the structure, the tabbing typically just refers to the laminate used to do this.

[apex1]

Do´nt know why repeatedly people are talked into polyester on wood? Leave the crap where it is and use the cheapest "real" Epoxy resin instead. It is not that much a difference in price. Polyester has severe bonding issues on almost every material, including polyester. Epoxy sticks to almost every material, polyester included.

Your plywood dealer is a liar! It is not only the glue what makes a marine grade ply, it is the quality of the single veneer layers too! Especially the inner layers of almost all ext. ply sold in North America can hardly be named wood, it is (well you know).

The inner layer of chopped strand mat you´ve found in your transom was a cheap trick the manufacturer used to have no gaps between the wooden surfaces. If you have a reason to fear gaps you can go the same way. If the shape of your transom is simple and you do´nt have a issue with uneven surface and possible gaps, you can just thicken the resin with sawdust (finest grain, almost no grain), and you have a very nice and strong glue.
Yes you should get rid of the screws and either drill holes for dowels which you glue in with Ep, or just fill the holes with thickened resin (a bit tricky).

That will last much longer than 5 years, but a insufficient repair might last just one, and then? Then you know the poor man pays twice.

Regards
Richard

[ondarvr]

As you can see by Apex1's response he does not like polyester, this is a common opinion on this site and for good reason. Most here are into building larger craft of far more value and for what they do epoxy is the product to use.

On small boats of little value and a budget even lower, you need to evaluate the need for some of the higher end products. If you planned to pass this boat onto your grand kids, then yes, you should use marine ply and epoxy, if you want this boat to last five years its not going to make a difference which product you use.

[CTMD]

As you can see by Apex1's response he does not like polyester, this is a common opinion on this site and for good reason. Most here are into building larger craft of far more value and for what they do epoxy is the product to use.

On small boats of little value and a budget even lower, you need to evaluate the need for some of the higher end products. If you planned to pass this boat onto your grand kids, then yes, you should use marine ply and epoxy, if you want this boat to last five years its not going to make a difference which product you use.

Your missing the point a little here. Polyester is a fine product on a straight fibreglass boat. However it does not bond well to marine ply. Hense the advise in this case to go expoy.

[Stumble]

Lets consider...

Polyester is hard to work with, doesn't stick to anything well, and wood even worse, absorbs water, is mechanically weaker, chemically active, and causes all sorts of problems if you want to paint it with compatability.

Epoxy is aesy to work with, adheres to almost anything, makes a stronger bond to wood than the wood fibers themselves, is effectively waterproof, is mechanically very strong, chemically inert, can be painted with almost anything, and costs about 30% more than Polyester.

For my money there is no competition. Particularly when you remember that a polyester boat has to have an EPOXY barrier coat on it to keep the hull from absorbing water.

For the size of the repair you are talking about there probably isn't more than $10 difference in the material cost of the two.


As for Marine grade ply vs exterior ply:

The definition of marine grade ply is that the veneer must be B-grade or better on both sides, may have knots but no knot holes, and may contain wood or synthetic patches. Internally the maximum void size is 1/8 of an inch, and must be made entirely from Douglas fir or Western Larch.

Standard exterior ply may contain any other permissible species of wood, may have core gaps up to 1 inch, and knots or knot holes up to 1.5" across and only has to be finished on one side.

They both do use the same waterproof contruction adhesive however.

Again this comes down to cost vs reward, but in five years a lot of things could happen, and it might be nice to know that if you decide to keep the boat you won't have to rip the transom out again and replace it.

[Frosty]

If you get half way through the job and things dont go perfectly and the polyester starts to go off before its clamped up or screwed, then the whole thing, Ply and all is scrap.

You will have to chisel it all out and grind back. A bigger job than fitting the transom in the first place.

Does this transom hold a motor?

[Ilan Voyager]

Using a polyester over wood it's a waste of time and materials. I'm almost sure that the stuff Bondo is more expensive per pound than an epoxy. On a transom, if the required thickness is enough you can use a strip-plank of one or two layers of a light wood and a good fiberglass. All bonded with epoxy. That will be less expensive and of better quality that a scrappy plywood bonded with some polyester stuff.

[fasteddy106]

For advice on how to go to this site................

http://www.fiberglasssite.com/servlet/StoreFront

there are lots of tips there plus all the products you might need and they will resond to emailed questions, or you can go to this site for products as well, both offer pricing well below that of retailers..............

http://www.uscomposites.com/

Seeing as how you are new to this you might want to heed conventional wisdom and stay with epoxy resin.

[ondarvr]

I still say I'm always amazed at these responses.

"Most" everything said about epoxy is true, and "some" of what's been said about polyester is true, or at least has some truth in it, but most of it is an exaggeration of both the benefits of one and the negatives of the other.

A repair like this can be done very well with polyester and will last a very long time, the typical DIY repair (done with a little care and some guidance) will far out last the desire for the boat.

I’m not concerned (biased) about which product is used on most repairs and there definitely are situations where epoxy is the product that should be used, but this type of repair isn’t one.

[mark775]

"Marine plywood" was made by Simpson in one plant in Oregon and does not exist annymore. Please research Shelmarine product when thinking "marine plywood". The okume is void-less and put together with a rot and water resistant glue. The meranti is denser, stiiffer, stronger. I know of a scrap of Shelmarine okume (In itself, an unremarkable light-weight wood) that has been sitting in a rotting dory in a temperate rainforest for decades. It has moss growing around it until the dory partially fills up with water and the piece floats. Summer comes and dries out everything, making mud of the detritus leaves, etc.. The boat is literally turning to earth. The sample in the boat - with it one could make a violin.

[SamSam]

Polyester will work, rough grind it first, and yes, you take the screws out and fill the holes with resin worked around with a toothpick to get the air out. You can also drive rot resistant wood pegs into the resined holes. If you drill any holes through the new transom for drains, engine bolts, screws etc, you should also resin those holes before proceeding.

[Ilan Voyager]

The main interest of epoxy, specially for a beginner, is a part the precaution of a very good mixing, is practically fool proof. You have time to work, it glues with no problem, it's intrinsically waterproof.

Take an excel sheet of this small project: calculate the cost of a light wood, some yards of fiberglass cloth and a few pounds of epoxy, plus an estimation of the work and compare with the same in good plywood and polyester resin. The difference is small.

But there is a huge difference; the epoxy version will be easier to make and WILL LAST, being lighter. There is no comparison in quality and duration.

Unless you use the plywood as "lost mold" and use a lot of fiber and polyester to make the transom. That becomes heavy and finally expensive.

FastEddy gave some good links, I'll add one http://www.raka.com There is a small and useful manual.

[ondarvr]

Back to the old E vs P.

Yes epoxy is a better product for many applications, the problem is in the small boat world it just doesn't make that big of a difference either way. Cost saved with polyester is minimal in many cases, but not always, weight saved with epoxy in minimal in most cases, it comes to a few pounds at best.

The better bonding with epoxy is a plus, but for the most part polyester is up to the job, the main reason for failure in these older boats if from rot due to poor workmanship during construction, not an inherent flaw in polyester.

For transoms the bond between the wood and polyester is rarely tested, the forces applied and the numerous bolts clamping the two skins together result in few bonding issues. Its the bolt holes and poor workmanship that result in leaks and rotten wood, it would be the same with either resin.

As for ease of use, one of the main reasons polyester is used in mass production is precisely because of how easy it to use when compared to epoxy. It can be tailored to do just about anything you need it to do and be used by a relatively low skilled work force, this is one of the main problems.

Craftsman building and/or modifying larger wooden craft should never use polyester. But those rebuilding a $200.00, thirty year old polyester boat will see little or no difference in the finished product. These rebuilt small boats get used for a few years and then either sold or scrapped, they aren't high quality items of value that get handed down to the next generation like what many on this site work on.

[apex1]

Unbelievable that this crazy dispute comes up every single time a novice mentiones Poly.

A amateur builder has two choices:

leave it

or use Epoxy



Et basta!

There is no IF, or WHEN, or SOMETIMES ONE CAN and such nonsense!


EPOXY RESIN ON WOOD, OR GOLD PLATED CORTEN STEEL! and even that is only second best.

Was that clear now? And loud enough for the alltimes deaf?



The better bonding with epoxy is a plus, but for the most part polyester is up to the job, the main reason for failure in these older boats if from rot due to poor workmanship during construction, not an inherent flaw in polyester.

For transoms the bond between the wood and polyester is rarely tested,

As for ease of use, one of the main reasons polyester is used in mass production is precisely because of how easy it to use when compared to epoxy. It can be tailored to do just about anything you need it to do and be used by a relatively low skilled work force, this is one of the main problems.

Craftsman building and/or modifying larger wooden craft should never use polyester. But those rebuilding a $200.00, thirty year old polyester boat will see little or no difference in the finished product.

And , sorry mate that was the sheer nonsense too! You may ask PAR about the "rarely tested" issue for example, he did and as a result he has a very straight opinion on that subject!

Regards
Richard

[Ilan Voyager]

Apex said it loudly, I'll use a softer voice:

Polyester is inherently not waterproof nor a good glue. Polyester is a product for laminating nothing more. Whatever the level of craftsmanship the wood and polyester will delaminate and rot, I have a long experience of this fact. None of the trials of wood polyester I have seen since 35 years, whatever the precautions taken (polyurethane primary, phenol inhibition by cobalt naphtenate, mechanical "keying", and others) has been successful. Delamination appears within the first year.

Wood and polyester are simply incompatible like oil paint and galvanized steel.

Transoms on small boats using outboards have a lot of stresses. And truly I do not understand the rage of using polyester with an exterior plywood while you get easily better and more durable results with some cedar or pine and epoxy/glass for a very little difference of price.

I'll add that the shell life of epoxy is very long (I have an epoxy 10 years old that I use for fixing doors and small items) and shell life of pre-accelerated polyester very short. A matter of weeks in tropical climat. If the reseller gives you an old polyester you are "F....d". And I won't talk of the problems induced by paraffined polyester, which is the most common.

Using polyester is far more technical and ask for higher skills than a common 2/1 marine non blushing epoxy. Besides polyester, because of the styrene, is far more toxic than epoxy (and smelly).

[ondarvr]

It looks as if you may not have understood what I said or meant by "rarely tested", it has nothing to do with actually testing the bond with each resin, epoxy does it much better.

What I meant was transoms don't typically delaminate at the bond with either resin. When you take apart an old transom (small ski boat), even when the wood is almost pulp, the polyester laminate is typically still bonded to what little wood is left, it may pull off very easily, but was still stuck in place. I meant the bond doesn't get stressed to the point of failure.

The other factor is that in production these boats were built with poor practices, rarely was the wood pre coated with resin, it was put in place and then chopped over, resulting in an even poorer bond.

Many people get very emotional about this subject, mostly on the “hate polyester” side.

Like I said before polyester is not the product to use on wood boats and when engineered correctly epoxy can be far superior polyester, its just that on these small old ski boats it doesn’t make much of a difference.

[ondarvr]

Depending on the type of epoxy and the hardener used, it can be far more toxic than polyester, this one of the other reasons for it not being used in mass production. Styrene does have a very strong odor, but the actual toxicity and health issues are less.

This has nothing to with aged product, or using the wrong type of polyester.

Polyester can also be purchased in an unpromoted state, this extends the shelf life dramatically.

The waterproofness of polyester has little to do with the failures on small ski boats, they sit on trailers for 99.9% of their life. They need to be leaf and weed proof. They get used for a few years and then sit in the side yard under a tree for the next 6 or 7 years and fill with debris, many times the plug was never even removed, so it turns into a frog pond. The poor methods of production now come into play, with thin laminates and unsealed wood, there’s little hope for survival.

[Ilan Voyager]

Mexico is the cemetery of the old American motorcycles, trucks and boats. A lot of used items are sold to the Mexican who are too "poor" to buy the new item.

So I'm continuously asked about how to fix a surprising array of polyester boats since the 12 feet to the 45 feet. Almost all (let's say from the smaller to 36 feet, about 98%) have a structural web, decks and transoms of plywood and polyester and 100% are delaminated everywhere and most rotten at least at the web and transom.

My general advice is "if you are not ready to a total rebuilding of the boat, just keeping the outer fiberglass hull, use one or two gallons of gas and matches to burn it"

At five years old, all these hulls I have examined show structure damage at different extent. At 15 years old it's generally junk: the hulls are "soft", needing a general rebuilding. It's cheaper to go to Tampas or Corpus Christi and to make the bet of buying another used boat.

It's incredible to see the amount of work, and material (crappy plywood and lot, but lot and lot of fiber and polyester) used in those ill fated structures when a simple 1/2 inch marine plywood, some 1*1 and 2*1 inch pine and good epoxy resin would have done the job for less work and money.

[mark775]

"polyester, because of the styrene, is far more toxic" but dead is dead. Don't take epoxy lightly because it smells pleasant.

[apex1]

Apex said it loudly, I'll use a softer voice:
I still could hear you Ilan!
Transoms on small boats using outboards have a lot of stresses. And truly I do not understand the rage of using polyester with an exterior plywood while you get easily better and more durable results with some cedar or pine and epoxy/glass for a very little difference of price.



Nice and practical idea, I must say.

Just calculated a theoretical layup using my (yard internal) data, but should be valid in general. Based on 4m² two strips of WRC 18mm slightly offset, glassed with 240 gsm multidir., 3 layers Ep both sides is a tad cheaper than the same layup in marine ply, isophtal poly. Pennies only.. but quality sure worth it.

Regards
Richard

[ondarvr]

I V

(Qoute) At five years old, all these hulls I have examined show structure damage at different extent. At 15 years old it's generally junk: the hulls are "soft", needing a general rebuilding. It's cheaper to go to Tampas or Corpus Christi and to make the bet of buying another used boat.

It's incredible to see the amount of work, and material (crappy plywood and lot, but lot and lot of fiber and polyester) used in those ill fated structures when a simple 1/2 inch marine plywood, some 1*1 and 2*1 inch pine and good epoxy resin would have done the job for less work and money.


----

I agree, the construction is poor and these boats were built to a price point, not to last. Had they been made from epoxy they would still be failing due to the poor methods and workmanship though, poorly done epoxy laminates and cheap ply still add up to failure.

Remember, the polyester resin used to build many of these boats was purchased for its price, not for its strength and water resistance. Every time a cheaper resin was formulated it went right into production, as long as it got hard it was approved for use.

It may have been a blessing that epoxy was tougher to work with, had it been easier and used in production more often, the product would have been degraded and sold on price like polyester was. This would have destroyed its reputation also

[Ilan Voyager]

No chemical product is innocent. A smell is not a criterion of toxicity. Prussic Acid has a pleasant smell of almonds... But epoxy is mainly a contact (skin) toxic with almost no vapor and it's rather easy to avoid its contact with gloves, creams etc... Styrene is a vapor you breathe, a toxic for the brain and the liver, directly by the lungs, straight into the blood stream. it's far more difficult in a DIY shop to have active carbon filter special respirators, or outside breathable air than to put gloves and cream, that you have also to use with polyester.

Just search the security sheets of epoxy resins and styrene. With epoxy you'll use little solvent, with polyester you'll use lots of delicate products like peroxide, cobalt naphtenate or octoate (good explosives mixed together, highly corrosive), and solvents in high quantity, from acetone to some chlorated stuff.

Polyester is highly flammable and uses a lot of dangerous adjuvants. Epoxy is hardly flammable and apart a few drops of xylene as solvent won't use dangerous products.

Besides I find easier to mix 2 parts of resin/one part of hardener with a tolerance of 10% (better to go a bit on the side of the resin), than 1 part of polyester with 2% of cobalt and eventually paraffin diluted with styrene, and after catalyse with 1 to 3 % of peroxide following the ambient temperature and the "jellification" time wanted .

And I hate this horrible smell that can last years in a boat. A I precise again; the short shell life of polyester makes if you have bought an "old" polyester resin you're "F....d" even if the resin looks good. I do not see an amateur making the mix of accelerator for small quantities.

A last thing, no often you can finish a work in a day. A cured polyester resin needs sanding until exposing the fibers to insure a mechanical key.

A lot of non blushing epoxies have until 2 days of tolerance. Generally a cleaning with hot water and soap plus a light sanding insures a good bonding. Better you can use delaminating cloth; a bit expensive but fast and effective.

[Ilan Voyager]

Nice and practical idea, I must say.

Just calculated a theoretical layup using my (yard internal) data, but should be valid in general. Based on 4m² two strips of WRC 18mm slightly offset, glassed with 240 gsm multidir., 3 layers Ep both sides is a tad cheaper than the same layup in marine ply, isophtal poly. Pennies only.. but quality sure worth it.

Regards
Richard

Thanks for the compliment. Here I use Chiapas cypress, a kind of light white cedar, very durable, rather cheap I can find locally. With 2 layers (0-90 and 45/45) of about 240 gr cloth each side is more than strong as I use a resin with good resilience. I make even the floors and decks this way now, the scantlings being adapted. I do not bother anymore to import plywood here in Mexico.

[Ilan Voyager]

I V

(Qoute) At five years old, all these hulls I have examined show structure damage at different extent. At 15 years old it's generally junk: the hulls are "soft", needing a general rebuilding. It's cheaper to go to Tampas or Corpus Christi and to make the bet of buying another used boat.

It's incredible to see the amount of work, and material (crappy plywood and lot, but lot and lot of fiber and polyester) used in those ill fated structures when a simple 1/2 inch marine plywood, some 1*1 and 2*1 inch pine and good epoxy resin would have done the job for less work and money.


----

I agree, the construction is poor and these boats were built to a price point, not to last. Had they been made from epoxy they would still be failing due to the poor methods and workmanship though, poorly done epoxy laminates and cheap ply still add up to failure.

Remember, the polyester resin used to build many of these boats was purchased for its price, not for its strength and water resistance. Every time a cheaper resin was formulated it went right into production, as long as it got hard it was approved for use.

It may have been a blessing that epoxy was tougher to work with, had it been easier and used in production more often, the product would have been degraded and sold on price like polyester was. This would have destroyed its reputation also

I agree with you.

[TripleBBB]

Well thanks to all for the reply's and information you all have provided.

After weighing all that has been said, the polyester resin went back and I picked up West system 105 epoxy resin and 206 hardener. After looking at there chart I also selected the 403 microfiber adhesive filler. I hope this was the right selection to laminate the 2 (also heeded advice and went with the marine grade plywood) together and then secure them to the the transom shell?

BTW this is a smaller boat, 15 1/2 foot open bow with a 60 HP on it.

BBB

[Ilan Voyager]

You're welcome and I'm very happy of being of any help. Do not hesitate to send a message if you have a problem or a doubt. Best wishes for your project. (yes you have bought the right products, a bit expensive but good ones. Buy a few ounces of colloidal silical or cabosil to control the thixotropy of the resin)

[Manie B]

A amateur builder has two choices:

leave it

or use Epoxy



Et basta!

There is no IF, or WHEN, or SOMETIMES ONE CAN and such nonsense!




and i fully agree
finally epoxy works out cheap anyway

[apex1]

Welcome 9B
and I would like to backup Ilans statement.
Thanks Manie.

[TripleBBB]

Well after a nice vacation I'm back at my little project and chugging along slowly, right now I have my 2, 3/4" sheets of marine grade plywood cut out and coated twice with un-thickened epoxy. I am about to bond the 2 together and am not 100% sure so looking for advice ... Do I have to wet them out before applying the thickened epoxy? and I plan on applying the thickened epoxy with a 1/8 notched trowel, will this be a thick enough layer to bond the 2 sheets?

[PAR]

There are a few different techniques for bonding the transom pieces together, but your notched trowel will work fine for spreading goo. Just make sure you use a "fibrous" filler material (silica, milled fibers, cab-o-sil, etc.).

Since your plywood has been precoated, you don't have to wet it out, but it does have to be scuffed up with sand paper, 80 grit or less will do. Also since you only have two coats of epoxy, you may want to wet out anyway (after scuffing) just to insure water proofness.

I use temporary screws to hold the pieces together while the epoxy cures, but clamps or weights will do also. Remove and seal the holes when cured.

When you bond the plywood to the transom, make sure there is plenty of ooze out around every edge of the plywood, where it rests against the hull. Gently radius this ooze out epoxy, to form a nice fillet around the full perimeter of the transom/hull joint. You may have to mix up more thickened epoxy for this. This fillet is very important.

After the fillet is completed, then tab the transom repair into the hull shell with several layers of cloth tape. You'll want several inches of overlap on the plywood and hull for a good tab.