Plastic transoms !!!!!!

[phillnjack]

first off im Not sure if this is the right section to post this, so i am sorry if its wrong place

Has anyone here had or use a transom made from recycled plastics ???
i am renovation (destruc t and rebulid) my boat as the transom was totaly rotten.

i was going to use brand new marine ply inside the back but have since been looking at some stuff called ecosheet and also stokbord.
'this stuff is made entirely from recycled plastic and the information on it says its stronger than ply and will not rot.
it good for fresh water tanks,can be used in salt water as well,is never gonna rot and can be cut with noram tools.
Its not the same as the coosa board, this stuff is just about the same weight as ply in same thickness etc, but seems to be ideal if it can be stuck down with epoxy or polyester resin and cloth etc.
i just wondered what is the downsides to something like this and has it been used by one on this forum.
i like the idea of a transom that cannot go rotten as my boat is not like a normal boat thats easy to take the top off and just replace the transom and stringers etc.
the boat i have is like a classic 13 boston whaler and ive managed to get it apart in two halves.
The boat will again be filled with foam between the 2 skins and will have a new transom put in,but i am thinking should i go with the ply or try the plastic transom.
i dont want to be putting it in then finding its not gonna work, as once back together this boat will NOT ever come apart again.
It took 5 days to get the 2 skins apart and only lucky that i made a special tool by pure accident to let me get at the foam and cut it.
you can see by the pics below that this was a bit of a task.
any info on a plastic type transom would be great

also my transom is just 2 x half in boards with small centre section of another 1/2 inch board.

the transom board did not go all the way across, but will be when put back and tabbed in realy well and also the back corners toughened up as well
proginaly rated to 50hp, but i am going to probably end up with 70hp when i get bigger carbs.


phill

[zul8tr]

Not a fan of the plastic for your transom repair because it tends to creep flex under load and not return.

I would clean out all the bad wood and just leave the outer fiberglass of the hull at the transom. Clean rear fiberglass well with acetone or laquer thinner. Then make a good fitting marine grade 3/4" x 2 piece plywood transom piece. Laminate (weights or clamps or stainless screws as needed) the 2 pieces together with epoxy thickened with some cabisil before install on the transom. Then epoxy all edges and back face (aft) then install this unit to the transom bedding it with good dose of cabasil (fumated silica) thickened epoxy on aft and edges. Come up with a rig to force the plywood unit to the hull at all areas till epoxy sets. Fill in any low areas around perimeter and transom top with thickened epoxy. Sand transom wood unit and adjacent areas of hull. Epoxy all interior exposed transom wood with unthickend epoxy. Then lay the fiberglass cloth on the inside of the wood unit and wrap to the existing hull. Use more unthickened epoxy to fiberglass the cloth down. Before complete set up apply another layer of fiberglass and unthickened epoxy. Add fiberglass to corners as desired. Use three coats of unthickened epoxy to seal off. Prep and paint color as desired.

I would not use polyester resin for any of this repair it will not hold up. Epoxy bonds much better to wood and old polyester and is stronger. Here are some resources on the subject of epoxy repair.

http://www.westsystem.com.au/west_sy...s/publications

Use a good brand of epoxy. West is one of the good brands but not cheap.

[David Mason]

One Add

If you do decide to go with wood, and in the instances ZUL8TR indicates using thickened epoxy, i would use a high density filler and not the other. If you look at the West Systems products, the 404 Filler is the one to use, it has superior strength vs the other fillers. Other than I would probably do it the same way he describes depending on how hard it is to get at. And in my opinion, a transom needs that strength. Be sure to paint or seal off any exposed epoxy, as it is not 100% water proof or UV proof. It needs sealed.

[zul8tr]

Dave

As you note the West high density filler 404 will work but so will their silica 406. I just use the silica for structural bonds in my hydroplanes and other structural repairs and no problems and they last without rupture.

The West article section 5.3 deals with a transom repair similiar to what is contemplated here and they use either 403 or 406 for the new plywood piece install.

http://www.westsystem.com.au/files/p...aintenance.pdf

This West table indicates the uses for the fillers.

http://www.westsystem.com.au/west_sy...oducts/fillers

They list the 404 high density as a hardware mounting filler and 406 silica as a structural filler.

[David Mason]

Unless they changed something, the tensile, flexural, and elongation stengths were much stronger in 404. Could be they changed something, I have not looked at the techincal data for a while. I just use what I have experience in and can predict the results in from my own expereinces.

[zul8tr]

Who knows? They always change things. Maybe Phillnjack should call West to get the straight? BTW both 404 and 406 contain silica per their MSDS.

[phillnjack]

well the west system stuff is not going to be used for sure.
Its an absolute mental over the top price over here in the uk, as is epoxy resin

Now i know everyone is saying use the epoxy etc,but i am going against this idea, and will only have myself to blame if it all goes wrong.
the advice is probably what i should of gone with but thats now not happening.
(
its gonna take a long while beforethis rots or falls apart, so hold all the "i told you so" for little while.
Because many boats have been succesfuly reapired using poly and csm in the past. !!!

As for thickness of the ply !!!!
I cannot fit 2 pieces of 3/4 inch boards in this boat due to there not being that amount of space in between the two shells of the boat.
This is very similar to boston whaler classics in that there is not much room beteween the two skins.
in the centre of the transom it is 3pieces of 1/2inch ply, but only for 20 inch wide at the top and 11 inches at the bottom.
then its back to 1 sheet of 1/2 inch ply on the hull section and 1 piece of 1/2 inch ply on the superstructure.
The superstructure shape gives the boat a lot of its strength, plus the foam that gets inserted and creeps around all the cavities.
I have ground the hull back to fibreglass and its 100% clean, and will be using poly resin and csm on the transom.
I have completely encased the main transom board with poly and 225csm , plus also covered the centre section ply with the same.
This means before the wood even goes in the boat all the wood is completely encased with cloth and resin to help preserve the ply.
The only place that water will get to the ply is through the transom hole inbeteen layers of glass/wood/glass/ wood/glass if i dont seal this area when it goes back together with a new drain fitting.
On the transom ply i have cut out a 3 inch diameter circle where the transom drain tube will be fitted and covered the edges with epoxy resin to seal the wood, then filled the area with resin and csm.
The hole when drilled out will have a 1inch diameter all around it that is glass and epoxy not just bare wood, this will also be sealed when it goes in with epoxy resin to make a good seal. (i hope)
If any water gets in the boat on the main floor this cannot get to the inner hull due to being bonded and a complete seal all around.
This i have done before with skikaflex and it does make a very good waterproof seal.
I found a couple of damaged areas in the hull bottom and repaired those by grinding the inner hull back to fibre strands and put down 2 layers of 450 csm and it has bonded extremely well.
in one other place i bonded in a small piece of wood to see just how good the bond will be to test it.
I have tried as hard as possible and cannot get it apart, so the theory of the new poly not adhearing to the old seems a bit of a myth to be honest, as this is a very strong bond, maybe if people dont go all the way back to strands its a
weak bond i dont know ?, but by grinding with 24 ggit silicone carbide disc's i have the hull looking in a raw state if that
makes sense and very rough to the touch and this takes the new resin and cloth very very good..
Like i say i have found 2 areas where the hull had been penetrated at some time and i have done very good strong repairs.
The transom i have also ground right back to fibres and again got a very good bond on it with layer of 450 csm.
On just the transom of the hull (not on the superstructure transom) i will have used a round 5 kilo's (11 lbs) of resin.
on the superstructure i will use around 3 kilo (6lbs ) of resin.
i will of used around 6 square meters of cloth on the hull transom and around 3 square metres on super structure.

The Boat originaly had the transom ply just 36 inch wide, i have used 53 inch wide as this is where the transom starts
to bend round at the corners.
i have also kept the transom board a touch higher at the sides of engine well to help with strength.
The original ply was also only bonded to the transom with some rubbish sort of glue and relied on the ski eyes mainly
to hold the board in place.

There was fittings for original rope type steering pulleys on the outer edges of transom but these fittings did NOT go through wood just a void filled with foam.
Now new bolts will be going through 2 layers of ply and 3 layers of cloth as will be used for small fittings on the inside.
these will ofcourse be sealed with epoxy then re-drilled and sealer used to make sure again no water penetration.
All engine bolt holes have been drilled to 1 inch diameter and filled with epoxy resin and glass cloth then re-drilled to 1/2 inch for the transom bolts.
So again this gives a waterpoof seal to the wood and will also have sealer on the bolts when engine is re-fitted.

The original section of wood that was attached to just the small space where the engine was fitted was the only place
where 1 of the ply pieces was glassed in.
This was also the only piece of wood to have survided in tact and not 100% rotten.
If all 3 pieces of ply had been covered with resin and cloth then the transom would of been still good and servicable.
It was rotton due to the boat being allowed to have water enter the lower cavity where the wood was not sealed or encased in anything and not repaired and water allowed to just penetrate uncovered untreated
ply.
The ply was not treated in anyway whatsoever, and was just in put in by very lazy boatbuilders.
This type of boat never has a transom rebuild, and i dont know of another one thats ever been taken apart to this extreme.
(not saying its never been done,but i do not know of another, and the makers of this boat have never heard of one being taken apart)
The boats are built exact the same way as classic whalers in that they get bonded then filled with 2 part closed cell foam to fill the entire cavity and to give strength and this causes what they all claim to be a unique bond that cannot ever come apart , and makes the boats unsinkable (Titanic was unsinkable ??)
Now this is where the poor workmanship comes in big time, your never supposed to be able to see any
of this very poor and cheap work !!!!!!!

When i spoke to the makers of this boat and asked about how it was built, i was told it was very much like i am going to be doing to it.
But when i managed to get it opened up,it was not even close to what they had claimed.

If just 1 metre of cloth had been put on to the cover the wood, it could of saved all this work i am now doing.

On the superstructure they did cover the wood with cloth ,BUT they left the bottom corners without
bending around the wood to cause a seal, so ofcours the wood uses its capillary action and draws
up the water to rot the wood even though encased in a single poorly laid piece of cloth.
again the sizes of ply they said are fitted are nothing at all like what i found in mine.
it was 10 inches narrower at the top and the bottom again narrower than said.
I honestly think if just 10 minutes more attention to detail had been done at time of building,then this
boat would of lasted many more years to come.
This boat was built in 1979, ok its 34 years old and im moaning about the rotten wood, but if you go and buy a new boat that is very expensive for its size then it should last a lifetime unless damagaed ofcourse.

On the rear corners of the hull there is also a lot NOT to be desired, strengtheneing pieces of cloth that look like they should of been chucked in the rubbish bin were used instead of some nice larger pieces.
These corners i will ofcourse be re-enforcing with large amounts of cloth and again plenty of resin used.

The inner hull bottom is getting 2 new extra layers of 450csm put on as well and will continue to the transom and up the back to give more stability to the hulls rigidness.
it will make me happier to know ive got a slightly thicker hull than the 1/8th of an inch original !!!.

The amount of wood going back in works out to almost double, and the grade is better as well.
It will all be encompassed in glass and all edges sealed with epoxy before the boards are put back
into the hull and on the superstructure.

I have had a few people tell me i am going way over the top with the rebuild, but i think im just doing
what should of originaly been done when the boat was new.
These boats when built the way mine was are rated for 50hp, mine i hope will be well capable of taking my 60hp and not snapping the transom off especially if a fit a jack plate later on. ?
I didnt get a great deal of movement with the old transom, i am very suprised at that seeing as
how rotten the plywood inside the boat was.

Now i know a lot of people claim that poly resin is no good and dont stick and is not waterproof, but i
have not found this with the stuff im using.
I got my resin and cloth from a place that sells all different types of resin and sells about 10 different types of poly resins and also about 7 different types of epoxy resin.
The stuff recommended to me by this company is the stuff that is Lloyds aproved for boat repairs and
for ship building.

This stuff is call "Crystic 2-446 resin if that makes any sense to those in the know !!!

over the next few days i have a good few repairs to be done to the superstructure and also plan
to make a few pieces stronger as well ,then hope to start putting it all back together.
Then i have the job of re-foaming the boat,
That bit i think just might cause its own set of problems, as i dont want holes everywhere on show.
I am thinking of 4 large stereo speaker holes to aid in putting foam back in the large cavity of the boat.

when ready to go back together i will take planty of pics to show how its all been done (or not if it goes wrong).
before i put the new glass on the seam of the 2 shells i am going to do a dry run to make sure
everything lines up and fits back together ok.

if anyone can think of or know of any thing i might be forgetting to do on this rebuild please let me know, i am
sure there must be something i am forgetting, but once this gets re-joined then its stays joined, never to be
opened again by me thats for sure.



phill...........

[zul8tr]

Ok Polyester resin it is. So sand and clean well with acetone all areas of the existing fiberglass that will be overlapped with new glass and polyester resin. Fit whatever thickness of ply works for the clearance.

[phillnjack]

now the acetone thing

ive heard many people say tp use acetone, and also a few people that say under no circumstances use it as it can leave traces and cause the resin to fail

is there something else that can be used like white spirit or turpentine ?
i do know that acetone is actualy a paint stipper and is sold as nail varnish remover as my wife bought some ?

phill

[hydroc888]

Hi Phil . I dont normaly get involved here but I have fixed , foamed, built, changed many boats in my life. Took a Glastron 173 and made bass boat out of it . Took 5 Avengers and made [ what would be called COR 100s ] out of them.
Epoxy will stick to polyester , Polyester wont stick to Epoxy . Polyester stick to polyester just like you were putting it in a mold. Age dont matter as long as you gring the old down to good stuff, like the strands you were talking about.Grind it down , clean off the dust and glass , dont be afraid to get it real wet with resin Fiberglass cloth or mat or roving has no strenghth on its own , and you know that , but when inpregnated [ can I say that on BRF? ] it has all the holding power it takes to go 100 MPH, that has been proven over the years. Acetone is used to clean your brushes , and rollers as it will CUT THE RESIN and you can use it for thinning resin for spraying but I would recommend Tuline instead. I wish I was young enough to play with the new Kevlar products.
Foaming a boat= The way I did it was cut 3" holes about 2 ' apart in the double bottom from transom to bow, if you have stringers then you have to make holes in everyplace you want to foam and save the pieces ,attach plywood pieces to the 3" plugs so they will span the openings. Most important is raise the bow considerably above the transom height so YOU DONT TRAP THE FOAM . If you trap the foam to where it cant expand it Will worp the bottom beyond repair , seen it done, Pore fome in the first hole and let it expand when it get close to the second hole and looks like it will overflow put a plug in with screws and got to the next hole making sure you get all the hull full. This works for any foaming on your boat.
Thats it for me .
Hydroc888