What ply for transom?

[Sea-Dog]

For a 25mm transom, should I use 1x piece of 25mm ply or 2x 12mm resined together.

Which would be stiffer?

Also which resin is going to have the best bond for joining to the existing glass - Epoxy or Polyester?

Many more questions to follow as the repair/refurbishment proceeds.

Some of the old transom was like paper - It used to support a 115 HP outboard on a 4.5M glass half cab. (Only rated to 85HP, but that's the way I bought it)

I'm glad the glass was thick. :P

[BM]

If you can get 25mm thick ply (go structural/CD grade) then go with that.

Poly resin will be fine but if you feel so inclined to use epoxy then go for it. I use poly.

[Sea-Dog]

Thanks BM, I can get 25mm ply from a mob called Mr. Ply in Underwood.

I remember reading somewhere that Poly doesn't adhere as well to old glass as epoxy does. Is that your experience?

I have to build this thing to last.

Another product that I have come across is "Techniply"

From website: Techniply GRP (R) - AS/NZS 2269 - Structural - F8. Specifically designed for advanced adhesion to fibreglass laminates.

Ever heard of, or used this?

Price for 2400 x 1200 x 12 = $66.10

Compared with CD Structural Plywood -
2400 x 1200 x 12 = $62.20
2400 x 1200 x 25 = $133.60

I don't mind doing the resin laminating of the 12mm if the Techniply is going to be better.

[Marlin_Mike]

Sea Dog, I sell ply for living, give me a ring during business hours
I sell 17mm form ply and 12mm structural.


Mike
0401 895 856

[BM]

I have done a few transoms and have always used poly. Guys I know in the game with over 40 yrs experience each use poly in most situations also.

The techniply works out around th esame money but more effort involved. Be interesting to see if their claims are proven or simply BS. No boatbuilder/repairer I know uses that stuff (of course many could be) but its up to you I guess.

I have had zero comebacks using CD ply and poly resin and 600 matt. And one of the boats I did we used for a season for skiing (deep start slalom and wakeboarding/kneeboarding) with no issues.

Obviously opinions will differ but my method has seen no comebacks and thats satisfactory for me.

Cheers

[Edencraft]

Use the 25mm structual ply and ploy resin.

Cut the the ply to the shape of your transom then drill about 6 or 8 6mm holes in it all over. Put down about 6oz of resin rich chopped strand mat on to transom and wet out the back of the ply with resin then using g clamps clamp the ply in place ensuring that resin comes through the 6mm holes this should ensure you don't have voids and have a good pond between the old glass and the ply. Leave the clamps on untill the resin has gone off then put another 6oz of csm over the exposed ply. Job done.

[blaze]

IMO I would laminate the 12mm to get the required thickness, round out all corners and fill gaps with Qcell. As BM said 600 matting, in some hard to laminate places I split the 600 to make 300 as its easier to work that way, just remember to add layers to build to strenth required.
cheers
blaze

[Sea-Dog]

Thanks for the responses fellas,

Unfortunately this boat has had some butcher working on it previously who has done a partial transom replacement through the rear skin. It looked crappy So I have removed the rear skin, leaving a lip of approx 40mm all the way around. Once I do a bit more removal of material including part of the floor, I may find that the stringers need replacing. (Fingers crossed they don't)

A couple of supplementary questions if I may:

Blaze, Is there an advantage in strength to use 2 x 12mm sheets laminated?
Wouldn't a single sheet of 25mm be more likely to be straight and flat, compared with the two laminated sheets.

E dencraft (had to add spacing to avoid hashes): Considering that I will be replacing both front and rear skins on the transom, is there still an advantage to drilling the holes through the ply?

Marlin_Mike: If I decide to go with the 25mm sheet, do you sell that? (Thanks for the offer)

I'd have more questions, but the wife is hassling me to get out the door at the moment.

Cheers, Ross

[Marlin_Mike]

Gday Ross,

yes we sell 25mm and 12mm structural ply.

Mike

[fish-freak]

For a 25mm transom, should I use 1x piece of 25mm ply or 2x 12mm resined together.

Which would be stiffer?

Also which resin is going to have the best bond for joining to the existing glass - Epoxy or Polyester?

Many more questions to follow as the repair/refurbishment proceeds.

Some of the old transom was like paper - It used to support a 115 HP outboard on a 4.5M glass half cab. (Only rated to 85HP, but that's the way I bought it)

I'm glad the glass was thick. :P
Hey seadog, just enquiring about rotten transoms. I have a 5m half cab that has a dodgy transom! . There is slight flex in the transom itself and certain areas sound hollow. I am up for a new one soon, and have quotes ranging from $1500-$3000. I would be interested to hear how you go with yours!! cheers daz...

[Sea-Dog]

Hey seadog, just enquiring about rotten transoms. I have a 5m half cab that has a dodgy transom! . There is slight flex in the transom itself and certain areas sound hollow. I am up for a new one soon, and have quotes ranging from $1500-$3000. I would be interested to hear how you go with yours!! cheers daz...

Hey Daz, I hope to get out of it cheaper than that. I am prepared to take my time and do it properly. Besides that, my labour is at very cheap rates :P.

I reckon I can buy the tools & materials, AND do the job for around the same price or less than having someone else do it for me.

Time will tell though... time will tell. At least I get some new toys :D

Also I won't be wondering if its been done carefully or not. And that is something else I won't have to be concerned with when out in the boat.

Cheers, Ross

[Edencraft]

Replacing the entire transom not just the ply is a far bigger job and to do it right will take a considerable amount of skill, 40mm is not enough to do a 16:1 fillet where the new laminate meets the old laminate so there may be some strength issues at the join. Are you going to 2- pack the hull after the repair is finished?

[fish-freak]

Totally agree with you e-craft! I am hoping not to pay upwards of $3000 but i will be getting the job done by a qualified tradesmen who has done plenty of transoms before. I will first ask him exactly what he will be doing and what i get for my money! I also what to see photos of previous work and pics of the entire process of my boat. Its just peace of mind knowing the job is done right the first time and i wont have to touch it again.
cheers daz...

[dnej]

http://www.rotdoctor.com/glass/GLrotrepair.html
This is a good site to have a squiz at.
David

[dnej]

http://transomrepair.com/zk/fullrepair.shtml

This site shows how to repair a transom, without replacing the ply.Apparently very effective method .Is anyone familiar with this method?
Would save a lot of time and effort.
David

[SO70]

E craft,

which method of transom replacement do you recommend, from inside or outside.
can you explain the 16:1 ratio you mention previously.
do you do fibreglass repairs or is it just new boat building.

thanks

[Sea-Dog]

http://transomrepair.com/zk/fullrepair.shtml

This site shows how to repair a transom, without replacing the ply.Apparently very effective method .Is anyone familiar with this method?
Would save a lot of time and effort.
David

Hey David, I sent an email months ago to ask them if "Sea-Cast" was available in Aus. They said they were working on it.

I like the idea, but not all of the reports are great. Apparently it is heavier than a plywood transom and can also be brittle.

But for the ease of being able to just pour it in - I'd love to be able to use it.

- Ross

[Sea-Dog]

E dencraft, do you mean by 16:1 fillet the same as in welding where the fillet depth is "1" and the width of the tapered join is "16" ?

ie. 1mm deep and 16 mm wide in a Vee shape?

So for 6mm thick glass, the width of the tapered join would need to be 96mm??

It looks reasonable to me. (holds up fingers and imagines layers of glass)

Need to be pretty accurate with your grinding to feather the join that much!


:-/:-/:-/:-/:-/ My brain hurts.