Thread: Transom Replacement

Use marine ply garfy, exterior ply is nothing like the quality of marine ply. It uses the same glue but the quality of the veneers isn't as good - lousy outer veneers, dodgy inner veneers, voids and rubbish glued in there. Hell, even some marine ply has that problem. On that boat, lightness isn't going to be an issue so get some Hoop Pine marine ply - a very good plywood with excellent surfaces (gaboon usually doesn't have as fine a surface though it is lighter while pacific maple is the cheap stuff).

For sizes? What's wrong with what's on the boat now? Just copy what you've got. Hartley have a good reputation and ask yourself this: how long has it lasted up to now? None of these boats were designed to be heritage pieces, they do wear out naturally.

Why do you want to glass it? Glass is useful abrasion resistance and can add a bit of strength if using really thin ply (something done mainly in canoes) but do you need it on this job? Maybe all you need to do tape the seams. There might be very good reasons for glassing her, I'm just wary of doing it without thought.

And yes, pictures are essential or some bugger will wonder if the project really exists

Richard

Thanks Richard
I'll post up some piccys soon as a picture paints a thousand words !

Garfy, as Richard said, just copy the original size, there plenty strong enough and as for the glassing, thats a well discussed topic on this forum and i am sure those that know will offer there advice indue course, as it happens we had a "New Flairlane" (familly boat) she was 19'5" so yours could be "New Superstyle" or "New Interceptor", ours was built in 1963, purchased by our familly in 1978 and sold off in around 1990, it never had any more than good old Taubmens Butex enamel and she had no rot no leaks no problems, a touch up or repaint every year or so, $40 for the paint and she always looked good, the trick is to keep it "aired" and not let moisture build up in her. Out of interest, is she a curved chine or straight chine hull, inboard or outboard ?There is a couple of variances of the design, lets see some pics as Richard said.

Kev

Transoms are standardized for specific outboard HP ranges. 1.5" through 2" are the thicknesses, with 1.5" being the most common. Generally, under 80 HP will have a 1.5" transom, 1.75" up to about 160 HP, with 2" from that point on up. All outboards are designed to fit 1.5" - 2" transom thicknesses, except portables (less then 20 HP) which may be able to fit on thinner transoms. Frankly, there is no reason to have a transom thinner then 1.5", unless it's an I/O, inboard, sailboat or other "specialty" craft that uses a very small outboard.

You can use construction grade, exterior plywood, but I would strongly recommend you increase the sheet count. An example of this would be a 1.5" thick transom and instead of using 2 pieces of .75" plywood, you use 3 pieces of .5" plywood. Of course, if you use exterior grades of plywood, you need to embalm the thing with epoxy or it'll rot.

Use 12 ounce biax, 6" wide tape to attach the transom to the hull shell, at least three layers of tape, with staggered overlap, up to 80 HP, 4 layers to 140 HP and so on. The tape should have a "purchase" on the transom of at least 6" and the hull shell the same, up to 80 HP. Use 9" of "tabbing" (purchase) overlap up to 140 HP, etc., etc., etc.

You can under tab the transom, but it's not possible to over tab her, so if you have to error, then do so on having too much tabbing and overlap. Of course, this all assumes epoxy use.

Thanks Daddles,Par and Kev
I'm looking for 50mm Thickness and wondered whether I could use 3 layers of 12mm exterior and 1 layer 12mm Marine for the outside . Can I use purbond for this or should I use epoxy , I know epoxy is better but purbond would be quicker/ less messy . I know marine is the go but you know where i'm coming from . She will be taped with 100 and then 150 mm biax tape and then sheathed with 450 gsm cloth .
Thanks Very Much
Garfy

Hi Garfy,
If this helps, my hartly vamp/vixen has a transom made from two sheets of 12mm australian standard marine ply (rather than BS1080) with solid pieces of spotted gum in between them. All expoxied with heaps of bronze screws and some bronze bolts helping out as well. Materials were a bit pricy but I have been on a boat where the transom started to separate from the boat and it wasn't pleasant. Unfortunately, I didn't photograph my transom before I encased the lot in epoxy and paint. I have included a little scan from a section of the plan for the boat showing the transom construction to better explain what I have tried to describe (hopefully those wonderful people at harley don't consider this a breach of copywrite).

Hope my piccys uploaded ok , am trying to get 50mm width in my transom and some have said Marine Ply and some have said Exterior is ok . Went to Bunnings ( i know ) because they have 12mm Structural CD Ply for $47 and after going through 15 sheets realised it must have come from Sherwood Forest because they all looked like Robin Hoods bow , plus the knots . So have on order ( not at bunnings ) 2 sheets of Premium A bond BC Hoop Pine sheets . This isn,t enough for 50mm but i'll see how I go with them . If these are ok could I put 25 MM Extruded Polystyrene between them to get my 50 mm . Am I being too clever for my own good . I,m using 36 MM x 150 MM
LVL s not treated for my stringers which will be epoxied / glassed to the hull .
Thanks tda307 Was that solid core between the plys to make your transom ?
As you can see there was before and then after pics so have know idea how interior was framed before . Have been looking at the stitch and glue chaps and aim to rebuild her in that method IE Eggbox Stringer/Frame/Foam /Sole Caper
Thanks Garfy
Thanks Garfy

Wow, all that stripping and sanding. What fun you must have had. Yes I have a solid timber core between the ply sheets. Used Spotted gum but you could use Ash from your local Bunnies. However, the internal structure of your boat looks VERY different to my Hartly (see my album).

Thanks tda0307 , yes it was lots of fun grinding and sanding . Thats why its been a couple of years , I have only just got somewhere inside to work on her so i'm having another go . Maybe she's not a Hartley but everyone who knows boats say she has good lines a lovely flared bow and whats left of her is sound .
Right now i'm here with a blank canvas could I extend from the stingers through the transom and form a pod say 500-600 from the transom and make an outboard pod swim platform and gain all that extra space inside . From a work point of view I can't see it taking any longer than forming an outboard well ?
Thanks Garfy