Is this ok for transom replacement

[jloch]

Hi all, I'm trying to get an old (196?) 12' aluminum boat back in the water.
Anyway I want to replace the transom which is 7/8" plywood.
My plan is to laminate a piece of 1/2" and 3/8" std spruce plywood
together with pl construction adhesive, then bolting her up as is.
The old plywood doesn't look like it had any protection on it (maybe paint at one time)
Just wondering if this would be ok ?
Is pl ok?

Thanks.

 

[bassmanhb]

Re: Is this ok for transom replacement

hi j ,

welcome to Iboats....

yes the pl would be fine or you can use titebond wood glue which is water proof once dry.

at a minimum I would paint a couple coats of a good outdoor oil based paint on it will last much longer that way .

or a couple coats of epoxy resin like I just did with my transom.


good luck


bass

 

[bakerjw]

Re: Is this ok for transom replacement

Make sure that the plywood uses waterproof glue.

There are other things to look for in an aluminum transom replacement. Check for corrosion on the aluminum where the wood made contact. There are paints and primers that should be used on the aluminum that will be under the transom. Do some searching and you'll find a lot of good information.

 

[Watermann]

Re: Is this ok for transom replacement

You'll have a ton of left over wood buying 2 sheets, 7/8" seems like an odd ball size. Is the current transom laminated with 2 pieces or does it look to be only one? It may just be a swollen and partially delaminated 3/4" (6/8ths) piece of ply which has swelled. That's normally the reason the old transoms are so tough to pull out of the channels is that they've swelled.

I wouldn't spend the money on epoxy resin, primer the wood, paint it and then cover with spar urethane. That will also add some thickness to the ply as well.

 

[jigngrub]

Re: Is this ok for transom replacement

Yeah, your transom is more than likely swollen and it was 3/4" originally. I'd just go with 3/4" or 2 pieces of 3/8" laminated together. The 3/8" will be cheaper and you'll have less leftover after you cut 2 pieces out of a sheet.

 

[jbcurt00]

Re: Is this ok for transom replacement

All ^^^ good advice, but to be clear:

..... you can use titebond 3 (TiteBond III) wood glue which is water proof once dry.......

W/out the 3, TB isn't waterproof :watermelon:

 

[bassmanhb]

Re: Is this ok for transom replacement

jb,

good catch... somehow I missed/forgot the III in there :facepalm: .


bass

 

[wolfsmurf]

Re: Is this ok for transom replacement

just to make sure, someone may have said and i didnt see but be sure your wood isnt treated on that boat as the chemicals in it will eat the aluminum.

 

[jloch]

Re: Is this ok for transom replacement

Thanks for all the reply's

So I'm seriously thinking about the expanding wood theory...

Here is a pic of the old wood next to new 3/4" plywood.

The old wood is definitely 1/8" wider (expansion?)
Do you think I'm ok replacing with 3/4" plywood?

Here's the old wood in all its glory...

Looks original, which would make it about 50 years old.
The 2 supports (gussets?) are damaged where they bolt at the top
Here's a closer look(yellow arrows)

I'm thinking of drilling new bolt holes just below(white arrows)
Would this be Adequate?

Also there is a aluminum cap that covers the entire back..

This is cracked at about the middle, would this piece be structual
or is it just there to keep the water off the wood?

Thanks again for any and all input.

 

[jbcurt00]

Re: Is this ok for transom replacement

What motor was hanging off the transom when you got it?

A 12' tinny will probably not 'need' that extra 1/8".

Perhaps plywood has changed standard sizing in 50yrs, not unlike our 2X4's that are now barely 1.5X3.5 :watermelon:

That transom cap is to protect the plywood from both the weather & the weight of the motor bearing down against it...

I'd add an aluminum angle to the length of that gusset. It's a common failure on tinny's that are over due for a new transom. Thru bolted at the original thru transom bolt locations, and rivet/thru bolts back thru the 'body' of the gusset.

 

[jigngrub]

Re: Is this ok for transom replacement

Yeah, that's old swollen 3/4" plywood.

I would bring the new transom wood down to the bottom of the flange on the transom brace and do away with those 2 fillers. It won't hurt anything and will actually make your transom stronger.


You'll need to seal your new transom wood on both sides and all the edges before installation, a good exterior grade enamel paint will work and won't be too expensive. Use multiple coats.

 

[jloch]

Re: Is this ok for transom replacement

What motor was hanging off the transom when you got it?

It was a 66 johnson 33hp (200lbs). New motor will be 99 4stroke 8hp johnson (90lbs ish).

That transom cap is to protect the plywood from both the weather & the weight of the motor bearing down against it...

Do you think its ok as is, with some silicon to seal?

I'd add an aluminum angle to the length of that gusset. It's a common failure on tinny's that are over due for a new transom. Thru bolted at the original thru transom bolt locations, and rivet/thru bolts back thru the 'body' of the gusset.

Great idea! thanks

I would bring the new transom wood down to the bottom of the flange on the transom brace and do away with those 2 fillers. It won't hurt anything and will actually make your transom stronger.

Thanks, but unfortunately it won't work. The bottom of the boat is wider (by inches) than the top and the plywood has to go in at an angle just to get it in. It has to be 3 pieces at the current size just to get in.

 

[jigngrub]

Re: Is this ok for transom replacement

Ok, I understand your problem.

I'd remove the transom braces to install the transom wood in one piece, but I realize some people wouldn't be comfortable with doing that. It's not that hard to do if you want to do it though.

 

[Watermann]

Re: Is this ok for transom replacement

If it were me, I would do as JnG suggested by increasing the transom size down to the bottom of the knee braces. I would do it by drilling out the rivets in the bottom and removing the knee braces then replace with SS machine screws and nylocs. Use some 5200 sealant too.

With the braces out it will be easier to repair them. Start by drilling a small hole at the end of the cracks to stop them from continuing to crack. I would take that aluminum skin off that someone put inside the transom and reuse some of it to do the brace repairs. Cut a strip of the aluminum about 2" wide and make bends to where it covers the the flat part, up over the gusset and then down on the other flat side. Drill the mounting holes through, then bed it in marine epoxy over the cracks and bolt the 2 pieces together until it cures. It won't win any awards for beauty but should take care of the issue. Let me know if you don't understand what I'm thinking, I will try to do a paint shop drawing.

 

[jloch]

Re: Is this ok for transom replacement

Thanks for the replies, really appreciate it.


I really like the idea of the one piece transom extended down to the bottom of the braces,
but that's a bigger project and time is tight, was hoping to get on the water within the next week or so.
I think I'm going to keep the aluminum skin, drill out the cracks like Watermann suggested and get some
1x1 angle aluminum. Do you think JB Weld would be usefull here?

So is this the general idea you guys are thinking?

4 pieces like that. What thickness aluminum would you recommend?
also I have some G-Flex epoxy I could use in between.
Thanks.

 

[Watermann]

Re: Is this ok for transom replacement

Yeap that will work good with some 1/8", not sure with it bedded in epoxy that you would need to go thicker. G flex is too runny and made for sealing rivets and seams. I would use some 2 part epoxy for metal.

 

[Woodonglass]

Re: Is this ok for transom replacement

Well, I'm NOT a Tinner, but if I were and if it were me, I'd do like JNG suggests and make a transom deep enuf to go to the bottom of the Knees but...I'd make it only wide enuf to fit the top of the gunwales and not worry if it conformed to the sides of the hull. You could make filler pieces if you wanted , but it would still be a much stronger transom doing it this way and easy to install. You could still use the Aluminum angle to reinforce the cracked Knee Braces. Tha's how this Old Dumb Okie would do it.

 

[Willyclay]

Re: Is this ok for transom replacement

Maybe some ideas for you in this old thread with a similar repair done by member Tim Frank that IMHO is outstanding. Good luck!

http://forums.iboats.com/boat-restoration-building-hull-repair/transom-repair-268432.html