epoxy/transom bonding question

[chrishayes]

Guys, I finally got to fiberglass this weekend! It was MUCH better than grinding. I feel I did an excellent job on it too. 8 yards of 1708 and 15' of 8oz cloth tape and No air bubbles whatsoever. I will post an update in my thread soon.

ANyhow, on to my question, I have built the transom out of 2 peices of 3/4" ply and used thickened epoxy to join the two together along with screws every 6". Those screws were countersunk and filled with the PB. Now I am ready to install this chunk into the boat. Since I am using epoxy, is it ok to just use PB to hold it to the outer hull or should I use a layer of 8oz cloth to help with the bond? Does it matter?

Should I sand the epoxy surface that I put on both sides of the ply to seal it before clamping it to the hull?

Also, when I sat the finished piece in the boat there is a couple finger widths of space at the top center of the transom but the bottom and sides are butted against the hull. Is it going to create a problem if I clamp and screw this thing in to pull that gap closed? I am thinking that having a rotted transom may have allowed the hull to bow at the point that the motor hung on(150hp ob). What do you think?

 

[Yacht Dr.]

Re: epoxy/transom bonding question

hello chris..

Just as a suggestion you might want to put some small ( 1/2" round ) clay balls on your trans skin and push your wood up against it. It will kinda tell you where and how much gap you have across your new trans.

YD.

 

[jonesg]

Re: epoxy/transom bonding question

heres a good way,

http://www.youtube.com/watch?v=lh6RkYNxiHw

 

[PaulyV]

Re: epoxy/transom bonding question

That is a great video....

 

[jonesg]

Re: epoxy/transom bonding question

I just reattached the splashwell to my new transom using this method, getting the splashwell to line up with the transom was a lot of sanding and theres no way to know if the fit is perfect where you can't see, so I used matting to make the joint, I used poly resin and it came out good.
Lots of C clamps and thru bolts do the trick.

I like docs idea of using clay balls too. That would help to get the fit close enough that the matting will take care of the rest of the gaps.

 

[chrishayes]

Re: epoxy/transom bonding question

Thank you for that video, that is exactly how I intend to do it. I think that I will get some help and put the cap back in place to see if the bow in the transom skin is factory or from rotting and sagging.

The only thing that I noticed that they did that I have done differently is that I left the screws in and epoxied over the heads of the screws. I figured that if they were fully incapsulated with epoxy and glass that there would be no problems. Do you guys see any issues with this?

 

[chrishayes]

Re: epoxy/transom bonding question

Bump

 

[erikgreen]

Re: epoxy/transom bonding question

To answer your question, thickened epoxy is fine. No need to use mat with epoxy. You could try the clay ball trick to see where your gaps are if you like, but hopefully you have a pretty good idea where the transom should sit when it's fully installed, so you'll know you don't have gaps.

The epoxy you used for lamination will be much stronger than the screws you left in there. Personally I'd have removed them, but they should be ok as long as the rest of the transom is dry. If it gets wet, pockets of corrosion will form to complement the pockets of rot in the wood

You'll also have to be careful if you drill into the transom to mount anything or make a through-hole for something that you don't hit metal.

I recommend using through bolts or allthread rod to clamp your transom in place while you glue it. You can repair the holes easily and it'll make sure it's fully attached.

Erik

 

[jcsercsa]

Re: epoxy/transom bonding question

yep agreed !!!! with the screws in there you will have to be carefull when drilling threw , and if you get some gaps in there after you clamp the transom to the skin , you can allways drill a hole in the skin and fill the gaps with epoxy, I had to on mine !! also when i was doing this i over drill the motor mount hole and filled them with epoxy , that way water will never have a chance getting to the wood !!! John

chris how many threads do you have going for this ?? the guys really like it when its all in one thread !!!

 

[Mark42]

Re: epoxy/transom bonding question

.....

ANyhow, on to my question, I have built the transom out of 2 peices of 3/4" ply and used thickened epoxy to join the two together along with screws every 6". Those screws were countersunk and filled with the PB. Now I am ready to install this chunk into the boat. Since I am using epoxy, is it ok to just use PB to hold it to the outer hull or should I use a layer of 8oz cloth to help with the bond? Does it matter?

Should I sand the epoxy surface that I put on both sides of the ply to seal it before clamping it to the hull?

Also, when I sat the finished piece in the boat there is a couple finger widths of space at the top center of the transom but the bottom and sides are butted against the hull. Is it going to create a problem if I clamp and screw this thing in to pull that gap closed? I am thinking that having a rotted transom may have allowed the hull to bow at the point that the motor hung on(150hp ob). What do you think?

A common method to install the ply is to make thickened epoxy, and coat the transom skin and the ply. Install the ply and tighten by having another piece of ply on the outside of the skin, and run screws right through the outside ply, through the skin, and into the inside ply to pull it all together snug. But not too tight, you want at least 1/32" of epoxy left between the skin and ply to make a good bond (Thats what I read on a builders forum about epoxy glue up/laminations with wood). There should be some space around the sides and bottom, maybe a half inch, to fill with putty and form a fillet. After its all set, remove the screws (don't forget to coat with grease so they don't get glued in) and fill the holes with more epoxy. Be sure to use some acetone to get the grease off.

 

[chrishayes]

Re: epoxy/transom bonding question

John, this is the only thread on this. I have had others for other parts of my build but unfortunetly I have trued posting these questions in my build thread and they dont get looked at because the title doesnt appeal to those of you that help. Sorry if I am making it hard on you guys, thats the last thing I want to do.

Mark, I like that idea. I think I will drill out the screws that I capped with epoxy and then fill them back up with PB. That way I have no issues later. Then I will follow that advise of how to get it in the boat. Thanks guys, hopefully I wont have too many more questions. Sorry.

 

[erikgreen]

Re: epoxy/transom bonding question

Why be sorry? You're asking questions publicly, which means everyone gets a chance to learn, us fat head types get a chance to show off our knowledge, and we all get some entertainment watching your story happen.

That's what this board is for

 

[chrishayes]

Re: epoxy/transom bonding question

Why be sorry? You're asking questions publicly, which means everyone gets a chance to learn, us fat head types get a chance to show off our knowledge, and we all get some entertainment watching your story happen.

That's what this board is for

That a fine quote there Erik! Love it. So deal with it John!!!!!

 

[Yacht Dr.]

Re: epoxy/transom bonding question

Hello all..

erm.. Did you notice that in the vid they did REMOVE the screws after the bond had cured ?

Alot of fuss and muss for peeps not paying attention IMO..

YD.

 

[getusummm]

Re: epoxy/transom bonding question

Dr Yacht, I think they are referring to ChrisHayes. In the video they removed the screws, but on Chris' transom, he did not remove them.