Q with picture & drawing

[rburlington]

I will try again with picture and drawing in this post.

My question is this:  Is it necessary to go any further into this transom, or can I rebuild only the cavity currently open in the picture below?  The question arises b/c the expossed cavity below is 1 & 1/2 inches deep and more or less the shape currently open.  Between the cap of the transom down to the drain hole, a distance of 25 inches, a 1/2" thick portion of the splash well provides upper strength and from the bottom of the transom there are two very big stringers to provide further strength.  The top portion of the transom apparently prevents the engine from falling off backwards under thrust and the stringers take up the forward push of the engine when power is applied.  The risers do not seem to have anything to do with support for the engine and the remaining wood in them is high and dry and appears to provide mainly strength for them.  Here is the picture:



The drawing below shows (in the top drawing--not to scale) a 1" thick plywood core (now removed) and (in the bottom drawing--not to scale) a !/2" thick core.  These were screwed together.  The opening in the transom in the photo took wood from both of these, but left the 1/2" core in the risers (or wings as some call them).  

My question remains the same: Will replacing the middle section be sufficient to hold the engine up and deal with the torque it produces?

Here are the drawings:



Thank you for any comments on my question,
RGB

[JimCt]

If you go the route you're planning, be sure you have all the bad wood out of the transom.  If you are back to solid wood, make scarf joints between the new & the old plywood and use epoxy.

[JimCt]

OOPS!  You've got two threads going on same topic.

[rburlington]

Sorry about the 2 threads.  I felt I messed the first one so bad nobody would find the pictures.  The administrator has my full permission to either combine them back into one and eliminate my entery where the pictures failed or just delet one thread entirely in order to save space.  My apologies.

Thanks for your input Jim.  I gather by a response in the other thread and your remarks on scarfing that my idea may not be the best and I should go ahead and open the whole thing.

I am going to use Seacast on this transom mostly (as noted in a response to the other thread) b/c going in from the outside requires me to jig-saw-puzzel wood or coosa to get it back in, thus making it weak.  And I did not go in through the back because the risers and splash well are the key structural portions of the boat and cutting them up to get at the back really worried me.  I was afraid I would never get them as strong as they are now.  Seacast, for whatever its faults, allows me to make one continuous poor and leave the major support structures as they are.  Also, Seacast does not bond with wood and therefore another reason to go ahead and open the whole transom.

Thanks again.

[JimCt]

Probably the best plan.

[RickK]

RGB- I don't know how to combine different topics (or even if it is possible) - and there is valuable responses in both of the topics, so it's probably best to leave them alone.  I did delete some of the redundancy out of the other, but left the replies.
My shift started today, so I'll be able to catch stuff early now.

[rburlington]

Rick,
Perfect.  I'll try not to create two threads on one subject in the future!
RGB

[rburlington]

The transom project continues.  I am going to use Seacast.  Below are som pictures of the progress from the outside in.  My borther did the beveling work

This picture is of the beveling job.



A close up of beveling.



We then  added a layer of mat with the polyester resin required.



Next comes mating the glass we cut out and then fitting it back as a form before pouring Seacast.

There was no need to go higher with the transom as I see it.  Above the highest bevel was a section of solid glass.  The two eyes above that are mounted to wooden backings that have their own pockets not really connected to the engine supporting portion of the transom.

RGB

Will post those when done.
RGB

[JimCt]

Nice progress!  That transom will be solid as a rock when you're done with it.

[DRAMBO]

LOOKS GOOD ! I'M WATCHING YOUR PROGRESS. SEACAST FOR MY 250 XF JUST CAME IN TODAY. ILL BE READY TO POUR NEXT WEEK.

[RickK]

Well I tell ya, I learned something here.  I'd of thought that the transoms would be one section, not pieced at a 45.  No structural integrity at all. The only thing keeping them together was the glass I guess.  But as you say, the sections are doing different things and getting different stresses.
Learn something new everyday. Good or bad.

[rburlington]

You are right rickk, you would think it would all be one thing, but it was not in this case.  Meanwhile, here are some pictures of the project poured.

First, we had to mat and resin the back of the skin we cut out.



Then fit the skin back in, being careful to maintain the original shape and position.



Then attach the skin so it could not shift position.  The duct tape was used to prevent Seacast from oozing out of the slot between the skin we were putting back and the skin that was left on the transom.



Poured it and clamped it to be sure and have the correct size at the top for the motor to fit back over.  Additional duct tape to stop all oozing.



Finally, we used heat lamps to insure a better temp (only about 67 here today, 77 is better for this product).



 By 6 pm this evening the stuff was getting hot and setting up.  We will see what we see tomorrow and hope I don't have to report a failure!
RGB

[RickK]

So you left about 1" of wood in there, put a layer of glass over that so the seacast would have something to stick to, glassed the back of the skin for same reason and then poured about 1" of seacast.  I don't see an access hole in the top to pour through. Magic?
I remember someone else here doing the same approach but I don't remember if they took out the transom cap too and then used a plywood "outside" to contain the pour.  Maybe they'll pipe in here too.
No, what is the plan for the bevel?  Do you have to grind the entire "skin" you put back in down to glass and then glass the entire area?

[rburlington]

RickK,
Good questions.  No wood was left at all.  All the wood came out.  We then put a new layer of mat and resin on the inside glass wall of the hollowed out transom and the same on the back side of the glass skin cut out for access to the transom.  

The transom cap was cut out to provide access for pouring.  When the Seacast reached the top, a glass mat was laid over it and pressed down inside between the material and the inside and outside transom wall.

The old outside skin is the dam from holding the Seacast in and we hope it bonded as the material is a core material depending on good adherence between skins.  The thickness of the material is 1 1/2 "s.  

The bevel is designed to provide something between an 8 to 1 and 12 to 1 ratio to assure that the outside skin will be as strong as when it was originally poured.

The key problem was that the risers really contain three different cavities that were cored with 1/2" ply.  Above the eye you can see in the picture is one of those cavities and between it and the cut out you can see is about 1" of solid glass as there is between that eye's cavity and the cavity for the eye above it.  The wood in those is sound as it has never been wet.  In short, it seems the risers are sound and that the one portion of them I am filling is a kind of final disapation of the troque generated by the engine.  

RGB

[rburlington]

Found the Seacast was setting nicely this morning.  Will take 3 more days for a full cure at local temps.  Meanwhile, we have begun filling back the bevels.  Two pictures below show where we got to today and that will be all until next week.  Have to go back to work; retail clerks live a hard life!