27’ Ocean Master transom rebuild

[cvincent]

I suggested cutting a short section of the cap to allow access to the sides of the boat to fillet and glass your core from the inside. I understand now that your plan is to use the existing interior laminate and bond the core to that then glass over the outside.

[fallguy1000]

I am concerned about your glass plan based on the cutout I saw and now the verbage in the last post. It appeared, and I could be wrong, as though you had left an edge of fiberglass at the top of the transom on the vessel centerline and for a foot or more each way and then on the angle to the cap. Looks white to me...

If you are adding a bracket; you’ll need to tab into the well; perhaps more. You would also be wise to built the transom up higher than the existing. This would allow more tabbing.

I would want my glass to go up and over and you can’t do that with the cap.

I could be wrong about what I saw, but if I am right; you are doing it wrong okay..

I think you ought to see if Jacques would take a look at it.

There is little reason to glass inside the decored portion; you’d end up with voids there and it’d be weaker than just epoxy n cab.

[fallguy1000]

I drew a picture on my thread, just click the boat build link at the bottom of this message.

It looks like you left a fiberglass edge where I drew the red line. It looks like the full thickness of the original transom. That is not what I would do...just so you know.

The black line in my picture is where you ought to consider your new transom going. Doing so would allow you some new tabbing of the new core to the old hull on the inside. (green lines are places you really need to get some glass and perhaps not over gelcoat?)

You get a much safer hull this way with a full height transom.

I put a few question marks on the drawing==hoping you develop enough strength there...

Let me know once you see the picture so I can delete it. Thanks.
If I am jumping the gun, so be it, I just hate for you to cut up all the core and then give you a recommendation.....but your demo seems wrong...

I don't undertand where you intend to glass the interior of the transom. Do you mean over the gelcoat on the inside of the hull or inside the decored area?

tired and wordy, manyana

[fallguy1000]

I suggested cutting a short section of the cap to allow access to the sides of the boat to fillet and glass your core from the inside. I understand now that your plan is to use the existing interior laminate and bond the core to that then glass over the outside.

That isn't strong enough for what he is planning.....if it were, there would be boat builders gluing on transoms all over the world....just sayin

[fallguy1000]

When I say tab into the well; I mean the existing boat motor well; not the bracket from Hermco.

If you are planning to run the transom full height; sorry for all the warning bells; I just see the old transom fiberglass top wrap left on and the controls left in and it concerned me. That all needs glassing.

The before and afters on Hermco website show them going up to full heights; just so we are clear. That full height gets glassed into the inside of the boat where you have controls...you need lots of strength. Hermco should advise.

[Maine Priority]

fallguy1000- I appreciate your time and efforts in trying to steer me in the correct direction, it is very much appreciated. As it likely appears, I have never done anything like this before so I am very open to ideas and what not to do. I have done glassing before but nothing really structural.
The answer to your transom height is yes, I am going to raise the height to at least the horizontal plain of the top of the cap. I plan on tabbing in the new transom from the inside at the outboard edges of the motor well. I will remove all gelcoat to bare glass and then run structural glass continuously from one side of the motor well to the other. Do you have a suggestion on what glass to use and how many layers? I was thinking 1708 but that is a guess on my part.
The exterior perimeter for the new transom will be tabbed in on both sides and at the bottom of the transom. I am starting to understand what you are saying in that the structural integrity needs to be forward of the transom and not tabbed in on the same plane as the transom itself. This is why I plan on glassing the interior skin of the existing transom and the new coring into the motor well. Do you think that will suffice or do I need to lay glass on the outboard corners where the transom and the sides meet? It would be virtually impossible to tab in the corners except for a very small area in the storage compartments just outboard of the outboard well. But a little is better than none.
part of the build is adding a work station on the top of the transom gunwale. I want to add 4 swivel rod holders for my 130's when I am steaming. Any good ideas for parts or design of such station?
Friday is my next day off and I will go out to the boat and snap some pictures of the interior. This ought to help the discussion.
Thanks again to everyone who has contributed to this thread,
Glenn

[Maine Priority]

I contacted Hermco to order the bracket and he is going out of business. He is not taking any more orders. So I have decided to go with an aluminum bracket made by Custom Marine Welding in Miami, http://custommarinewelding.com/

[fallguy1000]

If it were my boat, I’d probably turn the corners on the outside of the hull with the glass-head min 8” onto the hull sides...pay a guy to gelcoat or fair n match the gel with paint..

Probably not what you want to hear...someone might put 300 horse on there someday...lotsa torque...lotsa torque

4 layers of 17 oz biax..not enough for 300hp ..turn the biax 30 degrees each time, too. If you lose dimension; overlap it.

Go post at boatdesign.net. The designer here doesn’t like sticking his neck out on the bracket transom jobs. Can you blame him? Transom falls off and four people end up in the ocean....he has to hire lawyers to defend free advice..

Very few of the people here are doing these massive engines on brackets...mbiggerstaff, daytrip are the guys I would recommend; despite my backnforth on thickness, as far as I know they are the ones hanging big engines on...but the Bertrams they are rebuilding start off as tanks.

Even my boat is just holding a 70hp... I used 4-5 layers of 18 oz; wrapped 8” first layer around the hull sides and bottom in and out...6”, 4”, 2”. Just sayin...get a good glass plan in place..

Your demo bothered me....sorry...carry on!

[Maine Priority]

No worries, this is exactly the info and critical thinking I am looking for. Only want to do this once, correctly.

[Maine Priority]

Thought I would post afew pics of the OM 27 transom rebuild.

Templating the transom

Layed in some CSM before first layer of Plywood

Final layer of Okoume ply. All layers had excellent squeeze out but not too much.

This picture shows the old engine well. The horizontal piece running horizontally is part of the old surface of engine well. Very stout!

The inside well will be glassed in 1708. The layera will extend from top of transom down to deck and forward to gray deck. It will also be tabbed into the sides of engine well. I also plan on installing a cap on the inside as an extension of the gunwale. This will give not only a flat surface for fishing but also offer more structuarl support to the upper half of the center transom.
The exterior transom will have several layers of 1700 Biax staggered in several directions on successive layers. I did not go with 1708 becuase the CSM offers no structural benefit and only takes up more resin. The exterior transom glass thickness will end up being around 1/4” thick minimum. The plywood has been glued witwh Gel Magic troweled on with both sides being wet out before hand for grain saturation.