Transom repair and structure redesign help needed

[lbhsbz]

The boat is a 1983 Bahner Mod V style hull. I believe it was originally designed to be a jet, but a few got outboards. This particular design has a center pod that extends about 5 inches past the transom. The engine is mounted on a plate set up that straddles this pod. 6 bolts on each side hold the mount to the transom. There are 2 braces going from the 2 top bolts on the inside of the transom down to the stringers, which are in good shape. There is no wood that spans the whole transom....there is only wood on each side..from the tops of the tunnels to about 1 inch above the highest plate mounting bolt. Here's the only picture I have at the moment:



The boat has been taking on water at the mooring at night...and it's getting to the point where I'm afraid to leave it in. I'm beginning to see cracks at the cap line and at all of the "corner of a cube" type corners where the pod meets the transom. My theory....the wood in the transom does a fine job of holding the engine on, but lacks rigidity to deal with the beating that that the transom takes running a surfacing prop through chop....The center of the transom is flexing towards to the front of the boat I believe, and that's what's making the cracks, even though nothing is bolted to the pod...it's still serving duty to hold both sides of the transom together. My initial plan is to grind out all the cracks and reglass.....heavily. Then cut a piece of 3/8" plate aluminum to span the entire transom and stick that to the inside with some short strand filler/thickened resin and then bolt the motor mount plates through that. Am I on the right track here?

I also though of simply chopping off the pod, but unsure of what that will do to the way the boat runs. I know stoker and a few others generally stop the keep a few inches short of the transom while keeping the sponsons full length. Right now I'm opposite that. If I chop the pod off, I'd also be effectively shortening the boat 5 inches. Not sure if this matters or not, but would certainly make the repairs easier, and I'd have a flat surface which is much easier to strengthen.

[rgsauger]

Any clue how easy or not it would be to pull the cap off of the lower hull? If not too bad, then rebuilding the transom will probably not be too bad. I would leave the pad as-is and build more setback into the transom during the rebuild. Just some thoughts...

[Smoking Joe]

http://www.screamandfly.com/showthre...ve-to-Outboard Have a look at my thread above and see how we built our pod. In your case if your transom is sound then you could use my method as a means to strengthen your existing pod/transom. Run two new longitudinals on each side externally of your existing pod. Cut slots in your transom and extend these longitudinals through the slots and along the inside of the boat, maybe as far as your first bulkhead. Then glue glass to existing pod, transom, inside of hull and finally to the first bulk head. I guarantee any rigidity problems will disappear.

[Greg G]

The boat is a 1983 Bahner Mod V style hull. I believe it was originally designed to be a jet, but a few got outboards. My theory....the wood in the transom does a fine job of holding the engine on, but lacks rigidity to deal with the beating that that the transom takes running a surfacing prop through chop.

You need to pull that rear seat and post some clear photos of the entire width of the transom area.

[lbhsbz]

Any clue how easy or not it would be to pull the cap off of the lower hull? If not too bad, then rebuilding the transom will probably not be too bad. I would leave the pad as-is and build more setback into the transom during the rebuild. Just some thoughts...

Not to sure I'm comfortable doing that. I've got 2 weeks to fix this thing. I'm going to try to do it all from the inside without pulling the cap. The wood is wet, so I'll need to replace that too. The wood only comes up to the cap line, so it's a fairly easy job to cut it out and replace whats there now.

[lbhsbz]

http://www.screamandfly.com/showthre...ve-to-Outboard Have a look at my thread above and see how we built our pod. In your case if your transom is sound then you could use my method as a means to strengthen your existing pod/transom. Run two new longitudinals on each side externally of your existing pod. Cut slots in your transom and extend these longitudinals through the slots and along the inside of the boat, maybe as far as your first bulkhead. Then glue glass to existing pod, transom, inside of hull and finally to the first bulk head. I guarantee any rigidity problems will disappear.

I read through a few pages of that...I'll try and go through the rest of it this week. The difference between your setup and mine is that my engine does not mount on the pod. The pod was there to extend the keel for a setback jet pump installation. The pod is more of a hinderance with the outboard...and the only reason all that hardware is back there is to straddle the pod and make a flat surface for the engine to bolt to. In a jet, the transom needed no real structure...all it had to do was keep the water out. Now, it has to have structure. I think there are too many angles involved in the whole bracketry/transom assembly to provide adequate support.

The boat is still out at the river...250miles away. I didn't have my spare for the trailer so I opted not to chance towing it across the desert. I'll be picking it up in the next week or 2, and I'll get more pictures.

Thanks.

[bb21xd]

3/8" aluminum plate won't be strong in the direction you need it. The transom flexes fore and aft and the flat aluminum plate is weak in exactly that direction. You would be much further ahead to rib the entire transom which will create bridging for the full width of the hull. Think of the sheet of aluminum as a piece of paper, it bends easily in the middle exactly where you don't want it to.

[tmoore]

Why not rebuild it like a regular flat transom on the inside... All the way across. If you glass the back side of the new transom wood thick as the regular outside glass and let the be pod extension an open cavity behind it. maybe fill it with foam or something.

[south599]

Or you could rebuild it flat like tmoore suggested, which is very easy and cut the pod off and replace it with a jackplate.

[bb21xd]

Why not rebuild it like a regular flat transom on the inside... All the way across. If you glass the back side of the new transom wood thick as the regular outside glass and let the be pod extension an open cavity behind it. maybe fill it with foam or something.

Agreed! This bridging helps tie the two halves of the transom together. Also, some bracing to the floor stringers and/or ribs across the flat transom goes a long way toward reducing mid-transom flexation, especially in high horsepower applications.

[afr]

The boat is a 1983 Bahner Mod V style hull. I believe it was originally designed to be a jet, but a few got outboards. This particular design has a center pod that extends about 5 inches past the transom. The engine is mounted on a plate set up that straddles this pod. 6 bolts on each side hold the mount to the transom. There are 2 braces going from the 2 top bolts on the inside of the transom down to the stringers, which are in good shape. There is no wood that spans the whole transom....there is only wood on each side..from the tops of the tunnels to about 1 inch above the highest plate mounting bolt. Here's the only picture I have at the moment:



The boat has been taking on water at the mooring at night...and it's getting to the point where I'm afraid to leave it in. I'm beginning to see cracks at the cap line and at all of the "corner of a cube" type corners where the pod meets the transom. My theory....the wood in the transom does a fine job of holding the engine on, but lacks rigidity to deal with the beating that that the transom takes running a surfacing prop through chop....The center of the transom is flexing towards to the front of the boat I believe, and that's what's making the cracks, even though nothing is bolted to the pod...it's still serving duty to hold both sides of the transom together. My initial plan is to grind out all the cracks and reglass.....heavily. Then cut a piece of 3/8" plate aluminum to span the entire transom and stick that to the inside with some short strand filler/thickened resin and then bolt the motor mount plates through that. Am I on the right track here?

I also though of simply chopping off the pod, but unsure of what that will do to the way the boat runs. I know stoker and a few others generally stop the keep a few inches short of the transom while keeping the sponsons full length. Right now I'm opposite that. If I chop the pod off, I'd also be effectively shortening the boat 5 inches. Not sure if this matters or not, but would certainly make the repairs easier, and I'd have a flat surface which is much easier to strengthen.

Do all that and just put a tab back there to make up the 5 inches you lost and a new jack plate to get the motor back where it is now

[lbhsbz]

OK, finally got it home and somewhat torn down. Here's a few pictures....

Left side transom from the back where the bottom of the motor plate contacts:



Same view, but right side of transom



Left side, top of transom where pod ties in



Now, an inside shot of where the transom meets the floor on the left side of the pod. I've cut some of the glass and wood back..



What I found somewhat odd, is the fact that the transom wood was not, in any way bonded to the floor. I used a Fein saw (some call them a multi-tool) and plunged straight through the glass...there was no wood behind where the cracks in the gel exist....just air. As you can see, the wood, while a bit discolored, isn't too badly rotted.

I was planning on using 3/8" x 3" x 3" angle (because I have about 20 feet of it) to span the entire transom as well as act as a backing plate for the motor plate mount bolts.

At this point, I'm not quite sure what to do. This is getting a bit over my head. I suppose I'll cut the rest of the wood out of the transom and see what things look like after I finish the cutting and grinding.

[afr]

bring it down here we will get it right for ya

[lbhsbz]

bring it down here we will get it right for ya

That's a bit of a drive....not to mention, the boat ain't worth the gas money one way.

[1FASTLASER]

I am no expert glass man but have done my fair share of repairs with no failures yet. I just can't get it in my head how you will be able to relate correctly without removing the cap or splitting it in the rear portion. I am a small man and don't think I could get in there and do it correctly.