Transom - dual to single

[ian_upton]

I am looking to convert a 1962 25 foot Bertram from Twins to Single.

Let's assume that transom is dry and only moisture is directly around the drive 'keyholes'.

Also let's assume that going to a single V8 is not negotiable.

Do you tear out the whole transom core in the drive 'bump out' and replace with a solid 1 pc contigious piece of core material or do you only remove the core materail around the drive 'keyholes' and leave the rest in place?.

I have seen it done both ways... Which is preferable, easier, adaquate, stronger, etc.?

Thanks!

Ian.

[david aymar]

Hi Ian Dave here My post is just above yours ever herd of anybody trying what Iam dooing ? twin straight drives to a single outdrive. On yours I have read other posts and they sugested redooing the whole transom since you have to holes to fill thanks dave.

[ian_upton]

I decided to tear everything out. Here are some pictures.

http://gallery.bateau2.com/albums/userpics/22690/2-9_Transom_5_Awlcraft.jpg

http://gallery.bateau2.com/albums/userpics/22690/normal_Transom_core_removed.jpg

I have laminated two sheet of BS1088 Meranti marine plywood together and hope to get them in the boat soon. I decided to sandwich the plys with 1.5 oz mat, 18 oz wovenroving and 1.5 oz mat. I pulled the two sheets together with deck screws on a 6" X 6" pattern. After everything cured, I removed all screws and drilled completely through on the the 6" X 6" pattern. My thought is that this will create some bleeder holes to help make sure I do not have any air between the core and outer skin when I put it in the boat.

Using vinylester on everything.

Ian.

[ian_upton]

Here is the cross section of the core.

Look at all those layers!

1.5" total thickness.

http://gallery.bateau2.com/albums/userpics/22690/normal_Core_CROSS_SECTION.jpg


http://gallery.bateau2.com/albums/userpics/22690/normal_Transom_Core.jpg

Ian.

[david aymar]

Good choice

[ian_upton]

Core was installed last night from the inside. Thru-bolted with 17 bolts.

Put a nice fillet in this morning and proceeded to put in the inner skin.

I was able to get 3 layers of 1708 wetout and rolled before running out of resin. Each layer inceased in size by about 3 inches.

I am fairly certain that this is thicker than the original, but I had my sights set on 4-5 layers (no reason, just because...)

I won't be able to get back to this for a while, so I am wondering if the 3 layers of 1708 are enough?

Ian.

[ian_upton]

Here are a few more pictures from last weekends work.

http://gallery.bateau2.com/albums/userpics/22690/normal_IMG_6170.JPG

http://gallery.bateau2.com/albums/userpics/22690/normal_IMG_6169.JPG

Sorry for the glare. 3 layers of 1708.
http://gallery.bateau2.com/albums/userpics/22690/normal_IMG_6174.JPG

Ian.

[david aymar]

Nice work Ian it looks professional and strong enough to hold down a fully blown 454. You must have some experiance with glass. and think out of the box. I have not started my conversion yet but have just installed and proved my power train on an old hull saturday I will remove it and start my conversion soon. rock on . Dave Good choice starting fresh

[ian_upton]

Thanks Dave!

Actually before this, I probably had only wet out a few yards of glass.

Most of my experience is reading on forums such as this.

I have still not decided if the three layers of 1708 are enough. One shop that I spoke with said that 2 layers would be more than enough, one advisor said I should really have 4 on there, others think as much as I can put on but keep the transom under 2 1/4" thick because of the outdrive.

If you have any suggestions, I would be open to hearing them. At this point, I'm leaning towards staying with the three layers because it is thicker than most of what I removed and it was all done in 1 lay-up so no secondary onding between layers.

Ian.