Rebuilding bottom on 57 OffShore

[carromdave]

Hi All,

Some of you may have seen the recent Ebay auction for a 1957 Thompson 18' OffShore, located in Saranac NY. Well- I'm the fool that brought 'er home.

If you didn't see the auction, the listing is still there with some pictures:

http://cgi.ebay.com/ebaymotors/ws/eBayI ... 761&rd=1,1

Number on transom is V 71044

This boat has some great attributes- most of which are above the waterline. The mahogany is in super shape- seats, windshield, decking, coaming, all need sanding and varnishing but are in pretty good original condition. The hardware is all intact and in good shape.

As for the hull, the plywood planking seems sound, but below the waterline things get wacky. The line of the keel waves up and down where it has sat on the trailer rollers, and the hull heaves up where it sits on the 2x4 stringers on the trailer. The ribs from about the dashboard to the stern have significant rot on their bottom halves, and there are patches and strips of oak that previous owners have put in to try to stabilize things. The success of those efforts has been limited.

Due mostly to the condition of the ribs, I believe I need to rebuild the bottom of the boat. Once in my garage, and flipped onto a cradle, my plan is to remove the garboard planks, and maybe two or three more planks, remove the keel, keelson, sisters etc.. and take out all the bad ribs. Then replace keel assembly (white oak, I know, I've got a great local sawyer), ribs, and reattach planking. I don't think I can scarf in rib extensions in a lot of cases as the rib is bad right from the keel to the turn of the bilge.

Questions:

When disassembling, is it better to try to take things apart mechanically (dig out filler and unscrew the screws, pry the nails) or cut the fasterners (maybe a hacksaw blade between the planks) and push the remaining bits out. Any suggestions?

What is the proper order for reassembly? I have built lapstake canoes, where the ribs are inserted after planking, but from reading here it seems the ribs are fastened to the keel sisters? Which means the ribs would have to be in, then planking goes on. That could be difficult in this case.

Thanks for any suggestions- and for all I've learned so far just reading about everyone's experiences. This is a great resource!

I'll see everyone around,

Dave
Sandwich, NH

[thegammas]

Sounds like you have a lot of work to do - but sounds like fun!! I have a Custom Sea Lancer that looks similar to the offshore (Andreas is probably cringing right now what with all my rookie commentary on these boats). I'd be interested in a picture of your interior, especially the drivers seat. I have to wait for Christmas for my CD-Rom of brochures.

[a j r]

Welcome Dave,

I assume this is a Peshtigo built boat??? by Thompson Bros. Boat Mfg. Co.???

What are those blocks on the outside of the transom?

You need to get the bottom straightened or this boat will never perform properly in the water. Yup, replace all the broken, out of shape, and rotten wood.

These boats were built upside down. The keelson and sister keelsons (stringers) were the first thing to be installed along with the inner stem. Then the ribs were steam bent and attached to these pieces. Next came the planking. I'd take it apart in backwards order and also put it back together the same way it was built. I would not cut the fasteners unless they won't budge.

Take things apart very carefully and try to maintain them to use as patterns for new wood. Mark them and make a diagram. Take lots of pictures. Who knows how long it will take to put it all back togteher. you will need photos and diagrams to get everything back in the proper location.

Use only marine grade wood and fasteners. Do not reuse old fasteners.

Ribs and keelson... are white oak (all heartwood). Planking is Douglas fir plywood. Phillepean mahogany is used for deck plywood, seats, windshield frame, transom, etc..

And Peter, remember that a 1957 Thompson of Peshtigo boat is going to be very different than a 1962 Thompson of NY boat.

Andreas

[carromdave]

Thanks Andreas,

I was told this was a NY built boat, but have seen no documentation or markings that support that theory. The only numbers I have found are the transom number that I mentioned, and I don't see the 'Thompson' name anywhere. I looked around the steering wheel and dashboard (as you mentioned this location in another post), but I don't see anything.

It does, however, look exactly like pictures of other 57 OffShores that are out there on the internet...

The blocks on the transom were obviously added later, perhaps when it was repowered by the 100 hp Johnson that's on it now. I assume it was to strengthen and stabilize the transom, but I'm not sure. The mahogany of the transom looks and feels sound. I haven't taken the motor off so I don't know if the particular mounting bracket required some modifications..

So, thanks for your tips on disassembly/reassembly. The process you describe is what I had imagined, but I guess I wonder how I'm going to steam bend each rib to the proper shape when I have no mold to go to, and the existing hull shape isn't much help. Any idea there? You don't happen to have a table of offsets for this boat kicking around the shop, do you?

Best,

Dave

[a j r]

Offsets, drawings, dimensions. LOL There are no such animals!

If it's a Cortland built boat, the hull ID would indicate she was built in 1950 or 1960 and that it was the eighth year that this particular model was built. Thompson did not have an 18 ft. lapstrake in 1950 and it definately does not have the hull shape or details of a 1960 boat.

If Peshtigo built, the hull ID indicates she was the 1,044th boat made in 1947, 1957, or 1967. Definately NOT 1947 or 1967. She has the attributes of a 1957 model. The "V" is the code for the "builder" in the factory, the guy in charge of this boat getting out the door.

So, I will assume that this one was made in Peshtigo. I note she has Michigan registration. That would point to her being made in Wisconsin as well.

Sorry, there are no written details of the boats to hep you inyour restoration.

Andreas

[carromdave]

Sounds like she is a Peshtigo-built 1957 boat. I was told that the last owners were originally from Michigan and had moved to the Adirondacks. Nice to know it had at least 1043 sisters and brothers out there. I wonder how many really are left.

I guess I'm winging it on the rebuild. I have looked extensively at John P's pictures at http://www.aerialimaging.net/john which, though it's a different boat, give me an idea of what I'll be looking at I think. I'll see when I get there!

[john]

If you have any questions please call me at 832 473 8928. John

[txcaptdan]

Dave, Welcome to the world of wood boats! A friend of mine has one of these hulls in beautiful condition. Check out my Classic Outboard site at http://groups.yahoo.com/group/classicoutboards/.

There is a boat named Leviathan in photos that should be a match for your boat.

Some one has sandwiched your transom at one time , I suspect to strenghten or hide damage. transom should only be two layers thick with some blocks inside at ski tows.

I have a very similar engine that is a 90hp.

Good Luck