New Deck and Decks Beams on 20 ft Offshore Model

[Alan Sturgess]

Hello Dockside members. I am looking for some advice and or suggestions on redoing the front deckbeams and deck on a recently acquired 1962 20 ft Thompson Offshore 1000 model with an outboard. It came with the original Evinrude 1962 75 HP Starflite.

I will detail my questions and you can then click on my website of

www.accentart.ca/boat.html

and see the photos that I have just taken of the boat. The front deck has been removed and this weekend I am levelling the boat with proper supports under the stern area and putting a proper supports under the bow area.

I would love to make contact with anyone who has an OFFSHORE 20 model of a year close to 1962. From my examination I have determined that the deck beams and the bow hatch were constucted off the boat in some sort of jig and then they were lifted in place and fastened to the gunwales.

The ends of the deck beams were fastened to a 3/8” 5 ply 4” wide plywood strip with the outer edge of the deck beams cut at the angle of the sloping hull at the top lapstrake. Screws were driven into the ends of the deckbeams from the outside of the 3/8” plywood. Then the whole section was set down on the foredeck area. Shims were then slipped in between the ribs and the 3/8” plywood to line up the assembled section and screws were driven in through the plywood outward into the ribs. Of 16 ribs, 10 required filler pieces and on the starboard side each rib has a filler and on the port side about ½ needed filler pieces and each was a different thickeness. You can easily see these filler pieces in the looking forward starboard side photos. When you look at the photos of the boat looking aft from the bow you can see how this “deck hatch” assembly would “float” in the forward area and could be shimmed up to make sure it appeared level and lined up to the “eye”

First I think this was a rather poor way to construct the deck and attach the deckbeams to the hull, but time was money and the way they did it made it fast and could be done by someone with basic woodworking skills. My thought is to put in all new deckbeams and fasten them directly to the top lapstrake and fasten through from the outside of the hull. A inner gunwale would likely be required running forward to the bow and the deckbeams would be notched at the outer edge to fasten to it and to the top lapstrake plank. It will be more work to angle, taper and notch the end of the deck beams, but it should give me a much stronger deck that one can walk on without trepidation. To my eye the starboard forward area has “fallen” a bit, possibly from the deckbeams pulling away from the hull on that side.

Was this method a common way to attach the decks on the Thompson boats or just exclusive to the OFFSHORE models?

To those of you who have done this before you can see that this is a “project”. The hull planks and ribs appear to be in above average condition for a boat this age.

Your comments and advice would be appreciated

www.accentart.ca/boat.html

[Rodney Syverson]

[
Alan:
I just installed my deck on my 62 Sea Lancer 17'. I agree the construction of the deck support beams appeared to accomodate a one assembly fits all hulls with various shim philosphy.I suspect the hulls come of the jig and settled into a slightly different dimension for each copy, so this shim trick allowed the mfgr. to make up an assembly and then fit it to any hull with the use of the shims.

I also did not like the idea of shimming the plate to the ribs so I cut a new plate and temporarily secured the plate solid to the ribs. As my deck beams were good for the most part I isolated them one at a time from the king plank support beam and I moved them forward until I was able to locate them tight up against the plate. I then fit the ends to the new angle or curvature of the plate and shaped the ends of the beams and moved them further forward until I had good contact with the plate. When I located each beam fair with the edges of the gunwhale, I epoxied them in place one at a time and resecured them to the king plank support plate.

Obviously all my deck beams moved forward to fit tight to the plate. The only beam I made new was the one that supports the dash, as I wanted the same length deck as original. My hull had changed dimensions slightly as I replaced all the keels, frame and transom. When the epoxy cured I removed the deck structure, placed screw through the plate into each deck beam and then reinstalled and secured the entire structure via the plate to all the ribs.
Using a flexible strip of wood that laid fore and aft across the beams, I then faired the top of the beams with a plane to get good contact to the underside of the deck plywood using the thin flexible strip as a guide. It took very little shaping and after installing and bonding the deck plywood I have a good looking and well faired deck.

I think the use of the plywood plate is good as it allows you to tie into more than one rib. You might have to do some things differently with the hatch but I think you can make it work this way. If you would like I can send you some photos of my deck support beams installed. Rod Syverson

[Alan Sturgess]

Rodney, thanks for the description of the innovative way you solved your deck problem. I would like to see your photos - can you send them to alansturgess@gmail.com ? - thanks.

[JRPfeff]

Rodney, thanks for the description of the innovative way you solved your deck problem. I would like to see your photos - can you send them to alansturgess@gmail.com ? - thanks.

Alan & Rodney - With the new forum software for Dockside Views, you can post the photos directly here. It would be good if you could share them here with everyone.

Jim

[txcaptdan]

Alan, I am restoring a 1965 20" Seacamper and the deck beams on my boat reach out to the hull and not an inner plank like yours. my hull had splayed open and required it be plulled back to original shape. i used several comealongs and pulled hull back to ends of beams then redid screws and added screws through the planks. Seems to have done the trick. You can see progress at http://groups.yahoo.com/group/classicoutboards/ in photo section under "A New Boat. ihave remade kingplank and cabin windows, lots more to do!

[Alan Sturgess]

Do you need to join the Yahoo group before you can see the photos? The photo sidebar on the left is under section marked members or am I looking at the wrong place?

[txcaptdan]

Yes join and I will approve asap

[Rodney Syverson]

Rodney, thanks for the description of the innovative way you solved your deck problem. I would like to see your photos - can you send them to alansturgess@gmail.com ? - thanks.

Alan & Rodney - With the new forum software for Dockside Views, you can post the photos directly here. It would be good if you could share them here with everyone.

Jim

JRPfeff; not sure where this post will end up but I tried to set up on Image Schack and was not having much luck so went to Yahoo Address posted by txcaptain and posted some photos of my project. Is this how you meant to post photos here? I did mail some photos to Alan but you are right in that it would be more interesting for everyone to share and view. I am just not PC savvy enough to figure out how to do it. Not sure how to make the direct link to my photos but I believe you can access by using txcaptains link. Which is http://groups.yahoo.com/group/classicoutboards/ Check it out and let me know if you see my photos of the 62 Sea Lancer Project und the name bdmdcnman Thanks for your help: Rod Syverson

[a j r]

Yes, Alan, your interpretation of how the deck was constructed is correct. It was made on a jig and then installed in the boat. When building 5,000 boats a year, pre-assembly of components was mandatory. The various components were then installed in the assembly line.

The person with the 20" Seacamper (that's a tiny boat - I assume you meant 20 ft.) was made by a different company, Cruisers, Inc. not Thompson Bros. Boat Mfg. Co. The two firms didn't necessarily have the exact same techniques for constructing the boats.

And the techniques changed from year to year if they found a better or more efficient means to do so.

Andreas