thompsondockside.com

I have a 62 Sea lancer. Do these boats torque and twist in moderate seas or at speed? I’ll be making some upgrades and repairs this winter and while I have the floors up, etc,
is there any reason to contemplate adding additional, non-intrusive, bracing to stiffen the boat? I was thinking some metal strapping screwed to the Keelsons and Sisters in a triangulated pattern under the floors. Then some vertical triangulation under the bow deck and transom.

Thoughts, experience?

Yes, the boats do twist and turn to a certian extent.

I would highy recommind against adding steel or other metal strapping.

Andreas

Andreas is right, these hulls move when under way. This basic design goes back to the viking ships that where actually flexible.
If you notice that no upper floor members attach to keel but to only to keelsons, I believe that the keels in these boats move so much that it would transfer that movement , ever so slight to floor surfaces.
Any bracing would counteract designed give and take in hull.
These hulls ride so nice because ribs and laps absorb shock unlike a ridgid fiberglass hull.

that makes sense - no plans to do anything at this point since I've never had her out, and doesnt sound like good idea anyway - thanks for the input. Gret pics of your seascamp by the way.

Dan... I am not sure I understand your last post... I see the keelsons as being lag bolted to the inner keel... so attaching the floor to the keelsons essentially ties them to the keel...

I didn't really pay a lot of attention to NOT screwing my hardboard flooring to the center three piece keelson... Are you saying that the center needs to flex independent of the floor, to absorb upward movement? In fact, I am not sure that putting rigidity across the top of the hull bottom members, will restrain the bottom of the hull itself from flexing upward...

Frankly, I just used the old holes, which rightly or wrongly attach the flooring to the center laminated keelson, stringers, and the curved bent 1"x1" strips (floor risers per Andreas) . The stringers are about a foot on either side of the inner keel and parallel to the keelson to increase rigidity.

John Hart

On the 1957, 1958, 1959, and 1965 Thompson Bros. Sea Lancer's I have worked upon, ALL had white oak framing members that went from sister keelson (or stringers as some call 'em) across the top of the keelson to the other sister keelson. These cross supports were attached to the sister keelsons of course, and also attached to the keelson (at the center of the bilge). These cross-supports held up the floor boards and also provide lateral stability to the boat.

Just as a point for terminolgy, the KEELSON is inside the hull and it is made up of three wood pieces mechanically "laminated" together. It is in the middle of the boat and is the principal backbone. The KEEL is on the outside of the hull planking and is completely seperate from the keelson. The SISTER KEELSON or STRINGER members run parallel to the keelson about 18 inches either side of it.

Andreas

Sorry, Andreas is right I am just using wrong teminology. My floors are supported by oak framing that run from stringers to stringers and do not contact keelson, I refered to it as the keel, anywhere at all. This shot is from intial inspection of bilge before restoration, see how keelson is independent of floor joists. My hull is a 20' so there are two sets of stringers.



The Cruisers Incs I have owned have all been that way and I always asumed to allow for movement or vibration to be segregated from floors.

Sorry for the poor terminology, but hell, I knew what I meant to say-LOL

Cruisers, Inc. must have done it a bit differently than Thompson Bros. Boat. Because on all those Sea Lancers I have worked upon (1957, 1958, 1959, and 1965) the transverse floor supports are definately connected to the keelson. They used a brass angle that was screwed to the floor support and to the keelson.

I'll see if I can dig up any pictures and if yes, attempt to post 'em here.

Anderas

thanks guys - this is great discussion, very helpfull to a novice - andreas, would love to see any sea lancer pics you have, be they NY boats or otherwise. I wont have the change to take mine up any time soon, but will post pics.

A number of my boat pics are on my website: www.freewebs.com/thompsonboat/index.html

Andreas