convert cold molded frame to batten seam planking

[dave g]

I have a new set of plans from Glen-L Marine Designs. They are for the Monte Carlo runabout. The framing details call for sawn/gusseted frames similar to the original Chris Crafts, and longitudinal battens spaced evenly but not to exceed 6".

The intended hull covering is diagonal veneers with longitudinal planking, giving the appearance of the original '30's and early '40's boats.

I'm not convinced that epoxied core/thin outer planking will stand the test of time. Too much work in a barrelback to not do it the best way possible.

I have implied to others about a thin 1088 skin over the designed framing, bedded in 3M 5200, and nailed/screwed with bronze as required. The outer plankling would be 1/2" to 9/16", screwed, bunged, and also bedded in 3M 5200. Then painted and varnished as the originals. ( CPES coating on all parts prior to assembly.)

I'm having a bit of a problem coming up with a full set of plans or at the least, a set detailing the Chris Craft framing and dimesions. I'm sure that I need to add some additional strength somewhere, if nothing else because of losing the ridgity of the epoxy.

Anyone try this conversion ??

dave g

[Hunter25]

Cold molded hulls have easily stood the test of time. Your planking schedule sounds a fair touch heavier then the original layout, probably altering the displacement requirements of the design. 3M5200 will let go from soaked wood, you should reconsider you thoughts of using it, in this method. 3M101 is a much better underwater on wood bedding/sealant. 3M5200 or 101 is also a lot more costly then epoxy with much less grip and no structural strength. What part of the engineering of this design do you specifically have issues with?

[dave g]

Hunter25

I have read reports, and seen pictures of classic type reproduction runabouts that were built using the west System. There is too much flex in this type of boat to NOT develope cracks. These cracks allow water to saturate the wood beneath the epoxy, and this usually occurs within the first 5-6 years. The epoxy is perfect for a lot of other craft, but even some of the WEST techies admit that it is being misused on the contemporary classics.

Also have had a small amount of chat with Don Danenberg regarding this problem, mostly because he is one of the best in the business at rebuilding or restoring wood runabouts and other craft. He has repaired and or inspected several boats built with epoxy that did not last as long, or even close to the useful life of the originals.

I have no problem with the WEST System as such, just not going to use it on a contemporary barrelback. As a note, Don uses 3M 5200 exclusively when not bound by historical guidelines, and has had great success.

I am currently checking the scantlings on my plan and refiguring dimensions, frame spacing, etc., to see what I have to add or modify to do away with the epoxy.

From all the research I have done, the 3M 5200 should be pretty foolproof unless the builder is trying to keep costs down by applying the caulk too thin. Too thin a layer will surely leave voids behind the planking. These will always allow moisture to accumulate and eventually cause a rot pocket or soak the wood to the point that the fibers adhered to the caulk just let go.

On a 27' barrelback I would expect to use 50-55 tubes of 3M 5200 by the time everything is said and done.

I'm sort of stuck here. The original ways were not the best, but the current trend of epoxied everything is not the correct solution either. I'm game for something midstream. Besides, the barrelback will take a while to build. I'm not game for wasting 18-24 months on anything with a questionable future. I have quite a good reputation for anything wood related, and would not hesitate to burn a boat that ended up being a monster.

Thanks a bunch for your response !!

dave g

[dave g]

Problem solved I believe. Switching designs.

Thanks to Woodenboat mag. , and plan by Nelson Zimmer. Exactly the situation I was hoping for. The Bermuda 28 is constructed like the originals, and with a few upgrades in fasteners, glues, protective coatings, etc, should be around for a long time.

dave g

[Raggi_Thor]

Originally Posted by dave g

Hunter25
I have read reports, and seen pictures of classic type reproduction runabouts that were built using the west System. There is too much flex in this type of boat to NOT develope cracks. ..
dave g

I don't know this exact design, but I believe cracks, broken frames, leakage and short lives where quite common among these boats.