lapstrake boat design

when I started playing with this I went to a junk yard and picked up a 3 inch square block of steel, drilled a hole into it and used a setting punch, by placing the big end into the hole I drilled and filed the small end down to the size of the nail heads I was setting.

cost two bucks..

you can buy the same thing for 30 to 45 bucks if you want a PROFESSIONAL one. I build several boats with my home made one..

The trick is to keep the head on the nail, it is difficult to do when reaching into the garboard and lower planks, If you hve oranatane arms and are some kind of super hand to eye guy you may do it buit I would get a friend and make a day of it. I set my nails about 1/8th inch into the wood and cover that with what ever filler is compatable to the paint I am going to use..''have fun

c/r

 

clench nailing

Well I have found the the culprit strakes on my boat that are the cause of my leaks.The wood along the strake seems solid but the nails have let go or loosened up to the point where it has caused a pretty good leak.So can some one help me with indepth directions on renailing these strakes.And what kind of nail is used.Also I need to understand how the nail is turned back into the wood by what ever tool is used to do so.I hate to sound so nieve but I learn by visiuals and hands on. So thats why I ask for an indepth description of the task at hand. Thanks in advance. Jeff

 

Update on leaking Wooden Lapstrake

This is a 1963 WHITE 20' wooden lapstrake I am looking for folks input on how I should aproach this repair.I would like to do it myself depending on what it entails.If I am in over my head after getting all the info I need to make the decision weather to attempt to do this job myself or start saving my pennies to have someone else do it.Hears the story.I noticed the boat was leaking pretty good. I removed the flooring to find eight ribs broken on the port side of the boat right where the bend in the rib is the strongest.These ribs are about mid ship.The ribs are about an inch wide and five eights thick running from under the gunwale to the otherside of the hull.These ribs are about six inches apart from each other and go under the floor supports.The questions I have are as follows.Would I need to steam these new ribs to install them.Should I take the floor framework up to replace these ribs or do I work around the floor frames?As I said the only hard bend in these ribs is at the point just where it passes under the floor frame and heads towards the center of the boat.It woul be a big job to take all the floor frame work up.My concern with steaming and useing a form is that most of the rib is pretty straight except for the sharp bend where the side of the boat meets the bottom.I invision running sisters right between the old broken ribs.Then refastening the new sistered ribs to the strong part of the strake.Don't get me wrong I love this boat and it is still quite pretty to look at but it's not a one of a kind and I would never expect to get out of it what I have into it.So with that in mind I am looking for a way to repair this craft that will be strong but not to concerned about keeping it original.Thanks in advance

 

You would want a rove iron or holding iron, duck-trap .com sells em. It's pretty much a 2 man job unless you have a very shallow hull or very long arms.

 

Question:Say you have a board the thikness of one and a eigth inches by say six inches.Would it be ok to rip the ribs by taking them from the edge of the board.Say 1 1/8 by 1/2 inch which happens to be the thickness of the ribs needing to be replaced.My guess is it shouldn't matter as long as the grain is followed.The other option would be to rip the board to the 1/2 inch thick and then make your 1 1/8 ribs out of that.I'm just wondering if there is any difference in strength , bending and steaming milling the ribs one way or the other.I hope my description of what I am asking is clear enough.I really want to save this old girl and I'm just trying to get as much info as possible befor I take the mighty jump.I have built small houses and additions on my house but when you get into this intracate kind of work I get a little scared.Look forward to anyones input.Also is white oak the stuff to use these days to make these ribs out of?The original is red oak I beleive. This boat lives in salt water

 

White oak is far more rot resistant than red, it also steams and bends better, it is also virtually impossible to find in Maine. They say red oak gets whiter the closer to the coast it gets.

 

Red oak and white oak are different structurally. I've seen red used in deadwood assemblies, but few other places other then interior trim. Red is quite porous and sucks up moisture like a sponge. This is fine for continuously immersed timbers, but isn't for frames. It's weaker and has considerably less rot resistance then white. Live oak is better then white, but likely difficult to find too. White oak should be available through a specialty wood supplier, have fresh shorts when you here the price.

 

Lapstrake Repair for Jeff Goldberg

What you have is an excellent boat. I recently purchased a 20 ft 1962 Thompson Outboard Runabout of similar design and construction. I have done a lot of research and there are some excellent sites to go to see what is involved to rebuild and repair these boats. These boats are made out of 3/8” marine grade plywood and constructed in the lapstrake method. The wood evolved out of the technology using plywood for boats and airplanes in the Second World War. The biggest manufacturer of lapstrake boats was Chris Craft and the plywood manufacturers actually stamped plywood in those days with the letters C.C. grade which stood for Chris Craft. I think the longest boat Chris Craft built was 43 ft in lapstrake and you see them for sale fairly regularly through brokers and sometimes through e-bay. There was a layer of paper glued to the ouside face of the plywood for protection and to give it a smooth facing surface for painting. I bought my boat from a friend who started the project.. When I told him there was a paper coating (that he was unaware of) he told me there “wasn’t one there now" since he had scraped the paint off down to the wood and primed the hull.

If your boat is in fact made from lapstrake plywood, there is not the tendency like "real wood" for it to swell and seal on its own when put in the water.

The best known brand is LYMAN followed by a number of others and yours was known as Grady-White and the Thompson name is still well known. Those owning them are very receptive to providing information and assistance. So here are some web sites to visit.

This one documents the rebuilding of a 17 ft Grady White by a very helpful fellow named Ralph.
http://www.shareaproject.com/pages/projectThumbs,p,110,00.html

This is the Lyman site

www.lymanboat.com

This is the Thompson site
www.thompsondockside.com

This is Dan Dannberg’s site and he has written two excellent books well worth purchasing on how to restore these boats and he has restored over a hundred of them.

www.danenbergboatworks.com/

This details restoring a Thompson Sea Lancer on the wooden boat forum.

http://www.woodenboat-ubb.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=005897

From all the research I have done DO NO USE epoxies to refasten your planks. Use CPES (Clear Penetrating Epoxy Sealer) to seal any bare wood as this acts as a preservative. These boats were made to flex and do when you are cruising 20 to 30 knots. They were constructed with flexible sealants and epoxy can be used to protect and or restore the wood or as a sealer, but adhesives like Sikaflex and 3M 5200 are best for sealing the planks to getting rid of the leaks. These are not rowboats.

My project includes replacing the deck, stripping all the wood to bare, sealing, staining and varnishing and replacing all the floorboards with teak strips over ¼” plywood. Amazingly this boat was so well kept that none of the ribs are cracked or rotting where they tuck into the keel and the inside needs a good cleaning, sanding and multiple coats of varnish.

If you need any further help contact me.

Alan Sturgess
Vancouver Canada

 

Alan, this White is not built by Grady White, but was built by White Canoe Company in Maine. They are different companies and used differing techniques.

You seem to have thumbed through many pages of material on ply lap boats, but have lost some of the details.

Chris Craft built most of their lapped hulls from MDO. In fact CC had custom plywood constructed for them (hence the CC grading) much of this was in sizable lengths and typically "dog legged" to accommodate the anticipated plank cuts.

There are many differences in the construction methods between the manufactures. The same is true in the design elements of the structure. Chris Craft for example mixed sawn frames with bent ones, Lyman used all bent frames as did White Canoe. Every aspect of these boats are treated differently, though they all share the plywood planking stock, hung lapstrake style. White screwed their frames to the planking from the inside, Lyman screwed from the outside, both companies clench nailed between the frames, Chris Craft screwed and bolted from the outside as did Thompson and Owens. Some manufactures used evenly spaced structural floors, others did not. A few used pocketed frame ends on the keel, while other left them hang. Some were roved, other clenched, yet others nailed, screwed or bolted.

CPES isn't a wood preservative. It's a flexible, cross linked, long chain polymer molecule (a plastic) that weeps into the surface cellular structure of the wood fibers and dries. This (if done properly) serves to seal the wood, particularly the end grain, from moisture penetration. This material (CPES and other penetrating epoxies) have major draw backs, just like most things in life and these must be considered before the application. It isn't a cure all in a can as the advertising might suggest. It's a big decision (the use of epoxy or penetrating epoxy on traditional construction structures) and one that will effect the expertise, maintenance schedule, material and labor costs significantly. Most of these structures can survive quite well without it. I just replaced 40 year old planking on a Lyman last summer. All original, no sealants, no epoxy, just plain old oil based paint and reasonable care. The last 5 or 6 years of it's life saw considerable neglect, so the planking suffered. Had it seen the same care it had in the first 35 years, it would have been a much smaller job. I'm doing a 1957 White now and it's planks are original, no sealant, just oil paint. The planks are fine, it's getting a new transom and fore deck, plus a few ribs have tension cracks (typical on trailered boats) and will be replaced.

Lapped ply does swell with increases in moisture content, but nothing like solid lumber planking does. All the ply lap manufactures eventually got around to using sealants in the laps (not as early as one would think, Lyman waited until 1966), but they didn't use polyurethane (3M 5200) but rather polysulfide or other material, such as gummy varnish, oil based heavy bodied goos, oakum, tar, pitch, cotton and a host of other things to help seal the laps until the moisture content could force the lap against their fasteners. In fact using 3M 5200 in the laps is a real bad idea unless the boat will see very limited in water use and will live on a trailer. 5200 will release from saturated wood pretty easily.

Lyman was designed for the "Finger Lakes" area, are well known up there and through out the great lakes. Chris Craft is easily the more recognized manufacture, pretty much pioneering the light weight ply lap construction methods used. All the companies that built these boats had different issues associated with them, mostly related to the methods and materials used in construction, a few had design contentions, but most were good boats.

It sounds as if you have your project(s) well in hand, Alan. Your Thompson was known for rot in the frame heels, so it seems you've gotten a "low hours" boat. Other points to look at on that boat are the frames and knees at the transom where water could pool and cause trouble. Also the turn of the bilge, in the last third of the boat, will be the most likely areas for tension breaks (or cracks) in the ribs. These can go unnoticed by the untrained eye, literally hiding under the paint and completely covered. I've removed ribs that looked perfect, just to have them fall into two or more pieces when placed on a bench for sanding. A key to look for is any discontinuous curves in the shape of the rib. Eye ball each one, they should have a smooth curve from heel to head. If not, it's probably cracked or broken and the paint is holding it together.

Good Luck . . .

 

Par is right where he says that it is not advisable to poor liquid epoxy in the seams - hard spots will form an irregular pattern and breakage may considered.

However, what will happen if you use a polyurthane type of glue, that foams a bit, may take a little bit moist and remains flexible? What I believe, it's the only solution to keep the water out.

Or?.........

 

Brien, polyurethane (3M 5200, 4200) will release from saturated wood, pulling off like a piece of rubbery string. Polysulfide works. In traditional lapped seams, the best thing to do is have really tight fitting seams and well secured fastenings. 3M 5200/4200 could work in a trailer boat, if it wasn't subjected to overnight or longer stays on the hook or docked.

Polyurethane adhesive (the foaming stuff) could convert the construction type from fastened lap to glued lap, but those laps would need to be especially clean and applying pressure enough on the laps during the cure could prove some interesting inventiveness with clamps. braces, etc.

 

Broken Ribs

Well I have removed the floor and found that I have several broken ribs on the port side.I have built a steamer that seems to work very well.I have purchased some very nice quarter sawn white oak.I can't wait to try and pull one into place.I have a question on the fastening.When putting the screw to the rib and strake should the screw only bore into the strake and basically the head of the screw hold the rib or should the screw grab both the rib and strake.?Par I hope you see this as I have complete faith in your advice. Look forward to hearing from you or anyone else familiar with White Lapstrake boats built in the sixties.Thanks Jeff Goldberg