Will this work?

Can I do this? I am thinking of using Cedar wood, solid stock. I will plane it to 7/16" thick or 3/8", then dado the edges. I'm thinking I will Gorilla glue every seam and attach with finish screws to the frame.

From 6" above the waterline all the way under the hull I want to fiberglass and gel coat, then above I want to seal and finish.

How far off track am I?

Thank You.

 

You would be better off with a traditional tongue & groove joint IMHO.

Glass & epoxy, painted over, will work. Gelcoat is generally used when building molded FRP (fiberglass) boats. It is the first part of the hull skin sprayed in the mold. Probably not needed nor desireable for what you want.

Epoxy would be a good choice for glueing in general. Gorilla glue is good stuff though the price I think would be higher than epoxy. I have not heard how well it stands up to the marine enviroment.

Hope all works out well for you.

Welcome to the forum.

Tim

 

Thanks Tim.

Traditional tongue and groove? Where do I buy it?

What about the cedar? Do you think it will be just as good as Mahogany?

Thanks.

 

You may be able to get it milled close to home.

Check into "strip planking" for other ways to fasten the hull together.

Wood type preference depends on how and what you are doing with it. Give more details on the boat you want to build, size, intended usage, hull type, ect...

Hopefully PAR or others with more knowledge (alot more) will chime in.

My biggest area of interest is steel boats.

Give it awhile, and if you do not get sufficent responses reword your title and update with more specific details & post again.

Take care.

Tim

 

Hi Winingar,

Terminology--- you show a shiplap, a dado is a groove.
Your project is to make a substrate, and cedar is a good substrate. You show what appears to be a hull that has chines, meaning corners along the sides--- am I right?
Assuming plywood isn't what you want, first, in regards to the size of the pieces that make up the hull--- and the thickness too---- there will be appropriate dimensions for your particular boat. You are fine with the thicknesses you mentioned if your boat is the size I think it is.
Let's say it's a 15 ft boat. Further, let's say it's a trailerable boat weighing 200 lbs. Now we have some idea of where to start in choosing the size of the pieces that make up the substrate planking.
My suggestion would be to use something 3 1/2" wide. Narrower and you'll be doing too much gluing. Wider, and several issues pop up. Moisture entering due to the smallest scrape or cut will migrate throughout the entire piece. Pieces will also be harder to bend around curves. There will most likely also be more waste. And finally, smaller pieces can be chosen to be vertical grain, which shrinks and expands only half as much as flat grain, or plain-sawn. You want to see lots of lines closely spaced on the face of the board, and wider boards may be harder to find without some flat grain.
regarding the joints: Nothing wrong with tongue and groove except finding it in the appropriate dimensions for your particular boat. There is no strength advantage--- the reason for using t and g would be for speed of construction, because the boards self-align.
That said, there are ways to have good alignment without using anything but a butt joint. Many joints will fall nicely into place anyway, but if not, an air stapler with 1" long staples going through both pieces into a single temporary block of wood behind (with wax paper or plastic sheet to avoid gluing the block too).
Screws through a small hole drilled right at the crack will work too--- washers on both sides (remove before full cure of epoxy).
Wire works too--- two holes, one on each adjacent board, and twist the wire to draw together and create enough pressure to tap into alignment.
All of these holes will fill up when glassing.
then there're clamps, of course. The point is, with modern construction, epoxy adhesives and glass cloth, nothing is gained by a fancy joint except speed, and what is speed if you have to make all those joints in the first place? And if you're using Gorilla glue, there will be more attention to fits required. Pieces should fit together just as if being glued with Elmers glue. Epoxy can span relatively huge spaces, as it doesn't depend on close fits for strength.

Alan

 

Gorilla glue bubbles as it cures. These bubbles can push out air pockets in some of the tightest clamped joints. The last thing you want to see is an air pocket between some of your clamps.

Stick with epoxy, It'll give you consitent joints throughout.

 

The first thing that jumps out at me, is a square shiplap and a rolling plank edge that will have ever changing angles inside the lap. This is one reason this particular joint isn't used in lapstrake or dory lap construction methods. The other and primary reason this joint isn't recommend is the likelihood of stress risers on the inside corner of the lap. This will be amplified when the laps don't perfectly align and the edge set necessary to hang the planks gets worked into the joints. Lastly the joint construction naturally traps moisture against the inside of the joint, which is a no-no in boat building technique. The dory lap and traditional lap strake joints, will let moisture run out of the joint, from gravity, which is just one reason they are preferred.

Clearly, you're trying to get a carvel like hull, without the trouble of caulking seams. There are several construction methods that can accomplish this smooth hull surface, that don't require caulking seams. You should strongly consider one of these methods. Reinventing the horse is a wonderful thing and you should continue to think outside the box, but any choices you do make regarding a new joint, should be at least as good as what is commonly used, if not superior.

 

Thank You for all the insight.

First I have to let you guys know that I have very limited knowledge of the correct methods used for proper construction, this is why I'm here.

I am going on my knowledge of the woodwork I have been involved with over the past 15 years and also some of the knowledge that I have learned over the years growing up on my Dad's boat(s).

I have seen several different Chris Craft runabouts over the years (18'-21') that I would like to build and I think I understand the construction proccess but thinking I understand it and knowing it for sure are two different things.

I really don't have a set proccess in my mind that I must do, so all recomendations are very welcome.

Thanks again for your thoughts and insight. I will put them to good use.

 

I'd suggest you buy some books on wooden boat construction. Also spend some time looking at previous posts concerning wood boats & thier construction. Wooden Boat magazine will spark alot of thought to.

The research phase should be an enjoyable time, not a burden. There may be a post(s) on good books for the above, if not, and you are interested, you could post one.

Tim

 

I've given thought in the past to dory and other chine construction where panels are assembled and glued on the bench to make plywood type pieces of any legth and width--- using white pine, spruce, or preferably, Western Red Cedar. In 3/8" to 1/2" thickness, this seems to me to be a superb semi-production method, ensuring tight fits, better use of lumber, less sanding, and better self-fairing. The drawback is only the difficulty in bending the tighter curves (a dory would be no problem, but some boat designs would be tough to do with this method as the pieces could get large enough to stress the building jig---- more than plywood of the same thickness, as all the grain runs fore and aft).
In most cases, the panels could be skinned inside and out on the flat, and very accuarately tapered on edges where needed for taped chine seams, which might have three layers of tape applied without standing proud of the planking. The process would be very clean, allowing the chines to determine the fairest of curves, with no frames except further in to align the chines.
Frames could be added afterwards, fitted to the fair panel rather than the planking being fitted to the frames.
No doubt this has been done before. Basically, you are making custom panels having no scarfing, and the results are halfway between plank on frame and strip construction. A large table could be set up (maybe 30" x 24' maybe made up out of formica countertop), waxed, with overhead flat panel on ceiling to use for T-sticks for holding down all pieces at once. Bar clamps would tighten joints.


Alan