Strongback for Prospector 16'

Welcome to the new Bear Mountain Builders Forum - an interactive internet service we provide to encourage communication between canoe and kayak builders
Post Reply
skate
Posts: 2
Joined: Fri Jan 07, 2005 5:36 pm

Strongback for Prospector 16'

Post by skate »

I am working from the Canoecraft book, 83 edition, and am stymied before even cutting out the station moulds for the strongback. Following instructions in the book, I cut the 4x8' sheet of particle board into two 2x8' lengths only to find that the station moulds are more than 25" high and therefore will not fit on the board.

I extended the strongback line 2" above the horizontal line from the highest plotted point, which was on the stern/bow piece. However, when I look at the pictures in the book the bow/stern piece is always cut horizontally from the highest plotted point without the two inch increase. I have read and reread the relevant sections and can only think that all the other canoes in the book don't have such a high bow/stern and so don't encounter this problem. But it still does not solve the discrepancy between what (I think) the book is telling me to do and what the photos looks like.

Any suggestions? Is there an error in the book or am I doing something wrong?

Thanks
Kate
P.S. I appologise if this is listed in the wrong section. I tried to list it in the project directory but was informed that only administrators had the power to do this.
User avatar
Glen Smith
Posts: 3719
Joined: Sat May 08, 2004 9:08 am
Location: Baie-St-Paul, Quebec, Canada

Post by Glen Smith »

It looks like you selected a design with a lot of depth which played a trick on you. It is preferable to have the molds riding a few inches above the strongback to make it easier to work on the ends. For any molds that won't fit on the 24" plywood, you could add an extension piece to increase their height.

An alternative is to have the stem molds hanging over the ends of the strongback with the tips actually sitting lower than the strongback surface. This would require modifying the strongback if it is already built.

Not a fun way to start a project, eh?
Michael Freeman
Posts: 13
Joined: Tue May 18, 2004 7:01 pm
Location: Truro, Nova Scotia

Re: Strongback for Prospector 16'

Post by Michael Freeman »

Kate,

It is possible to cut all the Prospector molds from 24" wide plywood. The trick is to remove 2" from the overall height of all the molds EXCEPT the stem molds, which have a 2" notch cut from the bottom. In other words, the station "0" mold, which is approximately 25-1/2" high on my plans, can be made 23-1/2" by removing 2" from the bottom extension of the mold.

This will only work if the strongback is SHORTER than 16' (IIRC I made mine 15') so that the end of the stem mold can drop below the base of all the other molds to accommodate the notch.

It is a lot easier to show you what I am trying to describe, so here is a photo of what my setup looked like:

Image

Note the notch on the bottom of the stem mold, and the taper to the end of the strongback to allow clearance for the planking at the stem. ALL the other molds are simply 2" shorter than the overall height shown on my plans (the 2" being removed from the bottom extensions). Looking at the bottom photo, I think you could probably eliminate the taper on the strongback ends (if your strongback is a boxbeam instead of a T-beam) by going with an overall strongback length of 14' 6", which should give enough clearance for the stem planking.

If you can't do this setup, then as Glen suggested the simplest solution is probably to add a piece to the bottom of the molds that are more than 24" high.

Good luck,
Michael
User avatar
fz7m0d
Posts: 39
Joined: Thu Dec 02, 2004 5:10 pm
Location: Welland, Ontario

Post by fz7m0d »

Glen Smith wrote: It is preferable to have the molds riding a few inches above the strongback to make it easier to work on the ends. For any molds that won't fit on the 24" plywood, you could add an extension piece to increase their height.

I have just started stripping my Prospector (my first boat). I can see now that I'm going to have trouble later. I didn't elevate the molds at all......the shear line of the stem mold sits on the strongback. And to think I thought of everything.

Is it possible to elevate everything above the strongback by a few inches just before I fill in with the short pieces along the shear line at the stems, or should I leave it and work around it? I don't look forward to glassing with the stems sitting on the strongback, either.
User avatar
Glen Smith
Posts: 3719
Joined: Sat May 08, 2004 9:08 am
Location: Baie-St-Paul, Quebec, Canada

Post by Glen Smith »

If you have started the stripping, I wouldn't move the molds. Do all of the stripping that is possible and leave the end filler strips for last. Then maybe you could modify the ends of the strongback by cutting away enough material (from below) to allow you to do the filler strips. Just a thought. Someone else here might have a better suggestion. :roll:
Rick
Posts: 727
Joined: Thu May 27, 2004 9:23 am
Location: Bancroft, Ontario

Post by Rick »

You could also shorten the entire strongback by several inches on either side, using a saber saw to make the vertical cuts, and then a hand saw held upside down to finish cutting through the strongback's top, until the blade just touches the mold.

Hmmm... maybe this is what you were saying in the first place, Glen. The first thing I thought of was to cut a wide U-shaped opening in the strongback's top to let the cedarstrips down past the sheer.
fisherguytoo
Posts: 66
Joined: Tue Jul 27, 2004 9:25 pm
Location: Central Calif. foothills

Your thought on cutting a hole in the surface of the strongb

Post by fisherguytoo »

:roll: :P :D I am a novice building my first canoe also, so I hesitate to give advice.
But, I will tell you what I did. I found my proposed canoe and strongback in the same
situation that you have.

I did cut a hole in the top of the strongback to allow the ends of the canoe (15' Ranger-
Prospector) to sit just below the top of the strongback and this has worked out well.
I am now shaping the stems that are on the forms and would like to have a little more room, but it is workable. Actually the planking ended approx one inch above the strongback surface, but, the hole provide room for the ends of the stem to fit through until such time as they are cut off.
User avatar
fz7m0d
Posts: 39
Joined: Thu Dec 02, 2004 5:10 pm
Location: Welland, Ontario

Post by fz7m0d »

Thanks for all the input. I hope this is the only mistake I make..............or at least the worst one.

Bob
User avatar
fz7m0d
Posts: 39
Joined: Thu Dec 02, 2004 5:10 pm
Location: Welland, Ontario

Post by fz7m0d »

After completing all the stripping except for the filler strips, I cut 18" off each end of the strongback. This left me with all kinds of room to finish the hull.
Bob
(Confucius Say... Asking a stupid question is better than repairing a stupid mistake.)
User avatar
Glen Smith
Posts: 3719
Joined: Sat May 08, 2004 9:08 am
Location: Baie-St-Paul, Quebec, Canada

Post by Glen Smith »

Hi Bob, I'm glad to see it is working out for you.
Post Reply