Some thoughts on weight

[jdupre']

Boat weight, that is. Consider this. The last 3 feet of each end of a 16 foot and a 13.5 foot pirogue (or canoe) are about the same as far as shape and weight. Pretty much the same dimensions. So the 2.5 feet of difference is mainly in the middle section of the boat........the section that has the most wood/nails/glue/paint/glass/epoxy..... which translates to less weight for the shorter boat..... if you change nothing else.

I didn't see any great disadvantage to my boat's 13 ft 8" length. Not saying that you should build a shorter boat, but to consider if a shorter boat could do what you want and need it to at a lower weight.

I've been corresponding with beekeeper on some other weight saving ideas. I'm not keen on glassing an entire boat again. Just too much fiddly stuff. But, epoxy is some magical stuff when used where you need it. For my next pirogue I'm thinking of doing away with the head blocks and using epoxy instead .......maybe a pound or two savings.

Glueing up a boxed type gunnel of cedar and cedar chines would also save a pound or two. Tiny breast hooks could save as much as a pound. On the subject of breast hooks. The only reasons I can find for breasthooks for MYSELF are as a handhold, a step and a place to tie off a rope. For that, I don't need more than about 7". Now I simply LOVE keith and seedticks's beautiful finely crafted breasthooks.......no doubt. Beekeeper builds some really nice ones also. But if you're going for lightweight, less is more.

More ideas as I think of them.

Joey

 

[Kayak Jack]

Some good thoughts, Joey. Instead of a deck (breast hook - WTH did THAT name come from?) I sometimes just mount a short chunk of 3/4" dowel crossways a few inched back from the stem end. Tie a rope to it.

 

[Wannabe]

I have always tought the breast hook was to give more strength to the bow and stern. Is that correct or not? Jack's dowel does the same thing and they do make convient hand holds.
Bob
';

 

[seedtick]

on a boat with a lot of side flare, the breasthook (bresthook) also keeps the sides spread out more - increasing the interior volume of the boat. Pretty much like a thwart, but not obstructing interior space.

That center section of the boat may have the most nails, wood, glue, etc. but it also has the most displacement. The ratio of volume of displacement vs. nails, wood, glue,etc is greater at the middle than at the ends. That why a 14' pirogue can carry a lot more than a 12', whereas just straight line scale up says that a 14 footer can only carry 17% more (14/12).

Don't know how big your stem pieces are, but we can use a 3/4" X 2 " piece on a plywood pirogue. Plywood is pretty stiff on edge so the stem piece just holds the sides together untilyou can put on the bottom and breasthook. The stem piece also gives you something to nail the batter board to on the front of the stem

 

[jpsaxnc]

Hi Joey, One thing I do is take a small bathroom scale with me to Lowe's to weight the wood. The weight of the Revolution ply varied from 15lbs.-18lbs. a 6 lb. difference on a 2 sheet boat, I also weigh the wr. cedar, the weight can vary greatly. hth.

 

[jdupre']

Good point, jpsaxnc . To keep it light, you have scrutinize every part. Seedtick, building shorter is just one consideration. The builder has to make the call if it's right for him. I can get by with 22" x 14', beekeeper .........uh......may not. :wink: Your point about nailing the batter board to the stem makes sense. Maybe just a smaller version of a typical stem piece. Breasthooks can extend further back for strength but made out of much lighter material..
The way I build, breasthooks have very little static stress on them. They probably see more tension loads with the sides wanting to splay out from bracing on them to get in and out. On the aluminum pirogue, the sides are way too flexible for just the decks to brace them so I added a thwart behind the seat to take the load. In a more substantial boat, a little longer decks would probably be enough.

Good points, fellows.

Joey

 

[Kayak Jack]

Joey, you hit the nail on the head that thwarts experience much more tension loads than compression. In my 13' S&G canoe, the thwarts are rope, not sticks.

 

[john the pom]

the thwarts are rope, not sticks.

Yeah Jack but to play safe you could build a thwart out of a skinnier stick and a skinny piece of rope glued together :lol:
cheers John.

 

[Kayak Jack]

In some (most?) of our cases, it isn't the weight of the boat that's the source of extra weight. (It's those darned 100 pound paddles!)

 

[john the pom]

Jack can't spell "paddlers" 8)

 

[Kayak Jack]

Yeah, he misspelled "100 pound" too. :wink:

 

[jdupre']

Don't know how big your stem pieces are, but we can use a 3/4" X 2 " piece on a plywood pirogue.

Tick, that sounds mighty small. How exactly is that cut?

Joey

 

[seedtick]

3/4 X 2 is the cross section, it fits on top of the inside chine and below the breast hook so its about 10" or so long. You can leave the profile straight or cut it curved depending on if you have staight or curved sides at the stems. You bevel the leading edge of the stem piece on both sides and slip it between the sides of the boat and nail and glue. It doesn't have to be a perfect, gap free joint - it's simply holding the sides together and just needs enough strength for that. Of course you can always drizzle some epoxy syrup if you want to fill in the gap. The waterproof joint is is needed when you nail the batter board on the front.

i'll post a picture if i can find one

 

[seedtick]

 

[jdupre']

That makes sense now, seedtick. Thanks. The weight of a little piece of WRC that size would scarely be noticed.

Joey

 

[jdupre']

I did some calculating on the weight difference in a 16' pirogue using Douglas fir or Western Red Cedar for the chines, gunnels, etc . Came out to be almost a 7 lb reduction using the Cedar. Pretty good savings on a 60 lb boat.

Joey

 

[Kayak Jack]

Kinda hard to believe that those ancient Indians who invented the canoe knew what they were doing. Truth be known, I think Matt probably was there helping them all the time.

 

[jdupre']

Jack, I'll bet those Indians went through a whole bunch of prototypes to weed out what worked and what didn't...... kind of like we do here. Just imagine hundreds of builds, each tweaking something from the previous one to make it work better. After years or centuries, the resulting craft would be almost perfectly adapted for the use and the enviornment at hand.

And , yes, Matt might have shortened up that time span some.

Joey

 

[Kayak Jack]

<SNIP> And , yes, Matt might have shortened up that time span some.

It's a well documented, historical fact that several birch bark canoes unearthed in Ontario show graphical evidence of CADD activity. Two or three dugouts, pulled from a watery grave in Florida, are also suspected of being CADD designed.

There are, of course, a few skeptics, but pay them no nevermind.

 

[JEM]

Kinda hard to believe that those ancient Indians who invented the canoe knew what they were doing. Truth be known, I think Matt probably was there helping them all the time.

Well if Jack was there when fire was discovered, I'll take credit for tribal canoe designs. :mrgreen: