How Much Will My Boat Weigh?

[beekeeper]

This might be more helpful for those building with wood and glass more than for plywood builds. Plans usually state a finished weight but if you make any changes or you are doing your own design this will give you an idea.

Canoe Weight Calculator

No more guessing. Use this comprehensive weight calculator to automatically determine how much your canoe will weigh. Inputs include a complete array of wood types, hull shapes, fittings and finishes.

ashesstillwaterboats.com

 

[jdupre']

Here is a little helpful hint I've noticed on my plywood pirogue builds. Find the weight of a 4 x 8 sheet of the ply you're using. Divide that by 8 and multiply that by the length of the finished boat. Example: 1/4" pine ply weighs about 28 lbs. That's 3.5 lbs per foot. 3.5 x 14 = 49 lbs for the 14' finished boat with sturdy gunnels and chines. Subtract 4-5 lbs for lightweight structure wood.

 

[beekeeper]

That is without glass and epoxy, correct?

 

[jdupre']

Bee, it's pretty close either way. Old school with wood gunnels, chines, etc without glass works out about the same as stitch and glue with a lot less lumber and the addition of epoxy and glass. The hull plywood makes up the biggest percentage of weight in a boat. Your mileage may vary.

 

[beekeeper]

Gotcha, one way or the other. My mileage ls about the same as yours. It takes a lot of attention to details to reduce the weight significantly. Like all other desirable boat design features and goals "light" is not always possible or the most important, if it compromises other needs.
A real boat builder told me "anything you add to the boat adds strength, Anything you add also adds weight."
If one builds a pirouge with ribs and stem pieces and then adds fiberglass and epoxy, the boat is stronger but weighs more.

 

[Kayak Jack]

Similarly, when two or more pieces are joined together, the joint will be (1) heavier than, or (2)weaker than, or (3) BOTH, than the parent material.

 

[jdupre']

It's a general guideline. Can't make a 30lb. 16' boat with two 28lb pieces of plywood. Well.......maybe a REALLY skinny boat.

 

[beekeeper]

Over the years we have road this "boat weight" horse several times. I was moving some lumber around today and weighed some plywood and boards out of curiosity. Bathroom scales and some differences from past efforts. Nothing to fret over.

1/4" pine bc 4'X8' = 26 lbs.
3/8" " " " = 36 lbs.
9 mm luan " = 29 lbs.
5mm " " = 19 lbs.
2X4 X 8' stud pine = 7 lbs.
2X4 X 8' rough cedar = 4 lbs

 

[beekeeper]

Over the years we have road this "boat weight" horse several times. I was moving some lumber around today and weighed some plywood and boards out of curiosity. Bathroom scales and some differences from past efforts. Nothing to fret over.

1/4" pine bc 4'X8' = 26 lbs.
3/8" " " " = 36 lbs.
9 mm luan " = 29 lbs.
5mm " " = 19 lbs.
2X4 X 8' stud pine = 7 lbs.
2X4 X 8' rough cedar = 4 lbs

Using a better/accurate digital platform scale I need to correct some of these weights.
1/4" pine bc 4'x8' plywood = 28 lbs.
9 mm. luan " " = 21.65 lbs. average
5 mm. " " " = 15.3 " "

The two 9 mm. sheets weighed 21.8 and 21.5 lbs. One 5 mm. sheet weighed 10.7 (lightest). The heaviest one was 19.3.
I assume different species of wood? Probably should take the scales when shopping. Probably why my last boat was 5 lbs. heavier than the previous one and they were almost identical size.

 

[jdupre']

You don't always get what you think you're getting. I've looked up the specs on wood designated as " spruce". It actually could be spruce, hemlock or who knows what else. So a specified weight could also be different from what the specs normally show. Carrying a scale when wood shopping is probably a good idea.

 

[oldbuffpilot]

You don't always get what you think you're getting. I've looked up the specs on wood designated as " spruce". It actually could be spruce, hemlock or who knows what else. So a specified weight could also be different from what the specs normally show. Carrying a scale when wood shopping is probably a good idea.

This is especially true for Cedar often it's the green Rough cut available at the Box stores. There can be a tremendous difference in the weight of these boards I try to keep and store Cedar strips that I cut 4 or 5 years ago make a huge difference in the weight of the boat

 

[jdupre']

I bought some cedar years ago that was so light and soft, I think I could have taken a bite off of the board, chewed it and swallowed it. It was almost as light and soft as balsa wood.

 

[beekeeper]

The last two boats I built had floors 12' long X 28" widest beam and were 9mm luan. Using the weights posted above the floors would have weighed 9.52 lbs. Using 5mm they would weigh 6.72 lbs.
The 5mm would need glass and epoxy to be strong enough. Using weights for fiberglass and resin calculated from these test; https://www.southernpaddler.com/community/attachments/1794_001-1-pdf.1198/
One inside layer and one outside layer of 4oz. would add 3.12 lbs. + 6.72 lbs. of wood, equals 9.84 lbs. No weight savings there. The builder would have to decide if any other gains are worth the extra work and $.
I know the 9mm works for me, so I'll stay with simple and cheap.

 

[jdupre']

To go lighter, you would probably have to go with 3mm in a more expensive plywood and minimum glass and epoxy. When a normal sized boat gets around 40 lbs or so, losing 8-10 lbs of weight becomes much more difficult and usually more expensive. There are boats out there about 25 lbs but they're like 4 THOUSAND dollars!