Guidelines for scaling drawings?

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Fludlow
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Guidelines for scaling drawings?

Post by Fludlow » Mon Dec 05, 2011 4:31 pm

I've already built the free Laker and now I want to build the Northwind. However, what I learned with the Laker was it was too big going downriver and bobbed like a cork. While the Northwind is sleeker it still has a lot more displacement than I would like and at 17' is pretty long to mount on my truck. I plan to portionally size it to about 13" 6" or so. Anyone have any good guidelines on doing this? I realize there is a minimum width of about 24" or my butt will never fit! :!:

tx river rat
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Re: Guidelines for scaling drawings?

Post by tx river rat » Mon Dec 05, 2011 5:32 pm

I dont understand what you mean about bobbing like a cork , 13 ft is short in Kayaks .
If you brought the Northwind down to that length you would take away what it was designed for , caring a big load and a high cruising speed .
I have built both .
Just my 2 cents
Ron

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jem
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Re: Guidelines for scaling drawings?

Post by jem » Mon Dec 05, 2011 9:44 pm

You'll have to scale it 2 ways to get an exact match. But then you'll have to do 2 splices per panel for a 13' boat.

The avoid the "bobbing cork" select a hull with an appropriate payload capacity. What's the weight range you'll have on board? Include paddler, gear, cooler, etc.
-Matt. Designer.

Fludlow
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Re: Guidelines for scaling drawings?

Post by Fludlow » Tue Dec 06, 2011 12:54 pm

I use the kayak for going down the Shenanndoah or Rappahanock in Virginia. No real white water. No real payload except me ~180lbs. This is usually in conjunction with Boy Scout river floats. I considered using the Laker as a Scout project and have them build it but after I built mine decided against it. I may be wrong but the Laker appears, from a hull form, to be nothing more than a decked version of the free canoe plan. I mention that because you might expect two paddlers in the canoe and with another 50 - 75+lbs in it I think the Laker would have been much more stable.

I since sold my Laker and I think the Northwind is better looking. But from a float characteristic and loading on my truck, I think a shorter version would be a better craft. Maybe I need to build one to plan and scale another and post the results.

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jem
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Re: Guidelines for scaling drawings?

Post by jem » Tue Dec 06, 2011 1:57 pm

Fludlow wrote:I use the kayak for going down the Shenanndoah or Rappahanock in Virginia. No real white water. No real payload except me ~180lbs. This is usually in conjunction with Boy Scout river floats. I considered using the Laker as a Scout project and have them build it but after I built mine decided against it. I may be wrong but the Laker appears, from a hull form, to be nothing more than a decked version of the free canoe plan. I mention that because you might expect two paddlers in the canoe and with another 50 - 75+lbs in it I think the Laker would have been much more stable.

I since sold my Laker and I think the Northwind is better looking. But from a float characteristic and loading on my truck, I think a shorter version would be a better craft. Maybe I need to build one to plan and scale another and post the results.
The Laker has 2 versions: The free version and a pay-for version that has has some more features and is delivered by postal mail instead of download and print yourself. It very different than the free canoe plans. Different shape, size, entry, number of panels, etc.

One of these might be more to your liking: http://www.jemwatercraft.com/Buccaneer.php
-Matt. Designer.

LesForgue
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Re: Guidelines for scaling drawings?

Post by LesForgue » Mon Jan 30, 2012 6:37 pm

Matt,
I am considering making a scale model of your Trapper 15’3” x 35” canoe.
Exactly as designed would be my first choice were it not for storage and handling considerations.
I am thinking of an end result 13’ long with about 32” max beam,
achieved by multiplying all the ‘length’ dimensions in the plan by 85%
and all the ‘beam’ dimensions by 92%.
I figure the .92 for beam would change the 20-13-20 heights to about 18-12-18.
Does all that make sense?
Would doing this preserve most of the benefit of your design?,
or would it more or less wreck your design?
(I do need to have a shorter canoe and I fell in love with the lines of your Trappers, as opposed to the short Sasquatches, but my primary objective is a professionally designed boat, not one messed up by me & my calculator.)
Thanks in advance for your opinion.
Les
Les Richard Forgue

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Re: Guidelines for scaling drawings?

Post by OnkaBob » Mon Jan 30, 2012 10:27 pm

LesForgue wrote:messed up by me & my calculator.)
When it comes to scaling that little snippet of your post sums it up fairly well Les.

There is a reasonable amount of discussion on this topic on the net and if you do a search you should be able to find enough to convince you that it just isn't worth the effort. This applies to all sorts of boats not just canoes and kayaks. A very small scaling can work but then what is the point? Scaling from 17' down to 13'6" is a large change. Stability is the main issue but all factors of performance are affected.

If anyone decides to go ahead and do this then they should do so in the knowledge that they are not building the original Jem design and the result is their own responsibility.

And just a word on the Laker - my 13' laker and I were caught in open water by a 20 knot breeze producing significant whitecaps and although it was scary and uncomfortable that little boat remained upright and controllable enough to take me home safely. Pretty good performance for something design for good glide on smooth water 8) .
Cheers, Bob

Laker 13 - christened and slimed (just).
Laker accessories underway.

tx river rat
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Re: Guidelines for scaling drawings?

Post by tx river rat » Tue Jan 31, 2012 1:31 am

x2 on what he said.
The Laker is closer to a perow than a canoe and for a 13 ft boat has some awesome performance.
The one thing I have learned about boats is there very job specific and when you change designs they suffer most of the time.
It is a whole lot easier to haul a boat that is four foot longer than it is to paddle a bad design a few miles.
Ron

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Mick
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Re: Guidelines for scaling drawings?

Post by Mick » Tue Jan 31, 2012 2:19 am

X3.

I built the prototype Laker and was so impressed with it, I built a second one. :D I have had my laker in grade 2 -3 rapids and in the surf numerous times.

I taught my partner Evie, who has never paddled anything before, in a Laker and she can't swim.
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Evie and her brother (both first time paddlers) in Lakers

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She even shot some gentle rapids in it on her second day out.

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My Grand-daughter in one.

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Re bobbing around like a cork in a laker 13 when the paddler is 180 pounds, I call B.S. on that. Sorry mate, but I call a spade a spade. Likewise, the Laker is absolutely nothing like the free canoe on Matt's site. Actually, Laker is so bloody good that several big name, stitch and glue kayak mobs are now all but copying it.

Life is good, Paddle a Laker. :D

Image

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jem
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Re: Guidelines for scaling drawings?

Post by jem » Tue Jan 31, 2012 7:21 am

Scaling in 3 dimensions works but trying to do only 2 dimensions will be troublesome. The panels are laid out on the wood for best usage of material. They are not orientated for scaling.
-Matt. Designer.

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