Shortening canoe plans

[Iskweo]

I am seeking some input from the builders out there. I have a set of plans for a 17 foot Morris cedar strip and am thinking of shortening them to 15-15.5 feet. The intent is for a solo canoe of lighter weight and just to have something different. ( I missed the 15 footer that was on Kijiji a few years back) .

So my question is....do I simply shorten the distance between station molds or do I reduce the width of the stations as well. Or do I just remove the center station. Thoughts, or experience in doing so would be appreciated.

My backup plan is to just build another Jacks Special.

 

[Jim Dodd]

I've shortened and lengthened several hulls in my day. Made a few Asymmetrical hulls also.

The main thing is to Fair your forms, and stems.

I'd start by shortening the form spacings, equally. You will likely need to shorten the Stem forms by at least double the amount as the forms

I used C-clamps as it made it easy to do small adjustments.

Lay a strip along the sides, at the shear, and at the bilge area. If it makes contact, or very close (1/6") I'd be happy.

Characteristics you will likely notice by shortening a hull, is a speed reduction, but easier to maneuver.

A friend, did this by accident. He shortened a solo by 6". It turned to be a fun hull for small creeks, a leisure paddling. It was good enough, that I built the same hull.

Good Luck Christy, and post here as you go ! Always good to see a new build !

Jim

 

[Mihun09]

We were thinking if we take 10% off the length it would be down to 15' 4". If we do it this way should be reduce the width of each form by 10% to avoid making a bathtub shape. Easy enough to do as we need to make forms either way.

This plan set also has 21 forms over the 17 feet. It has them numbered such as 1, 1 1/2, 2, 2 1/2, etc. I see no reason we cannot drop the extra forms and still maintain the shape.

Karin

 

[memaquay]

What's the width at the center?

 

[stripperguy]

I’ve shortened plans before... I shortened by a given amount, say 10%, and reduced the center form by the same amount. Then I proportionately reduced the reduction as I approached the stems, that’s worked out well for me.

Edit:
Previous comments were from my phone, I can be a bit more descriptive here on my PC.
I shortened an 18'6" USCA competition cruiser to 17 ft. This was a reduction of 8.1%. I removed that 8.1% from the center of the center form. Obviously, I didn't (or couldn't) reduce the beam at the stems. I proportionately removed less and less beam as I approached the stems, but always maintaining most of the hull profile, removing beam from the center part of every form. This slightly altered the section profiles...a shallow arch morphed into a shallow vee, and there was a side effect of additional rocker.

 

[Traveler]

Wow - 21 forms - I thought cutting out 15 plus stems was a pain.

I am looking at doing the same thing, but by much less - going from 17’9” down to 17’2” or so, to let me build in my garage and leave some maneuvering room. Jim’s point on adjusting the stems caught my eye - I was just planning on spacing the forms a 1/2 inch closer and leaving the stem length as is. I am pretty sure this won’t be a problem given that this is less than a 5% reduction, but if I am wrong would appreciate any points from you guys who have done this before. Just started placing the forms today, so still time to fiddle with the stems. The plan is for a Freedom 17’9”, asymmetrical. Thanks

Tony

 

[Jim Dodd]

Most of my solos are 13 forms, plus the stem forms.

If you are set on that design. A trip to a good print shop, with the original plans or even a tracing of the forms, and they can computer reduce plan sizes. You should also reduce form spacings accordingly.

As Mem stated, what width are you wanting ?

 

[Jim Dodd]

Wow - 21 forms - I thought cutting out 15 plus stems was a pain.

I am looking at doing the same thing, but by much less - going from 17’9” down to 17’2” or so, to let me build in my garage and leave some maneuvering room. Jim’s point on adjusting the stems caught my eye - I was just planning on spacing the forms a 1/2 inch closer and leaving the stem length as is. I am pretty sure this won’t be a problem given that this is less than a 5% reduction, but if I am wrong would appreciate any points from you guys who have done this before. Just started placing the forms today, so still time to fiddle with the stems. The plan is for a Freedom 17’9”, asymmetrical. Thanks

Tony

Temporarily set your forms, and a Fairing strip will tell, if you need to adjust stem forms.

A 1/2" inch per form doesn't seem like much, but when you Fair the stem. I'll bet you will have to pull the strips in quite a ways to make contact with your first and last forms.

 

[Mihun09]

We have the option of asking the plan maker if there is an easier way to shorten, perhaps he has plans for a shorter Morris. It is Roland Thurlow of Northwoods Canoe. There is a 15' Morris on his site we could order for $4400 US but there may be plans as well.

Considering Christy is the one who bought the plans for me for Christmas and she is retired, she should contact Roland for further instruction.

 

[Iskweo]

So apparently the 15 footer is 2.5 inches narrower than the 17 footer.....30.5 compared with 33. Not quite 10% reduction, it in fact being the 7% solution. A Jacks Special ( chum) comes in at 32 wide, which I did not find tubby at all. My Hurons were closer to the 33 mark or slightly over and I did not find them objectionable either.

I like the idea of a print shop making me a reduced copy, but simply using a fairing strip would likely be as easy as anything. I could also alter the top of the forms to give me extra tumblehome or reduce each form by 1.0 inch to give me a 32.0 wide boat.

The plot thickens.

 

[paddler123]

One thing to keep in mind is how the different options affect the total volume of the hull. If you shorten the length by 10% but leave the width and depth the same, you have 90% of the volume of the original hull. If you shrink all three dimensions by 10%, the volume will be 0.9*0.9*0.9, or 73% of the original. Which one is best depends, among other things, on how many people/how much gear you plan to put in the canoe.

 

[Seeker]

When I built my stitch and glue Eureka 155 (actually making it a 145), I just cut 6" off each center, essentially removing a foot from the middle of the design... It worked. If I were to tamper with a stripper, I'd ask here, as you have done.