PDA

View Full Version : Scaling plans



Philip H
09-13-2000, 01:43 PM
I have ordered the building plans for the 11'6" Charlotte featured in Tom Hill's "ultralight Boatbuilding". They haven't arrived yet, but they are full scale plans. The boat is for my young daughter and I wanted to make it smaller so she could comfortably launch and paddle it. My current thought is to reduce the patterns for each component by 25% on a large format photocopier.

Do any of you have any insights into trouble I may be asking for with this method? First question is will the boat go together properly proportioned. Second question is what performance gremlins will I stir up. Narrower beam is less stable and there is less freeboard, but these are the two measurements I am most trying to reduce to accommodate my small paddler. (She is 4, but will most likely be 6 by the time it's in the water)

Thanks in advance.

Philip

Michael Horrisberger
09-13-2000, 02:12 PM
Philip,
Your reasons for scaling down the plans appear to be misguided. The reality is that if your daughter is currently 4 you should anticipate the paddling at launch to be done by a girl of 12-14 years of age. Perhaps a scaling down in the 5-10% range would be more appropriate.

Philip H
09-13-2000, 02:21 PM
Its probably worse than you think, if I proceed at my usual pace it will be my 12-14 year old granddaughter!

htom
09-13-2000, 02:45 PM
Reducing the length by 25% (11'6" --> 8'7.5")
seems possible (I'm not sure that it would still be a good canoe design, though); doing this shrinking to all of the measurements I don't think will have the results you desire.

I'll ask you to consider Platt Monfort's Sweet Pea, a child's canoe with a length of 7'5", instead, or his Toy Whitehall, another child-user boat.

You can use the Charlotte yourself to accompany her, until she grows enough to want it for herself.
http://www.geodesicairoliteboats.com/sweetpea.html http://www.geodesicairoliteboats.com/toywhitehall.html

(I think the Toy Whitehall page has a typo where 11 pounds became 1 pounds.)

Tom Dugan
09-13-2000, 03:14 PM
Philip,

Where did you get the Charlotte plans? I've been wondering where to get them.

As far as scaling your plans, Walter Simmons has something to say about that in his "Building Lapstrake Canoes" book. He built his first canoe for his daughter, IIRC. The gist of it (since this is from a poor memory) was that you still need the beam for stability, and you won't get into too much trouble if you shrink the distance between molds by no more than 20%. This will get you down into the 9' range, which may be good enough. After all, you don't want her to out-grow it right away!

One other thing you may want to do -maybe- is to drop the shear a bit to accomodate shorter arms. Maybe leave off the shear planks. Hey! If you left the stems long, you could add them later when she gets bigger! Or have I just been staring at my monitor too long?

-T

Ian McColgin
09-13-2000, 03:22 PM
I second all who discourage scaling.

If you want quick and cheap to get her going try the 6 hour or one sheet of plywood canoe.

Then move up as she gets bigger.

Ron Williamson
09-13-2000, 06:32 PM
Imagine that!
A practical reason to built another boat.
"The kid outgrew it,what else are we supposed to do?"

Philip H
09-14-2000, 08:00 AM
Thanks to all for the input. I appreciate the suggestions for other designs, however, as some of you may understand, this is the boat whose image has taken up permanent residence in my brain somewhere and the only way to evict it is to get it built.

When the plans arrive I'll mock up the midship sections and do some testing with my daughter. Perhaps a couple inches of beam and an inch of freeboard and raising the seat off the floor is enough to make the difference. That's a 10% reduction, which would still allow me to use it as well (I'm on the light side.)

To answer Tom above,I called him at(802)658-9150. Talked with someone else, not Tom. Was able to use a credit card.

Todd Bradshaw
09-14-2000, 11:01 AM
The last thing that you want to do if you scale down a canoe is to raise the seat. Making it shorter and narrower both decrease stability. Raising the seat will just make it worse.

Matt J.
09-14-2000, 11:21 AM
Hey, Phillip. I've got a large format copy machine here at my office I'll use for you... so long as you sign a waiver with my lawyer so you don't sue me for the 5-10% error possible on these machines. For instance, our business cards have scales on the back of them (e.g. 1"=40') and there is a 7% error along the top and bottom scales... that adds up over a couple of feet.

If you really need to scale it down, there'd be 2 things I'd have to suggest, and are worth more than MHO:
1. see if Tom Hill would do it for you for a small fee. that'd ensure accuracy and save you the headaches.
2. if you're gonna scale them, please find a top end engineering, surveying, drafting, graphics "reproduction company" and see if they have a Digitech machine. These are the next generation of copying large format documents, and are digital. You HAVE TO find a good repro company, because we've found two local companies claiming digitech and they were the same Xerox format we have. The difference can be indistinguishable to the human eye, unless you've been doing this for many years like my coworkers. The difference will likely not be indistinguishable to the water.

Lots of small designs out there already in that range, although, I know, you want the Charlotte. Sure you don't want to keep looking?

Philip H
09-14-2000, 12:30 PM
Emerson, that's a great tip, something I never would have realized.

Regarding stability, I would guess that a significant component of the stability calculations of a canoe is the passenger. In this case the passenger will be well below the weight of even a small adult. I am willing to sacrifice some stability from an otherwise very stable design, the question is how much am I sacrificing. I just don't know. My gut tells me 90% scale would not dramatically affect stability given the even greater "scaling" of the passenger.

Ross Miller
09-14-2000, 11:03 PM
Aw, címon, leave it alone. Get her a used plastic nine-footer to bash around and learn in while you build the Charlotte. Why make her wait? After you build the C. you can get your tinkering ya-yas off by designing one for yourself.

ishmael
09-14-2000, 11:22 PM
Sartain truth thaaaar Ross. Or bang some awkward punt/paddle boat together, in a weeeek end. She won't care, kids are like that. Goof/serious her on to the pond and let'er feel the woof wankle woofwankel of the little waves beneath her hull, HER HULL. You know the waves I mean, woofwankel.

Ross Miller
09-15-2000, 12:31 AM
You didn't have to splain.
Woofwankel. That's a boat name.

Ken Hall
09-15-2000, 12:57 PM
I second the recommendation of the One Sheet Skiff...Charlotte should be her second boat.

Ken

Weaver
09-23-2000, 03:15 PM
The Charlotte is a fine canoe to paddle. They have one at the WoodenBoat waterfront which I have paddled several times. It is also very light which will be a good feature for a little girl. It is fast, I could easily keep up with sea kayaks. It is not particularly stable so I would be reluctant to reduce the freeboard.

salmoneon
11-26-2000, 02:10 PM
Charlotte is fantastic boat. Highly unstable until one's butt hits the bottom, then improves considerably. I would strongly agree with those who would discourage you from raising the seat. I have had 8-9 year olds in mine, very happily. I think for a longer paddle the width at the beam would prove discouraging, however.

I would support you in your fascination with this boat. An indication of a good eye IMHO.

Happy building!

Ian

John Gearing
11-29-2000, 08:09 PM
If you want a smaller Charlotte for your daughter my advice would be to simply call up Tom Hill and ask him about it. He's got the experience to tell you if what you want to do is feasible, if it's dangerous, or if it's a great idea he just hadn't thought of. And he may well be able to modify his design for you for a small fee. If I were in your shoes, that's the route I'd take. Even if my kid was going to be wearing her PFD I wouldn't want to put her in something that was too likely to tip over. At the least she might come away hating boats and the water and that's not the idea.

Philip H
11-30-2000, 06:50 AM
Thanks again for all the comments. I decided to build it as is because, in the end, its me that really wants to paddle this thing. And as Ishmael commented, "she won't care." Which of course is all you can expect from a little kid. Cutting of forms will begin after I finish the workbench I'm currently building.