Creating Tumblehome on a Royalex Canoe

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Sep 13, 2013
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I found a 1994 Mowhawk Challenger 14' Solo canoe on Craigslist and decided I needed it. The seat had some kind of missing back brace and the ends of the thwarts were starting to rot. I've paddled the canoe a few times and enjoyed it but wanted to try and introduce some tumblehome to it.

I ordered new thwarts and a contoured web seat from Ed's Canoe. Then I removed the thwarts and seat, added some ratchet straps to crank in some tumblehome and installed the ones.

Mistakes were made but I got through it. I haven't paddled it yet so I hope I haven't screwed up the canoe by changing its shape. I also hope the Royalex is resilient enough to not be adversely effected by the new shape.

The seat height was OK so I made no changes there.

It's now around 3-4" narrower at the thwarts and I may have introduced a very shallow arch to the bottom of the canoe. Then again, maybe it was already there as I didn't think of putting a straight edge on it before the work.

The photos tell the story:

Before:

MowhawkChallengerTH.jpg


MowhawkChallengerTH-5.jpg


MowhawkChallengerTH-3.jpg


MowhawkChallengerTH-2.jpg


During:

MowhawkChallengerTH-6.jpg


MowhawkChallengerTH-14.jpg


MowhawkChallengerTH-16.jpg


MowhawkChallengerTH-15.jpg


MowhawkChallengerTH-11.jpg


After:

MowhawkChallengerTH-21.jpg


MowhawkChallengerTH-22.jpg


MowhawkChallengerTH-30.jpg


MowhawkChallengerTH-29-1.jpg


MowhawkChallengerTH-28.jpg


MowhawkChallengerTH-27.jpg


MowhawkChallengerTH-25.jpg


I may have to wait a few days to see how it does. I'm keeping my fingers crossed.
 
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I found a 1994 Mowhawk Challenger 14' Solo canoe on Craigslist and decided I needed it. The seat had some kind of missing back brace and the ends of the thwarts were starting to rot. I've paddled the canoe a few times and enjoyed it but wanted to try and introduce some tumblehome to it.

I haven't paddled it yet so I hope I haven't screwed up the canoe by changing its shape. I also hope the Royalex is resilient enough to not be adversely effected by the new shape.

It's now around 3-4" narrower at the thwarts and I may have introduced a very shallow arch to the bottom of the canoe. Then again, maybe it was already there as I didn't think of putting a straight edge on it before the work.
I may have to wait a few days to see how it does. I'm keeping my fingers crossed.

Hanz, that’s a nice, clean looking used canoe find.

The seat back mounts were part of a truly uncomfortable rigid “back rest” system, something like this:

http://store.oldtowncanoe.com/produc...094/Seat_Backs

I doubt you screwed up the canoe by changing the gunwale width.

There are apocryphal tales of altering the rocker on a canoe by changing the width at the gunwales. I won’t say that I totally disbelieve them, but I’ve drawn in a bunch of old RX canoes by a few inches at the gunwale line with zero appreciable effect on the rocker

Maybe if the Royalex was still green with an uncured foam core. Maybe if you stripped the boat to a buck naked hull, pulled it in and then reattached everything. Maybe if it was a very thin and lightweight RX build. None of which apply to the Challenger.

I expect that drawing in the gunwales on the Challenger reduced the beam and might have added a little arch to the bottom, but beyond that it probably just made the curve at the chines a little sharper.

Nice job, nice boat. You’ll know how you like the sharpened chines when you cross the first eddyline.
 
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I widened a royalite wenona sandpiper to increase rocker-it did.
Turtle
 
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The eddy line is the final judge. You no doubt have a rounder bottom. I've fiddled with the DragonFly a little. 2 inches. It made the boat a little less round bottomed as the two inches was wider
 
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I have pulled in some Royalex boats, but only a maximum of about 2 inches. Like Mike, I observed little or no effect on rocker. I do think that there will be a significant change in the hull bottom cross-sectional contour, however, which may be good or bad depending on your perspective.
 
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From the looks of your result, it looks like that boat originally had a fairly flat bottom. You should expect to see a bit lower initial stability but more predictability as you lean it from flat to its limit - and maybe even better secondary stability. And you probably have a little less rocker.
Years ago I bought a Royalex Wildfire (now the Yellowstone Solo) whose thwarts were too short. It was ridiculously unstable, and much less predictable than my BlackGold Wildfire. I put in 2" longer thwarts and now it handles almost as well as the B/G model (as my friend the whitewater and freestyle canoeist will attest). I measured the height of the bow and stern decks before and after the modification and found that the longer thwarts induced another half inch of rocker in both ends.
 
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I think it looks awesome! Can't wait till you get it on the water and give us a report.
 
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Can't wait till you get it on the water and give us a report.

Me too. Most of the canoes on which I’ve changed with width have been drawing the gunwales in, usually around two inches at center. I did draw in an old kevlar Blue Hole Starburst by four inches. That hull had a lot of flare in the sides and drawing it in four inches made for some very sharp chines.

The result was two-fold; the hull became very tender and the secondary stability almost non-existent and I induced a lot of stress in the chines, which eventually cracked and needed reinforcing.

I guess the material matters as well. Many Royalex hulls will draw in on their own when the thwarts and seats are removed. When I have regunwaled composite canoes the naked hull has flopped outwards.
 
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I too have found that Royalex boats tend to collapse inward when gunwales and thwarts are removed, but I have generally observed the same (to a lesser extent) when the thwarts, seats, and rails are removed from a composite boat. Standard advice when replacing gunwales on composite boats is to use a spreader stick amidships to bring the molded hull out to specified width when installing the rails, to avoid stressing the gunwales and hull holes when the thwarts and seats are replaced.

Pulling a hull in even a few inches can have a fairly profound effect on hull cross-sectional contour. Last year or so, Nova Craft reincarnated the Ocoee, a whitewater solo canoe previously molded by Dagger and Bell. I believe that the Bell boat came off the same mold as the Dagger boat, but I could be wrong. The Nova Craft mold was taken from an Ocoee that had been pulled in a couple or few inches for slalom racing.

I know a few people who own or have paddled that Nova Craft Ocoee and they report that while it is faster than a Dagger or Bell Ocoee, it is very significantly less stable.
 
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I too have found that Royalex boats tend to collapse inward when gunwales and thwarts are removed, but I have generally observed the same (to a lesser extent) when the thwarts, seats, and rails are removed from a composite boat. Standard advice when replacing gunwales on composite boats is to use a spreader stick amidships to bring the molded hull out to specified width when installing the rails, to avoid stressing the gunwales and hull holes when the thwarts and seats are replaced.

Pete, that’s interesting. I know that on two fiberglass Explorers the hulls flopped outwards when de-railed. I believe the Starburst did as well.

I wonder if that has to do with the cross-section (vee bottom with straight-ish sides on the Explorer, and flared sides on the Starburst )? Or with how I support canoes in the shop (sawhorses with angled foam blocks bow and stern).
 
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I don't know, Mike. I generally have my hull supported on some home-made stands that use 2" flat nylon webbing to support the hull. The length of the straps loops is adjustable but I usually do not have the straps extending up the sides of the hull at all so I don't think they would tend to push the hull in at all. In the past few years I have had the gunwales off 3 composite boats. The boats were a White Gold Bell Flashfire, a Black Gold Bell Wildfire, and a Curtis Dragonfly. I took note of the amidships beam of the molded hull in each case before removing the rails and they all went in between 1 and 2 inches.

Perhaps this has something to do with the "shouldered tumblehome" that these three hulls all share?
 
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Thank you for the nice words.

I took it out this AM to paddle a local pond and yes, it's a bit more tender but not terribly so. I split the time between sitting and kneeling and all was well. I can still stand in it so that's fine by me. I also did lose some rocker, the boat tracks harder and the stems are stickier. That's something I did not predict.

I didn't test secondary stability (I brought my camera) so there still may be a surprise waiting for me.

That seat is very comfortable and I'm going to see about installing some knee pads into the hull.

I'm feeling relieved that I didn't screw it up and will still be able to use my canoe pole with it. Whew!

MowhawkChallenger-4.jpg


MowhawkChallenger-3.jpg
 
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Hanz, nice work.

That is now a unique Challenger. Knee pads are easy with a few coats of contact cement application and if you can stand and pole in it I doubt you’ll have many eddy line surprises.
 
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