C-Forum

I was tempted to "side" with Craig here; because, I can see how you could end up modifying the rocker of a boat by modifying the width (and thus the curviture of the top outside edge); but... for a modern size of boat, I can't see how you'd make a big enough change the to affect the rocker significantly, without applying enough stress to seriously damage the boat.

But... and I address this to both sides of this argument: Pics or it didn’t happen!

By which I mean pics of a modded and un-modded boat side by side (or with a common point of reference/scale) so that we can see for ourselves.

My reason for saying that is that I have a suspcion that you can both be right at once, and that there's actually more to consider about pulling boats than we might collectively think right now. (also I like the excuse to use huge orange text)

Larry Horne wrote:so glad I paddle a decked boat.

Larry, you CAN increase the rocker on a decked boat. I've done it.

And Joshua pretty much nailed the truth in the rocker issue (I have a suspcion that you can both be right at once, and that there's actually more to consider about pulling boats than we might collectively think right now.)

So, what is the truth to these arguments?

In order to increase/decrease rocker, what MUST happen? (hint: think... ...length)

What actually happens when gunwale width increases/decreases? (hint: Smerda pretty much answered that one).

Craig Smerda wrote:[img]
you can change the flare of the sides, the depth, shear line and even the shape of the bottom and the overall length a little by pulling a canoe in at the gunnel line... but the rocker doesn't change.

Just took an old viper 11 hull, at 24" beam the height of the bow measured 17 3/4" and the opposite measured 19 7/8". Two spreader clamps at thwart locations spreading to 28" brought the bow to 19" and stern to 21 1/4"...

... explain please

BTW, I do have pictures but are they really necessary???

eddyhops wrote:BTW, I do have pictures but are they really necessary???

It would be nice, but I suppose we can trust each other here at c-boats, so it's not strictly neccsary.

Could you tell me the end to end length and the length following the gunnels* before and after you pulled the boat in.

*(the chord and arc segment lengths of the curve followed by the gunnels if my original description made little sense prefer)

Short boats want change that much. Longer boats will change the rocker depending on the width. short roto molded boats prob want change much.

This is an interesting thread. I didn't know this was an acceptable practice. Is it easy to go back and forth, or will that eventually damage a royalex hull? I could see tuning a boat to suit certain rivers - a speedier river runner one day, a more agile creeker the next. Heck, you could tune it for specific rapids! I can see it now - "hang on guys, just gimme a minute here while switch thwarts" LOL

Just use one of those adjustable paddle shafts as a thwart and you can do it on the fly (so to speak) - wait, didn't Mohawk have this as an option years back?

Yep we sure did Dont know why we stopped selling them but we did.

an idea ahead of its time...

You know, it wouldn't be THAT hard to set it up with a turnbuckle in the middle, so you could indeed crank it in and out as needed (like the top link of a three point hitch tractor hitch). I've seen aluminum turnbuckles too... weld the ends to make a new thwart, and away you go....

Hmm....

I can just hear the wood gunnels cracking now...

As far as I know, the adjustable thwarts were only factory installed in Challengers and Odysseys, not in whitewater boats. Don't know why. Anyways, they got discontinued probably 10 years ago, don't know why on this point either.

A motivated individual (with more time and patience than I) could go way back and see...

http://wayback.archive.org/web/20010601 ... canoes.com

(I don't think phpBB likes that URL...)

So I took the thwarts in this weekend. Before the width at center was 28.5 inches, well wider than factory. I took them in to 26.5 inches.

I can't really speak to the rocker, but the boat was faster, tracked better, and flipped easier. At first I thought I had screwed the pooch because I was having trouble with the boat, eventually flipping and swimming out on a light Class III rapid. It was then that I realized that my outfitting was causing the problem, so I adjusted that for today's run.

Today was awesome, one of the best days I've ever had in a boat. I didn't flip, and probably braced two or three times over nine miles of Class II-III. I pushed the boat, hitting hard eddies with big eddy fences, surfed, side surfed, stuck it into a ledge hydraulic, and the boat really kicked some tail.

I still have to play around with the trim, but the boat is a lot better at 26.5 inches. Cross bows are easier, the chine is more defined, and the turning seemed to be about the same. The only thing I noticed was that my surfs weren't quite as good, but that might also be a testament to a) the poor surfing at these particular waves, and b) my lousy surfing ability.

Next weekend of Savage, LY and maybe some others will give me a better idea if this was the right decision.