adding more rocker to cedar strip canoe

[mark123]

Hello all,
I am in the process of building my first strip canoe , 15' ranger.
I have all the stations mounted on the strongback , and have got
a good feel for its lines. My question is if I wanted to add about 3/8"
more rocker , can I just shim up the three center stations 3/8 and
then taper off the shim towards bow and stern ending 2 stations be-
fore the stems . I hope that makes sense?
thanks mark

[Glen Smith]

I believe a modification like this is best handled before cutting out the stations since you have to relocate the waterline and the sheerline.

[Rick]

I wouldn't try it (inability to predict results)... if a more rockered canoe is wanted why not shorten a Prospector down to fifteen feet? This has been done by manufacturers with good results.

The lines may have been faired with the aid of a computer for more efficient hydrodynamics and altering them could degrade performance. An email to Steve Killing could provide info from a designer's POV.

[mark123]

Thanks Glen for your quick response, my thought was that 3/8" wouldn"t be enough to
throw off the lines.Yet it would make it slightly more manuverable and more personnel.
I might try putting in the shim and see what it looks like? I don't know. Is the Ranger a dancer ? when I chose the design the description said it had good rocker like the Prospecter but no numbers to compare. I measured it at being 1 5/16" ,oh well I'm probably just putting too much thaught into it
thanks again mark

[Glen Smith]

You could simply shim the desired stations then lay a batten across the stations to check for fairness. If the lines are fair, build it. If the lines are no longer fair, re-think the process before committing to building the boat.

[mark123]

Thanks Rick you make a good point about the hydrodynamics. I would think that shortening
a canoe by 10-12 inches would be more drastic than adding 3/8 more rocker.I know that I don"t know squat about this so your input is really appreciated.
thanks mark

[One Norse]

You could also build it according to the oringial plan, and paddle it for a while. If you later decide you must have more rocker and do not want to build another boat you could install slightly wider thwarts. If you push out the gunnels, it should pull up the ends a bit.

I expect that after you paddle your new craft you won't want to change it. The plans that get published tend to be the ones that have worked...

[mbolton]

personally, I'd go with just giving a bit more rocker just at the ends...last 2' or so. That would give much better results than a slight curve from all the way. It'd be kind of the way the Mad River Guide is...you can flat turn that hull. It'd result in a bit slower boat, but not appreciably and the basic feel of the canoe would be the same.

[willo]

Having built three Rangers I am not sure why you would want more rocker unless maybe you are building it for mainly river use. I would not want any more rocker than already there, they dance nice.

[mark123]

willo I'm glad to here from someone with a Ranger makes me feel better knowing it maneuvers well. I actually am building it for mainly river use. I think I'll wait for the second
build to do any mods if needed thanks
mark

[SpiveyMtnMan]

personally, I'd go with just giving a bit more rocker just at the ends...last 2' or so. That would give much better results than a slight curve from all the way. It'd be kind of the way the Mad River Guide is...you can flat turn that hull. It'd result in a bit slower boat, but not appreciably and the basic feel of the canoe would be the same.

I've had a lot of experience with whitewater canoe designs and mbolton in correct. Shimming the middle stations will result in a profile that will be slower to propel and require a great deal of correction to maintain a course. The canoe in my avatar is a proto of a design I did to take my wife and two labs fishing on East Tennessee rivers, and it is essentially flat until the last 18". It's 14' long with a 42" beam (yes it's very stable) but I can flat spin it with one sweep stroke.