Distribution of rocker.

This is a club that I definitely belong to.

It is a damn good question IHMO, but it’s also one of those things that cannot be dealt with in isolation from other design questions. A boat design is an integrated whole and full of interaction and compromise - that's what hooks us poor souls who become their willing victims.

I have noticed some things and learned a little by designing and building several canoes. Rocker does a couple of things for my little boats, it makes them more maneuverable by reducing lateral area at the ends and more stable by lowering the CoG. On the other hand it slows the boat when I am paddling hard. My last boat has a fraction of an inch of rocker, for use on lakes; but it is a bear on a noarrow stream. I don’t need or want an awful lot of stability as it can make a canoe uncomfortable in the presence of fast moving powerboats; lower stability allows the waves to pass underneath with rocking the boat.

The canoeing and kayaking fraternity are particularly sensitive to rocker, because of the pitiful amounts of power available. On the other hand, once a power boat starts to plane, or a saling mono starts to heel or a multi starts to fly one or two hulls all sorts of weird stuff starts to happen underwater. Looking at different boat types is very revealing, I think after a while you will identify several trends. But it seems to be an art as previously noted.

It’s a look and learn thing, although I prefer to learn by my mistakes: Dryfeet seems to have figured out how to avoid them . . .

 

However, there are cases which would probably made me reconsider my previous affirmation...

 

AK, I am not a kayaker (prefer the power of sails than my own ), so excuse me for a possibly stupid question: what is the speed you normally attain (and maintain) when paddling? Is it beyond or over the so-called (and the non-existant, I know) "hull speed" of the canoe/kayak?

 

What a waste of a see thru guitar--- Do you have a see thru Kayak ??

 

At the moment it is zero since I am recovering from a long illness and I have been warned off paddling until I have recovered some of the muscle mass that I lost

I am dealing with that through training by building another boat

I figure I could maintain "hull speed" for limited amount of time perhaps a half-hour or so. Over longer distances I tended to loaf. My canoes/kayaks are short and relatively dumpy so they do not exceed hull speed easily and I am 72 and was only paddling for about 7 years so I am not as fit as I would like to be.

A serious and younger paddler in a boat designed for speed rather than comfort would esily exceed the hull speed, as do rowers in racing shells. Current K1 (solo kayak record) is better than 10 k over 500 m in a 17' boat with a "hull speed" of about half that speed. Speed maintained over longer than sprint distances are still well over the hull speed, possibly in Eric's body of work on design ratios.

Somewhere in the forum there is a table showing approximately how much hull speed can be exceeded by skinny displacement hulls.

 

It has been done but you need clean underwear . . .



This what they call the food wrap test before a proper skin is applied. Not a forever boat . . .

 

I've used clear vinyl before.

1. It's much tougher than you might think. The 18 gauge I bought was thicker than I needed. A 12 gauge or maybe even 10 would have worked fine.

2. It's cheap. With a coupon, it was $20 to skin a 16 foot boat.

3. It's quick. No painting or finish (which can add to cost substantially). Literally staple it on and you're ready.

But....it doesn't heat shrink. So you can get ugly wrinkles that you can't get rid of.

And, for me at least, I couldn't see anything on the bottom. The skin flexes like a magnifying glass that obscures everything.

People won't know what to make of your boat that looks like a floating skeleton....and kick up a wake as they get by for a closer look.

 

This is an interesting question.

F

 

Neat-- Terry the important thing, by that smile, you're having fun. I've often thought about using that white boat wrap heat shrink covering, I think thats literally free in the spring of the year, especially off those big yachts-- Geo.

 

Oh, that wasn't me, I have too much chicken DNA; I wouldn'd dare trust my life to Saran Wrap! I grabbed the pic off the net . . .

 

I often relate my first build to new comers to the field. I grew up in an area where they were building a huge U.S. military base and got my hands on a piece of left over rebar concrete mesh. I formed it into a canoe shape and stole one of my fathers painters tarps using it as the skin. (he was a civilan worker). It actually floated and performed quite well. Can't get more basic than that and considering it was the 1950's I lay claim to being the non native father of the geodesic skin on frame technique.

 

I guess there were no photos that long ago, pity you couldn't get a painting!

 

Rock carving rock being the key word from which derived the word "rocker" and now we're back on thread topic.

 

I was just rereading the thread and your post reminded me that one can buy clear film intended for applying to windows. I comes with a double-sided adhesive tape and can be heat-shrunk with a hair-drier so the wrinkles can be removed. I don’t know what gauge it is, but it is quite tough. I recall using it many years ago over a leaky patio door before we had a new one installed, and on windy days it would stop the drafts from a nor-wester, which would push hard on it but couldn’t break it. It was holding back a lot of pressure, so I imagine it would hold up a kayak.

I still have a roll of it someplace I think; if I ever do a skin-on-frame boat I may try it out . . .

 

I participated a few times in an annual river race for paddle craft. A hundred or more boats fly down the Alafia river that empties into Tampa bay. I was in the geezer class with a common 16 foot sea kayak. Several "super" kayaks, equipped with super athletes, would show up. These boats were probably about 21 footers and just wide enough for the paddlers pelvis. The slower classes start first with three minute intervals for the successively faster classes.

The serious super class boats were mind boggling fast. The river has negligeable current and the course is eleven miles long. The supers complete the run at a rate of five minutes per mile including the extra annoyance of passing slow clowns like me. The boats all had small rudders and almost no rocker at all. The paddlers use a very short and powerful stroke at cadences of 90 strokes per minute more or less. They go well past twice hull speed. Awesome!