The last of the one sheeters.

It's sounds close and the method seems reasonable. The VCG may be a little lower than you calculated:

- things sink when vertical
- arrangement of arms wqould be important as they are far from the baseline
- baseline to Scale Centerline measurement is critical
- the dreaded squishy bum syndrome may require an allowance

 

I agree. I am sitting in a hotel and don't have the means today to use real numbers, so I was plucking estimates out of the air last night to run the equation.

I suppose I could lay against a wall and measure bum to head distance. Then sit up and get a floor to head distance and subtract a percentage of the difference. 50% maybe. (?) We'll call it the SBS coefficient.

Now on the other hand, we could almost dispense with the scale all together. You have to build a partial box that you can sit in that has a high side to provide lateral support. Tip the box until it balances on the corner with you in it. Measure the angle and run that up from the lower corner and it will intersect with your centroid, or something. Kind of sounds like a different nautical calculation we do.:idea:

 

Sea Trials

We got her wet this weekend. She floats about as expected. She trims by the stern a bit, but I don't have the cushion for the seatback in place. A 2" seat cushion slides the CG forward to where she trims to her waterline. Excuse our lack of life jackets. We realized only after we got to the water that they were left at home. We the a quick initial test and photos and went back to the house for proper attire before continueing.

The little boat tracks like an arrow. She's almost too directional. At the end of the power stroke, she would instantly stop any induced turn and track straight from that point on. Hard turns at speed were not possible through power strokes alone. A dipped paddle had to be used. At slow to no speed, she would respond well to a sweeping stroke. A downsized skeg is mostly in order.

She points well and she is a good coaster. A little bit of momentum would keep her gliding for an extrordinary length. My wife was paddling my first creation and she was constantly paddling to keep pace. I believe that a small wetted surface and an efficient hull form are resposible for such nice coasting abilities. We played a little faster speeds and the hull does reach it's limit rather rapidly. Kaper resistance at 3 kts is about 2 pounds force while at 4 kts, it jumps to about 8 pounds force. For a casual pace though, the little boat performs well. We'll have to bring the GPS next time to get some performance numbers.

She is a little tender, especially with my mass in her. For smaller people, she'll do well. A smaller skeg, a thick seatback and a lowered seat with optimize this little boat.

It's time to stop playing with these little boats and build one that fits me. I have to admit though, that it is very interesting paddling around in such a small water craft.

 

That was a big skeg that I saw in a previous post. I suggest that you see how she behaves in a cross wind before you cut it down. IMHO the ideal kayak and canoe requires very little effort to keep on course aross the wind, and this benefit is well wort the slight cost of a little extra effort when turning.

 

I did some more messing about with the little "yak" yesterday. My comfort level with it increases with increased use. It's initial stability is low, but it starts to stiffen up when it is heeled. The padded seatback moves my CG forward enough that it floats on its lines. I short little boat like this is very sensitive to CG position and changes.

I've been paying close attention to it's tracking and turning abilities. Moving at speed, I'm estimating a 25-30' turn radius when paddled only from a single side. It works well for course corrections. If I want to reverse direstion, I can dig in deep with a reverse stroke and a strong sweeping stroke on the opposite side to get a full 180 degree heading change. I suppose that works and it's kind of fun as I have to pay close attention to balance in the procedure.

I did a full up speed test and could get about 3.7 kts on the GPS. Hull speed a 7.5' is 3.6 kts, so that seems to check out about right. There is quite the wave train when pushing hull speed. She goes nicely at 2-2 1/2 kts. Almost no wake or bow wave.

 

This little 'yak is proving to be a rediculously versatile little boat. The low initial stability makes it ride through waves very nicely. The wife and I went up to Georgian Bay, north of Toronto, a few weeks back. We only had one day to paddle and the forecast was calling for stronge winds. I studied the map and tried to pick some protected waters. We found protected paddling for the most part, but if we wanted to go adventuring, we were going to have ro traverse some exposed expanses. I'm going to say the the waves ranged from 8 to 12 inches. Most likely the lower end of the scale with a few to the higher end. Both of the little kayaks handled the waves admirably. Mine would rise and lower to broadeside waves with almost no rolling tendency. Very nice! Head into the wind and waves would cause some hobby horsing, but that is expected with the amount of rocker in the design.

Most recently, we just added a new aircraft (a Phenom 300 by Embraer) to the home base fleet that has a very large baggage area. So large that I am able to load all 7.5 feet of kayak into the baggage area and still have room for all of the requisite bags. This means that when there is a trip to warm water, my little yak is going too! This is quite the bonus as it will add a nice leasure time activity while on the road.

 

Perhaps it's an optical illusion but it looks like you are standing in the water and wearing the boat like a wood tutu!

Just kidding . . . I'm amazed it will support you so well. How does it handle in a cross-wind?

 

Terry,

Good to hear from you.

"it looks like you are standing in the water and wearing the boat like a wood tutu!"

LOL

It has a tendency to point downwind if drifting. While paddling, it also veers downwind, but this tendency is so slight that it is almost unnoticable. I have bunged the skeg a few times and also hit submerged objects with the "belly" of the thing so it's in the shop for a skeg-ectomy and a belly "wrap" (a couple of layers of glass tape down the keel line). I cut the skeg extention off and rounded the aft corner so as to be less vulnerable to damage.

 

Thanks LP: it's nice to be back and able to sit on a chair long enough to type out a post.

Trimming the skeg should take care of the windsocking tendency. My own canoe tends to head up into the wind, although it was improved by adding a skeg, but it tracks too well and is a bit clumsy in the narrow streams that I like to explore. I built it with no rocker, it's at its best heading across a lake. I put a thin keel down the centerline, about 3/4 x 3/8, which also contributes to the tracking. I think I was a bit obsessed with getting it to track well after paddling a plastic kayak that would not, could not be paddled in a straight line.

 

On the last two builds, I've done water trials prior to their completion to check certain aspects of the builds. With the single-sheeter, it confirmed my expectations. On my current build, a 12 footer with a very straight keel line(no keel or runner), I half expected a straight tracker, but it too, falls off left or right. It also is receiving a skeg for directional control. My current paddling areas don't require heavy maneuvering so a straight tracking boat is desirable.

 

Loaded and ready to head south!

 

I wish i had one of those to haul my kayak around in! Hate to pay the fuel bills though.

You could probably sell a line of biz jet compatible kayaks to people with too much money.

 

The guys that sit in the back are the ones that wll be buying the full size versions (most likely in the 60' plus range ).

It's us guys up front that need the cheap entertainment at the pricey destinations.

 

Just stumbled on to this thread and immediately recognized the hull form as something I'd seen before. After going through several books I found it. Phil Bolger designed such a hull as a row boat ...11'4" X 3'10". A little wider and not quite as much deadrise but basically the same hull. I've often thought of building an OB skiff like that w the deadrise constant aft. The Bolger boat is called Poohstics and is on page 7 of his book Small Boats. I'll be looking for you in the future LP.

 

Hey, Easy!

That's interesting stuff. I have no books by Bolger at all. Which book is it that has the similar hull design? I need to purchase one of his books just to have it in my collection. I'm a fan of more traditional inspired designs and that might explained why I have not been compelled to purchase any of Phil's books. I'm assuming there is more than one. I'm sure it's still good study material.