Catamaran like Rowboat for lake fishing

That's one which came to mind when I saw this thread.

http://www.boatdesign.net/forums/al...ndom-picture-thread-11052-339.html#post627428

 

Upchurch, since you used strips, you had the freedom to shape the sections pretty much at will. I presume that you used a half circle bottom. I'm guessing that the boat will draw about 6 1/2 inches and have somewhere in the vicinity of 20 square feet of wet surface.

At a centerline width of 60" the wave interference point could occur before the sternposts. Of course these skinny hulls will not make much of a bow wave in the first place. What is your take on this?

Technical query: I have read that 19 degrees is the angle to use when calculating interference point. Is that number velocity dependent, bow half angle dependent, or ...... ???

My apologies to the OP for continuing to derail a perfectly legitimate thread. Well, I think most of us urged him to build a mono. I'll stick to that advice but continue to be fascinated with your elegant little cat.

 

Messabout,

If you wish we could do a PM.
Since I would be facing aft I have never seen the bow waves while rowing, but what I see from the shore is non existant.

On my boat, 11' x 5' total width with 12" hulls, I can watch the inteference peaks forming under my feet. At my fastest speed there are 7 of them trailing out behind the boat. I pull such a suction on the sides of the boat that at one point there is a peak around the rear beam that is hitting the beam. As a consequence I widened the boat to 7' overall. There are minor peaks but just a couple and I can almost catch my wife.

The wifes included bow angle is 10 degrees which is very narrow and there are no specific features to throw out a bow wave.
I am not knowledgeable about the theory, just reporting what I see.
Remember that these are relatively slow boats at any rate.

For me the reason to continue here is to let the OP know that there are other "facts" than those of the monohull majority.
My suggestion if he still wants a cat is to go longer rather than fatter, and limit the area you would walk on to make that reasonable.

The hull shape was completely round bottom until about 2 feet from the stem and stern where it becomes a rounded V. Flat sides and deck. Given the weight of the boat and rower the draft is probably right around the 6.5" you estimated. My estimate comes from the ~4" freeboard but was never actually measured.

I actually have a very short video of my son in law's first three strokes ever, if you are interested.

 

Having already built a catamaran monstrosity. I agree wholeheartedly. Performance of the Teotwawki boat is markedly below my expectations for it.

 

Hoytedow,

I don't remember the "Teotwawki" boat. Any reference to a thread or whatever?
It is always interesting to see what didn't work as you wanted.

 

http://www.boatdesign.net/forums/boat-design/teotwawki-boat-42752.html

It works, just not very well. Will try again next year, hopefully.

 

The inteference drag between the hulls must be fierce.
There is a new plastic catamaran rowboat out that has the inner walls straight and the outer sides curved (more than I would have considered normal).
Under power it might do a lot better due to less total drag.

 

I intend to do as has been suggested and add a planing surface between the hulls, thereby eliminating much of the drag and hopefully improving the overall performance.

 

I think I better read the rest of the thread, I can't imagine what you just said.

 

Upchurch, could you perhaps post a few more photos of your amazing rowing cats please?
Especially re the sliding mechanism.
Yours is so much simpler in every way than the Ro-Cat, no wonder it never 'took off' - I think that if they had managed to get it into production it would have easily cost US$ 5,000+.

 

Bajansailor,

Always happy to try and show off, thank you.
The boat is hanging on the fence, an easy place to store it out of the way.



This is looking from the front, almost like the rower will see.
If you stand just beyond the seat, you can grab the slider rails in each hand and easily balance the whole boat for transport.





If this doesn't explain it, I will take it off the fence. It was just late when I got home.

 

I found the similar unit to mine.
If I remember right I created mine independently, then found this one.
But this is nicely made, just more than I would pay.
An yet I would like a professionally made one. Just a little extra quality would make mine work nicer.
$50 extra would probably do just fine.

The real key to the whole concept is good wheels, with accurately located axles. Lighter weight wouldn't hurt either.

http://www.slidingrigger.net/

 

6 meter sculling cat

I used to own this 6 meter row cat. Wish I'd taking offset measurements as I now want to make another one. The one in the photos was a production model that I was told was built in Florida in like the late '80's.
Great exercise, fast and light. I also used it for inshore fishing as I lived in Oceanside CA at the time. With the longer hulls the simplicity of a sliding seat made sense.