Jersey Sea Skiff Performance?

That Allweather is a robust looking boat, hull looks a lot like a motor lifeboat. I'm sure it will get you where you're going
moT

 

Maybe it's just me, but none of these boats look like true Jersey Sea Skiffs or Sea Bright Skiffs. Their keels are much too pronounced. In fact, the Jersey Speed Skiff had no built down keel. The box keel aided in launching the boat from the beach through the surf. The later power boats had smaller and smaller keels as the years passed, until boats built in the 50's and 60's had bottoms similar to a Lyman.

This isn't to say these designs aren't good, just that they always seemed to be a development based on some of the concepts incorporated in the Jersey shore boats. If anyone is interested in the history, check out a book called The Sea Bright Skiff and other Shore Boats by Peter J. Guthorn. Probably long out of print, but may be available in used book stores.

That being said, I love Robb White's interpretation of the Rescue Minor. I was always amazed at how light he could build his boats. I am sure if you calculated the structure it would probably fail all the typical criteria, but they seem to work anyway.

 

Don't Forget shaft angle.......

If your shaft angle is too great, the blades will only be generating thrust on the bottom half or each revolution as you get up to higher speeds, so the horizontal ( or nearly so) shaft of the sea bright skiff more than makes up for the appendage drag. As long as you're not trying to go too fast, anyway.

On the Penn Yann pocket tunnels, they were a compromise for shallower draft only. You lose planing surface and prop effeciency

 

This is what one builder found, lifted from the net. FF

August 1, 2002
Yes, Atkin Was a Genius
By Robb White

We launched the Rescue Minor June 20th and she ran most marvelously. There was no ceremony to it. My wife and infant redheaded granddaughter and I just wheeled her down to Lake Lamonia about twelve miles down the road and untied the jackleg lines that held her on the trailer and she rolled off into the water.

The boat sits about an inch and a half down by the stem at rest but it is actually that she is up by the bow.... the toe of the stem is right at the water. It is because the boat is so light. I knew it would be like that and hoped it wouldn't be worse. When my wife and the baby got in up in the bow, she sat right down where she belonged. I hadn't brought the engine house, so, when we fired her up, she cackled pretty loud (about like a Kubota tractor) but didn't vibrate or shake the boat at all. While she was warming up, I checked all around to see how much exhaust water the little Shurflo diaphragm pump I adapted to run off the camshaft was giving (plenty) and what the oil pressure was and all. I think I was a little scared to put the power to the wheel and see what was what.

As soon as the propeller began to revolve, the stem picked up what felt like three inches and the boat began to move much faster than I would have expected from any planing boat at dead idle. Lake Lamonia is one of those lily pad lakes we have down here and there is only a narrow trail through the bonnets out to the clear water in the middle and I had fooled around looking at the engine and let us blow off so that we were heading for the lily pads but just a hint of rudder brought the idling boat right around. I have never seen an inboard boat turn like that.

There ain't no idle zone, so I ooched up on the throttle a little bit and the boat picked up speed just like a regular boat. I gave her a little more and she gave me a little more. I ran her on up and she ran on up. There was no perceptible rise to the bow at all and the wake never changed. The little engine smoothed out so that it was hard to detect any vibration at all when I put my hand on the cylinder head to see if she was warming up or not. The boat steered so stably that I could hold the tiller and walk all around the engine to check on my doings. Which, the copper tubing wrapped exhaust manifold ran cold and the inlet pipe from the keel-cooler stayed cold. There were no oil leaks and no hint of a diesel fuel stench or exhaust but I did have a damned tiny coolant leak from the plastic overflow reservoir. The outlaw graphite ceramic well pump shaft seal never gave a drop and the belt-drive transmission ran smooth as all get out.

Which, I hope I ain't ruined my credibility too bad. She ran 18.6 knots on the gps and that with the 10" pitch propeller that I put on there to make sure I didn't lug the engine while it was breaking in. That wheel let the engine run up to where the governor backed her off at 3,600 rpm. Me and Atkin think she 12-1/2" of pitch and I have that prop standing by ready to put on there. You know, I have the jackleg push-button prop nut and can change wheels by just reaching up under there with one hand. As an aside, that's a wonderful fig. I can take the propeller off a sailboat while she is luffed up in the mouth of the river. I wish I could lay claim to the invention, but it ain't nothing but something like a quick-disconnect like on a garden hose.

The boat ran most marvelously. I would have been satisfied with 12-1/2 knots (my speed) and a slightly tender feel (about like a deep "V") but the boat was so stable that my wife and I could hardly alter the running trim by both us, and the baby, sitting on the same side. She turns about level and, even then, weight distribution doesn't seem to affect the trim. I think the dynamics of the hull that control the wake hold the boat in a tight grip. It feels like it weighs about 10,000 pounds. There was never much wake at all but, like Alex's, there was a sporty looking rooster tail erupting about 8' astern. I have a little clamshell water pickup right behind the prop to give a little supplementary exhaust water at speed, and it is mighty effective (I could probably eliminate the engine-driven pump). The beautiful exhaust-water rainbow around the rooster tail made a most charming sight.

All my fears are put to rest. She ain't tippy at rest and she don't rise up by the bow and try to skitter off on that little pirogue she carries on her belly. I couldn't make her cavitate to save my life and the boat will turn, at speed, shorter than any outboard boat I ever had. I tried to make a wake to run back across so I could see what was what with that, but the boat doesn't make enough wake for a valid test. I ran across the wake of an aluminum butt head-skiff with a nine point nine that was much bigger than the wake of the Rescue Minor. I don't need no wake in no lake to tell me how she'll do in rough water. I know a sea-boat when I see one.

It is a wonderful boat and, as Alex said, "Atkin was a genius".

 

Chose this thread instead of the "box keel" now running in powerboats... Interesting topic. To get a better idea of the shape, I roughly modeled the lines from the "Grampus" in the motorboating article. Neither fine overall nor surface fairing done. Also a bit bigger dimensions, etc.
Here's the .fbm for anyone who wants to play with it. If I had time and software I'd scale, fair, etc. to try to learn more about this hull form. Does not look like a panacea, but it is interesting....

 

BWD - what's a .fbm file? Nothing I have will open it...are you able to post in another format?

 

Freeship

 

I tried but got a "not valid freeship file" message --

moT

 

Sorry, I didn't try it, I just looked at the suffix and the icon...

 

Sorry, I didn't try it, I just looked at the suffix and the icon...
__________________

Can you send it in PDF ?

FF

 

".FBM" is the freeship/delftship CAD file format. i authored it in delftship so the older program won't open it.

I don't have a lot of CAD ware and lack a good way to go FBM to pdf. Sorry. Anyway, delftship is free and fairly compact, if you want to play with it. From there you can easily export to serious CAD of your choice, thence to PDF....

Here's a picture from the model for illustrative purposes. As you can see it's not fair, the model's keel is merely a convenient curve (original is straight I think) and the keel chine is different. Still ok to look at, which is all I wanted to do in the 1st place....
Although if anyone builds one i would love to go for a ride!!

 

I think you can find rescue minor lines there :
http://www.boat-links.com/images/RescueMinorLines.gif
BTW, on other forums, the displacement is said to be 840lbs.

 

ahh, now that looks like a better starting point than the magazine article!

 

Hello Gentlemen,

Can anybody help me in finding a supplier who can supply me rescue boats of 6 person capacity? I am located in Sharjah, UAE and I can be contacted in the Tel No: +971 6 528 5345, email: aravindg@mis.ae.

Bye & Thanks
Aravind.G
Naval Architect
Engineering Division Structural Dept
Maritime Industrial Services, P.O.Box 4596
Sharjah UAE

 

".FBM" is the freeship/delftship CAD file format. i authored it in delftship so the older program won't open it.

I don't have a lot of CAD ware and lack a good way to go FBM to pdf. Sorry. Anyway, delftship is free and fairly compact, if you want to play with it. From there you can easily export to serious CAD of your choice, thence to PDF....


With the unusual underwater shape aft , do you think the computer generated performance can be relied upon?

FF