Crazy Engine Question....

Z

Zed

.
Aug 19, 2015
96
West Wight Potter 19 Bar Harbor
MY WIFE, the Admiral, has just informed me that her long term wish was to be able to propel our little 19 foot West Wight Potter to about 15-20 mph(on a plane I assume, how else?). She wants to remove the 5 hp Honda and put it on the dinghy. She wants to get where she wants to go fairly quickly going 3-4 times hull speed. BTW, a WWP19, weighs in at about 1600 lb with 2 adults and some gear---and we are talking about a gasoline Outboard.

So... never having known this secret desire of hers, how much HP would I need to do that? And maybe a lighter fuel injected/oil injecting 2 stroke might work, as long as I don't have to drive to Canada to get it.

Thoughts about what HP I might need would be welcome so I can tell her what she needs to spend to make this happen.

If you are going comment how crazy this is, I already know that, so you don't need to do so.
 
Stu Jackson

Stu Jackson

.
Feb 26, 2004
22,986
Catalina 34 224 Maple Bay, BC, Canada
It's not crazy at all.

It is impossible.

Your hull is a displacement hull, means that no matter how much hp you throw at it, it simply isn't going to get up on a plane and scoot.

These are laws of physics. No wife gonna mess w/'dem. :)

You can learn more by Googling hull shapes, displacement hulls, etc.

Buy a Mac or a powerboat. That is if you want to go with her.

PS

How long ya been married? How much is it worth to you to recognize you may have married a powerboater? :)
 
C

Calif. Ted

.
Jun 8, 2004
2,928
Catalina 320 Dana Point
My 16 ft. powerboat will plane at 20, cruises at 45, and weighs in at 1600 lbs., unfortunately 600 lbs. of that is the 88 hp 2 stroke and fuel.
Maybe you could make it "foil" instead, couldn't be any tougher than making it plane.
 
Z

Zed

.
Aug 19, 2015
96
West Wight Potter 19 Bar Harbor
Stu Jackson said:
Your hull is a displacement hull, means that no matter how much hp you throw at it, it simply isn't going to get up on a plane and scoot.
Click to expand
Actually.... a west wight potter 19 has a semi-displacement hull that is in the aft panels a planing hull. While there is a 4 foot dagger board, its pretty narrow. This means that on a run with a spinnaker it is not unlikely to get to 7 knots despite the hull speed of 5.48 knots. The boat has a draft of 6 inches with the dagger board up.

This is because which you lift the bow even a little bit, it becomes a planing hull aft.

You can learn more about the semi-displacement hull of a WWP19 at: http://potter-yachters.org/manyways/hullspeed/
 
Z

Zed

.
Aug 19, 2015
96
West Wight Potter 19 Bar Harbor
Calif. Ted said:
My 16 ft. powerboat will plane at 20, cruises at 45, and weighs in at 1600 lbs., unfortunately 600 lbs. of that is the 88 hp 2 stroke and fuel.
Maybe you could make it "foil" instead, couldn't be any tougher than making it plane.
Click to expand
I'm sure the boat won't handle a 600 lb engine hanging on the transom. But if it does, it sure would get up on the aft plane real quick.
 
Stu Jackson

Stu Jackson

.
Feb 26, 2004
22,986
Catalina 34 224 Maple Bay, BC, Canada
Zed said:
You can learn more about the semi-displacement hull of a WWP19 at: http://potter-yachters.org/manyways/hullspeed/
Click to expand
Thanks, nice link.

If we go back to the OP, then the Conclusions of this link still won't help him, since all that the article did was debunk the old 1.34 sqrt WL nonsense from 1610 for a WWP.

A P19 with 700 pounds of crew and gear can theoretically reach sustained speeds of 6.3 knots, comparable to a 25' displacement hull with a 23' LWL. An almost empty P19 theoretically can sustain 7.2 knots, comparable to a 30+' displacement hull with a 29' LWL. Clearly, an empty P19 can't sail because there's no skipper, but there is a point -- the less gear you put in your boat, the closer it can get to the theoretical limit of 7.2 knots, given enough wind.
 
frankies56

frankies56

.
Mar 5, 2012
152
Hunter 37-cutter Saint Augustine
Zed said:
MY WIFE, the Admiral, has just informed me that her long term wish was to be able to propel our little 19 foot West Wight Potter to about 15-20 mph(on a plane I assume, how else?). She wants to remove the 5 hp Honda and put it on the dinghy. She wants to get where she wants to go fairly quickly going 3-4 times hull speed. BTW, a WWP19, weighs in at about 1600 lb with 2 adults and some gear---and we are talking about a gasoline Outboard.

So... never having known this secret desire of hers, how much HP would I need to do that? And maybe a lighter fuel injected/oil injecting 2 stroke might work, as long as I don't have to drive to Canada to get it.

Thoughts about what HP I might need would be welcome so I can tell her what she needs to spend to make this happen.

If you are going comment how crazy this is, I already know that, so you don't need to do so.
Click to expand
It would be easier to get a new wife with common sense. you want fast get a motorboat
 
Kermit

Kermit

.
Jul 31, 2010
5,669
AquaCat 12.5 17342 Wateree Lake, SC
If you're married to my ex-wife you could save 600 lbs. by leaving her ashore.
 
Picflight

Picflight

.
Jul 21, 2013
333
Searching for 1st sailing boat 27-28, 34-36 Channel Islands, Marina Del Rey
Can be accomplished by tabbing skies under the hull.
 
S

Sock Puppet

.
Aug 14, 2013
308
MacGregor 26S High Desert
Zed said:
I didn't ask for easier. Its the wife who wanted to know. I like my WWP19.
Click to expand
I didn't only address 'easier', I also mentioned cheaper and safer, which should be considerations.

From your original post:
Thoughts about what HP I might need would be welcome so I can tell her what she needs to spend to make this happen.
Click to expand
Just trying to offer an alternative solution. Have a nice day.
 
Z

Zed

.
Aug 19, 2015
96
West Wight Potter 19 Bar Harbor
Sock Puppet said:
Just trying to offer an alternative solution. Have a nice day.
Click to expand
Turns out the guy who did it with a WWP19, put fiberglas chines on the hull on the starboard and port side :

http://forum.trailersailor.com/post.php?id=1407868

I'm not willing to make a modification like that. But its nice to see that it could be done. It means he also had to majorly modify his trailer, and it likes like a lot of precision is necessary to get it on the trailer too.
 
S

Sock Puppet

.
Aug 14, 2013
308
MacGregor 26S High Desert
Zed said:
Turns out the guy who did it with a WWP19, put fiberglas chines on the hull on the starboard and port side :

http://forum.trailersailor.com/post.php?id=1407868

I'm not willing to make a modification like that. But its nice to see that it could be done. It means he also had to majorly modify his trailer, and it likes like a lot of precision is necessary to get it on the trailer too.
Click to expand
Man, that's a lot of work! It looks surprisingly decent; have you read how it impacted the sailing characteristics? I guess you've got to be pretty committed to a project like that, as it has to hurt the resale. Still, I like seeing owners try new things and innovate.

I've always like the Potters, especially the 19, but they didn't quite have the room I needed for a family of 4. If the family every gave up on sailing I'd be tempted to buy one for solo work. Not to get too far off track, but can you rig and launch your alone?
 
Z

Zed

.
Aug 19, 2015
96
West Wight Potter 19 Bar Harbor
Sock Puppet said:
Not to get too far off track, but can you rig and launch your alone?
Click to expand
I could.... But without a dock, its very hard. Up here in New England where I live, all the ramps are all by themselves. Having two people even another person who doesn't know much makes it much faster. Raising the mast for me alone would have required an electric winch, although supposedly there are techniques to do it alone with block and tackle. My wife pulls it up on a line that would have been on the pulley for the forestay if I didn't have roller reefing.

Consequently, I have a mooring instead. She(the boat) sails along pretty well since all lines run into the cockpit, but again, getting on and off the mooring in seas that are anything other than calm(not a usual occurrence where I am moored) really requires someone to pay attention to keeping the boat in one spot, and someone to deal with the mooring lines, and the dinghy lines. Just a little forward and backward on the trolling motor is all it takes. One person could do it, but when they get close to the mooring they will have to run forward, and get the mooring line on the first pass. Not always possible....

Two people, even if the other one is not really experienced makes all the difference in the world.
 
Z

Zed

.
Aug 19, 2015
96
West Wight Potter 19 Bar Harbor
bawlmer said:
Why not just buy a speedboat and become bi-nautical?
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Don't really need another boat with another mooring and another trailer. Already have two sailboats, a sailing dinghy/motor boat, and a double kayak.

Was just a thought. Reality is that a lot of hull work as well as reinforcement would need to be done to make it happen. Not worth it.

AND BESIDES....in reality the 5hp Honda moves the boat at hull speed under 1/4 throttle.
 
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