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Old 02-02-2016, 22:17   #16
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Re: Question about speed...

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Originally Posted by valhalla360 View Post
Sorry but NO.

A 20,000 planning hull only gets away with something on the order of 700hp because the hull shape causes it to lift out of the water and essentially skim across the top (skim being relative with a 20k lb boat).

Theoretically, you could get a displacement hull up to 25-30kts but you are likely talking many thousands of HP and the boat would break up from the stress long before it actually got up to those speeds.

Some modern flat bottom sailboat hulls straddle the line between planning and displacement but really still need special conditions to get much above 10-12kts. Those conditions are not easily duplicated under power.

80 foot displacement hulls, 800 hp, 30 knots, not planing:


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Old 02-02-2016, 22:19   #17
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Re: Question about speed...

The MacGregor is basically a small planing power boat hull and they added some balast and a mast.

Now if you took a 40' hatteras, melted some lead into the bottom and stuck a mast thru the flybridge...
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Old 02-02-2016, 23:48   #18
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Re: Question about speed...

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Originally Posted by 44'cruisingcat View Post
80 foot displacement hulls, 800 hp, 30 knots, not planing:


The rules change once you get over about 11:1 LWL:Beam ratio (like with narrow cat hulls)
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Old 03-02-2016, 02:02   #19
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Re: Question about speed...

Hey 40'cruisingcat, what would happen if you strapped 2 200hp outboards on the back of your cat. Curious ?

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Old 03-02-2016, 02:09   #20
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Re: Question about speed...

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Hey 40'cruisingcat, what would happen if you strapped 2 200hp outboards on the back of your cat. Curious ?

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NO expert, but sounds of splintering wood, glass and foam echoing around the bay come to mind... before or after starting the engines!

The weight and thrust of such large engines would over tax most sailing vessels, mono or multi.

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Old 03-02-2016, 04:23   #21
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Re: Question about speed...

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80 foot displacement hulls, 800 hp, 30 knots, not planing:


Kind of difficult to stretch a 40' mono to 80' and put it on a pair of hulls....

In the context of a production dispalcement monohull, no, you can't get them to go 30kts with any reasonable HP.

Of course, I wouldn't be suprised if the 40' mono had nearly the load capacity of the 80' you show. Overload that 80' boat and I bet you lose the 30kt top speed very quickly.
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Old 03-02-2016, 05:45   #22
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Re: Question about speed...

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You posted this in another thread you opened:



You should probably ask this on SA
They probably have it as a template on SA to post over here to see who can win most replies for stupidity.
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Old 03-02-2016, 05:48   #23
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Re: Question about speed...

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No. There is not need for them on a Beneteau. Just install a hydronum activator to the keelson primary load point. From there the fulcrum will reach dynamic potential and the resistance loads of the water will diminish to the point that a pair of oars should see the boat planing at 11 meters per second Celsius.

Btw, this will only work on Beneteaus up to 38 foot. If you buy a bigger one you will need to apply the 8th law of thermodynamics and heat the surface of the hull. That will make the electrons in the fiberglass flow in the direction of your secondary fluxgate attenuators. Remember to reverse the polarity on the termination diode else you will go backwards.

Thats enough frivolity from me for now..
But No.. Just no to putting outboards on the back of a beneteau of that size.
I nominate this for best answer of the day
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Old 03-02-2016, 06:07   #24
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Re: Question about speed...

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Originally Posted by ozskipper View Post
No. There is not need for them on a Beneteau. Just install a hydronum activator to the keelson primary load point. From there the fulcrum will reach dynamic potential and the resistance loads of the water will diminish to the point that a pair of oars should see the boat planing at 11 meters per second Celsius.

Btw, this will only work on Beneteaus up to 38 foot. If you buy a bigger one you will need to apply the 8th law of thermodynamics and heat the surface of the hull. That will make the electrons in the fiberglass flow in the direction of your secondary fluxgate attenuators. Remember to reverse the polarity on the termination diode else you will go backwards.

Thats enough frivolity from me for now..
But No.. Just no to putting outboards on the back of a beneteau of that size.
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I nominate this for best answer of the day
Spot on OTR....

The only way to achieve the OP's desired velocity.... Or this...
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Old 03-02-2016, 06:14   #25
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Re: Question about speed...

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Spot on OTR....

The only way to achieve the OP's desired velocity.... Or this...
Is that a jet engine in your pocket or are you Happy........????????
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Old 03-02-2016, 06:20   #26
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Re: Question about speed...

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Is that a jet engine in your pocket or are you Happy........????????
I'm a shower.... In moderation of course....
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Old 03-02-2016, 06:32   #27
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Re: Question about speed...

you can have a speed sailor by macgregor or you can have a sailboat.
or follow ozskippers instructions to the letter.
rodlmffao.
yer not gonna get more than hull speed from a sailboat with an outboard or any other engine.
happy planing.
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Old 03-02-2016, 06:37   #28
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Re: Question about speed...

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Hey Guys and Gals,
I've been thinking about putting a couple outboard 200-300 hp engines on the back of a Beneteau 33-47 footer. The reason for the engines is to get to shelter in case a bad storm pops up quickly or there is no wind I could use a single engine to go. My question is,is this an absurd idea? If so,why? Do these boats have a speed limit or capability? I've watched several videos of sailboats but everyone seems to get nervous above 15 knots except for the racing boats or cats. Would it be wiser to just go with a powered boat. My dreams are to do the Greater Loop and travel as far as Puerto Rico. I know if I go with a sailboat I will be taking lessons in Florida somewhere as I have never sailed before. Thankz for any and all input.
Not on a Beneteau, only on a boat properly designed to do that and not with an outboard. There are not many and even fewer that are designed to sail relatively well. On the North of Europe they have one that has impressed testers, in fact one has crossed the Atlantic. That really impressed me.

I made a post on my blog about that Atlantic crossing. Look at the blog search engine for Sailjet.

But that idea to run from storms to shelter is only practical in what regards coastal cruising. On ocean sailing the fuel to do that will be no compatible with the boat tankage.
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Old 03-02-2016, 06:45   #29
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pirate Re: Question about speed...

Forget the diesel engine.. forget the outboards..
Fit a couple of Yamaha 750 Jet Bike engines in her.. one each side of the back end of the hull/keel join..
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Old 03-02-2016, 08:10   #30
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Re: Question about speed...

Here it is.....



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