Option 1 cruising speed...

[Polarity]

There has been a lot of discussion about the performance of the poll winner "Option 1" (which is not a bad name for a boat!).

1 Coastal hopping
2 Trailerable
3 Range 300 miles
4 Crew, 2 minimum
5 Price range, under 50K US, for home built.
6 Must be able to carry on a normal conversation at 3/4 throttle

See this thread for links to her specification so far:
Option 1 Design Ideas (Trailerable, 300 mile range, Coastal hopping)

Please can we have 4 (or more) performance profiles and then (suprise ) we can vote on it! - that will then tell us more about quite a few things...

Cheers

Paul

[Willallison]

Paul - you just pipped me at the post - I was just about to start a thread along similar lines - and you're right "Option 1" is a good name - I vote we adopt it!

Ok here's my suggestions as far as cruising speed are concerned:

1. Able to maintain planing down to approx 12 knots. Like Tom, I consider "on the plane" to mean running cleanly, without the bow pointed towards the sky...
2. Max speed around 25 to 28 knots.
3. Max cruise around 20 - 22 knots
4. Must be economical and comfortable to operate throught its speed range - including displacement speeds.

In many instances, it is not comfortable to cruise at speeds beyond those that I have listed, unless you are travelling on a very specialised boat like a wave-piercer (which is unlikely to be much use as a cruiser). The abilitiy to very your speed to suit the conditions, without enormous costs to economy, is to me paramount to the success of any boat.

[Willallison]

Just to prove that I can sit on the fence just as well as anyone:

1. Max speed 45 + knots
2. Cruise 30 - 40 knots
3. Economical at cruise as well as displacement speeds.

This would allow for early morning, or late afternoon dashes up the coast when it is generally reasonably calm. Economy at displacement speeds means that when conditions prevent fast cruising, it is still possible to move without using all your fuel.

[duluthboats]

[Willallison]

...well, both are possible, even desirable - and would make for interesting design concepts... just throwing up ideas for everyone to consider....

[duluthboats]

LOL!!!
Yes they both would fit. I think most know me well enough now, that I can add nothing new at this point. I have seen a number of new members the last few days. Many of them from down under. Also I see we picked up a NA from Algeria. Wecome aboard to all. Please join in. What would you like to see Option 1 do?
Gary

[duluthboats]

So how long do you think I could sit on my hands. We need more than just 2 to choose from.

Max speed 7 knots
Cruise speed 5-6 knots
Definitely a turtle, but it will get you there and you'll have some money for beer when you arrive. I would think this would be perfect for the ICW.

Someone else?

Gary

[Willallison]

Thank goodness!
For a moment there I thought the only to alternataives would be mine and I'd have nobody to argue with but myself!

[8knots]

Hello all!
Sorry I have not been able to help much. Work Work Work that is all i can say. Im glad to see so much happening. so I will bring back my potential version 3 the 1 hour sketch
I am with Gary on the turtle boat deal. We that can stand to go a little slower than the ripples on the water will no doubt have a considerable wad left after our week on the ICW. I allso agree that a boat capable of a modest 20-24 Kts or higher Will allways be a EPA nightmare gas hog. Please do not mistake this as a milklappin bunnyhuggin stab at big power. If i were loaded I would have a boat that could have a pair of detroit 16v-149TTA'S
Say 50 GPH.......each Hmmmmm.... I am not rich so i tend to focus on economy. Anyway Ill put the soapbox away. My opinion is that an economical home-build (high speed) boat is quite a challenge.
Those who would attempt the design work are brave. It allso poses a challenge to the budget A pair of good 200 hp engines outboard or otherwise will take a good chunk of our proposed 50k
I see our boat having having a lot of creature comforts so this will contribute to a good deal of our budget.
Just thinking outloud here guys (spring has come to Alaska)
8Kts

[Polarity]

.. the budget - but also the

6. conversation at 3/4 throttle... 2x 200 hp OB's ???

You could put them on soft mounts I guess, then soft mount the transom, cover them in a shell with a 2"/50mm () polymeric barrier. Of course if we make her light enough - and aerodynamic enough you might not need all that muscle.
No exotics though as she's under 50K...
This might need some lateral thinking ...

Paul

[Polarity]

PS dont forget the oil pan with those screaming gimees! (....experience!)

[tom28571]

Originally posted by 8knots


I am with Gary on the turtle boat deal. We that can stand to go a little slower than the ripples on the water will no doubt have a considerable wad left after our week on the ICW. I allso agree that a boat capable of a modest 20-24 Kts or higher Will allways be a EPA nightmare gas hog.

My opinion is that an economical home-build (high speed) boat is quite a challenge.
Those who would attempt the design work are brave. It allso poses a challenge to the budget A pair of good 200 hp engines outboard or otherwise will take a good chunk of our proposed 50k
I see our boat having having a lot of creature comforts so this will contribute to a good deal of our budget.
Just thinking outloud here guys (spring has come to Alaska)
8Kts [/b]

8Knots (we need a name)

Having done the ICW a few times at 6kts, I am not in the mood to do that forever. It's fine once, or maybe twice. Wanting to go a bit faster was one of the main drivers for me to take on the design of my own power cruiser.

20 to 24knots does not have to be a gas hog. My Yamaha T50 can easily deliver over 8mpg at a speed more than twice the displacement speed you mention. Not many displacemant cruisers will do as well. I don't know what the fuel use would be at 20kts since I don't run at full throttle very long. A 90hp Yamaha or Honda could cruise at 20kts and probably get near the mpg that I get. I don't have the bucks to try different engines.

Yes, it is a challenge to design a cruising boat that is economical and can run at 20 or above but that is the whole point. Why bother to duplicate what has already been done with only styling or facility changes? Now, a real challenge would be to design an answer to Will's above wish list (one of his many). Economical cruise at 30 to 40kts with a top of 45!!

Shucks Will, couldn't you come up with something a little more difficult? I work that out, along with some of Will's other weight wishes, to need about 300hp. My budget won't feed those horses, much less buy them. And the low speed cruise would be hard (maybe impossible) to get with that too. Also building the boat strong enough and with a hull shape to tolerate those speeds may ruin the whole enterprise. My guess, Will, is that no normal monohull is possible with your requirements.

My splash of cold water for the day.

[duluthboats]

[Willallison]

Hey! I never said it would be easy!
I think there may be a little confusion over some of my suggestions / wish lists (you're right Tom - they do seem to be somewhat prolific....obsession can be a terrible thing ) The 2x 200hp powered boat wasn't meant to be connected with "Option 1" - more in line with option 4.

Tom, I'm glad you responded to 8knots remarks re fuel consumption. I knew that "Liz" should be capable of at the very least equalling the economy of a small displacement cruiser. As far as the power requirements for my 45 knotter, how do you work that out? I know I have a formula for it somewhere, but I haven't been able to track it down......
You're probably right in saying that a "conventional monnohull" would be unable to fulfill the stated objectives - but then who says that we have to design a conventional monohull? Though producing the boat for less than 50K US may be asking too much. The ideas I put forward in the image posted in regard to option 4 may address some of the issues. http://boatdesign.net/forums/showthr...=2032#post2032
A very fine entry to slice through waves, with flatter aft sections to allow slow speed planing would be my suggestion for the 20+ knotter. The same could be incorporated in the 45 knotter but would result in an uncomfortable ride in rough water as the boat would undoubtably spend a considerable amount of time in the air! - hence the requirement for economy at displacement speed. This can be achieved with the use of 4-stroke or dfi o/b's. That's why this boat would do most of its long distance cruising in the calm of the early morining / evening.

[tom28571]

Will,

I used a form of Crouch's formula for planing hulls.

P = C(V/W)^2
P = shaft horsepower
C = constant of about 180 for cruisers
V = speed in knots
W = displacement in lbs

It assumes that everything in the design is is balance for the best efficiency.

There are some interesting factors on the table that need input from everybody. I'm going to back off and let someone else have a go.

And to you too Gary! 90 degrees here today. Varnish dries fast and I'm moving to the slow epoxy hardener if this keeps up. Take down your ice fishing hut yet?