I have a concept - and a lot of questions

I want to go fast simply because it's fun. My fastest boat is a 15' Fletcher that goes about 55, and I would like something as fast or faster.

I obviously don't drive that fast all the time, but when the mood gets me...

 

200 HP won't get you the target speed on that type of boat. A 3 point hydro or a flat bottom skiff will though.

 

It would be cheaper and easier to buy two boats, a hydro with that type of top end speed, and a runabout in the 30's. If you want a runabout that can hit 55-60 it's probably going to need to be a custom design from the get go.

 

The problem is the limited power the OP wants to install.

 

The problem is, the OP doesn't understand the realities of designing a high speed powerboat hull, that can attain it's SOR goals.

 

he certainly will not be achieving the speeds he talks about in the size he mentioned ( 7 metre ?), in fact well short of it, unless it is very light, in which case it won't be a deep vee, and will hammer badly in a chop.

 

The problem is many fold, power available, speed targets, appropriate hull form and conflicting SOR goals.

Low 40 knot speed targets can live with most shapes, given that flatter ones will pound, but also provide the better speed to HP ratios. Once you start thinking about 50+ knots, things change pretty dramatically. Longitudinal stability issues, ride quality, handling all start to become serious concerns, in fact deadly ones in some hull forms. Couple this with modest power, which needs quite light scantlings and relatively shallow deadrise (given the HP available) and you have a real set of problems to contend with.

Can it be done, yep sure it can, but not by someone that's going to "study up" on the principles and concepts in the next several months. My last custom speedboat was 30' on deck, weighed 2,400 pounds without crew and carried 700 HP. It was fast, but about as delicate as I dared make it, given the class rule restraints and speed targets.

 

Thanks - you're basically confirming my gut feeling. Next question is - where can I find someone to help me design this boat? What would a sensible budget (both for me and designer) be?

 

How are you measuring the speed of your current boat(s) ? The figures you gave seem high.

 

Using GPS

 

Gonzo, Stumble, Par and all have the right commentary. Two boats, one for furious speed, and the other for varnished mahogany eye appeal are sensible options.

The OP has said that he wants to go fast because it is fun. Very well. He wants to go fast without having to use outrageous horse power. Very well. I suggest that he consult the APBA.com web site and see what can be done in the world of go fast boats.

With an aim of 70 MPH one of the SST type boats will do that and some of them can approach 100 MPH all with a near stock outboard. I think that the SST60 class will be fast enough for one to get his jollies, or maybe kill himself. SSTs are damned sexy looking boats too. It is more than possible to buy a frighteningly fast ready to run rig that is no longer competitive in the furiously contested SST classes. Such a rig can be had for far, far less than its construction cost.

There are other alternatives to fast boats in the racing classes too. The Stock outboard classes have categories of incredibly fast boats. More than a few of which are patiently waiting for a non racer person to buy and enjoy....or live dangerously.

Look at the APBA site or a similar site in Europe or the Baltic areas.

 

Have you ever been 50-70 knots on a boat? For most people that haven't it is mine blowing. If your lake is not perfectly flat you can spend some time in the air and control can be an issue. A lot of hull designs simply become unstable at these speeds. I had an old retro boat with an outboard that once it got to speed it wanted to spin around. I tried a few things but basically, I would not take it to full speed or risk a major incident.

 

@messabout between me and my dad we have 7 boats, and we simply don't have room for one more. I am prepared to sell the Fletcher when a new boat arrives, so the new boat will have to be a fast one as well.

@mydauphin I got my first speed boat 27 years ago, and as I've mentioned previously, my currently fastest boat goes about 55 knots. I've borrowed my neighbors' Hydrolift F-23 on several occations. This one goes to about 65 knots. I'm very comfortable in both boats.

My dad has a Pioneer 235 (similar to this http://pionerboat.no/privatmodeller/pioner-8-mini-2/) that we use a 8hp on, and it Scares. The. ****. out of me, despite only going about 18 knots.

It's not the speed, it's the unpredictability of a boat that's the issue.

Now, I'm fully aware that I'm asking for a lot in this "dream boat". Perhaps I have to make some concessions. Perhaps I have to have a bigger engine, or perhaps I have to settle for a slower boat. Perhaps 50 instead of 65 knots. So be it. My vision for this project remains.

It is obvious, and I had my suspicions before I posted here, that I can't pull this one off on my own.

What I need to know is
1) Do you know of any naval architects or designers that can help me get as close as possible to these goals?
2) What would be a sensible budget for designing such a boat? (both for me and the designer)

 

Hey there,

I'd contact Rolf Eliasson (Rolf Eliasson Yacht Design AB) to at least get a dialogue going. He's the designer behind the 20m, 12m and 11m classes used by the swedish rescue society.

 

Tackar