Stretching of a hull / relocating the CG

[67-LS1]

Like this one maybe?
Dennis

[gonzo]

That hull needs at least 900 HP not to be a pig. The deep vee with equal deadrise is designed for high speed on offshore racers. It keeps the pounding down, but requires lots of power. What price range are you looking for? I assume that if you want a boat of this type, you are willing to spend at least $250,000. The Cigarrette boat that had the world speed record for years is available. You can get it for less than that with engines. However, it will need a lot of labor to set-up and rig.

[Willallison]

If I were to start with an early hull as I describe above, leave the engines where they are but just reconfigure the deck and cockpit to a more "cab forward" or "cockpit forward layout, how much would this affect the LCG?

The only way to really establish the LCG is to do at least a preliminary weight study - estimate the weight of all the different bits of the boat and establish where they are in relation to one another. Without an actual boat to base it on, of course, this is made somewhat more difficult. Having said that, it's usually pretty easy te estimate its position once you know where the major items (like engines, tanks, cabins etc) are going to go.
Another thing to consider is that the most comfortable place to sit in a planing hull is near the transom - the further fwd you go, the rougher the ride becomes....
Reconfiguring an existing hull shouldn't be too hard - though you'll have to be carefull about removing anything that contributes to the structural integrity of the boat - like bulkheads.

[67-LS1]

I assume that all hulls have at least some degree of change in their deadrise along the keel. Some more then others right?
Does the hull in the picture look like a constant deadrise design? I believe this hull is listed at 24 degrees at the transom and while this is deep and would require lots of HP, is it a constant deadrise design?
Can someone give me a couple of sample planning hulls that would be constant and variable deadrise.
Dennis

[gonzo]

Cigarrette boats have no change in the deadrise. That is what gave them the speed potential offshore. The boat in the picture looks to be of that style. It has the same angle along the planing surface of the hull.

[67-LS1]

Can you give me an example of what a variable deadrise hull might be? I'm assuming your talking about a hull that would have a fairly steep deadrise forward and would transistion over the legth of the hull to something less then the 24 degrees typical of offshore deep vee hulls.
What would the deadrise be forward, amidship and at the stern. Does it transistion equally along the length or ??
Dennis

[Willallison]

It's horse for courses Dennis - or boats for moats as the case may be
Every boat is different - some will feature a very deep forefoot - with angles of 65 degrees or more, others may have as little as half of that. Transom deadrise varies from completely flat to 18, 20, 25 - I've even seen a very succesful hull with 30 degrees of transom deadrise (though it was a constant deadrise hull). Most succesful variable deadrise designs will have less than 6 or 8 degrees of angle change between midships and the transom. So at amidships it may be say 18 degrees, flattening to 10 or 12 at the transom.
Examples are many and varied - true torpedo boats (like those you are trying to emulate) had variable deadrise. The Huckins Fairform Flyer, many current sportsfhishing boats, etc, etc.
Unless you plan of charging flat out through big seas (like Cigarettes etc are designed to do) then this is probably the way for you to go. Warped plane (or variable deadrise) boats tend to run at lower trim angles and can plane at lower speeds.

[67-LS1]

Thanks Will,
Where I boat and how I boat would keep me from ever (hopefully) having to see "big seas". Economy, a flat wake, minimum planeing speed and minimum rise during the transition to a plane are more important to me.
Dennis

[gonzo]

A flat wake is not possible with a hull of the sportfisherman or torpedo boat type. For that look at ski boat design. The former make huge wakes.

[67-LS1]

I guess a "flat wake" was a poor description.
I've mentioned before that I boat 99.9% of the time in the California Delta, which is a series of rivers and sloughs. I have seen other boat come up these rivers with their bows pointing towards the sky and a 4' wall of water fanning out to shore behind them. They never break stride for people in smaller boats such as ski boats, sail boats, jet skis.
I wouldn't want to be one of those types.
I do drop my speed and wake as I approach others that may be stopped or swimming.
I would like to have a minimum wake at cruise and be able to transition to/from a plane as quick as possible with minimum bow rise.
You know, I want it all.
The current trend in jet powered picnic boats such as the Hinckleys, the Santa Cruz Coastal Flyer, etc, seem to perform closer to what I envision. Do the jets leave huge wakes?
I can't afford one but that's a seperate story.
Dennis

[gonzo]

I think one of the wave piercing catamarans would fit the ticket perfectly. They make little wake, use low power and are economical to run.

[Willallison]

I think one of the wave piercing catamarans would fit the ticket perfectly. They make little wake, use low power and are economical to run.

Incat - the originators of the (current) wave-piercing catamarans are bult here in my home town - indeed I went to school with the owners son. I can tell you that a wavepiercing cat of this type makes an ENORMOUS wake. There are low-wash cat designs, but they are different designs altogether.
I couldn't agree that variable deadrise hulls (such as those incorporated in many sportsfishing boats) produce a huge wake either. It's more that owners insist on carrying so much crap around that their boats are overweight and often underpowered. A lightweight, variable deadrise boat would, in my opinion produce a lower wake than a comparable vessel with a constant deadrise. I've only ever seen pictures of Huckins' travelling at speed, but they don't seem to cast a big wake...?