What makes a "fast hull"
 

so I have recently changed to a smaller boat due to lack of time to use, docking, family, reastoring an old house etc..I have a 1994 221 liberator with a 502 (375 at the prop) I picked it up last August to have something to trailer for occasional use. The boat is very clean and should work perfect for my needs. Everything I read tells me this is a 60-62 MPH boat. I have scene over 60 on GPS in it in the couple times I have used it with me the wife, the kid and full of fuel gear etc.. note this is running an old raker prop that looks like it is probably original and not exactly pristine

so i'm trying to figure out why this should only be a low 60 boat with 420HP, 21 deadrise, 4000lbs I know it is a fairly heavy hull for its size but I see others with 25'-27' boats with stock 502s claiming to run 70 and they are heavier or atleast as heavy

so what is it in the hull design that makes it fast? I am not talking stepped hulls either, I understand that

I do plan on buying a new prop and having it labbed once I get some accurate numbers early in the season

The x dimension is probably to low and it has a hook for safety reasons. Or there just isn't enough bout to have a high x and keep the motor under the hatch.

One other thing a good driver can be worth 3-10 mph.

BB, don't worry the "driver mod" is not going to be needed in this case

The drive is deep but the hull has no hook at all unlike the older Liberators

A black jump suit and a few gold chains can make a big difference.....

Yes but you have got to ha a pink thong on under the black jump suit...

Spray on black hair helps too.

c-mon we all know Reggie needs a little help with his personal style,

but on a serious note is there that much difference in th hull itself or more that these manufacturers spend the time on set up to get every MPH out og thier hulls

OOOH thats a visual I DON'T want to think about....

I would think that weight distribution would play a role in speed, so different props change your attitude in the water depending on what your after. My 02

Pads and shallow deadrise make vhulls fast. Im not talking Kotex pads either...they make boats slower.

I'm still trying to figure this one out! Pads can improve speed but also make a harsher ride. The Donzi 22 Classic has 24* deadrise and no pad. There is hull dragging through the water but they run 73 mph with stock 420 hp. They run near 85 with 540 hp. Put in 700+ hp and they run over 100. Maybe it has to do with the weight and weight distribution. The bow needs to be light and out of the water without excessive trim.

As was said above, so much goes into a "fast hull" it's hard to describe. V-entry angles, true running strakes, strake width and angle, where they terminate, chine angles, balance of the boat, there's just a lot of variables. Liberator is generally viewed as a performance boat, so I would figure a 23' boat with a 502 should bust 60mph. My Chappy 200SSi run about with 5L merc does 57 on GPS. Sounds more prop than bottom. My experience, Mirages Plus works well on larger boats, alot of blade to trim into and some transom lift too.

The Classics also have a very narrow beam, don't they? I would think that this would lessen drag in the water considerably.

I believe beam is 7'. Length is honest 22' 6". I'm thinking that what's slowing down the Four Winns is the cabin and all the weight up front. The Donzi has no cabin. This is why the Donzi ZRC, Fountain 42 Poker Run edition, certain Apaches etc are so fast. No cabins.

Yep, that's one of the reasons that my pig of a Baja Force 235 has so much trouble making speed. Cabin has fridge, porta potty, beer, other junk, beer, etc stuffed into it, and the helm is already trust forward to make more cockpit room.

Five basics: Excellent bottom, high X, right props, lots of testing, big HP and cubic $ for all.

What does "excellent bottom" mean? I have googled about blue printing hulls every which way I can think of and come up with almost nothing and vague!

An "excellent bottom" means a great combination of lift, deadrise, angle of entry, number and placement of lifting strakes, weight, center of balance, construction, etc. There's no absolutely perfect combination, but the original George Linder 21' Challengers had almost the perfect combination. (That's why so many companies splashed the hull.) And some folks who modified the hull so it didn't look like a blatant copy found out that small changes sometimes ruined that perfect combination.

You would have to go to a pro to help you with this project. Go to someone like Glassdave and you can expect something like $3000-8000++ range for bottom blueprinting. After the bottom is been blueprinted (close to perfectly flat) expect to spend more $ as your speed increases due hull efficiency, drive height, props, + HP, etc. The increased speed will require more strake changes to maximize the hull efficiency....more bottom work and back to Glassdave! Want a lower cost?..sell your boat as is and buy a boat that meets your speed needs. The polish to perfection approach has no monetary return....ask me how I know :daz:

Sage advice!

All good but I think the op only wanted to know what makes a particular hull faster than another.
Endless variables it seems to be, and a really good question.!:nicethread:

Sounds like some interesting info, I'll have to read up on the Challengers

I have a 21 superboat with a mildly built up 502,bravo 1. Running a mirage 27p. Best speed 87.1

Hp vs load. Most of a boats load = weight and water drag.

Your Lib is heavy and even at 60, a lot of it is still in the water. It's a wave crusher not a wave top rider.

Try to find a video of a 21' Velocity going 60 or higher. Riding on the pad there is near nothing in the water. Also becase it is light !