What makes a "fast hull"
05-16-2014, 11:08 AM
#11
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iTrader: (1)
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
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
05-16-2014, 11:19 AM
#12
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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.
05-16-2014, 11:22 AM
#13
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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.
Last edited by CDShack; 05-16-2014 at 11:24 AM.
05-16-2014, 11:33 AM
#14
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.
05-16-2014, 11:45 AM
#15
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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.
05-16-2014, 02:10 PM
#16
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.
05-16-2014, 06:03 PM
#18
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Thread Starter
05-16-2014, 06:49 PM
#19
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Gold Member
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.
Last edited by Too Stroked; 05-16-2014 at 06:55 PM.
05-16-2014, 07:09 PM
#20
Platinum Member
Platinum Member
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 
