Boatmad.com


Reply
 
Thread Tools Display Modes
 
Old 12-01-2014, 03:26 PM   #1
Registered User
 
glen76's Avatar
 
Country: england
Location: southampton
Occupation: engineer
Interests: lots
Boat make: scorpion 8.1
Engines: 250HO
Cruising area: solent

Join Date: Mar 2004
Location: southampton
Posts: 1,336
bow tank full to empty speed impact

Curious to know how much speed people loose when they fill their bow tanks up. Especially if you know how big your tank is.

ta gt
__________________

glen76 is offline   Reply With Quote
Old 12-01-2014, 04:51 PM   #2
Captain slow
 
andymac's Avatar
 
Country: england
Location: surrey
Boat name: terminal velocity no.120
Boat make: phantom20
Engines: 2.5efi smillin jack
Cruising area: solent

Join Date: Mar 2006
Location: surrey
Posts: 478
I wouldn't have thought to many people have calculated the difference,because the ballast tank is generally used in rougher conditions when top speed is not an issue.however I will say, when coming back from cowes last year,playing with Renegade,I was unaware my quite big tank was filling/loading weight up front,which then when I hit a bit of slop,stuck the nose in and put me into a semi hook.not funny at 70ish mph
__________________

andymac is offline   Reply With Quote
Old 12-01-2014, 05:58 PM   #3
Registered User
 
Country: UK
Location: Surrey
Occupation: Motorsport Development inc Engine Managment
Boat make: 21ft
Engines: Various
Cruising area: Solent / Kent / Cornwall

Join Date: Oct 2011
Location: Surrey
Posts: 375
How many litres do they typically hold in the 19-25ft boat range? I understand they are used to keep the front down in rough conditions? Surely as you said, makes you more likely to plant the bow in the sea?
beyondhelp is offline   Reply With Quote
Old 12-01-2014, 07:19 PM   #4
Captain slow
 
andymac's Avatar
 
Country: england
Location: surrey
Boat name: terminal velocity no.120
Boat make: phantom20
Engines: 2.5efi smillin jack
Cruising area: solent

Join Date: Mar 2006
Location: surrey
Posts: 478
Quote:
Originally Posted by beyondhelp View Post
How many litres do they typically hold in the 19-25ft boat range? I understand they are used to keep the front down in rough conditions? Surely as you said, makes you more likely to plant the bow in the sea?
I'm not sure, I think the one in mine is to big (approx 90lts).if I was to put a new one in, I'd proberbly go for about 40-50lts.that for my p20
andymac is offline   Reply With Quote
Old 12-01-2014, 08:08 PM   #5
Registered User
 
Country: UK
Location: Surrey
Occupation: Motorsport Development inc Engine Managment
Boat make: 21ft
Engines: Various
Cruising area: Solent / Kent / Cornwall

Join Date: Oct 2011
Location: Surrey
Posts: 375
Ok, so say 40-50kg. Having never been on boat with one, how does it help? I mean I'd have assumed that you would trim up/down as needed, or is it case over heavy chop, that a light front can get pushed up too easily regardless of trim?
beyondhelp is offline   Reply With Quote
Old 12-01-2014, 08:21 PM   #6
Registered User
 
S2art's Avatar
 
Country: United Kingdom
Location: Dartford
Occupation: Maintenance Engineer
Interests: What apart from powerboating. Football, other forms of motorsport
Boat name: Tintorera Racing
Boat make: Tintorera 20
Engines: Yamaha 90
Cruising area: Medway / South Coast

Join Date: Apr 2006
Location: Dartford
Posts: 58
bow tank

You're basically right on all counts. The idea is to get weight into the front to keep it down, if the set up is right it would allow for level flight, and to stop kiting where the wind picks up the nose and holds it up. If your using a bow tank your top speed would be down anyway because of the conditions. The only real issue with a bow tank is in a following sea, when it is quite possible to drive of a wave and stuff into the next. This is when the art of using a bow comes into effect, some may trim out to hold the nose up, when others may empty it and refill when required.
S2art is offline   Reply With Quote
Old 12-01-2014, 08:35 PM   #7
Ringle@der
 
gar163y's Avatar
 
Country: England
Location: Uckfield, East Sussex.
Interests: Water Ski Racing.
Boat name: Both called ‘Irresistible’.
Boat make: Bernico F1 Twin, Monterey 265SC.
Engines: 2 x Mercury 300XS's, Yanmar 315.
Cruising area: South and east coasts. Eastbourne Marina.

Join Date: Mar 2006
Location: Uckfield, East Sussex.
Posts: 725
Bernico F1 bow tank is 280 litres.
__________________

Irresistible Water Ski Racing Team
gar163y is offline   Reply With Quote
Old 12-01-2014, 08:56 PM   #8
Registered User
 
Country: UK
Location: Surrey
Occupation: Motorsport Development inc Engine Managment
Boat make: 21ft
Engines: Various
Cruising area: Solent / Kent / Cornwall

Join Date: Oct 2011
Location: Surrey
Posts: 375
Interesting stuff, thanks.
beyondhelp is offline   Reply With Quote
Old 12-01-2014, 09:36 PM   #9
Registered User
 
glen76's Avatar
 
Country: england
Location: southampton
Occupation: engineer
Interests: lots
Boat make: scorpion 8.1
Engines: 250HO
Cruising area: solent

Join Date: Mar 2004
Location: southampton
Posts: 1,336
Quote:
Originally Posted by gar163y View Post
Bernico F1 bow tank is 280 litres.
thats a big tank. I have just down sized mine, must have been 5-6m long along hull length.

I appreciate most people wont ordinarily use the tank unless its sloppy, but i sure as hell know ill be tryinh mine on pickup and fill to count the time, and note the speed. Unfortunately the boats not ready to answer my own question.
glen76 is offline   Reply With Quote
Old 13-01-2014, 08:52 AM   #10
BananaShark Member
 
Cookee's Avatar
 
Country: UK
Location: Salcombe South Devon
Occupation: Racer and builder
Interests: Winning races
Boat name: BananaShark
Boat make: BananaShark 34' Race
Engines: Twin Yanmar BY 260's

Join Date: Mar 2004
Location: Salcombe South Devon
Posts: 4,632
Quote:
Originally Posted by gar163y View Post
Bernico F1 bow tank is 280 litres.
Bow tanks for ski racing are a different thing, they are used to flatten the water for the skier as well as for handling.

We always go faster with a bow tank, otherwise there isn't a point! We never have any water in ours going downwind and never have a gauge for one either - it''s by feel, every boat is different but the tank itself will slow the boat down in very flat conditions when you take account of the weight of the tank itself in the bow - but not by much at all.
__________________
Cookee



British Champions! RIB Formula 1 2005
National Speed Record Holder at 90.15 (still)

www.bananasharkracing.com
Cookee is offline   Reply With Quote
Old 13-01-2014, 09:16 AM   #11
Registered User
 
Renegade's Avatar
 
Country: UK
Location: london
Occupation: Powerboat Skipper
Interests: Boats , bikes!
Boat name: Renegade
Boat make: GPV-RENEGADE
Engines: 150 HO etec
Cruising area: Thames, south coast, anywhere!

Join Date: Dec 2008
Location: london
Posts: 2,330
In contrast I fill mine and leave it for duration of the race.
__________________
Im re branding pepper spray as Arsehole Repellant.im going to make a fortune.
Renegade is offline   Reply With Quote
Old 13-01-2014, 09:57 AM   #12
Aged Member
 
DAVE's Avatar
 
Country: UK
Location: HAMPSHIRE
Occupation: Desk Jockey
Boat name: Voodoo Doll
Boat make: Sea Ray 270 Sundancer
Engines: Merc inboards
Cruising area: SOLENT

Join Date: Oct 2004
Location: HAMPSHIRE
Posts: 772
Cookee is spot on...its all done by feel as you go.....some even fill the tank with a hose at the pontoon, to make sure they can get on the plane, then let it out as they go till the boat feels right.
It all depends on how the boat is balanced. where and how big the fuel tanks are, where the crew sit in relation to the c of g etc...whole idea is to fly flat if you fly at all.....and identical looking boats can be very different.
Batboats are the worst in a following sea....been half drowned many a time trying to get the things to run sensible....
Probably doesnt help much but its mostly trial and error.....with empahasis on the error...
__________________
Land was invented to give boats somewhere to visit
DAVE is offline   Reply With Quote
Old 13-01-2014, 10:44 AM   #13
Registered User
 
Country: UK
Boat name: RR 880/ RR 300xs
Boat make: Scorpion 10m open/ Scorpion 8.1m
Engines: 2 x ???/ Mercury 300xs
Cruising area: Solent

Join Date: Aug 2011
Posts: 41
Hi Glen,

It takes about 90-120 seconds to fill my take up on my Scorpion at about 45mph, it does take top speed off but only 3/4 knots but at the same time has allowed more trim to be used.
RR 880 is offline   Reply With Quote
Old 13-01-2014, 11:48 AM   #14
Registered User
 
Country: Poland
Location: Warsaw

Join Date: Dec 2005
Location: Warsaw
Posts: 568
I have done some speed test on my SR23 last year
I had 130 litres bow tank.
Empty tank was 117 km/h
Full tank 109 km/h
That was riding on a lake on flat water
Mike_G is offline   Reply With Quote
Old 13-01-2014, 01:10 PM   #15
Registered User
 
Marinautic's Avatar
 
Country: UK
Location: Poole
Occupation: Mercury/Mercruiser Sales

Join Date: Sep 2007
Location: Poole
Posts: 505
On flat water I'd expect to loose somewhere in the region of 10% of your max speed, not that you'd need to use it in flat water of course.
__________________
https://www.facebook.com/Marinautic-...5205578496744/

"I think you're right" Cookee 13/11/13
Marinautic is offline   Reply With Quote
Old 13-01-2014, 05:52 PM   #16
Registered User
 
scottyboy's Avatar
 
Country: United kingdom
Location: West Sussex
Occupation: Grease Monkey
Interests: Makin my boat faster!
Boat name: S.B Racing
Boat make: Ocke mannerfelt canopied B23 / Zapcat
Engines: Merc 200XS Gen 2 / Tohatsu 50
Cruising area: littlehampton/Southampton

Join Date: Jan 2005
Location: West Sussex
Posts: 2,652
Quote:
Originally Posted by DAVE View Post
Batboats are the worst in a following sea....been half drowned many a time trying to get the things to run sensible....
Probably doesnt help much but its mostly trial and error.....with empahasis on the error...
You know when ya deep if you can hear the engine revvin to try and get to the surface and ya navigators voice slowly turns to a sort of gurgle! Hey Dave! Atleast we finished the race though! ilfracombe wasn't it?
__________________
Class 3C Mono EPA National speed record holder 95.35 mph Avg!
scottyboy is offline   Reply With Quote
Old 13-01-2014, 06:14 PM   #17
Registered User
 
glen76's Avatar
 
Country: england
Location: southampton
Occupation: engineer
Interests: lots
Boat make: scorpion 8.1
Engines: 250HO
Cruising area: solent

Join Date: Mar 2004
Location: southampton
Posts: 1,336
Really good feedback. Much appreciated.

Especially from another scorpion of similar size as mine
glen76 is offline   Reply With Quote
Old 13-01-2014, 08:10 PM   #18
Registered User
 
Country: Germany

Join Date: Feb 2012
Posts: 93
....150 Liter at my Piranha Carrera......
Piranha is offline   Reply With Quote
Old 14-01-2014, 08:00 AM   #19
Aged Member
 
DAVE's Avatar
 
Country: UK
Location: HAMPSHIRE
Occupation: Desk Jockey
Boat name: Voodoo Doll
Boat make: Sea Ray 270 Sundancer
Engines: Merc inboards
Cruising area: SOLENT

Join Date: Oct 2004
Location: HAMPSHIRE
Posts: 772
Quote:
Originally Posted by scottyboy View Post
You know when ya deep if you can hear the engine revvin to try and get to the surface and ya navigators voice slowly turns to a sort of gurgle! Hey Dave! Atleast we finished the race though! ilfracombe wasn't it?
Yeah...every bloody lap on that one leg....I wonder who has that picture of the whole boat (and us) right under...just an orange blur below the surface....I'll never forget that....we could have done with gills.
__________________
Land was invented to give boats somewhere to visit
DAVE is offline   Reply With Quote
Old 14-01-2014, 08:21 AM   #20
Registered User
 
scottyboy's Avatar
 
Country: United kingdom
Location: West Sussex
Occupation: Grease Monkey
Interests: Makin my boat faster!
Boat name: S.B Racing
Boat make: Ocke mannerfelt canopied B23 / Zapcat
Engines: Merc 200XS Gen 2 / Tohatsu 50
Cruising area: littlehampton/Southampton

Join Date: Jan 2005
Location: West Sussex
Posts: 2,652
I remember stirling sticking it in hard and retiring. We just kept plodding round to finish. Checked out Sunday though! Didn't see anyone for the whole race! 😎
__________________

__________________
Class 3C Mono EPA National speed record holder 95.35 mph Avg!
scottyboy is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Powered by vBadvanced CMPS v3.2.3

All times are GMT +1. The time now is 02:53 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×