|
|
05-10-2005, 06:35 PM
|
#1
|
Registered User
Country: uk
Location: brighton
Occupation: CABINET MAKER
Interests: SPEED BOATS,MOTO G.P
Boat name: MOTIVATION
Boat make: MARSHAN 21
Engines: AINT GOT ONE!!
Cruising area: sea
Join Date: Sep 2005
Location: brighton
Posts: 1,223
|
please advise(one for bob??)
shouldnt my boat be out of the water more,photo was taken doing about 60mph,my thoughts are that it should be,it has a cleaver prop maybe thats why,any ideas,perhaps one for bob?
__________________
|
|
|
05-10-2005, 06:36 PM
|
#2
|
Registered User
Country: uk
Location: brighton
Occupation: CABINET MAKER
Interests: SPEED BOATS,MOTO G.P
Boat name: MOTIVATION
Boat make: MARSHAN 21
Engines: AINT GOT ONE!!
Cruising area: sea
Join Date: Sep 2005
Location: brighton
Posts: 1,223
|
whoops forgot photo!!
__________________
|
|
|
06-10-2005, 05:33 AM
|
#3
|
Registered User
Country: england
Location: the grim north
Occupation: robot
Cruising area: tyne
Join Date: Nov 2004
Location: the grim north
Posts: 915
|
your engine looks very trimmed in.try trimming out more to lift the bow.
|
|
|
06-10-2005, 08:48 AM
|
#4
|
Traveling
Country: UK
Location: Alderholt
Occupation: Aerospace
Boat name: T/T D2S
Boat make: Midas 27' Cat, Argo 16 Cat. Avon Rib Thingy
Engines: Merc 280-ROS -JSRE,65Xs, 75 Stinger, Yam 60
Cruising area: Any Seedy Bar
Join Date: Sep 2004
Location: Alderholt
Posts: 4,225
|
What pitch & Dia is the clever?, try a approx same sized bow lifting prop. does the back walk when it breaks the surface?
__________________
It is impossible to lick your elbow.
Team25Racing.com
At least 75% of people who read this will try to lick their elbow!
|
|
|
06-10-2005, 08:56 AM
|
#5
|
BananaShark Member
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: 4,638
|
I would be more concerned about the performance - is it flat out at that point - what revs / speed are you pulling - remember they are very different hulls and don't behave the same as regular monos - especially cornering!
__________________
Cookee
British Champions! RIB Formula 1 2005
National Speed Record Holder at 90.15 (still)
www.bananasharkracing.com
|
|
|
06-10-2005, 12:07 PM
|
#6
|
Registered User
Location: Scotland
Interests: Hole maker
Boat make: Humber Ocean Offshore
Engines: KAD 300/DPX
Join Date: Mar 2004
Location: Scotland
Posts: 958
|
It looks nice and flat to me. You could hardly get that motor more square to the water. But I know fekk all about fast boats....
__________________
JW.
|
|
|
06-10-2005, 12:08 PM
|
#7
|
Senior Member
Country: UK
Location: Devon
Occupation: Garage Proprietor
Interests: PowerBoat Racing
Boat name: If Only
Boat make: Bernico F3 OCR, Bernico Prototype Inboard, and some Ribs
Engines: Yamaha Pro V 115
Cruising area: UK, France
Join Date: Jan 2005
Location: Devon
Posts: 3,095
|
Yes it is running very level but about what you would expect at 60ish.
Mine used to run best on a small hub laser & fastest on a Yamaha High performance (semi cleaver) !! as already suggested what RPM are you doing ,
When running properly into the high seventies it will literally be flying .
__________________
If Only
National Outboard Immersed Propeller Mono Record 103mph
|
|
|
06-10-2005, 01:14 PM
|
#8
|
Registered User
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: 2,656
|
Quote:
Originally posted by BluFin
What pitch & Dia is the clever?, try a approx same sized bow lifting prop. does the back walk when it breaks the surface?
|
What does it mean when the back walks when it brakes the surface?
__________________
Class 3C Mono EPA National speed record holder 95.35 mph Avg!
|
|
|
06-10-2005, 01:26 PM
|
#9
|
Senior Member
Country: UK
Location: Devon
Occupation: Garage Proprietor
Interests: PowerBoat Racing
Boat name: If Only
Boat make: Bernico F3 OCR, Bernico Prototype Inboard, and some Ribs
Engines: Yamaha Pro V 115
Cruising area: UK, France
Join Date: Jan 2005
Location: Devon
Posts: 3,095
|
I beleive they are refering to Prop Blowout which happens at a point where the prop loses drive for a variety of reasons usually down to setup ie engine too high, over trimming, poor boat balance etc.etc. it is caused by the gearcase tracking at an angle allowing high pressure on one side & low pressure on the other which at a certain point allows air to take the place of water around the prop resulting in loss of drive. Now because you are effectively holding against engine torque under normal running (hence the crab effect ) when that torque dissapears the back of the boat will walk sideways , if this happens over about 70-75 MPH you will probably need a change of underwear the first time but you do get used to it.
I may not have explained very clearly but i tried !!
There are a number of tricks to cure this one of which is the smaller hub props as they produce less torque I wont go into the others at the moment but if anyone wants to they cann ask.
__________________
If Only
National Outboard Immersed Propeller Mono Record 103mph
|
|
|
06-10-2005, 01:31 PM
|
#10
|
Registered User
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: 2,656
|
My tandem p21 does this at W.O.T but you cant feel it when youre driving , only when youre in the back when you land off a wave you can feel it kick back over to the right very slightly when it re-enters the water! strange feeling but the boat feels stable ?
__________________
Class 3C Mono EPA National speed record holder 95.35 mph Avg!
|
|
|
06-10-2005, 03:07 PM
|
#11
|
Senior Member
Country: UK
Location: Devon
Occupation: Garage Proprietor
Interests: PowerBoat Racing
Boat name: If Only
Boat make: Bernico F3 OCR, Bernico Prototype Inboard, and some Ribs
Engines: Yamaha Pro V 115
Cruising area: UK, France
Join Date: Jan 2005
Location: Devon
Posts: 3,095
|
Thats different , Thats merely the paddle wheel effect of the prop biting.
__________________
If Only
National Outboard Immersed Propeller Mono Record 103mph
|
|
|
06-10-2005, 05:48 PM
|
#12
|
numbskull
Country: United Kingdom
Location: South
Occupation: none
Interests: none
Boat name: Leviathan
Boat make: Phantom 28
Cruising area: South Coast
Join Date: Mar 2004
Location: South
Posts: 15,959
|
Blowout is caused by the water being unable to follow the contours of the gear case at high speed, either because the gearcase is way too blunt (Honda 225), or just because the speed is too high fora convensional profile case, and a gearcase with a more streamlined profile is needed, or a nose cone fitting to give the same effect.
Most stock gearcases (except the Honda item) are pretty good tho', so you shouldn't be experiencing this at the speed you're going. Looks to me like you just need a bit more bow lift, assuming you're going quick (ish) in that pic.
When it happens, it's as if at a certain speed (very high), the prop appears to start slipping, almost as if the bush has gone, but as your speed falls off, all returns to normal, until the critical speed is again reached.
__________________
.
"I Agree with everything you say really!" - John Cooke to Jon Fuller - 26-01-2013
|
|
|
06-10-2005, 06:05 PM
|
#13
|
Senior Member
Country: UK
Location: Devon
Occupation: Garage Proprietor
Interests: PowerBoat Racing
Boat name: If Only
Boat make: Bernico F3 OCR, Bernico Prototype Inboard, and some Ribs
Engines: Yamaha Pro V 115
Cruising area: UK, France
Join Date: Jan 2005
Location: Devon
Posts: 3,095
|
No it is'nt but i won't argue about it !!
__________________
If Only
National Outboard Immersed Propeller Mono Record 103mph
|
|
|
06-10-2005, 06:22 PM
|
#14
|
Registered User
Country: England
Location: Crayford, Kent.
Occupation: Electrical gezza!
Interests: Petrolhead
Boat name: Wayne Kerr
Boat make: Phantom xl
Engines: Mercury 2.5, 200(ish)
Cruising area: Essex, Hampshire, Mediterranean
Join Date: Sep 2004
Location: Crayford, Kent.
Posts: 1,199
|
Quote:
Originally posted by OCRDA
No it is'nt but i won't argue about it !!
|
Blimey Bob, your going for it here mate ain't ya?
|
|
|
06-10-2005, 06:44 PM
|
#15
|
hello
Join Date: Mar 2004
Posts: 2,739
|
Quote:
Originally posted by OCRDA
No it is'nt but i won't argue about it !!
|
Could it be that on a big heavy hull blowout meerly cause's a loss of drive and steering where as on a small light hull it also cause's the back end to walk round a bit? I've read that on very light hulls it can cause a hard right turn. Back in the day I remember seeing an F1 cat in Bristol docks do a 90 degree turn straight into a wall whilst traveling at speed down a straight. I was only about 10 at the time and so had no idea of the cause but in more recent years I have often wondered if it could have been blowout?
|
|
|
06-10-2005, 06:47 PM
|
#16
|
Registered User
Country: uk
Location: brighton
Occupation: CABINET MAKER
Interests: SPEED BOATS,MOTO G.P
Boat name: MOTIVATION
Boat make: MARSHAN 21
Engines: AINT GOT ONE!!
Cruising area: sea
Join Date: Sep 2005
Location: brighton
Posts: 1,223
|
thanks for all your replies,not really sure on revs as the counters a bit shagged,as for how much throttle left i would say about just over half way at that speed,boat feels very stable and no signs of walking,bob,not sure i like the idea of it flying but me plums are slowly getting bigger!!!would like to try the lazer prop as you suggested last time.
thanks for help again,
jamie.
|
|
|
06-10-2005, 06:52 PM
|
#17
|
Senior Member
Country: UK
Location: Devon
Occupation: Garage Proprietor
Interests: PowerBoat Racing
Boat name: If Only
Boat make: Bernico F3 OCR, Bernico Prototype Inboard, and some Ribs
Engines: Yamaha Pro V 115
Cruising area: UK, France
Join Date: Jan 2005
Location: Devon
Posts: 3,095
|
On the big heavy boat, what you describe is more likely to be Cavitation rather than Blow Out . The F1 Cat you refer to more than likely just Hooked or suffered steering failure . I was also not very old at the time but do remember.
__________________
If Only
National Outboard Immersed Propeller Mono Record 103mph
|
|
|
06-10-2005, 06:55 PM
|
#18
|
Registered User
Country: uk
Location: brighton
Occupation: CABINET MAKER
Interests: SPEED BOATS,MOTO G.P
Boat name: MOTIVATION
Boat make: MARSHAN 21
Engines: AINT GOT ONE!!
Cruising area: sea
Join Date: Sep 2005
Location: brighton
Posts: 1,223
|
bob if your ever down brighton way let me know please
|
|
|
06-10-2005, 06:56 PM
|
#19
|
hello
Join Date: Mar 2004
Posts: 2,739
|
Quote:
Originally posted by OCRDA
The F1 Cat you refer to more than likely just Hooked or suffered steering failure . I was also not very old at the time but do remember.
|
Ok thanks!!!!
|
|
|
06-10-2005, 06:57 PM
|
#20
|
Senior Member
Country: UK
Location: Devon
Occupation: Garage Proprietor
Interests: PowerBoat Racing
Boat name: If Only
Boat make: Bernico F3 OCR, Bernico Prototype Inboard, and some Ribs
Engines: Yamaha Pro V 115
Cruising area: UK, France
Join Date: Jan 2005
Location: Devon
Posts: 3,095
|
Likewise if you find yourself in Devon !!
__________________
__________________
If Only
National Outboard Immersed Propeller Mono Record 103mph
|
|
|
|
|
Thread Tools |
|
Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
» Recent Threads |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|