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Prop for a Phantom 25 w/PM 300 SVS

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Old 01-25-2004, 03:44 PM
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Default Prop for a Phantom 25 w/PM 300 SVS

Hi!

Got an email today from Steve Baker, the oiginal constructor of Phantom. I have a Phantom 25 from 1985 with a Promax 300 SVS. It runs 76-78 mph at wot spinning a blueprinted Tempest 26 at 6.100 rpms. The boat weight is approx. 1.200 kilos incl. engine.

Steve had this to say about the hull and setback / props:

"As far as I can remember your 25 was fairly heavily built and as a result the calm-water max. speed will obviously be lower than for a lighter boat with the same power. ( For similar 'conventional' hull-forms the speed is directly proportional to the square-root of the power/weight )

There is a further disadvantage (max speed, calm water) with heavier hulls because the centre of gravity of the rig will be further forward than in a lighter, but otherwise identical,hull.

It is my opinion that mounting the motor on a set-back bracket, although moving the c.g. of the rig aft, does not always result in an increase in the top speed. My reasoning being that because the motor needs to run higher when moved aft compared to when mounted on the transom ( in order to run at the same height relative to the water ) then the amount of leverage available to lift the bows of the boat is reduced. There is a further complication in that if there is significant lift generated by the propeller, then this will also make the hull run flatter. Please note that this is my personal reasoning and I have never conducted exhaustive trials to determine the effect of set-back brackets on my range of hulls. I cannot give recommendatons based on actual experience."

I have experimented with setback, and it seem to that 7,5 inches is a good choice. If I use 5,5 inches (CMC powerlift only), the boat runs flatter and wetter. However, the prop is a blueprinted and balanced 3 blade Tempest which gives added bowlift. It may cause the transom to ”sit low” and drag water.

Maybe I should try fx. Hydromotive 3 or 4 blade that gives a mild bowlift and transomlift. Some have advised me to try elevated transom height (as much as possible without loosing water) and use props that do not give much bowlift, but some transomlift. It will translate to running high and flat without dragging the transom behind me. What do you think?

Cheeers!

Toffen
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Old 01-27-2004, 09:41 PM
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Toffen,

Who is Steve Baker, (the original constructor of Phantom?)
Will Smith is the Phantom builder. Am I missing something here?
Thanks.

GB
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Old 01-28-2004, 07:01 AM
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Yes you are,
Steve Baker founded 'Phantom boats UK' in 1969, he both raced, and built smallish race/pleasure boats (16-31') with a great deal of success in UK/European racing, he retired from boatbuilding in 2002.
(My Phantom 28 was the last 28 he built)

Phantom raceboats USA are a totaly seperate organization.

On page 351 of 'Searace' there is a pic of raceboat "Warlord 031", a 31' UIM class II boat, built in 1981 by Steve.
His boats are very well respected in Europe for their ability and build quality.

Pic from Searace:
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Prop for a Phantom 25 w/PM 300 SVS-warlord.jpg  

Last edited by leviathan; 01-28-2004 at 09:29 AM.
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Old 01-28-2004, 07:05 AM
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A better pic of my 28:
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Prop for a Phantom 25 w/PM 300 SVS-dscf00006.jpg  
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Old 01-28-2004, 08:19 AM
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Thanks for the info,

Very nice looking boat! Can you give me Steve Baker's E-mail address and Website if he has one?
Will asked me for this info, as he would like to communicate with him.
Regards,

GB

Last edited by georges; 01-28-2004 at 08:21 AM.
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Old 01-28-2004, 09:24 AM
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Georges,
Steve retired in 2002 and doesn't really get involved now, there is a website at www.phantomboats.co.uk but it's just a contact page really.
I spoke with him (Steve B) this morning re: this thread, and he said a boat was built for a customer in the U.S. back in the 80's, he doesn't remember many details, but thinks it was for racing, it was a 25' like Toffen's.

Here's a pic of Toffens boat.

And Here's a link to the gallery on my website in the UK of the build of my 28
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Prop for a Phantom 25 w/PM 300 SVS-toffen-brygga-.jpg  

Last edited by leviathan; 01-28-2004 at 09:32 AM.
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