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Message |
    
miro
Senior Member
Username: miro
Post Number: 631
Registered: 11-2001
| | Posted on Saturday, September 01, 2012 - 12:16 pm: | 
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I recently had the opportunity to visit with a boat restoration guy ( Tom Adams) in Port Carling.
He's working on a boat that was a racing hydro plane ( a BIG one).
The engine had come in from the restorer and I had Tom take a picture of me draped over it.
I'me not a small guy so you'll see the size of the engine. It's rated at about 3,000 hp at 2200 rpm. It has dual ignition, and a custom built gear drive / thrust arrangement to absorb all that push from the prop. The prop speed will be about 6,000 rpm.
My dispro engine is 3 HP just for comparison.
miro
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ernie
Senior Member
Username: ernie
Post Number: 1559
Registered: 01-2002
| | Posted on Saturday, September 01, 2012 - 12:59 pm: |
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Thats neat! |
raa
Advanced Member
Username: raa
Post Number: 50
Registered: 02-2007
| | Posted on Saturday, September 01, 2012 - 05:42 pm: |
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Its too big for your Dippy!
Dick |
rbprice
Senior Member
Username: rbprice
Post Number: 399
Registered: 11-2001
| | Posted on Sunday, September 02, 2012 - 10:39 am: |
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Did you really mean that the prop would be turning at 6,000 RPM Miro? It is hard enuf to keep a prop from cavitating in air at prop speeds over 2,500 let alone in water at 6,000. |
ldobbins
Senior Member
Username: ldobbins
Post Number: 95
Registered: 12-2002
| | Posted on Friday, September 07, 2012 - 01:21 pm: |
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6000 RPM and more and with only one blade in the water, hence the rooster tail. There is definitely some cool physics going on there that I do not fully understand but really LOVE!
And the sound...even compared to Merlin at 1650 CID or and Allison at 1710 CID, the Griffon at 2240 CID really demonstrates testosterone in a big way!
Cheers,
Lew |
rbprice
Senior Member
Username: rbprice
Post Number: 401
Registered: 11-2001
| | Posted on Friday, September 07, 2012 - 05:28 pm: |
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OK Lew - I just tried to do a search on very high speed single blade boat propellers and drew a blank. Could you provide a link that could help educate us lay persons?
Thanks
RBP |
ldobbins
Senior Member
Username: ldobbins
Post Number: 96
Registered: 12-2002
| | Posted on Friday, September 14, 2012 - 10:36 am: |
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Hi Bob,
Yep, strange number to get your head around. Piston boats used to use a 2 or 3 to 1 step up gear box for the unlimiteds and now the turbine boats are about a 2:1 reduction. Here is a reprint from an article on the theory. Link at the bottom:
The engine is (with the exception of one turbocharged Allison V-1710 V12 piston engine) a Lycoming T55-L-7 turboshaft engine rated at 2650 SHP, fitted in recent years with a speed output (N2) sensor and a fuel flow valve to try and equalize equipment and save on repairs. Although the boats have large exhaust pipes, these serve only that purpose and provide negligible residual thrust. The engine is actually installed backwards from helicopter use, with the drive coming off the front of the engine (as it�s installed) and going to a gearbox underneath which is connected to the long propeller shaft. The prop is a three-bladed, hand-crafted, steel unit which is incredibly small, about 14″ in diameter, and it spins at about 14,000 RPM. The fact that only half the prop is submerged is what causes the tall �roostertail� of water behind the boat at speed. When out of the water, the prop is usually covered, in part to protect anyone who might walk into its sharp edges, and in part to hide any secrets a team might have come up with! A well-heeled team usually has several slightly different props, to adjust for different courses and conditions.
http://www.progcovers.com/hydro/facts.html
Cheers,
Lew |
rbprice
Senior Member
Username: rbprice
Post Number: 403
Registered: 11-2001
| | Posted on Friday, September 14, 2012 - 11:39 am: |
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More WOWS Lew - thanks muchly for the info. The article did not talk about cavitation. Seems to me that a 14 in. diam. prop turning at 14,000 RPM would be cavitating really bad and if so, how does it develop enuf thrust and what keeps it from breaking up from the stress.? The yield strength of 17-4PH stainless is about 120-160 kpsi but I'll bet the stresses in the prop exceed that.
Crazy hobby.
Cheers
Bob |
ldobbins
Senior Member
Username: ldobbins
Post Number: 97
Registered: 12-2002
| | Posted on Friday, September 14, 2012 - 03:02 pm: |
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Hi Bob,
I think, read SWAG (Scientific Wild Ass Guess)that as the prop is actually half out of the water and only one blade at a time is beating the water into submission, the normal cavitation bubble of air does not exist. Sounds extremely inefficient to me. But then again, the purpose was to lift the boat out of the water and reduce the coefficient of drag of the wetted surfaces. Hence 3 point prop rider.
Now you have me curious to do some more digging too on the physics.
Cheers,
Lew |
rbprice
Senior Member
Username: rbprice
Post Number: 404
Registered: 11-2001
| | Posted on Friday, September 14, 2012 - 08:12 pm: |
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OK - the prop has only two blades not three as I supposed. And, as you point out, the theory is that if less than 5% ?? of the potential wetted surface of the hull is in contact with the water, then the thrust required to move the boat mass forward is dramatically reduced. So prop efficiency is not a major consideration. That said, it is obvious that the prop is doing a great deal of work: why have 2500 SHP if you don't need it?
And the need for a "turning fin" to keep the boat from wildly sliding sideways during turn says that there is very little of the boat in the water.
Why not just use an aircraft then none of the "boat" would be in the water? :o)
OH - would you plse translate the gobblygook numbers that you gave for the propeller?
RBP |
miro
Senior Member
Username: miro
Post Number: 633
Registered: 11-2001
| | Posted on Saturday, September 15, 2012 - 09:37 pm: |
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I will re-visit the boat shop next week to try and get pictures and / or more detail on the prop.
The boat was supposed to be water- ready this fall, so who knows, my next pictures might just be a big rooster tail.
miro |
miro
Senior Member
Username: miro
Post Number: 635
Registered: 11-2001
| | Posted on Sunday, October 28, 2012 - 05:41 pm: |
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I visited the boat shop again last week, trying to get info on the propeller.
They were in the midst of taking video shots of the boat builder being interviewed for the boat's story.
Afte rhte video creq departed, I asked Tom A ( the boat builder) about the prop.
His response was instructive - He said, Look - I rebuild the boats. How they are powered and what prop they use is so mired in opinions that I keep away from that subject.
I think it was ever thus. Props are a subject for lots of discussion around the campfire, cradling adult beverages and little or no hope of a clean definitive answer.
The boat will be in the water next spring. But in the meantime, I'll keep trying to get more on the prop.
miro |
bill_loveland
New member
Username: bill_loveland
Post Number: 2
Registered: 08-2009
| | Posted on Monday, October 29, 2012 - 03:54 pm: |
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Miro - Harold Wilson details the struggle to get a prop that wouldn't bend under the onslaught of the tremendous torque from that Griffon in "Boats Unlimited". My copy is hiding somewhere, but if IIRC, Rolls Royce spent most of one winter machining it out of a stainless steel forging. |
rbprice
Senior Member
Username: rbprice
Post Number: 409
Registered: 11-2001
| | Posted on Monday, October 29, 2012 - 05:48 pm: |
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Curiouser and curiouser said the Rabbit - or was it Alice? |
ldobbins
Senior Member
Username: ldobbins
Post Number: 105
Registered: 12-2002
| | Posted on Tuesday, October 30, 2012 - 12:44 pm: |
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I love the builder's take on the campfire and adult beverages.
Make mine a single malt please.
Cheers,
Lew |
Danimal
Visitor
| | Posted on Tuesday, September 16, 2014 - 02:04 am: |
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My grand dad Claude Victor"VIC" Brown built 3 unlimited hydro's, 2 in Port Stanley Ont. and one in St.Thomas Ont. The first one was built with a Merlin for Guy Lombardo, who hit a sand bar showing off, hence pushing the whip strut into the hull and also suffered severe rudder damage not to mention Guy's pride. The second also built in Pt. Stanley was named the MARGIE after his wife,Marge,my grandma,and it was used to run rum from Pt. Stanley to Cleveland and was powered by a Griffon. The third was the SILVER SPRAY also powered by a Griffon. This hydro meant business. My grand dad was a sheet metal worker and a man who could create anything out of anything and most often did, and it intimidated the hell out of a lot of people. Vic Leghorn and my grand dad "Vic" were the best of friends, they wrenched ROLLS together. Problem was no one else knew which Vic one was referring to. Vic Leg Horn was a proper by the book mechanic, my grand dad was a true HotRodder. He was playing around with EDM in the late 30's (commercial oil furnaces)and some how got a job at De Haviland London Ont. calibrating Rolls carb's. He made a fuel injection set-up for the SILVER SPRAY by making small passage ways along side of the intake valve in the valve guide shooting right at the back of the valve head.The int.valve timing operated the fuel on/ off. He hand made on a shaper a single ear super cavitating prop and internally balanced it from the hub. He made a dry sump 3.25:1 overdrive gear box and the engine ran 2950 rpm He scrapped the Rolls 2 stg impellers and made laminar discs to push cooler and ample cfm to about 26 psi. He did'nt like the carbs mounted before the SC. causes fuel /air separation. He used an off set"U" shaped skid fin to keep the boat planted on turns. He never got a chance to race the for the Gold Cup in 59, as his pilot Joe McCarthy (not Joe McManus) at the young age, April 20th 59 was killed in a auto accident and the boat sat and rotted on a trailer on Hamilton Rd.E London Ont. because few knew what it was much less how to run it.
Cheers the Danimal } |
bruce
Senior Member
Username: bruce
Post Number: 451
Registered: 07-2002
| | Posted on Tuesday, September 16, 2014 - 11:58 am: |
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WOW!!!! More please!! |
