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MANUKAU MODEL POWER BOAT CLUB Inc

 

Web Site:

HTTP://homepages.paradise.net.nz/nickbree/mmpbc/

Venue: Wattle Farm Rd Pond Manurewa

2nd & 4th Sunday of each month from about 10.30 am

 

President:        Malcolm Miller                         Editor   Chris Breen

                        93 Sykes Rd                                         12 Sunset Rd

                        Manurewa                                           Glenfield

                        Ph 268 2742                                          Ph 4445 482                  October 2002

 

HOT NEWS

Well, How Fast Are We Going?

Last month a few of us were down at the ponds testing our boats and with hardly any wind and fairly flat water. Merv decided to see how fast his Bud was going. With the GPS installed and racing around our racing normal course, Merv broke 100k barrier no less than 4 times with 2 different props and the fastest reading being 107 kph. Phil Leach had his 90 powered Cat out and did a few runs over 90kph and his fastest being 93.6kph.

These are great times which are as fast or faster than the NZ records set a few months ago down South on a surveyed course with long run ups. What you must remember though, is that times on the GPS are only the peak times and may have only been for a split second and there is also the accuracy factor of the GPS that has to be considered, but it does show that our boats are certainly moving. During another Day of testing, Malcolm had done some mods to his Miller and tried the GPS and did 101kph. Wow... Bring on the Speed Runs!!!

TECH NOTES

NACA air intake vents (by the Editor)

We will all have seen the air intake vents shaped much like the Concorde’s wing. What are the characteristics of this shape that make it so unique, and were did it come from? More particularly, what are the optimum dimensions?

History

When the first jets fighters took to the air, designers needed to solve the problem of the intakes sucking in foreign material including water and spent machine gun cartridges! The National Advisory Committee for Aeronautics (NACA) undertook research to find the best intake design that met two conditions:

Good separation of foreign objects from the air stream and,

To have no protruding scoops or bubbles. The intake had to be flush with the surface.

Testing of various shapes concluded that the V-shaped vent we now all recognise gave the best combination of low drag and maximum air volume.

Details

The diagram gives the key proportions. Standard ratio of length to width is 7:1 Floor is flat and the sides are vertical (but “S” curved). Ramp slope 7o and for the final opening, width to height ratio 4:1. Length can be shortened if necessary but do not shorten below ratio of 3:1 and do not reduce the final opening proportions.

The entrance lip at the rear of the duct should be a blunt airfoil leading edge shape (as indicated in the sketch above); however, the edge formed by the duct and the surface elsewhere should remain crisp. The shape of the “S” curve of the sides is important as it is this shape that creates the vortex that sucks the airflow down into the duct.

The following table gives the coordinates for laying out the planform of a "curved divergence" NACA flush inlet where X is the longitudinal distance along the duct, L is the total longitudinal length, Y is the width measured from the centerline of the duct, and W is the overall width of the duct.

X/L

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Y/W

.500

.497

.457

.382

.307

.233

.195

.157

.118

.080

.042

For convenience here is the plotted half shape.

The air flow is still not great as the vent is flush, so if you are supplying air for a carb make the final opening 2 or 3 times the throat area of your carb.

Tunnels as unlimited Hydros in 1/8th scale

The following Listbot discussion on RCboat.com raises some interesting possibilities for scale builders.

Mike_Neal

Does anyone have any information about a tunnel boat that was built (maybe in the 70's) that had 4 large outboards and was intended to run against unlimited hydros? It may have been called "The Arrow". There may also have been a second similar effort to design a competitive tunnel boat to run with the unlimiteds too. I believe one of the boats ran one race and then was retired.

Harry_M._Gatjens

The Arronow Unlimited ran in 1979. It was a tunnel boat but didn't have outboards. It had inboard auto engines and big "Arronow brand" outdrives on the back. Sort of like an inboard/outboard configuration. It qualified a few times but was never really too competitive.

I have several pictures. Look at this one and let me know if you need any more.

As for actual tunnel boats there was another boat called the Texmo that ran in 1984. It actually had outboards. It was less sucessful than the Arronow. I am afraid I don't have a picture on the web, but can find you one if you need it.

There was also a boat in 1986, The Arcadian.

This boat was a tunnel hull with all of it's engines enclosed underneath the deck. Very flat looking and odd with all the exhaust shooting straight up.

Not sure if this answers your question or not. Let me know if I can give you more help.

Harry_M._Gatjens

I found a photo of the Texmo.

Also I forgot to mention the Italian tunnel boat that came and raced in Houston at the World's Championship in 1983. It ran as "Louie's on the Lake" I am afraid I don't have any pictures of that one.

Randy Rapedius

OH NO Mike. Do I hear the ''wheels turning?'' Would be great to have something new in IMPBA District 1 Scale.

MIKE_SALEEBY

The Arcadian actually used six big block MERCURY outboard 2-stroke powerheads coupled to an outdrive. lets see, six .10 car motors with watercooled heads coupled to a single flex shaft. HMMMMM, interesting. this boat by itself would sound like a whole race.

Mike_Neal

From a scale perspective, does anyone have any idea what the specifications on these boats were (i.e., length and beam)?

Brian Schymik

Mike. Here are the numbers from the Master hull roster for the Texmo

8409 84 U-9 TEXMO 28 - 0 ft long

       11 - 0 wide          

         5 - 8 tunnel width       2 - 3 depth

This calculates out to

     41.00 - 43.00 inches long

       14.85 - 18.15 inches wide

         7.65 -9.35 inch tunnel width

Harry_M._Gatjens

I haven't found the other pictures that I should have of this boat, however I did dig out some more facts about it.

It was designed by famed tunnel boat driver and designer Bill Seebold and was owned by current owner of the unlimited hydroplane series, Gary Garbrecht.

Mike_Neal

I had always thought from a practical perspective that you would have to build the (scale)boat with one actual motor and one prop shaft. That suggests the ARONOW is the most likely boat to both meet scale rules and be easiest to build.

That leaves building a scratch tunnel boat and trying to place a .67 motor in it as an inboard -- duplicating the ARONOW. This would be a gamble, since you'd have to do a lot of guesswork on design, CG relative to engine, pipe, and fuel tank placement, while hoping that an inboard tunnel design could hang with the hydros.

I suppose it wouldn't take that much to build a wood-over-foam boat once you had a design drawn up -- and it would be cool to see something "different" running with the scale boats.

Randy Rapedius

Mike.Be sure to do your home work on this one. According to the back of the ''Thunder on the Water'' trading card the ARONOW had stern drives (not drive). This leads me to believe that there were more than 1 prop. Perhaps Rod's pictures will tell us for sure.

This is what is printed on the back of the trading card....

''Aronow, the first unlimited tunnel hull, was originally powered by two Cosworth DFX's with MercCruiser stern drives. It had good top end speed but not enough low end torque. The team switched to Keith Black Chryslers in 81. The Hemis accelerated better, but mechanical and handling problems continued to plague the project. In 83, re-powered with four outboards, the boat ran a consistent race in Houston and placed a surprising second. A Floridian later bought the wooden hull and allowed it to deteriorate in the rain.''

Owner: Don Aronow & Gary Garbrecht

Designer: Garbrecht-Seebold

Builder: Bill Seebold

Length: 30'-0''

Width: 11'-11''

Launched : 9-79

Crew Chief: Jerry Gilbreath

Mike_Neal

It sounds like all the tunnel boats that were fielded to run with unlimiteds had multiple drives. The only one I'm not sure of it the Arcadian, but it's a pretty funky looking design. While it's been interesting learning about the history of these boats, it looks like it's probably a bust from a scale project perspective.

Editor’s Note: I have pruned out a lot of dialogue regarding the number of propellers required or permitted under US scale hydro rules. Anyone planning to build needs to check our local rules

USA TRIP ??

The NZMPBA guys are canvassing interest in a trip to the Bill Muncie Memorial Competition in San Diego. This is held every September and combines full size hydro racing and scale model racing on the same week-end. Scale competitors also gain entry into the full size pits and other benefits. Probably in 2003, 2004 for a trip of 7 to 10 days. If anyone is interested contact Grant Binns direct 06 3551 625 or E-mail This email address is being protected from spambots. You need JavaScript enabled to view it.

Other Guys’ Boats

Skulduggery

Built by:Malcolm Miller

Painted by: Malcolm Miller

Hull: 55” Dumas KV Scarab molded by GRH Hobbies

Engine: OS .91 VRM

Pipe: Prather 10-15cc

Prop: Octura X460/3

Hardware: Octura Hum Dinger engine mount. Octura Strudder M with stainless strut blade

Radio: Futaba 3 channel wheel

Fuel: 1.7 liters 18% Castor 82% Methanol

Weight: 20 lb. (no fuel) (Editors’s note: with fuel a LOT heavier, that’s almost a milk bottle full !)

 

I built Skulduggery about three years ago, it has been powered by a variety of engines starting with an old Picco .80 through to the current OS .91 VRM that is powering the boat now. I am looking forward to an opportunity to put the boat through the speed traps and have a crack at the NZ record for C2 deep vee (81 Kph).

In testing with a GPS a top speed of 74 Kph has been recorded.

See you at the lake.

Racing on Sunday 8 September

Last weekend’s racing proved a mixed blessing. We had a good turn out and excellent racing but a couple of unfortunate mishaps left some damaged boats. Hydro 1/8th scale was first up with Miller High Life, Budweiser, Llumar, Winston Eagle and York competing. The first race was a cracker with all boats finishing and an unbelievable start. Heat two saw Llumar out with a broken piston but luckily no other engine damage. However heat three saw the worst accident of the day with a very close start but a few seconds away. Several boats entered the front straight at full throttle, Miller High Life bumped Winston Eagle and flipped. Budweiser, only a few boat lengths behind, had nowhere to go and no time to react and hit the stationery Miller High Life causing considerable damage to both boats. Damage is repairable but substantial. Budweiser was able to continue racing but sadly Miller High Life is out for a lengthy count.

Class I Sprint saw 10 boats including a new member Dean Harris with a petrol power mono of unusual design named Drago. Again the fastest boats often proved unable to finish with flips, spin-outs and buoy arguments. Glen scored top points in Blue Dealer followed by Chris in L&P and Jason in Coca Cola. L&P was a proving a bit cranky in the heats, starting fast but with speed dropping off as the race continued. Eventually (during the final Enduro races) we noted a lot of smoke emanating from all openings in the cowl. The speed problem proved to be nothing more than the boat interior filling with smoky exhaust and choking the carburettor. With the cowl off the boat was flying! A simple lesson, the engine MUST have clean fresh air. A leaky exhaust & poor ventilation can have a MAJOR effect - worth remembering!

Class II sprints saw only one heat with two boats. We then ran two 30 minute Enduros, each with one compulsory fuel stop. Again reliability rather than top speed was critical. Our newest member Dean took top points followed by Jason and Malcolm.

02/03 Club Points Standings (prev. total + 8 Sept race-day points)

Freq

Competitor

Hi Points

Boat Name

1/8 Scale Hydro Racing

   
       

40.83

Glenn Sayers

85+33

YORK

40.81

Merv Sowden

103+39

MISS BUDWEISER

29.925

Chris Breen

53+8

LLUMAR FILM

27.045

Malcolm Miller

69+20

MILLER HIGH LIFE U00

40.685

Terry Wilson

27

ULTRA BOLD & DASH

6

Jason Lester

+31

WINSTON EAGLE

Class I Sprint Racing

   

40.85

Malcolm Miller

93+33

SKULDUGGERY

40.71

Brett Harrison

96+36

BALLISTICS

29.925

Chris Breen

17+45

L & P

40.985

Adrian Milanesi

88+19

LAMBORGHINI

27.145

Graham Doggett

46

OHIO STEEL

40.83

Glen Sayers

46+46

BLUE DEALER

29.985

Wayne Lester

+25

 

27.175

Phillip Leach

+20

RED/YELLOW

40.79

Tony Belle

29+24

EXCITER

27.225

Bruce Burns

 

VICTORY

40.97

Jason Lester

14+40

COCA COLA

27.255

Brian Nesbit

 

PUSSY CAT

27.095

Peter Wright

25

OBSESSION

26.975

Dean Harris

+16

DRAGO

Class I Endurance

   

40.85

Malcolm Miller

44+8

SKULDUGGERY

40.71

Brett Harrison

44+5

BALLISTICS

29.925

Chris Breen

+7

L & P

40.985

Adrian Milanesi

17+6

LAMBORGHINI

27.145

Graham Doggett

29

OHIO STEEL

40.83

Glen Sayers

 

BLUE DEALER

29.985

Wayne Lester

   

27.175

Phillip Leach

+4

RED/YELLOW

40.79

Tony Belle

29+5

EXCITER

27.225

Bruce Burns

 

VICTORY

40.97

Jason Lester

+9

COCA COLA

27.255

Brian Nesbit

 

PUSSY CAT

26.975

Dean Harris

+10

DRAGO

Class II Sprint Racing

   

27.095

Peter Wright

20

OBSESSION

29.865

Glen Sayers

18

STEVES MODEL SHOP

29.825

Bruce Burns Red

28

RED DEVIL

29.825

Bruce Burns Ally

8

ALLY

29.985

Jason Lester Coca

+10

COCA COLA

29.985

Jason Lester Bud

29

BUD DRY

Class II Enduro Racing

   

27.095

Peter Wright

 

OBSESSION

29.865

Glen Sayers

 

STEVES MODEL SHOP

29.825

Bruce Burns

 

RED DEVIL

29.985

Jason Lester Coca

20

COCA COLA

29.985

Jason Lester Bud

10

BUD LIGHT

FOR SALE COLUMN

Red Devil

Bruce Burns is still looking for a buyer for “Red-Devil” (a 45 size Multi boat) Contact Bruce (09) 2662 662

Dumas Hot Shot

Steve Kent has a 7.5 K&B Dumas Hot Shot inc starter & radio gear for sale $650 ready to run Phone (09) 444 0270

 

I hope I have not omitted something that someone wanted included. It I have, tough, otherwise…

that’s all folks.

 

Next Club day is September 22nd

Next Race day is October 13th

 

 

Chris Breen – Editor

F:\My Documents\CHUFFS\mmpbc\oct2002\oct2002newsletter.doc


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HIGH PERFORMANCE MODELS is the factory-appointed distributor for CMB Motors Italia in New Zealand. We sell and race the full range of CMB engines plus the complete range of CMB Tuned Pipes, Spare Parts and Accessories. All engines are the latest versions direct from the factory.

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We are regularly adding new products to our range so please phone, fax or email Tony or Kim or if you are in the area please drop by for a cup of coffee and a chat.