MANUKAU MODEL POWER BOAT CLUB Inc
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
Ph 268 2742 Ph 4445 482 November 2003
November 9th is race day, which is this Sunday. Be early as setup is at 9am. We did not race last month due to the bad weather so racing is overdue for some of our Members. Also, expect some new boats and drivers. The dinghy will be at the ponds on Saturday for all those that need to tune up.
November 15th & 16th is the SUHA Meeting at New Plymouth. Most Members of our Club also belong to SUHA but only a few Members have entered. Your continuing support would be very much appreciated. If you are available to race on that weekend, please get your entries into Merv as soon as possible.
November 23rd is the “BURNS RUM RALLY” which is open to all boats and is raced on a handicap system. Last year we had some surprise winners and maybe this year it could be you!
Scale Hydros will also be racing.
The following is an edited discussion from the www.rcboat.com discussion board.
Drive Cable Drag
Had a very interesting phone conversation with a one of the sports Icon`s the other night. He tells me that the K&B has less cable drag than the Lawless. Also says that an S bend is better than shallow bend for drag. Can I get a second on these statements. Just don`t seem right.
That sounds like RG. I am currently redoing a gas cat with the s-bend. The theory, as explained to me, is that the s-bend forces two point contact between the drive cable and the tube it is in and that a single bend allows the cable to whip contacting the complete dia of the tube. At low rpms, such as hand turning the drive cable, the s-bend does have more drag, you can feel it. So I am anxious to get to the pond and test this theory. I agree, at first thought, it sounds wrong. But the more I thought about it, I thought it was worth a try. It would be interesting to hear from others who have tried this.
Concider the cable as being a bass guitar string. If you allow it to be free the entire length the resonant frequency is lower and is more apt to resonate and destroy the stuffing box and more.Because of the "S" bend, it raises the resonant frequency of the system and lessens the vibration by a great amount and therefore rides smoother.I proved this with a dremel and .130 cable to myself a few times messing around.This is more pronounced on smaller cables like .130 and .150 which I run on the .21 boats I have
When I started doing my own boats a while back I asked Gary Preusse why he used an S bend and he said he got it from Ed Hughey. Ed said with his quiet electric boats you can hear the difference - the S bend runs much quieter therefore smoother. Been running that way about 7 years now and have very little cable wear and have never broken one.
I actually built a little electric powered dyno for checking parasitic drag on oil seals in the Hi-rpm billet motors David Hall and I built.
Basically all it is a 12 volt 540 electric motor with a ammeter [Radio Shack VOM with amps capability ]in series in the leads from the battery.I just measure the amp draw with no load on the motor and then measure the amperage with a load on the motor. That difference in amperage can be calculated into a very close estimated HP loss. Man was this little test fixture an eye opener. You wouldn't believe how much drag is caused by castor oil in the oil seal of a Nova Rossi or by a full contact drum rotor. One of the ways David and I were able to get 45,000+ RPM out of the stock timed NR piston and sleeved motor we built was by eliminating as much oil seal drag in the motor as possible and still maintain crankcase compression. Volts X amps=watts and when you know 745.7 watts=1 HP it is real easy to figure what your HP loses are. I know,I know there will be some losses in the wire size and blah,blah,blah but I was looking for a relative figure to evaluate a design or system I graduated from motor oil seals to drum rotors to disc rotors to relieved sleeve surfaces and then on to drive lines and struts.
Chew on these facts for awhile;
- It takes 1/2 the amount of horsepower to drive a "s" bend driveline as it does to drive a gentle bend driveline. If you want to reduce that by another 70% install a perfectly aligned hard shaft and learn how to set it up with props and hull design.
- There is no more hp loss in a 1/4 drive system than there is in a 3/16" driveline or a .150" drive line of equal length. [I never tested an 1/8" shaft.]
- There is less drag in a K&B lower unit than in Lawless lower unit.
- There is no more drag in a 7.5 K&B lower unit than there is in a 3.5 K&B lower unit.
- It takes less than 1/2 the hp to drive a drum rotor that has been relief ground on the back if the intake window as it does to drive a full contact drum with the drum housing bushing.I also relieved the drum bushing with the same results.
To all you guys that have the burning passion for model boating and racing of the same[which I have been slowly losing for the past few years ] there are no speed "secrets".Most performance improvements are the result of just a little science and a ton of common sense and paying attention to detail when you apply it. A few people have seen this test device and have gone away shaking their heads just like I did the first time I spent a weekend with it. You would be surprised how much "free" performance there is out there if you are just willing to look for it.
Very interesting Rod! With the drive cables, were you applying end loads to them (to simulate the effects of prop thrust)?
I did it both ways.Load and no load. Results were the same.
Neat! Any idea the difference between driving a drum rotor and a disk valve?
A stock disc and relieved drum were very close to the same. A full contact drum was about twice the drag as the forementioned assemblies.
And Another VERY interesting matter
Did you know that a glow engine is a semi-diesel? Hot engines have been known to start without the glow plug hooked up. To best understand the difference between glow and diesel, it’s best to understand the basic difference between the combustion process in each system.
The main ingredient in glow fuel is methanol, which ignites at a rather high temperature. The compression of the engine plays a part in raising the temperature, but not high enough to ignite it under normal conditions. The hot platinum element in the glow plug causes the mixture to ignite. The nitromethane in the fuel liberates oxygen to help alcohol burn faster. The faster the alcohol burns, the more you can burn to produce more power.
The conductive heat of the glow plug, to the head, together with the heat loss of the combustion serves to produce lots of waste heat at the top of the glow engine. This heat must be removed effectively to allow normal operation of the engine. Running your glow engine slightly rich allows the fuel itself to carry off much of this waste heat. This of course reduces the power somewhat, a small price to pay for the benefits gained in extended engine life; it is, however, rather wasteful.
Exhaust back pressure also plays a part in heat balance, and thus the performance of your engine. Just as the carburetor restricts the inlet air and fuel, thus slowing your engine down, the muffler restricts the outlet air (exhaust) and also slows your engine down. The hot exhaust is rapidly expanding as it leaves the engine and enters the muffler. The muffler restricts expansion somewhat, causing a less than free flow of hot exhaust from the engine. This in turn causes the engine temperature to rise, since it can no longer freely expel its waste heat (exhaust). Mufflers, as you know, provide a measure of sound reduction and a ready source of pressure for aiding fuel flow to the engine. A very important point to remember based on these facts is that in glow operation, peak power can never be safely or reliably achieved in actual use due to the fine line between just right, and too lean.
The main ingredient in diesel fuel is kerosene, which ignites at a significantly lower temperature than alcohol. To raise the temperature of this mixture to its ignition point by compression alone would be impractical in a model diesel engine, since a means to create proper atomization cannot be achieved by stock carburetion at this time. To start the combustion of the kerosene, ether is employed. The lower ignition temperature of this combination of ingredients allows combustion to be achieved at a practical compression ratio. Ether and kerosene can be ignited by the heat increase brought about by compression alone; thus the fuel is burned faster, more completely, producing less waste heat, and thus more energy.
A diesel is a heat machine; unlike its glow cousin, the diesel can benefit from some heat buildup. The exhaust temperature leaving a diesel is much lower. This is due to the fact that less fuel is being burned more efficiently to produce more power than in a glow engine. Couple this with a more than generous muffler, designed for glow operation, and you have a condition where there is less back-pressure and thus engine operating temperatures is less than optimum for all conditions. This allows you to extend your exhaust away from your craft without fear of creating undo power loss, a desirable feature when it comes to cleanup time. Extending the exhaust also gives another side benefit, that of further reducing engine noise. Many modelers using diesel conversions have routed engine exhaust through a plastic tube through the entire length of the fuselage and out the tail, and by doing so have achieved a further degree of silencing impossible with glow operation.
(Editor’s Note: I am an old codger and remember getting covered in black crap from model diesels, and sore fingers !)
Yet another interesting bit of info (validity NOT guaranteed)
1)The angle of attack of the sponson ride surface should be at least 6 degrees.
2) The true sponson depth should be 1 inch.
3) The rear window should be 2 3/4 inches.
4) The depth of the bottom of the prop shaft at the transom should be equal to the true sponson depth.
5) The rudder should be mounted on the right side of the transom.
6) The prop weight of a fully loaded boat should be 3 ounces.
7) The weight of the boat should be offset to the left by 10%.
8) The pivot point of the rudder should be behind the trailing edge of the propeller.
9) The tunnel width multiplied by 2.18 will give the ideal distance from the back of the sponson to the leading edge of the propeller.
10) At the exact moment you think you have it all figured out, you will discover that you are wrong.
And yet Another !
Anneal your plug (heat the coil 2 or three times for 5 seconds) then carefully pull a turn of the coil slightly proud of the plug. Instant extra horsepower I am told ...
Believe it or not Department
You may not believe it, but this is a STEAM ENGINE powered model plane!
Dean, If you don’t believe in steam planes maybe you would believe in one of the engines on the next page !
Racing at the “Thunder Down Under” Regional Challenge Labour Weekend 25 – 27 October (thanks to Malcolm for the write-up)
Representing our region at this inaugural event were Tony Kockott, Warwick Kockott, Tony Belle, Rob Binnie and Malcolm Miller. The event was moved to Lake Whakamaru 20 minutes out of Tokoroa due to a sudden weed growth making racing impossible at Lake Moana Nui in Tokoroa as originally scheduled.
Morning greeted us with challenging conditions with a stiff breeze blowing down the lake causing a reasonable chop on the back straight with strong gusts making for even more challenging racing. The first event run was A mono matrix with Tony and Warwick Kockott competing in this class, Warwick placed 3rd overall and Tony placed 4th overall. The next event run was C Scale Hydro with Malcolm being the only Auckland competitor placing 4th overall in very choppy conditions, next to run was B tunnel matrix with Tony Belle having mixed results. After the fantastic lunch made by Scott’s better half, Warwick Kockott competed in B mono matrix placing 5th overall, the next event was to be C hydro matrix but the water conditions were not favourable so it was decided to postpone until Sunday and run P1 and P2 mono matrix instead.
Racing over for the day we went to the Tokoroa Cosmopolitan Club for a great meal and get together.
A cool fine morning with a moderate breeze and a mild chop, the first event was C hydro matrix held over from Saturday with Rob Binnie having mixed results, next up was C2 tunnel matrix with Tony Belle running his brand new boat placing 3rd overall and Rob Binnie placing 1st overall. After another wonderful lunch made by Scott’s better half , the water conditions improved for the next event C2 mono matrix with Tony Kockott having problems with his new engine and Malcolm Miller placing 1st overall. Next on the program, hydro King of The Lake had Rob Binnie placing 5th overall.
Racing completed for the day we went to Scott and Mel’s for a BBQ and social get together, man it was cold on Sunday night.
After the cold night we were met by a cold fine morning with water like glass, first up was mono King of The Lake with Tony Kockott placing 3rd with his A mono, Malcolm Miller placing 5th with his C2 mono and Warwick Kockott placing 6th with his A mono, for the last race for the weekend, tunnel King of The Lake Tony Belle placed 3rd with his C2 tunnel.
The trophy for the THUNDER DOWN UNDER regional challenge donated by the Annihilator Racing Team made by Gordon Homewood, is a very impressive stainless steel racing propeller and was awarded to the South Waikato/ Bay of Plenty team of Matt Lee, Steve Trott and Scott Pickering.
South Waikato/ Bay Of Plenty 1st 740 points
Wellington 2nd 480 points
Auckland 3rd 430 points
A great weekend was had by all competitors thanks to all the hard work by Scott Pickering and Steve Trott in organising and running the event and the social get together on Saturday and Sunday nights, and a special thanks to Scott’s better half Mel for the fantastic lunch both Saturday and Sunday.
To all those boaties who were unable to attend this year, you missed a great event and I highly recommend you plan for it next year.
Club Hi- Points Standings (after 3 race meets)
Editor’s note: No racing since last race day so no changes to these points standings.
The Last Word
Trap for young players,and old buggers who should know better !
Many of you have watched with some amusement as the normally bulletproof reliable Zenoah in Ohio Steel has recently refused to cooperate.
I have been lucky to complete one lap, let alone finish a race !
The engine would start and run quite happily on the bank but was very reluctant to exchange the warm dry dock for the icy cold water.
The engine and carb were dismantled and rebuilt to correct any air leaks - no improvement.
The radio gear was swapped from another boat - still no improvement.
The ignition system was swapped from another engine - still no improvement.
The exhaust O rings were replaced in case water was leaking into the engine - still no bloody improvement.
In desperation I even replaced the spark plug, I mean to say it was only 2 years old.
Even though the fuel system had been flushed and the line filter replaced I decided to remove and inspect the fuel tank
( probably because it was the only thing that had not been checked).
Well , I'm ashamed to confess that the filtered clunk pickup had all kinds of unidentified objects coating it ( I think some of them were happily breeding there).This was obviously restricting the fuel flow under load.
Talk about a basic problem with a simple solution.
Yeah, yeah, I know, I should have checked the fuel supply more thoroughly sooner.
But in my defence, when the primer bulb on top of the carb was pumped the fuel flowed fine. I guess in hind sight the pump inside the walbro carb is not as strong as my thumb on the bulb.
So there you are, never forget the basic requirements of a 2 stroke engine -
3) Spark ( or red hot glowplug for those of you that still insist on using methanol engines).
Ohio Steel is now going better than ever following the unplanned , but probably overdue rebuild , and is ready to do battle with all the cats that have enjoyed recent success due to the lack of real competition !
Watch out for more big rooster tails and deep ditches on the lake.
You have been warned.
That’s all for this month folks.
Chris Breen – Editor