LA 46 Fuel mileage

[Chris Belcher]

I have 2 LA 46s...both set up exactly the same: 272 venturi, ST needle, 1 head shim, metal backplate(FP40), Thunder bolt RC long plug, old FP 40 muffler, no re-works to p/l or crank, XOAR 11-4 prop.
The one is in an ARC Cardinal and does the pattern on 3-3/4 oz of 5% 11/11 GMA fuel with several (10) laps to spare, tank is 4 oz Brodak ATF, launch at 10,100-10,300, wet 2 with a little break, 63 ft eye to eye lines, 5.2 laps....flies wonderfully.

The other is going in an ARF Nobler which has a 4 oz Brodak ATF tank already installed...exact same tank as in the Cardinal.
Here is my question: what are the chances the one in the Nobler will have the same mileage?
Had a (later run)Brodak 40 with 280 (down form the 300 that came in it) venturi and could not get past the vert 8s. Thought what the hell...if my card does pattern on 3-3/4 ozs I'll just put the other in the Nobler and stop worrying about losing the model to fuel shortage. I liked the way the brodak did the old 4-2 but just can't get the mileage and the Brodak seems a little low on power. was having to use 59' lines. This is NOT a Brodak 40 bash as it is a sweet motor but just can't get the mileage down. It is WELL broken in...lots of flights and proper up front break in procedures were followed. the mileage did improve with age but has now leveled off.
Anyway...can i expect the same(close) mileage out of both LA46s? Please don't suggest putting a bigger tank in the Nobler. the 4 oz ATF fits perfectly and I DON'T like plastic tanks....another subject...

[Motorman]

I predict the mileage will be exactly the same.

MM

[Phil Krankowski]

I predict the mileage will be exactly the same.

MM

I agree, well, the nobler may go a lap or two more because it is 500 square inches instead of the cardinals 579 square inches.
Phil

[Chris Belcher]

Thanks guys....I guess my real question was what difference does weight, wing area, etc...make in fuel mileage. Kinda went the long way around the barn..
BTW...didn't know the Brodak 40 and LA 46 have exact same mounting bolt dims....easy exchange...just had to relieve the beares a little...

[Steve Helmick]

I'll go out on the limb and suggest that the mileage will be better on the Noblur, because the wing is much thinner. The problem will come if you use the same prop and launch at the same rpm (too fast), or less rpm by richening the mixture. I think you'll probably need to mess with the setup on the Nobler. General rule is that the smaller prop and smaller model load the engine less and fuel mileage improves.

Always remember that you can put a bit of Coleman fuel into your glow fuel to get enough laps in. Two to four ounces Coleman fuel per gallon of glow fuel will make a significant difference. Try .25 oz to .50 oz per pint for a few preliminary test flights.  Steve

[Chris Belcher]

REALLY!!! Coleman fuel...as in what I used to put in my pump up lantern? How do you guys learn all of this incredible s#$@?? So let me make sure I got this right. I add coleman fuel to my gallon and my mileage goes up? Is there power loss..burnt plugs...melts monokote??

[Steve Helmick]

REALLY!!! Coleman fuel...as in what I used to put in my pump up lantern? How do you guys learn all of this incredible s#$@?? So let me make sure I got this right. I add coleman fuel to my gallon and my mileage goes up? Is there power loss..burnt plugs...melts monokote??

1) Really!!! 2) Yup! 3) Pay attention to our elders! 4) Yes. 5) No problems you'll notice. But it will tend to start better, so be careful with that, if it's a problem for you.

Dave Royer posted this years ago, and said it was on the Merco .49/.61 instructions. Lots of furrin injins have fuel formulae in the instructions. Bob Emmett told him that 4 oz./gallon was the maximum. Dave says he runs it all the time. We sometimes have problems when the barometric pressure gets up around 31 inches of mercury and the temps 40*F. or below. One time, at the Fall Follies Stunt event in Salem OR, the density altitude was more than 1,000' below sea level, even tho the altitude is 210'. Fuel economy was a problem. Electrons tended to run low also!   Steve

PS: I recalled that I had gotten a copy of the Merco instructions from some kind soul, so could post them. Look in the RH column under "Recommended Fuels".

[Chris Belcher]

Interesting finds...I did get to try the same set up scenario in my Nobler this weekend and WOW!!! The nobler came to life. It was good on the Brodak 40 but the LA made it sing. Much more line tension everywhere and able to go to 63' lines with a 5.1 second lap. Fuel mileage was actually less though....hmmmm. The Cardinal does the pattern plus 12 laps on 3 3/4 ozs....the Nobler does the pattern and 6 laps on 4 ozs....interesting. And this is switching the exact same prop and muffler between the two planes to take out those variables...they're easy to switch...everything else is the same but only in size...like venturi, needle valve etc...
Now the Nobler flies great in the wind too...wonder if ol' George was right when he said noblers fdon't fly right until they're in the low 40 oz range...cuz mine did gain some weight with the LA and 1 oz tail weight to get the CG back...

[Steve Helmick]

Were you using the same line size and length and launching at the same rpm? Beyond that, there's no bets that two .46LA's will get the same run time on the same plane.  Steve

[Chris Belcher]

Yep..same set of lines...same launch...engine ran exactly the same as the other...wet two with just a little break into strong 2 at the tops. I'm happy now cuz the Nobler will do the pattern now with a few laps to spare...wouldn't with the Brodak 40. Both of the LAs have about the same run hours on them, they've both been in other planes. Very close to the same performance. And I do not mean this to be a Brodak 40 bash for readers...that is one sweet running motor. And now i found out that when I was told by Pat I think it was..or Jan..at Brodak that when I ordered the motor it was the last one. I ordered and she called and said it was out of stock. Then called back about 15 mins later and sounded REALLY excited and said "you got the last brodak 40" I thought she meant out of that shipment or something..but I think she meant the last one...like ever...I guess until they do a nother run...

[Balsa Butcher]

Just out of curiosity (and for comparison's sake) what RPM did you run your B-40 at with what prop? 

[Chris Belcher]

I used a T/T cyclone 11 x 4.5 and launched at 9100-9200 (no extra head shims) 5% 11/11 fuel. Originally had the stock .305 (i believe) venturi but I switched to .280 to get better mileage...didn't change a thing...mileage was actually worse!

[Balsa Butcher]

Just for grins, try an APC 10.5x4.5 prop. Launch at 10,400-10,600 rpm. Engine will hold that RPM in a solid 4 cycle and may get better gas mileage. I and another local stunt flier have tried about every combination of prop and fuel w/B-40s and find they do well running faster in a 4 cycle. Have found the TT prop loads them down too much. When broken in, (mileage improves with age) 4 ounces should do it but I still stay with 4.5 ounce tanks on B-40 planes...prefer 5 ounces for LA-46 and Aero Tigers but that's for another post. 

[Chris Belcher]

Well...i've put the B40 back in the box waiting for a different plane. I tried every prop in my bag, including the APC 10.5x 4.5 and I could never get that many RPMS... And couldn't get the pattern in on 4 ozs. The LA46 made the plane come to life and on 3 3/4 ozs.

[Steve Helmick]

It takes a good B.40 with the .305" venturi and big outlet muffler and 10% nitro to swing the 11x4.5 TT prop. Don't see many of them around these parts, anymore.  Steve

[Chris Belcher]

Yeah..that's true...my struggle the whole time was not with the motor...it was with the tank size. I tried putting a 4.5 oz ATF and bending the tubes but that didn't work out so well. And I have tried plastic tanks...a 6 oz sully RST will drop right in the tank compartment (with a little push) on the arf nobler..i did it..the rigid one...BUT the adjustable uniflow tube for tank height always migrates back to where it wants to live. i would run the uni tube out the side of the cowl and cut a travel slot so I could just grab it and raise or lower. Would work fine for couple of flights and then work its way back to its original location. The B40 ran really well...and responded to different set ups..on the TT 11 x 4.5 I had it breaking just perfectly...right up to the clover! And I did not know the bolt patterns for B40 and LA46 were the same. That helped in the switch over. I'm sure there is a chart out there of drop ins..I have not seen it but does anyone know where this might be?

[Brett Buck]

Yeah..that's true...my struggle the whole time was not with the motor...it was with the tank size. I tried putting a 4.5 oz ATF and bending the tubes but that didn't work out so well.

    I am not sure what you mean about an "ATF" tank. If you only have 4"  long by 2" wide, make it 1 1/4" deep. You should never compromise the engine because of fuel, unless you have a glued-in tank, which you should also never have.
    Brett

[Bootlegger]

 I remember that YEARS ago some one in the Dallas Texas used Amaco white gas added to glow fuel and got better mileage out of their engines with small fuel tanks.

  Is Coleman fuel about the same as white gas?

[Steve Helmick]

About as close as we can get these days. Unleaded Regular is ok, I think, but you'd really want the good stuff, without the ethanol. We can get it here, typically at Conoco stations, but not always predictable. There is a website that lists all the alcohol free gas sources, nationwide.  Steve

[Steve Helmick]

Since I was asked (awhile back), here's the link to finding ethanol free gasoline in the USA. Your MPG will go up, of course, and the price should actually be lower. Don't be shocked if the gas station you're headed to is out of biz, changed brands, or no longer has ethanol free gas. I'm sure there are "pressures" to knuckle under from the EPA and other branches of goobermint.  Steve

http://www.pure-gas.org/

[Phil Krankowski]

Since I was asked (awhile back), here's the link to finding ethanol free gasoline in the USA. Your MPG will go up, of course, and the price should actually be lower. Don't be shocked if the gas station you're headed to is out of biz, changed brands, or no longer has ethanol free gas. I'm sure there are "pressures" to knuckle under from the EPA and other branches of goobermint.  Steve

http://www.pure-gas.org/

I notice most of the Ohio listings are marinas and boat launches.  Ethanol is more a problem than a help.

If a small quantity is desired Trufuel ( Trufuel50.com ) is available in quarts, with or without oil, at most big boxes.

Phil

[Steve Helmick]

That's because ethanol is death to older outboard fuel hoses, and especially 2-cycles die young due to fuel starvation at high throttle settings. I think I'd still use Coleman fuel for spiking glowfuel, but the TruFuel site is interesting and great for somebody with a small 2-cycle landscaping tool to fuel up. My fuel for the blower is way too old to even consider using.  Thanks!  Steve