Author Topic: LA .46 (Read 6098 times)

Stephen · « **on:** October 12, 2014, 06:23:27 PM »

What size fuel tank should I use for my LA .46? Also I'm wanting to replace the rear needle with ST or similar where can I order one of these from?

Thanks for the help !!!

Jim Roselle · « **Reply #1 on:** October 12, 2014, 06:31:01 PM »

I have an LA.46 on my twister with a six ounce tank. I timed it today and was getting six minute fifteen second runs on 5oz of fuel.

Jim

Ron Cribbs · « **Reply #2 on:** October 12, 2014, 06:40:21 PM »

Wow!

I thought it would be more economical Jim. 4oz lasts almost 10 min on my Fox .40.

Probably an apples to oranges comparison though. I guess a 6 oz tank is what is needed for a full 8 mins.

What size venturi are you using?

Ron

Robertc · « **Reply #3 on:** October 12, 2014, 07:08:31 PM »

I run about 4.5 oz for about a six minute flight.

Tom Luciano · « **Reply #4 on:** October 12, 2014, 07:11:44 PM »

Ron,
I started learning to fly the pattern last year with a twister la .46, stock muffler, la .25 venturi with 4oz. of fuel. It would actually burb on the clover. This year I moved to a Vector and started with the same combo. I since went to a tongue muffler, .46 venturi, & Randy Smith needle. I now have a very nice consistent running engine with 1 flip starts. I seldom touch the needle and if I do it's within a quarter turn. Fuel consumption is 5.5oz. for about 6.5 minutes. I love the way the engine runs

10% nitro 22% oil

Tom

Garf · « **Reply #5 on:** October 12, 2014, 07:35:30 PM »

I have an LA 46 on a profile model with a tower 40 muffler using 3 3/4 oz for a pattern turning a 12-4 XOAR prop.

Jim Svitko · « **Reply #6 on:** October 12, 2014, 07:38:37 PM »

I need 3.75 to 4 ounces of 5/22 fuel. Randy Smith needle assembly and I enlarged the venturi to 0.300 since the spray bar is larger in diameter than the stock OS item. Four ounces is more than enough for the pattern with about 30 seconds to one minute of run time after the clover.

Mark Scarborough · « **Reply #7 on:** October 12, 2014, 08:06:11 PM »

Quote from: Stephen on October 12, 2014, 06:23:27 PM

What size fuel tank should I use for my LA .46? Also I'm wanting to replace the rear needle with ST or similar where can I order one of these from?

Thanks for the help !!!

do yourself a HUGE favor and read through this thread,, there are a few ways to set up an LA,,, of course I and my local guys have our favorite setup,, ( its listed),, there are others,, I was using about 4 to 4.5 ounces for the pattern,, ( not 8 minutes,, more like a little over 6 including starting time),,
10% 22% ( 50 50 castor and synth oil),, 9800 rpm,, .272 venturi and a Randy needle,,

http://stunthanger.com/smf/index.php/topic,21156.0.html

Jim Roselle · « **Reply #8 on:** October 12, 2014, 08:59:10 PM »

Quote from: Ron Cribbs on October 12, 2014, 06:40:21 PM

Wow!

I thought it would be more economical Jim. 4oz lasts almost 10 min on my Fox .40.

Probably an apples to oranges comparison though. I guess a 6 oz tank is what is needed for a full 8 mins.

What size venturi are you using?

Ron

Stock venturi, uniflow on muffler pressure, smooth consistent runs no matter what maneuver I put it through. That being said I have yet to wrap my mind around the cloverleaf.

Jim

Dennis Moritz · « **Reply #9 on:** October 12, 2014, 11:45:37 PM »

Fuel consumptions depends on fuel, venturi size (or more accurately intake area, fatter needle valve chokes area, same as down sizing venturi) drag and weight of plane, prop, needle setting, rpm. 5% nitro gives noticeably better mileage than 10% nitro. A small intake venturi (.265) better mileage than larger (.283). In between venturi sizes are a similar factor. The Twister mentioned above must be running sloppy rich. I've run LA46s like that on light planes like a Twister. Neat run. Just a bit of a break at the top of the figures. Very controllable. I have a Tanager that consumed every bit of 6 ounces, 5%, when run like that. Cardinals and the like need an engine to generate more power. Big Venturi, engine set to snarl. Much faster 4 stroke breaking pretty hard. I'd hang a six ounce tank on a plane like that. Pull fuel out if I need to. Vectors work well with an LA46, try to get a 5 ounce tank in there. Possible to fly with as little as four ounces with a small venturi and a lean setting. I've done it. But like a bigger tank and a richer needle.

John Stiles · « **Reply #10 on:** October 13, 2014, 01:42:30 AM »

My LA .46 has the R/C carb; throttle tied back, I'm wanting to get the venturi setup, just haven't found one I like yet. I'm wondering now if the tank I'm using will be sufficient. It's the metal 3 0z. Will the carb use more(?) or less fuel than a venturi sys.?

Perry Rose · « **Reply #11 on:** October 13, 2014, 04:43:17 AM »

The carb. venturi diameter is .231 with very little in the way of obstructions so the open area is more than a .282 venturi with a .156 spraybar. So at WOT the carb will deliver more fuel.

john e. holliday · « **Reply #12 on:** October 13, 2014, 09:29:16 AM »

Hey guys, contact Jim Lee at Lee's Machine Shop here in the Vendors Corner. He has various sizes for the LA engines. I have several I have been trying as it seems each plane needs a different set up for getting the power right for a pattern. In fact he has venturies for most engines.

Stephen · « **Reply #13 on:** October 13, 2014, 11:35:52 AM »

Thanks for all the help!!!!

Chris Belcher · « **Reply #14 on:** October 13, 2014, 03:16:55 PM »

I have a LA46 with 272 venturi and ST needle valve, no head shims and run 5% 11/11 fuel. 3-3/4 ozs does the pattern

Geoff Goodworth · « **Reply #15 on:** October 13, 2014, 04:37:46 PM »

Stephen, use the OS factory needle, part number 22311000, Tower stock number LXCR49. It's a straight bolt in whereas you need to drill out the venturi and the crankcase to fit the ST-style spraybar.

Using 22% oil, no nitro and the APC 12.25 x 3.75, I was getting time to fly the full pattern from a 4oz Brodak tank on a 59oz model.

I should add that my engine setup was the OS NVA and the stock (7.1mm ID) venturi.

Tim Wescott · « **Reply #16 on:** October 13, 2014, 07:36:53 PM »

LA 46, venturi adjusted with bits of pantyhose until I like the run, 11-4.5 TT prop, 10% nitro 11/11 oil VP fuel doctored up with 2 ounces of Colman lantern fuel per gallon.

4 ounces in a 4 ounce tank gives me time for the pattern plus ten laps.

Avaiojet · « **Reply #17 on:** October 14, 2014, 06:46:37 AM »

Quote from: Stephen on October 13, 2014, 11:35:52 AM

Thanks for all the help!!!!

Welcome to the Forum.

Allan Perret · « **Reply #18 on:** October 14, 2014, 08:31:22 AM »

Quote from: Tim Wescott on October 13, 2014, 07:36:53 PM

LA 46, venturi adjusted with bits of pantyhose until I like the run, 11-4.5 TT prop, 10% nitro 11/11 oil VP fuel doctored up with 2 ounces of Colman lantern fuel per gallon.

Exactly what is the Colman fuel and why do you use it as a supplement ?

John Craig · « **Reply #19 on:** October 14, 2014, 12:58:16 PM »

Coleman Fuel = white gas= gas with no additives. Normally used in camping stoves & Coleman lamps. Available in the camping/hunting section at Wally World. When used at an ounce or 2 per gallon, it extends the flight time per ounce of fuel.

Tim Wescott · « **Reply #20 on:** October 14, 2014, 01:07:32 PM »

Quote from: John Craig on October 14, 2014, 12:58:16 PM

Coleman Fuel = white gas= gas with no additives. Normally used in camping stoves & Coleman lamps. Available in the camping/hunting section at Wally World. When used at an ounce or 2 per gallon, it extends the flight time per ounce of fuel.

It's also handy to have in a squirt bottle on cold days -- it's a great assist to combustion in a reluctant engine.

Andrew Tinsley · « **Reply #21 on:** October 14, 2014, 01:51:30 PM »

There is a very interesting article in this months Aeromodeller on the LA46, written by Maris Dissler (Sp). Well worth reading, most people run low pitch prop in a wet two. Maris indicates a whole range of operation including a straight 4-2-4. Most people seem to have trouble doing this on the LA46. I got out today and tried his 4-2-4 suggestion and it worked remarkably well. Never did like to run low pitch props because of their low efficiency, but have always done so on the LA46. Might even go this way with a six inch pitch prop, I will wait and see if windy weather will upset it. I won't have to wait long as the next low is coming in.

Andrew.

EddyR · « **Reply #22 on:** October 15, 2014, 10:56:12 AM »

Andrew Did you do this running in a stand or flying. Almost all motors will run in a smooth 4 cycle in a motor stand. The LA/46 in a 4-2-4 run in the air puts the motor well below its power curve. Schnuerle ported model motors will lean with 6 pitch props on them and you end up going 90 MPH. People tried this for years and then went to the low pitch props because it works so well. What did he do to make it work??
Ed

Jim Thomerson · « **Reply #23 on:** October 15, 2014, 12:07:55 PM »

it is all explained in the article, with discussion of torque curves, etc. Incidentally, Aeromodeller is now monthy.

Andrew Tinsley · « **Reply #24 on:** October 15, 2014, 04:19:29 PM »

Hi Eddy,
I tried Maris's suggestions in the air using a 6 inch pitch prop. Probably like you, I was a bit cynical about it working well and all I can say is that it worked far better than I expected. I still have a sneaking suspicion that it will wind up in the wind, so I will choose my windy weather and try it again. In calm conditions it was quite a revalation. Better than my usual wet 2 setup. Maybe it is down the power curve, but a 6 inch pitch prop is more efficient than the lower pitch ones that are normally used, so the power loss is unnoticed. If you don't have access to the Aeromodeller article, I can scan it for you.

Regards,

Andrew.

P.S. Before someone jumps on my assertion that low pitch propellers are relatively inefficient, don't call me, go and look at Supercool Racing Propellers web site. Mr Sherlock has far more experience and knowledge on how our model props work, than just about anyone else around. If he says so, I believe it.

Steve Helmick · « **Reply #25 on:** October 16, 2014, 03:51:34 PM »

Andrew...could you please tell me which article would explain the improved efficiency of higher pitched props for stunt? I got this far and threw my hands up in horror! http://www.supercoolprops.com/articles.php

I can see that higher rpm and smaller diameter doesn't help efficiency, but it seems to me that the improved acceleration and resulting more constant speed and line tension is way more important for stunt than efficiency, and don't see what pitch would have to do with efficiency anyway...other than slightly increased rpm.

Steve

Andrew Tinsley · « **Reply #26 on:** October 18, 2014, 07:56:27 AM »

Hello Steve,
Not much point in me giving a garbled second hand version of what Stuart maintains about the low efficiency of low pitch props. Stuart is an extremely helpful guy and will respond to emails sent to him. I suggest communicating with him directly, his email address is on his website.
You may well be correct in your assertion re acceleration is much better with the low pitched props and this is more important in stunt than efficiency. In stunt, efficiency is not the name of the game. You get big engines like the larger Ro Jetts, that are four stroking all the way through the schedule, I have even heard talk about these things doing an 8 stroke! So efficiency in the engine/prop department is hardly important, unless you are flying with an engine that is marginal in power, something that doesn't happen much these days!

Regards,

Andrew

Tim Wescott · « **Reply #27 on:** October 18, 2014, 09:16:51 AM »

Quote from: Andrew Tinsley on October 18, 2014, 07:56:27 AM

Hello Steve,
Not much point in me giving a garbled second hand version of what Stuart maintains about the low efficiency of low pitch props.

You said "read the article", and gave a link to several dozen articles. So, I want to read the article -- which one of the several dozen should I read?

Brett Buck · « **Reply #28 on:** October 21, 2014, 09:25:15 AM »

Quote from: Steve Helmick on October 16, 2014, 03:51:34 PM

Andrew...could you please tell me which article would explain the improved efficiency of higher pitched props for stunt? I got this far and threw my hands up in horror! http://www.supercoolprops.com/articles.php

I can see that higher rpm and smaller diameter doesn't help efficiency, but it seems to me that the improved acceleration and resulting more constant speed and line tension is way more important for stunt than efficiency, and don't see what pitch would have to do with efficiency anyway...other than slightly increased rpm. Steve

   Of course lower pitched props are much less efficient, as my latest SN column notes. The parasitic drag on the blade is much higher at the required high RPM, and the induced drag is roughly the same, since it has the same in-flight thrust, at least in level flight.

   This low efficiency is just what you want from a stunt prop. This is why high-pitch props (like the 7-8" that Igor Panchenko and later, Bob Reeves, run on 4-strokes) are more about making the engine happy than being particularly good stunt props. The engines are much weaker and need the efficiency to be able to supply the necessary HP. Same with 4-2 break "st60 tribute engines" like the Double Star, which come with a recommendation to run 7" of pitch. And it works pretty well that way.

   If you have a piped 61 or 75, and you put it in an old ST46 airplane (which is about what we are doing), you hard darn well better have an inefficient prop!

   Brett

Tim Wescott · « **Reply #29 on:** October 21, 2014, 11:41:45 AM »

Quote from: Brett Buck on October 21, 2014, 09:25:15 AM

Of course lower pitched props are much less efficient, as my latest SN column notes. The induced drag on the blade it much higher at the required high RPM, and the induced drag is roughly the same, since it has the same in-flight thrust, at least in level flight.

With edits:

"The ~~induced~~ parasitic drag on the blade it much higher at the required high RPM, and the induced drag is roughly the same..."

(Brett's not expanding on the fact that induced drag is more or less a function of the diameter of the prop and the thrust it generates, while the parasitic drag is more or less a function of the area of the prop blades and the speed it's turning. With all sorts of complications that I'm only dimly aware of, and wouldn't have room to expound upon even if I were competent to do so.)

Author Topic: LA .46 (Read 6098 times)

Jim Roselle

Jim Roselle