Author Topic: Piped LA 46 (Update FREAKIN NVA!) (Read 4448 times)

Dwayne · « **on:** July 15, 2016, 07:33:18 AM »

Hi all I have some questions please.
I have a LA 46 on a profile with a RS 40 size pipe and header
1 extra head gasket
.281 venturi
Brodak NVA
4 oz Sullivan standard vent, pressure tapped on the header.
First prop was a Zinger 11X5 pipe set at 18.25 inches launching at 9,750 and I must have gotten lucky as it worked pretty good, but I decided to do some experimenting with props and it didn't like it at all, first was a zinger 12X4 and I couldn't get the engine to go above 9,900 with out going lean, I then went to a APC 11.5X4 I had to lengthen the pipe to get a good run but it's a dog overhead, you can hear the engine change pitch when overhead.
Just wondering, why couldn't the engine go above 9,900
Why does it seem to slow down overhead when it runs great level and inverted
Thanks guys

RandySmith · « **Reply #1 on:** July 15, 2016, 02:36:36 PM »

Something is wrong all of mine I setup will turn a 12 x 4N at over 11,000 RPMs, and goes to 12,000 in manouvers if setup a little leaner
need more info on your setup

Even my FP and LA 40s will turn the 12 x 4 at or over 11,000 RPMs with ease,

Ward Van Duzer has one of my setups with profile Stilleto type plane launchers at 11,000 and goes into a high RPM 4 stroke at about 1 lap after laucnh

Randy

Dwayne · « **Reply #2 on:** July 15, 2016, 02:50:23 PM »

Quote from: RandySmith on July 15, 2016, 02:36:36 PM

Something is wrong all of mine I setup will turn a 12 x 4N at over 11,000 RPMs, and goes to 12,000 in manouvers if setup a little leaner
need more info on your setup

Even my FP and LA 40s will turn the 12 x 4 at or over 11,000 RPMs with ease,

Ward Van Duzer has one of my setups with profile Stilleto type plane launchers at 11,000 and goes into a high RPM 4 stroke at about 1 lap after laucnh

Randy

Hi Randy, thank you
I bought this pipe used, he said it was a 40, is it possible it's for a 32? But even if it is to small I should still be able to to get more than 9.900, right?

Dane Martin · « **Reply #3 on:** July 15, 2016, 10:30:52 PM »

So I'll throw my tuning dilemma in just to show how much power is capable from a .40 la.... I was running a 40 la in my ARF nobler, and basically to get down to 9500 rpm, I had to go all the way down to a .250 venturi. I was spinning an 11x4 way over 12k.

Randy is right, something sounds fishy in your engine there

http://stunthanger.com/smf/arf's/nobler-arf-trimming-questing-pulls-like-a-mule/msg439920/#msg439920

Steve Helmick · « **Reply #4 on:** July 15, 2016, 11:20:29 PM »

Dwayne, First, I'd suggest Uniflow. That would make the engine run richer late in the tank. I would also expect that you might need more pitch...but also less prop load. Increase the pitch toward the last 2" of the tips about 1/4" pitch and see what happens. Worked for me on my .46VF, anyway. It let me richen the engine and lower the launch rpm about 100-200 r's, stopped the lean overhead nonsense, and much better "drive" in the overhead stuff.

It could also be that your pipe is a .32 pipe. I've read of folks running a bit bigger pipe, but I don't think a smaller than normal pipe will ever work well. A lot of it is also the venturi size vs. the muffler/pipe outlet size...read what Randy says about that in his pinned articles. I wish there was a way to ID the pipes somehow. Maybe Randy can make up a chart after the NATS?

Your pipe length (at 18.25") is 5/8" shorter than on my Randy Aero .46VF, and I launch it at around 10.3/10.4k. I've been told that too short is really bad for the engine, creating mucho heat, but I can't say I understand why.

I tried pipe pressure on my .46VF dog. The pipe was fitted with a tap by the previous owner, so I gave it a try, to fix the upwind/downwind, rich/lean nonsense, which it did. But I had trouble with fuel siphoning out of the tank and into the pipe, resulting in unrepeatable run times. Might be easier to deal with on a profile? Fixed that by routing a fuel hose from the external uniflow vent intake into the backplate cavity for a "null" or no pressure area. Works nicely!

Other than that, how's yer neck bones? Mine's about the same...misery. Knee and skin cancer surgeries have kept me down enough, but I've been out bass fishing some!

Steve

Dwayne · « **Reply #5 on:** July 16, 2016, 05:45:33 AM »

Quote from: Steve Helmick on July 15, 2016, 11:20:29 PM

Dwayne, First, I'd suggest Uniflow. That would make the engine run richer late in the tank. I would also expect that you might need more pitch...but also less prop load. Increase the pitch toward the last 2" of the tips about 1/4" pitch and see what happens. Worked for me on my .46VF, anyway. It let me richen the engine and lower the launch rpm about 100-200 r's, stopped the lean overhead nonsense, and much better "drive" in the overhead stuff.

It could also be that your pipe is a .32 pipe. I've read of folks running a bit bigger pipe, but I don't think a smaller than normal pipe will ever work well. A lot of it is also the venturi size vs. the muffler/pipe outlet size...read what Randy says about that in his pinned articles. I wish there was a way to ID the pipes somehow. Maybe Randy can make up a chart after the NATS?

Your pipe length (at 18.25") is 5/8" shorter than on my Randy Aero .46VF, and I launch it at around 10.3/10.4k. I've been told that too short is really bad for the engine, creating mucho heat, but I can't say I understand why.

I tried pipe pressure on my .46VF dog. The pipe was fitted with a tap by the previous owner, so I gave it a try, to fix the upwind/downwind, rich/lean nonsense, which it did. But I had trouble with fuel siphoning out of the tank and into the pipe, resulting in unrepeatable run times. Might be easier to deal with on a profile? Fixed that by routing a fuel hose from the external uniflow vent intake into the backplate cavity for a "null" or no pressure area. Works nicely!

Other than that, how's yer neck bones? Mine's about the same...misery. Knee and skin cancer surgeries have kept me down enough, but I've been out bass fishing some! Steve

PM sent.
Hey Steve, thanks I have converted to uniflow and I'm going to try it with out the pipe and see what happens, if it still won't go over 9,900 then I know I have an engine problem.

Brad LaPointe · « **Reply #6 on:** July 16, 2016, 11:26:10 AM »

Dwayne ,

First of all with the Brodak nva your intake area is a lot less than with a stock OS nva . This will cut down on your rpm's . Either try using a larger intake or a OS nva . Also try the rpm with a stock muffler and see if the pipe is too restrictive .

For a while I was running a .46 with a Mac's muffler / pipe , worked ok but the 12 + inch prop were a ground clearance issue. It looked evil .

Brad
MAAC 5418L

Target · « **Reply #7 on:** July 16, 2016, 11:43:28 AM »

Subscribing to this thread.
My own .46la on a profile with tongue muffler and uniflow tank....
Bought the plane used (brodak P40 arf) and it came with a cut down Zinger 12x4 or 5, set at 11.5 x 4.5. Tried a thunder tiger 11x4.5, not great...
Switched to a Xoar 11x5, and what a transformation. Plane flew 100% better.
I hope to learn from your thread here. Best of luck dialing it in.
R,
Chris

Dwayne · « **Reply #8 on:** July 16, 2016, 01:06:57 PM »

Jeeze it was the NVA the whole time, I switched to a ST nva and all is well, I thought Brodak made good NVA's but this
one is no good.

Oh well live and learn, thanks everyone for the replies.

Target · « **Reply #9 on:** July 16, 2016, 02:23:12 PM »

Since I don't know what the two look like, can you explain what you think might be happening with the Brodak NVA?
I would assume that they are the same diameter, and if that is the case, there was no difference in the cross sectional area of the venture then.
A needle valve seems like a simple device, as long as the threads are precise, and there is some way to avoid an air leak on the needle side, I don't really see how one could be bad if it is straight.
Thanks in advance for your reply.

R,
Chris

Dwayne · « **Reply #10 on:** July 16, 2016, 03:13:54 PM »

Quote from: Chris Behm on July 16, 2016, 02:23:12 PM

Since I don't know what the two look like, can you explain what you think might be happening with the Brodak NVA?
I would assume that they are the same diameter, and if that is the case, there was no difference in the cross sectional area of the venture then.
A needle valve seems like a simple device, as long as the threads are precise, and there is some way to avoid an air leak on the needle side, I don't really see how one could be bad if it is straight.
Thanks in advance for your reply.

R,
Chris

Hi Chris, I'm not sure what the problem is, yes they are both the same size in fact the collet threads are the same so it's a mystery and one of reasons I went through all this before finally changing the NVA, I didn't think it was the problem.

Target · « **Reply #11 on:** July 16, 2016, 03:43:10 PM »

Well, at least you are fixed up and can concentrate on flying now.
Perhaps Randy Smith can give some possible explanations.
I suspect that the needle could have been wobbly and or leaking air, but maybe there is more to it than that.

R,
Chris

Steve Helmick · « **Reply #12 on:** July 16, 2016, 04:55:36 PM »

Quote from: Dwayne Donnelly on July 16, 2016, 03:13:54 PM

Hi Chris, I'm not sure what the problem is, yes they are both the same size in fact the collet threads are the same so it's a mystery and one of reasons I went through all this before finally changing the NVA, I didn't think it was the problem.

Back when PW was flying the Saito powered "PW-51 Mustangs", once at Smokey Point, I saw him tearing his airplane open. Pretty unusual. I asked what was wrong, and he said the engine wasn't running consistently. It had a 2-Star venturi conversion in it, and he said the spraybar had a burr in it where it was cross-drilled. Later, I asked Paul how he de-burred it. "Threw it away!" was the reply. As a machinist, I was actually thinking about how to de-burr the hole on the inside of the spraybar. Probably better to use a sharp drill to start with? I've found stubby carbide drills work wonders for small holes in thin parts...round, instead of sort of triangular, a plus.

Seems this is not uncommon with 2-Star spraybars. I recall others with similar problems with them. Double Star makes the Brodak engines...and spraybars. I guess the burr flaps around in there and changes the mixture as it does so. It might be possible to de-burr one, however, I'm not sure how. Maybe as simple as running a drill in & out, but not if they used a "form" or "roll" tap to make the internal threads (which would be my choice). Anyway, if you come up with a way to de-burr your spraybar, please spread the word on how you did it.

Steve

Geoff Goodworth · « **Reply #13 on:** July 16, 2016, 05:28:54 PM »

One significant difference between the two spraybars is that the Brodak part has two holes in it while the ST clones have only one. I have seen fuel spraying out of the venturi on a Brodak 40 when the spraybar was not fitted with the two holes exactly square to the airflow in the venturi.

Dwayne · « **Reply #14 on:** July 16, 2016, 05:34:29 PM »

Quote from: Geoff Goodworth on July 16, 2016, 05:28:54 PM

One significant difference between the two spraybars is that the Brodak part has two holes in it while the ST clones have only one. I have seen fuel spraying out of the venturi on a Brodak 40 when the spraybar was not fitted with the two holes exactly square to the airflow in the venturi.

Good point, I don't think I had it miss aligned but you never know, also as Steve has suggested I'll check for burs.

Steve Helmick · « **Reply #15 on:** July 16, 2016, 07:34:12 PM »

If the Brodak spraybar has two cross holes, shouldn't they be just off center, like the Fabulous Fox?

Steve

Geoff Goodworth · « **Reply #16 on:** July 18, 2016, 08:40:14 AM »

Steve, I've only looked closely, not measured the position of the holes in the Brodak spraybar but they appear to be diametrically opposed. On the other hand, the offest on the holes in the Fox spraybar is pretty easy to see.

Brett Buck · « **Reply #17 on:** July 26, 2016, 04:27:15 PM »

Quote from: Steve Helmick on July 16, 2016, 07:34:12 PM

If the Brodak spraybar has two cross holes, shouldn't they be just off center, like the Fabulous Fox? Steve

A more interesting question is whether or not the holes were offset on the Fox on purpose, or by accident/tolerance stackup?

Brett

Author Topic: Piped LA 46 (Update FREAKIN NVA!) (Read 4448 times)

Dwayne

Piped LA 46 (Update FREAKIN NVA!)

RandySmith

Re: Piped LA 46

Dwayne

Re: Piped LA 46

Dane Martin

Re: Piped LA 46

Steve Helmick

Re: Piped LA 46

Dwayne

Re: Piped LA 46

Brad LaPointe

Re: Piped LA 46

Target

Re: Piped LA 46

Dwayne

Re: Piped LA 46 (Update FREAKIN NVA!)

Target

Re: Piped LA 46 (Update FREAKIN NVA!)

Dwayne

Re: Piped LA 46 (Update FREAKIN NVA!)

Target

Re: Piped LA 46 (Update FREAKIN NVA!)

Steve Helmick

Re: Piped LA 46 (Update FREAKIN NVA!)

Geoff Goodworth

Re: Piped LA 46 (Update FREAKIN NVA!)

Dwayne

Re: Piped LA 46 (Update FREAKIN NVA!)

Steve Helmick

Re: Piped LA 46 (Update FREAKIN NVA!)

Geoff Goodworth

Re: Piped LA 46 (Update FREAKIN NVA!)

Brett Buck

Re: Piped LA 46 (Update FREAKIN NVA!)