Author Topic: Crossflow on a Profile (Read 4777 times)

Motorman · « **on:** October 09, 2015, 05:52:53 PM »

Having bad luck with baffled engines on profile planes. Been flying my new Ringmaster with a Veco .19 and afraid to do outside maneuvers or fly inverted.

The set up seems right, see below. Level flight it's 2 and 4 stroking very steady through the whole tank. I pull up it breaks into a full two stroke but if I dive down it goes into a heavy 4 stoke like it's going to flame out. Tried leaning it down a little each flight it seemed to get a little weak directly overhead but I'm use to electric planes.

The plane itself flys great BTW, I credit StuntHanger for helping me build better planes.

Veco .19 great iron piston fit with one flip starts ect.
Glow plug Merlin Hot
ASP 15 muffler drilled out pretty good in the back.
9-4 MAS GF series (9-5 was fast)
.265" venturi Supertiger nva
10% nitro 15% castor 5% synth
Brodak 2oz uniflow tank set 3/8" above the center line

Started with the tank 1/8" above then went to 1/4" then 3/8" with no real change.

I've had this problem before with a Fox35. Is this just a thing with a single bypass engines on a profile planes, I have other engines but I hate to change the nose. What would you try next?

Thanks,
MM

Dennis Moritz · « **Reply #1 on:** October 09, 2015, 06:23:00 PM »

Try an Enya no3 or thunderbolt RC plug. Undo pressure to uniflo. Run pressure to vent. Plug uniflo instead of vent. Sounds like a tank issue. Lower tank in increments, see if that helps.

Phil Spillman · « **Reply #2 on:** October 09, 2015, 07:24:40 PM »

Hi MM, You might try adding some more castor oil to your blend. Those older engines have a tendency to not like quite as much synthetic oil in their brew as the more modern ones. I think that you were going in the right direction by raising the tank. Your approximation of height is close to where my old stuff prefers to purr along! In addition you might try adding on soda can gasket to the deck height under the head. Soda/beer cans are about .005 thick as opposed to many stock gaskets being about .010 thick. Just my thoughts FWIW!

Phil Spillman

Dennis Moritz · « **Reply #3 on:** October 09, 2015, 07:52:34 PM »

I think Raising the tank will increase over rich condition in outside maneuver. Centrifugal force pushing fuel up. Making mix richer. Not the same as adjusting tank height to even up mix upright and inverted. Chicken hopper tank might help. Or a clunk. These engines have run well on many profiles.

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Motorman · « **Reply #4 on:** October 09, 2015, 09:30:05 PM »

I'm sure it has something to do with the tank. Never thought to make it lower but might as well try it.

MM

Douglas Ames · « **Reply #5 on:** October 11, 2015, 06:30:13 AM »

I thought you always ran a Veco .19 in a rich 2 stroke with a low pitch prop.?
Seems like a small engine to try and get a 4-2-4 run?

Steve Helmick · « **Reply #6 on:** October 11, 2015, 04:27:08 PM »

Which Veco .19, sleeve bearing or bb? What's an "ect"?

Raising the tank will make it richer upright/insides and leaner inverted/outsides. Since you have raised the tank from + 1/8" to + 3/8", it suggests that (maybe) the tank is just a POS. Pull the back off and inspect it, maybe replace the tubes, or just put a different tank on the plane.

Steve

phil c · « **Reply #7 on:** October 11, 2015, 05:05:58 PM »

Quote from: Dennis Moritz on October 09, 2015, 07:52:34 PM

I think Raising the tank will increase over rich condition in outside maneuver. Centrifugal force pushing fuel up. Making mix richer. Not the same as adjusting tank height to even up mix upright and inverted. Chicken hopper tank might help. Or a clunk. These engines have run well on many profiles.

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If the tank is too low it will go rich on ousides and upside down. If it is too high it will go rich on insides and rightside up.

If it is way off either way the engine is more likely to quit in maneuvers. Usually 1/8-1/4 in. up was enough correction.

Agree with Doug Ames, the Veco is/was a high performance engine. Not set up for 4-2 running.

Also Steve Helmick's advice. A tank should not be that much trouble if it is clean and plumbed right.

Bill Little · « **Reply #8 on:** October 11, 2015, 08:33:13 PM »

Hi Walt,
It is important as to whether you are running the BB version or the plain bearing version. The old plain bearing will do a 4-2 but the Ball Bearing does not like to. It runs like a modern engine and does great with a high rpm/low pitch run. An APC 9-4 or 10-4 usually works very well. They also like 25% oil with most castor and a hot plug. I have run both types quite a bit.
Bill

Tim Wescott · « **Reply #9 on:** October 11, 2015, 08:51:37 PM »

Double what Steve said -- check your tank. While you're at it, check your plumbing, too.

Can't hurt.

Motorman · « **Reply #10 on:** October 11, 2015, 09:42:53 PM »

It's the BB version. ect. means it's a good engine that doesn't seize up or lose compression in the air, it responds to needle settings and it starts 1-2 flips even when hot.

I leaned it out just right and it pulls through everything ok no matter how it's running but it breaks 4 stroke in funny places like the horizontal lazy 8 when you first give it down then it leans out for the rest of the outside loop. Is that the Veco burp? It will also cool off and start 4 stroking if you do too many level laps.

Flying inverted laps it does lean out more so I guess the tank is too high (or too low upside down). The tank is too small, can't get through the old time pattern so, I'm making a bigger one. I only know racing tanks, where do you put the vent line inside?

It got me through 20 flights for the Ringmaster flyathon. Had fun remembering me and dad building and flying the first one 54 years ago.

Thanks,
MM

Tim Wescott · « **Reply #11 on:** October 11, 2015, 10:59:33 PM »

Quote from: Motorman on October 11, 2015, 09:42:53 PM

Flying inverted laps it does lean out more so I guess the tank is too high (or too low upside down). The tank is too small, can't get through the old time pattern so, I'm making a bigger one. I only know racing tanks, where do you put the vent line inside?

Search on "uniflow tank", you may find pictures. Basically you have one vent about 3/8" to 1/2" forward of the pickup, and a separate fill vent to the top of the tank for -- well -- filling. Plug the fill vent for flight.

This isn't the best explanation I've seen, but it isn't the worst, either: http://bjm-home.com/BJMEnterprises/page59.html.

Or go here and search for "uniflow" on the page -- looks like good stuff: http://www.aeromaniacs.com/Tips.html

Brett Buck · « **Reply #12 on:** October 11, 2015, 11:32:08 PM »

Quote from: Motorman on October 11, 2015, 09:42:53 PM

It's the BB version. ect. means it's a good engine that doesn't seize up or lose compression in the air, it responds to needle settings and it starts 1-2 flips even when hot.

I leaned it out just right and it pulls through everything ok no matter how it's running but it breaks 4 stroke in funny places like the horizontal lazy 8 when you first give it down then it leans out for the rest of the outside loop. Is that the Veco burp? It will also cool off and start 4 stroking if you do too many level laps.

   It needs to run at pretty high RPM with the stock venturi. I expect that the issue is similar to the Fox 35, which does the same thing with a vengeance, despite the many people lining up to tell you I am stupid/ignorant/unAmerican. Try something like a 9-4 or 10-4 APC. This engine is one of the few vintage engines in the ballpark with the 20FP. The 20FP has a touch more power, but the Veco doesn't mind a 10" prop, so you can make up for some of the difference by adding a bit of diameter. I would suggest the 9-4 first, however, since you hardly need the full power of the engine on a Ringmaster. We tried it, it's about 4.2 seconds a lap on 62 foot lines. The 20FP is more like 3.8 when the engine is set correctly.

   You need a lot of RPM to provide a lot of fuel draw, as well. That's the other area we haven't seen - how wide is your tank? Many times, you will have issues with low fuel delivery on profiles with a typical 2" wide wedge tank, and you are sort of inclined to do it because the tank has to be very short since there isn't much room. But you have to pull the fuel "uphill" from the wedge of the tank to the venturi, and it is an unstable system, since the faster it goes, the leaner it gets, which makes it go faster, which makes it go leaner, which is one of the mechanisms of the classic "runaway".

   People also usually run cooling baffles, but I am not sure how important that is.

   Brett

Dennis Moritz · « **Reply #13 on:** October 12, 2015, 06:16:36 AM »

Bad vibes. Perhaps. Resonances frothing fuel. Bypassing unifo often helps. Cap off unifo vent run muffler pressure to overflow. Neutralizing profile resonances can be tough. We've a long laundry list of attempted solutions. Every now and then one works. Definitely it varies model to model.

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Dennis Moritz · « **Reply #14 on:** October 12, 2015, 06:51:52 AM »

Yep. Running rich inexplicably during certain points of a maneuver sounds like a bad resonance. Stresses causing fuel frothing are momentarily relieved so engine receives fuel with less air bubbles. Runs rich. Since needle has been set to compensate for frothing fuel. Did you try a few spritzes of Armor All mixed into gallon of fuel? That helps reduce frothing. Switch out the plug yet? Thunderbolt RC and Enya #3, both hot plugs, help relieve over rich inconsistencies in run. (BURPS) Fixing bad profile vibes is like debating a T party zealot or the mentally unstable. Hard to know in advance what cools the situation out. (Joke emoticon.)

Motorman · « **Reply #15 on:** October 12, 2015, 09:42:39 AM »

What's a cooling baffle?

MM

Tim Wescott · « **Reply #16 on:** October 12, 2015, 10:27:49 AM »

Quote from: Brett Buck on October 11, 2015, 11:32:08 PM

People also usually run cooling baffles, but I am not sure how important that is.

Cooling baffles? On a profile? I'm baffled.

Quote from: Motorman on October 12, 2015, 09:42:39 AM

What's a cooling baffle?

Pieces of sheet metal or wood to direct the airflow over selected parts of the engine -- like on the original Piper Cub, or a Volkswagen air-cooled engine, or a multi-row radial.

Brett Buck · « **Reply #17 on:** October 12, 2015, 10:44:40 AM »

Quote from: Dennis Moritz on October 12, 2015, 06:16:36 AM

Bad vibes. Perhaps. Resonances frothing fuel. Bypassing unifo often helps. Cap off unifo vent run muffler pressure to overflow. Neutralizing profile resonances can be tough. We've a long laundry list of attempted solutions. Every now and then one works. Definitely it varies model to model.

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It is very unlikely to be a stray resonance in this case. It would be the same on inside and outside maneuvers.

Brett

Brett Buck · « **Reply #18 on:** October 12, 2015, 10:47:18 AM »

Quote from: Tim Wescott on October 12, 2015, 10:27:49 AM

Cooling baffles? On a profile? I'm baffled.

Pieces of sheet metal or wood to direct the airflow over selected parts of the engine -- like on the original Piper Cub, or a Volkswagen air-cooled engine, or a multi-row radial.

How well does air travel around the back side of a cylindrical body? It's not because of or in spite of a profile mount, it's because you are running it much harder than a typical stunt engine and it is known to at least varnish up the back side of the cylinder.

This from actual experience, not internet speculation.

Brett

Brett Buck · « **Reply #19 on:** October 12, 2015, 10:50:00 AM »

Quote from: Motorman on October 12, 2015, 09:42:39 AM

What's a cooling baffle?

As Tim noted. I will take a picture of David's next time I see it, but it's a sheet metal baffle that forces the air to flow around the back of the cylinder through the fins. Usually two pieces coming up to about 1/4 the way around the cylinder, with a gap of maybe 3/8" at the rear, and wired on.

Brett

Tim Wescott · « **Reply #20 on:** October 12, 2015, 11:01:00 AM »

Quote from: Brett Buck on October 12, 2015, 10:47:18 AM

How well does air travel around the back side of a cylindrical body? It's not because of or in spite of a profile mount, it's because you are running it much harder than a typical stunt engine and it is known to at least varnish up the back side of the cylinder.

This from actual experience, not internet speculation.

So this is something that's being done specifically on the Veco 19's? It makes sense (actually, the 46LA on my Twister tends to varnish up badly on the back of the cylinder -- I wonder if I should put baffles on my next profile plane. Hmm....

Ken Burdick · « **Reply #21 on:** October 12, 2015, 11:10:02 AM »

In reading all the advice, you really have the problem surrounded. I agree with Steve that the tank is likely the culprit, then the oil (not enough castor) then the prop. It should be interesting doing them in that order one at a time to isolate the issue.
Keep us up to date as it's an interesting problem.

Ken

Dennis Moritz · « **Reply #22 on:** October 12, 2015, 06:59:41 PM »

Change the plug. Lower the tank a bit. Oh. Did I mention changing the plug. It's running lean inverted lower the tank a bit. (Like I said.) Might also help with the burp. We have found in our club that the Thunderbolt RC long and Enya 3 reduce burp. Why would you add castor or figure out a baffle if the engine is already running too cool?

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Randy Cuberly · « **Reply #23 on:** October 12, 2015, 08:33:52 PM »

Quote from: Dennis Moritz on October 12, 2015, 06:59:41 PM

Change the plug. Lower the tank a bit. Oh. Did I mention changing the plug. It's running lean inverted lower the tank a bit. (Like I said.) Might also help with the burp. We have found in our club that the Thunderbolt RC long and Enya 3 reduce burp. Why would you add castor or figure out a baffle if the engine is already running too cool?

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Who said it was running too cool? Guess I missed that!

Hmmmm. Actually though Baffles can be used if an engine is running too cool. I've done it and also saw Bob Hunt correct a problem like that on his Webra 28 at VSC about 20 or so years ago...fixed it too! Different kind of baffle than the one mentioned since it actually prevented air from circulating on the very upper front of the cylinder.

There are many things in Stunt that can "Baffle One".

Randy Cuberly

Dennis Moritz · « **Reply #24 on:** October 13, 2015, 12:37:47 AM »

M said it would run 4 stroke cooling down when running without maneuvering. Not necessarily a problem. M thought it s problem tho.

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Bill Little · « **Reply #25 on:** October 13, 2015, 02:02:43 PM »

The most important problem I see in this scenario is the Walt is running the Ball Bearing version which is a higher timed engine than the old plain bearing Veco .19. The BB is meant to run high rpm/low pitch. See Brett's response also. This will serve to see how many guys actually read the other posts in a thread

Running the BB Veco .19 in a 4-2 style is like running a .20FP in a 4-2, it just doesn't work right.

BIG Bear
RNMM/AMM

Brett Buck · « **Reply #26 on:** October 13, 2015, 06:04:37 PM »

Quote from: Dennis Moritz on October 12, 2015, 06:59:41 PM

Change the plug. Lower the tank a bit. Oh. Did I mention changing the plug. It's running lean inverted lower the tank a bit. (Like I said.) Might also help with the burp. We have found in our club that the Thunderbolt RC long and Enya 3 reduce burp. Why would you add castor or figure out a baffle if the engine is already running too cool?

Oy vey. It's running *too slow*, forget the rest of it. Too slow means lower fuel draw and low gas velocity, which is *why* it is Fox burping in the places it does. The tank may also be too wide, but that's not the main issue.

Brett

Dennis Moritz · « **Reply #27 on:** October 13, 2015, 07:36:56 PM »

Ok lean it out. Oy vey yourself. Runs lean inverted compared to upright. Hmm. What do you do then. Ahh. Lower the tank. I wonder where you can put your baffle. Perhaps you can explain how lower fuel draw results in a burp which signifies too much fuel sloshing the plug.

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Dennis Moritz · « **Reply #28 on:** October 13, 2015, 08:02:48 PM »

I believe Motorman flies out of Millville NJ. Our club visited during the summer. Perhaps Motorman was there and saw our club fly. The Philly Fliers must have brought 7 or 8 profiles that all ran well. Typically we use Tower 40s, FP40s, Fox 35s, LAs, a McCoy or two, even Enyas. We use RSM profile tanks, chicken hoppers, clunks, bladders, even some inverse Tetras. (Long story.) Veco 19s were popular in our club years back. Used in clown racing. Folks got them to run well for that event. Seems to me John Saunders, a member of the Millville club, pushed them to the max. Why not ask him to trouble shoot your situation. Those engines definitely liked running fast. Screamers in their day.

Dennis Moritz · « **Reply #29 on:** October 13, 2015, 09:40:41 PM »

It's possible the burp when hitting an outside maneuver has an aerodynamic causality. Is the model hinging some pushing outboard wing up as you apply a hard down?

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