Author Topic: Sneeker's done (Read 2858 times)

Chucky · « **on:** July 10, 2011, 06:25:31 PM »

At long last, the long boom Sneeker's done. Thanks for the recommendations on boom length. CG came out spot on per plans. Flew it last weekend and liked the way it handled, but immediately ran into engine run problems. The CS Mk 3 seemed to run well in level flight and in inside turns, but goes drop dead rich in any outside maneuver or inverted flight. Seems as if anything that causes G forces to go toward the bypass side of the engine put into a severely rich condition. Return to upright level flight restores the good run, but one can't always get there prior to flame-out. Fortunately I was on a wet grassy field and only lost a prop trying to figure things out. The Sneeker with silk is a pretty tough plane. The motor is set up for slow combat with the aluminum venturi insert and clicker needle valve on the engine. Am using 10% nitro fuel with 21% total oil (amended Wilcat due to availability). In my youth, I ran the the 36 X on Voodoos with pacifier pressure, but this is first experience with the Fox CS. Don't recall anything like this on the 36 X. Any ideas/suggestions for the bad motor run will be much appreciated.

Paul Smith · « **Reply #1 on:** July 10, 2011, 06:51:44 PM »

My guess is that the engine in loading up because you're under-revving it with a small venturi and a big prop. Sometimes these high-performance engines just don't like being slowed down.

A 9/5 or a 8/7 prop might help. That engine was built tough to take 40% nitro and a wide open venturi. RPM is a goot ting.

Chucky · « **Reply #2 on:** July 11, 2011, 04:48:32 AM »

Thanks Paul. A local buddy with combat experience using this engine pretty much advised what you did. That's a 10x6 prop in the pic and the engine definitely didn't like it. Put on a 9x4 at the field Saturday and the engine sounded better, but still went rich as before. Am going to remove the venturi restrictor and see if it improves. Am puzzled as to why it goes rich when inverted or when turning anti-clockwise and runs ok upright or turning clockwise.

john e. holliday · « **Reply #3 on:** July 11, 2011, 09:37:35 AM »

Are you running crankcase pressure?? All my Fox Combats were run on metal tanks and crankcase pressure. Also 9 X 7 props. Back then I used K&B 100 fuel.

larry borden · « **Reply #4 on:** July 11, 2011, 10:53:46 AM »

Good looking Sneeker. We ran G21 ST's with 8X8 Tornado nylon props and Missle Mist. Seemed to work for us.

kenneth cook · « **Reply #5 on:** July 11, 2011, 01:09:31 PM »

check to make sure your plug isn't a cold plug since your running low nitro also could be your pick up position in the tank. I dont know where the pick up should be with those style tanks but if your running rich inverted it may need to be lowered. Also with this style mk engine those drive washer tend to wiggle on the crank causing broken cranks the only way to fix it is to file out some of the drive washer on the inside its kinda hard to explain. Also do not remove the intake insert if your running with a standard tank this will only cause more fuel draw issues unless you run crank pressure. the perfect prop I've found with this engines is a 8 1/2/7 but i am running bladder open intake 35% nitro you may like a 8/6 or something with lower pitches to keep the rpms up. with your style setup you should see around 90mph or better easily. Shawn cook

Steve Helmick · « **Reply #6 on:** July 11, 2011, 05:41:00 PM »

I clicked on the picture and got the enlarged version. It's pretty obvious to me that it has a pacifier tank of some sort, inside a Vienna Sausage can. The "fuel pickup" should be right at the front of the tank. If it isn's, then that might be a problem, but that's something I never did, either. I would love to get the details on what the source of the pacifiers are...brand name, model number, etc. I loved real Binky baby pacifiers! And I have a long boom Fliteline Sneeka kit and a WU Super Satan kit that need building.

While I never tried a pacifier tank on a small venturi or running very low rpm with one, I have a feeling that it wouldn't work very well. I never owned or ran any kind of Fox Combat either, but I'd put in a hotter glowplug, pull out the venturi restrictor, and see if I could control the speed with the prop. It might run ok on 5%, but would probably a lot better on 10%.

Steve

Chucky · « **Reply #7 on:** July 11, 2011, 06:42:29 PM »

It's a "pacifier" style fuel setup which is similar to a modern bladder -- no fuel pickup tube. The fuel compartment is the same size as a vienna sausage can, but this one is made from sheet balsa wrapped wet around a jelly jar to form.

I too loved the "Binky" pacifier, but as far as I can tell, they're extinct. I'm using a latex pipette bulb that I get from Electron Microscopy Sciences in packs of 24 for $8.50: http://www.emsdiasum.com/microscopy/products/preparation/pipette.aspx?mm=10 Size and setup are the same as the "Binky".

Thanks for the advice about the glow plug. Will make sure I'm running a hot one with the low nitro fuel.

kenneth cook · « **Reply #8 on:** July 11, 2011, 07:09:22 PM »

Ok i wasn't sure if it was one of the can looking tanks or something the old slow combat planes used. If your running a pressure system i would remove the insert but that still shouldn't explain your rich runs in the inverted maneuvers I would guess it is your plug or it could be that your needle valve isn't closing your fuel off all the way. When I run my mk engines i always used the OS 1a needle because of the finer threads hold more I just used a control horn on one of the back plate screws and the bladder runs to that as a remote needle. I hope this works but if it doesn't the last I would change is your fuel but there's no reason it shouldn't work with 10%. Shawn Cook

Chucky · « **Reply #9 on:** July 11, 2011, 07:37:44 PM »

Thanks Kenneth. Am hoping the additional air, hot plug, and smaller prop will get this motor out of the doldrums. A local buddy seems pretty sure that that should do the trick. I know that these old Foxes are being run successfully on 10% nitro fuel on Yankee Nippers, Coyotes, and other S/L combat planes, so mine should work as well. I've read rather vague descriptions of "unreliable" performance on the Mk 3 with restrictor installed. Apparently, Fox changed the restrictor on the Mk 4 and subsequent version to keep the slow combat guys happy -- must have been a reason, but I haven't been able to get details on what the problem was. My engine has the restrictor epoxied in, so I'm guessing it leaked air pretty badly. It may work much better with a suction setup, but that's not something I'm willing to go to yet on a combat plane. One of the joys of a pressure fuel system, when it works, is rock steady rpm regardless of attitude.

Steve Helmick · « **Reply #10 on:** July 12, 2011, 11:42:31 AM »

That, and it quits rich, vs. lean as the fuel runs out. Sometimes a bad thing in a match, but at the price of glowplugs these days (and that steady run!), it's a great way to go.

Good call on the rolled balsa tube, Chuck. I just added ribs and sheeted the top and bottom, closed off the rear, and fuelproofed it as best as I could by sloshing dope or resin or something around inside. It would be better to have a smooth epoxy finish inside, of course.

I guess Latex is what the Binky pacifiers were made from? They look very similar...I'm excited!

Steve

Chucky · « **Reply #11 on:** July 12, 2011, 01:29:26 PM »

Steve, I recall the Binky rubber being more translucent than the latex, so I'm guessing the formulation was different. Am not certain, but since some are allergic to latex, they probably didn't use it in the formulation.

faif2d · « **Reply #12 on:** July 20, 2011, 07:08:54 PM »

Wal Mart had a "binky" style pacifier several years ago. They had a larger opening than the ones I had gotten from England 20 years ago. On the English ones a tube inside the fuel line was a tight enough fit that about 4 wraps with a dethermalizer rubber band was enough to prevent leaks. I always thought the pipette bulbs had to high a pressure.

Tom_Fluker · « **Reply #13 on:** August 23, 2011, 06:53:18 AM »

Quote from: larry borden on July 11, 2011, 10:53:46 AM

Good looking Sneeker. We ran G21 ST's with 8X8 Tornado nylon props and Missle Mist. Seemed to work for us.

That's the way I remember flying them. The kid version was tough and heavy. The adults lighten them as much as you possible. Later on, we put .15s on them and called it FAI.

Tom

phil c · « **Reply #14 on:** August 23, 2011, 12:58:44 PM »

If I remember right, the Mark III always had this problem. It was very difficult to get a good run on a slow ship. On a Fast ship it had to run wide open, with no restrictor at all. Some folks used a two part NVA, with the needle threaded into one side and the seat into the other. At least 25% nitro. We had the best luck with an 8-1/2/6 Rev Up. I think the normal rpm was something over 17,000 on the ground, then back off 1000 or so to launch.

Getting the head clearance right, ~ .015 in. and using a double bubble head helped too.

Make very sure that the back of the prop drive washer doesn't hit the radius between the main shaft and the the 1/4 in. prop shaft. Some of the washers had a very sharp edge that would cause the front of the shaft to fatigue and break off.

As a last resort, the Stunt 35 trick of partially blocking the bypass opposite the exhaust might help. Back then we hadn't figured out that bypasses had to be matched to the ports.

Marvin Denny · « **Reply #15 on:** August 23, 2011, 01:53:26 PM »

Chucky, Like Phil C said, the MK III always did give that trouble when equipped with the restrictor. I have run them with 9 X 7, 9 X 61/2, 9 X 6, 81/2 X 61/2 among other sizes, But I have two suggestions, First remove the restrictor and run with an open venturi. second, It appears that you are running the factory supplied NVA. If so, I would remove it and replace it with a G21-35 Super Tigre type. You might try the NVA replacement first. The stock NVA has too steep of taper on the needle to get good reliable settings. If you have a couple of spare Pippet ends you could spare, I would like to purchase a couple.

Bigiron

Howard Rush · « **Reply #16 on:** August 23, 2011, 06:01:51 PM »

Quote from: Marvin Denny on August 23, 2011, 01:53:26 PM

...It appears that you are running the factory supplied NVA. If so, I would remove it and replace it with a G21-35 Super Tigre type.

That's what Duke Fox recommended.

Dwayne · « **Reply #17 on:** August 26, 2011, 07:25:02 PM »

Quote from: Howard Rush on August 23, 2011, 06:01:51 PM

That's what Duke Fox recommended.

I'd take it a step further and go with a remote O.S. 15 nva, keep those fingers away from the prop

Marvin Denny · « **Reply #18 on:** August 27, 2011, 09:18:22 AM »

Quote from: Howard Rush on August 23, 2011, 06:01:51 PM

That's what Duke Fox recommended.

Who do you think might have recommended it to Duke??? ( Among several others I might suspect).

Bigiron

Frank Imbriaco · « **Reply #19 on:** August 27, 2011, 02:53:00 PM »

Just maybe, Duke woulda recommended his 36xBB back when the Sneeker was in it's heyday. Built a nice yellow silk one in 1970, used a "Miss Clairol" hair color plastic bottle as a pacifier pod( mounted spanwise), and Binkys. That was the typical N.E set-up back then.

I flew it often for a few years, then it sat until 2008. Took it out at the District 2 AMA Fly-in in July 2008. That was the first time I held a handle in a couple of decades. On the second flight, the nylon bellcrank broke 1/3 of the way across and it outside looped itself forever until it pancaked it in.

Terrence Durrill · « **Reply #20 on:** August 27, 2011, 08:08:07 PM »

Hey Frank,

I built three standard Flite Line Sneekers back in the mid 1960's. One was covered with orange silk, another covered with black Silron, the third has orange Silron on the outside wing and black Silron on the inside wing (this color scheme screams COMBAT SHIP). All were flown with Fox .36xBB's, pacifier tanks, Top Flite 9/7 nylon Props and Missile Mist fuel. They all flew pretty good...sort of sports car handling compared to a Voodoo. I still have all three of mine although I have not flown one since the late 1980's. Great little airplane for its day and still a great sport flier............TDurrill

Frank Imbriaco · « **Reply #21 on:** August 28, 2011, 06:44:33 AM »

Hi Terry,
Yes, I agree that the Sneeker felt better than the Voodoo . More stable, turned tighter , but I always knew where it was when my eyes were off it. If I were to locate a sanely priced kit today, I'd definitely build it for sport flying. Fly it with a 10x6 or 11x5 to keep with my aging reflexs-( lol).Of course, it'd have one of my ole' trusty L.S. ( Larry Scarinzi) tuned 36xBBs and a pacifier to complete my trip back in time.
Don't think I can locate any Fox Blast( could barely afford a quart back then), and 50% nitro was truely insane when I think about it. !0-15% would suit me fine.
Frank

john e. holliday · « **Reply #22 on:** August 30, 2011, 09:16:04 AM »

Go to Barry baxter's site and get the full size plans and build all the Sneekers you want.

http://www.controllineplans.com/

Thomas Wilk · « **Reply #23 on:** August 31, 2011, 08:19:40 AM »

Frank;

Were you flying with the UMACers in NY in the late 60's and early 70s. I remember Steve West, Dan Domina, Butcher, Hatra, H. Orzech and a few others.

Tom Wilk

Frank Imbriaco · « **Reply #24 on:** September 01, 2011, 11:44:43 AM »

Hi Tom,
Yes, I was with the Union Model Airplane Club of NJ back then. We're all getting old, eh? I remember you and your boys- we had some fun times and that was really some club.

Best Regards,
Frank

Thomas Wilk · « **Reply #25 on:** September 02, 2011, 12:15:35 PM »

Steve in now flying F2C FAI Racing. he is at the team trials this weekend. he made the team last time and should do so again. his daughter holds a few Jr and Sr speed records. the other boys never stayed in modeling. i have retired from active modeling.

check out http://www.oldmagazineplansoncd.com/Home_Page.html
Tom

Author Topic: Sneeker's done (Read 2858 times)

larry borden

Dwayne