I finally tried a pressurized bladder tank - Page 3 - RC Groups
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Dec 09, 2011, 10:51 PM
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With the TD on the Stuntman chopper I have been using a 5.25x4 Top Flite nylon.
But on the Li'l Jumpin bean with a BW I use a 6x3 Cox. The Li'l Satan zooms with anything, but the loops are tighter with a 6x3 Cox.

I balance them on a home made tool. I stick a couple of single edged razor blades up parallel like rails and put a tight drill bit through the prop as an axle then lay it on the rails. Whichever way it rocks, I lighten.
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Dec 09, 2011, 11:04 PM
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Btw, I'm on my last Top Flite prop, so I'm cutting down some MA 6x3 and 6x4 props that I have. I do still have a TF 6x4, but I don't think I have a use for that.
Dec 09, 2011, 11:25 PM
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Originally Posted by earlwb
The TF bylon prop tended to flex out to a smaller pitch at slower airspeeds and flex back to a higher pitch when the plane was going full speed down the straights.
Bingo! The rubber ducky blacks excel at exactly that.. Load them up in an abrupt manouver and the revs stay mostly constant.. Brilliant :-) One can also 'repitch ' the things by twisting the bejesus out of them just before launch for that inevitable last minute 'tweak'.
Order a few rubber Duckies (even the later nubby ones are good .. just not 'as' good as the originals) from Bernie. As bonus they are indestructible.
Oooh . DIY magnetic balancer: Buy a couple of nickel or quarter sized Neodym Magnets and a Wee finger balancer.
Stick the mags onto vise jaws and open the things up to fit the finger balancer so that only one end touches the magnet.
Dec 09, 2011, 11:43 PM
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I'm up to my ears in 5x3 and 5x4 rubber duckies, no nubbies. Earlwb said he liked a 6x3 for aerobatics too, so at least I'm not a loner on that one. I'll keep switching and trying.

If it isn't too cold I'll fly this weekend. Can't wait for a taste of that hot fuel, I hope it comes tomorrow. But I still have some Sig 25 that needs a good filtering before I feed it to my freshly cleaned TD. I have an inline fuel filter ordered from the LHS but I don't have one on it right now.
Dec 10, 2011, 11:54 PM
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Got my fresh fuel today, SIG 35%. I didn't have the great time testing it as I expected. It was 7:00 PM before I could get out to the workshop. I used last weekend's pressure bladder and cranked the TD and ran one rich run since I just devarnished and rebuilt it. Then I fired it up again full speed and it ran okay and noticeably faster than it did on the 25% SIG fuel. But after that, all it would do is sputter and flood over and over. So I tried a Bee head and it was worse. Tried more and less gaskets. Put the Gallbreath back on it and it tried harder, but I wasted 60cc of new fuel trying to crank it. I hate wasting fuel, so I gave up. I think using that old bladder must have been my problem, probably not enough pressure after being filled full so many times and sitting wet for a week. Come to think of it, it felt too easy to push fuel into it.

So I filled the Black Widow on my Jumpin' Bean and it cranked right up. It ran okay, nothing special, that's about it.

I'll make a new bladder and try the TD again tomorrow and I bet it'll run fine. That seriously cut into my flying time, I never got the chance to clean up the Stuntman, not to mention mounting the engine and making the new bladder. Now I have to do at least one more test run on the bench first.

I might just have to settle for flying the Bean or the Satan if I get to go at all. Oh well, them's the breaks. This hobby has its disappointing days.

EDIT Sunday: Nah, too cold, as well as a 15 mph wind. I for once didn't even want to fly. So I have all week to tune up. I always do better when I'm not rushed anyway.
Last edited by RknRusty; Dec 11, 2011 at 08:59 PM.
Dec 12, 2011, 12:18 AM
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Originally Posted by RknRusty
...all it would do is sputter and flood over and over...I hate wasting fuel, so I gave up. I think using that old bladder must have been my problem, probably not enough pressure after being filled full so many times and sitting wet for a week.
I made a new bladder for it and it ran great. Now I can tell the difference in the hotter fuel, it screams. I can tell that tubing gets weaker every time I fill it up, so I'll start carrying plenty of spares in the flight box.
Dec 12, 2011, 12:58 PM
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Great! Once graduating to this technique.. there's No going back :-)
DO use a tach. Dead silence in the middle of a 'move' can be expensive now that one has to pay 'collector' prices for cox bits.
Erm thinwall tubing comes in 100 foot rolls :-)
Dec 13, 2011, 08:36 AM
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What's the best venturi bore for a pressurized fuel feed for my fun-flying? I know the one I have on it is larger than stock but not sure exactly how much it's bored. I tried to see what size drill bit will fit through it, but it's in between bit sizes.
I do have a screen on it, so that might change the bore requirement, but it's better for hunting gophers.
Dec 27, 2011, 02:09 AM
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Going from memory ...and it's been a while
5/32 nd's IIRC was the usual rebore size for the TD venturi hole.
Best to get in there and gas flow everything in the carb as well.
I'm a believer in underpropping... max 'reliable' revs...for flat and level so there will be No sag in abrupt manouvers. Most of my flying involved abrupt gyrations 90% of the flight, so a wee bit of flat speed loss was the giveaway price of ful power when needed most.
Stunt type flying is of another species, likely even a 6x3 might work,TD's are mildly timed, no experiences with that tho.

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