Gutless Wonder was "Fuel economy, ST 60, oxymoron?"

For those that followed the earlier thread, this is a status report...

Well, I dropped the Venturi to .280, and my powerful fuel pig turned into the "Gutless Wonder", and still only got 4:48 of fly time. It was not even happy swinging a Zinger 13x5. So, I am back to my original plan to do a larger tank. Is anyone out there doing "custom" tanks????

I have plenty of width, and could accomodate an almost 2 1/2" wide tank, instead of the standard 6"X2" 6 Ounce that I have now. I could also take another 3/4 inch in length to the backplate, if the vents go the right way.

Eric,

I make tanks.I had a problem like your's with my VECO Chief/VECO .35. I made a 5 1/5 oz uniflow tank the extended up between the engine bearers and was a little deeper on the bottom. It's a funny looking thing but It works beatifully.

What kind of time were you getting with the large venturi? We have to do some math first to make sure we can get there from here.

First, check with the new owners of GRW Hobbies. The GRW tanks include some models that are 2 1/4" wide and 1 7/16" deep, in several sizes. If you need a phone number for them, holler back - I have it in another room other than the computer room!

The problem of the Chief with a fuel-hog engine (Veco?) is often a problem with the oldest designs because of the change from spark ignition engines to glow engines. The sparkies are/ were much more economical than glow engines, so the noses of old designs quite often are too short for much of a tank, even for the somewhat "short" OTS pattern.

That said, the thought that a Veco 35 needed more than four ounces of fuel surprises me. The Veco combat model was thirsty, but I can't recall that either the pre- 1955 35's, or the Series 100 regular 35 versions, were much of a problem that way. The Chief had what I think of now as a sufficiently long nose, but a rather short tail. The Glow Devil that preceded it also had a fairly generous nose length, the way I remember it.

Kiwi

Hi guys,

Thanks for the generous offer and advice from you both. Since at first, it didn't look like I was going to get a response here, I had made the call to Big Jim and Windy. Both of which gave me some very good suggestions from their experience with ST60's.

1st I dug up a Hemi head I forgot I had (premature senility sucks!) and will bolt that on. Windy says it's good for darn near two minutes over the stock high compression head.

2'nd I have received 6 1/2 Oz & 7 Oz tanks from Brodak. Whichever will shoe horn in, will do.

3rd Put my old venturi back

4th I have head shims coming in, which I am told to add, if the hemi head still isn't enough.

5th Stop using the all castor 5% Sig and switch to half and half 5% R/C. I just bought some Omega.

The consensus is that these changes will give me more than adequate power and time to do the pattern. We shall see, and I will post the results if you're interested.

Thanks again!
Eric

Eric,

Please do keep us up on your progress.

Kiwi,

I too was amazed at the Veco's thirst, actually I changed to the Veco from a GH Torp .35 because of it's thirst. The GH ran well as a stunt engine, had I known the Veco was going to use as much fuel, I'd have just made the bigger tank in the first place.

Yes, please post your findings! I have a NIB early ST .60 (and a bench run only DS .60bb) that will no doubt benefit from your experiments. Steve

Ok --

I did the surgery last night. The 6 1/2 Ounce was the one that fit, and since I had the extra width, I shimmed it at an angle, with the pickup furthest outboard (As suggested by flying buddy EddyR) so I can empty the tank better.

Funny, the Hemi head, which has the fins milled, and the under side of the outer deck lightened weighs a full half ounce less! Wow! (I weigh everything these days)

I was real close before, so any improvement at all will give me what I need to finish the pattern. What I am shooting for is some margin for travel and weather. Ideally I don't want to fill the tank here at home. If I travel, and need more fuel, I want the room to be able to compensate. We'll see.

We have finally gotten some rain in our drought here, but I will try to get in some flights this weekend.

I'll keep you posted.

Do NOT use the Omega without some serious additional castor added. This is not 50-50 by any means, and is far too low in total oil content to begin with (about 17% by WEIGHT, or about 14% in actual content as has been reported to me). Basically Omega is a squirt of castor in what otherwise is weed killer fuel (or stunt engine killer if that is what you want to use it for.)

Now, for whatever reason, our 50-50 SIG fuel (20% oil content, good stuff) gives lower fuel economy than all castor of the same nitro and oil content. As the advertisements say, "Your mileage may vary" so I would be interested in learning your results with the ST 60.

The other advice sounds good, and I am sure you will get there.

(Your jump to a smaller venturi, by the way, was drastic. I am not surprised that you got significantly lower power. When changing venturi size, it is best to go in smaller increments until you find the right balance.)

Lenard,

I've come to the conclusion that with 29% castor fuel you not only have only 71% "fuel" but the heavy castor leeches away more power causing the economy drop in some of these engines, particularly in young (low time) engines. I can't figure any other reason for the poor economy I and some others have experienced. Of course I still use it, my little gems need a life beyond economy, and castor is their "fountain of youth".

Hi Len,

More than one "expert" has said to me that all castor fuel is a death blow to a ST 60, that the ring will eventually stick and score the sleeve, then you throw the motor away!. I chose Omega, since I know that Cool Power is all synthetic, and that Omega has at least some castor.

I also have Sig 5%Nitro/29%Castor Champion, and was told not to use it.

Eric

That's a bunch of BULL. To much castor.... yes I see that, BUT all castor give me a break. The ST-60 likes castor at least 20% All Castor. You need to remove the heat from to engine and castor dose this well. WHO reworked your engine? If it's a Tom Lay, Big Jim, they like castor. There are so many factors, DON"T get rid of your fuel. Write the engine man that reworked your engine and ask WHAT"S THE BEST fuel for this engine. Scott

My concern is the amount of castor and the total amount of oil, both of which I feel are too little in Omega. This is not a 50-50 blend or anything close to it. A ball bearing, ringed engine should run fine on a 50-50 blend of castor/synthetic. I think that the concern some people have is that all castor can sometimes form carbon which can cause the ring to freeze on the piston. A 50-50 blend gives enough synthetic to keep this from happening. If you added about 8 or so ounces of castor to the Omega you might get close.

Morgan once sent me two gallons of his fuel for free for me to try on my engines. He "guaranteed" me that it would not hurt my engine. I took a brand new engine that I had carefully broken in, and in one flight, using his fuel, saw that engine totally destroyed. I salvaged the needle valve, the prop washer, and the prop nut. It was the worst case of destruction that I have ever seen in my life. And, no, I am not sold on his fuel.

I agree that there is ALOT of fuel of there the should be WEED KILLER. COOL POWER,OMEGA,the blue stuff,the Green stuff, and others. If you fly C/L THAT'S CONTOL LINE go with the stuff that works. Don't try to re-invent the wheel. IT'S so simple. Do what the big boy's do.

Hi Guys,

Thanks for the concern, and Len, thanks for the heads up on the Omega not being a true 50/50 blend. I'll take care of that.

As to the people that question the advice I was given, I didn't want to quote them without permission, but since it was brought up, it actually was BOTH Big Jim and Windy who told me not to run all castor in the ST, along with the warning. I don't know of too many others that know Supertigres any better than those two. They did NOT reccomend OMEGA. I came up with that on my own, based on me believing what the label said.

OK, so If I take a half gallon of Sig Champion 5%/25% all Castor and mix with a half gallon of Omega, would this be sufficient?

Lets see, 128 Oz in a gallon, 25% castor would be 32 ounces of oil. A half gallon of Sig would have 16 ounces of oil, added to the "Squirt" of castor and synthetic in the Omega's half gallon. Assuming that the Omega had Zero castor, I would still have 12 1/2% castor in this mix. Am I even close?????? Would ratio make Len happy if it were his engine?

On my "one time" test of Morgan's brew I got a lean run. I don't know what caused it, but it went lean in the air. Insufficient lube? Insufficient cooling? Junk in the needle? I don't know. If it had stayed 4-cycling it may have been OK--for the short run. Long term affects are still going to be a shortening of engine life. We have a local hobby shop who stocks the stuff "because the RC flyers want it." But he added...to me..."I don't care. I'll sell them another engine." That's as great a product endorsement as you will ever see.

On the lean run situation, we don't want to ever see one, but we need to plan ahead. They do happen. I got some "junk" in the needle running a Fox 40 once on all castor. It ran for 15 minutes screaming its little head off. It damaged the rod at the wrist pin, but that was the only damage I could find on the engine. It had varnished the piston/cylinder, however.

Castor, when it gets hot, will form a varnish which will continue to protect the engine. Synthetic when it gets hot will burn away. Nothing is left. A lot of the RC types like all synthetic because it doesn't "goo" the plane. But if there is no oil coming out to "goo" the plane, imagine what it is doing to the inside of your engine. Besides, the oil coming out helps to cool.

The problem with castor is that when hot it will form varnish, which, if allowed to build up, can push the piston over and increase the wear on the engine. Thus, a lot of old engines run on all castor, if you clean them off, will actually lose their compression. In extreme heat (like on the top of the piston) it will actually form carbon. If this gets in the ring, it can actually freeze the ring. So there is the dilemma.

Synthetic will clean the varnish off the engine. (Read the Byron's label. He claims one flight will do it.) Working together the castor will continue to protect the engine, the synthetic will continue to keep its insides clean.

On a ball bearing ringed engine, or a ball bearing ABC engine, a 50-50 mix of castor/synthetic works well. On a Fox 35, or any of the all iron piston/cylinder engines, stick with all castor. On something like an FP with its plain bearing shaft and ABC (ABN) piston/cylinder, either works. I prefer all castor. Some prefer the 50-50.

Except for the Stalker engines, I don't know of any manufacturer or major engine reworker recommending less than a 50-50 blend. Big Art used to say use all synthetic on his FP 40 conversions in order to get away from that dreaded "burp" that occurs on these 40's when converted that way. But I like my engines too much to do that. I thus recommend the 40FP, when modified this way, for side mounting only.

Now 50-50 is only a "recommendation". There is nothing inspired about that number, like as if 49-51 or 48-52 either way won't work. How much synthetic is needed (what is the minimum) to keep the engine clean I don't know. How much castor is needed to protect it, I, also, don't know. A lot will depend on how the engine is run. If you never run it hot, you will have a lot of leeway either way. If you do run it hot you will want the castor to protect, you will want the synthetic to clean. If you mix 25% all castor with Morgan's Omega, by my estimation you will end up with about 19 to 20% total oil by volume, and about 2/3 will be castor. You could go back to Windy and Big Jim and ask them what they think.

I guess I would start with the mix I wanted from the very beginning. But then, we buy fuel ten cases at a time.

Thanks Len,
That's a helpful visualization.
Along those lines, I was interested to hear from a friend at my club that in the "good ol' days" when the Supertigre was at it's peak in C/L, that Taffinder actually made a fuel labeled "Tigre Fuel" or something similar, as requested by the likes of Windy, Tom Dixon, Big Jim and others, and that it was a 50/50 castor/synthetic blend.

It's funny, what was common knowledge in the past, I am having to re-learn in the present. I guess that's what I get for running 30-year-old engines!!!!

Thanks again,
EricV

Eric,
I've just run about 40 oz's of fuel through my ST-60K. (break-in duty) This is the pseudo converted RC engine. At this point all I've done is installed the venturi and needle assembly from the recent ST-51 C/L engine into the front end, ....a bolt on. Turning a 11 x 7W J-Zinger at a constant fast 4 stroke it's running between 8 min.'s. to 8.5 min.'s. before running out the contents of a 6 oz. R/C clunk tank on the test bench. I remember this thread , and just thought I'd pass along the inf. for comparisons sake. Static -vs- airborne run time may change somewhat perhaps, ...any idea's on this one guys? What might I expect given the bench run performance so far? Running 5% nitro content at this stage. Thanks.
Tony

Eric,

Just to share my experience with running an ST60 for the first time this year.

I started with a reworked ST60 (Aldrich), 6.5 oz tank, 10/25 Sig all Castor fuel, and tongue muffler (important later)with a 12X6 Prop (pitch verified). At a launch RPM of about 8800 I was getting 8 minute runs on 5oz of fuel.

With Brett Buck's help, I started to work on improving the compression (removed 3 of 7 .003 head gaskets) reducing the venturi size, a true sprinkler venturi by adding an air filter (green/fine), increased the engine load with a 13X5.5 Rev-Up. Still was getting 7:30 engine runs on 4.75 oz of 10/25 Sig all Castor. Launch at 8200 RPM.

Then I drilled out the muffler exhaust holes from 8 holes of .12 inch to 12 holes of .125 inch. Now 6 oz of fuel gives a 6:25 engine run with a 13X6 BYO prop at a launch RPM of about 8000RPM.
And, MORE POWER!

The back pressure of the muffler is a SIGNIFICANT factor on fuel economy! And I would pass on my experience with a tongue muffler on a OS 40FP. After 200 flights, I started getting better and better fuel economy; but also a loss of power. That's when I found that carbon build-up in the holes of the muffler was gradually restricting the exhaust. Cleaned the holes out (burnt castor varnish build-up) and the power came back and the fuel economy disappeared.

Bruce Hunt
Salem, OR