Running time on 1 oz.

I have to pick a tank.

The MVVS .49 will run, how long on an oz.?

A guess is fine, then I can do the math.

I noticed some tanks are 7.5" long!

CB

You can take fuel out of a tank which is too large. You cannot put more fuel in a tank which is too small.

<>

Grasshopper, exactly how much time does that add up to?

Well, all added up it's a sizable nose moment.

Unless, of course, the thrust line is well above the wing.

Anybody else read "Zen flesh Zen Bones?"

CB

><>You cannot put more fuel in a tank which is too
>small.>>
>
> Grasshopper, exactly how much time does that add up to?
>
>Well, all added up it's a sizable nose moment.
>
>Unless, of course, the thrust line is well above the wing.
>

You can pretty easily get 8 oz into a 6" long tank compartment, even with a header in the way. Just make it deeper. And you really can't get most engines in a 2" wide inside dimension fuselage, either, so you can make it wider as well. Just because Veco decided to make them 2"x1" in 1949 doesn't mean it's the only way to go.

Brett

Brett,

Thanks for the reply, I appreciate it!

Understandable.

However, my engine thrust line is only .75" above the cord center line. AND I only have 2.5" from the back side of my firewall to the leading edge. and this is if I keep the tank centered on the thrust line.

I don't want to make my own tank and I don't want to trim away the center rib so as to allow for a longer tank at the correct height.

The correct height on the center thrust line would bring the tank, part of it, recessed into the wing.

CB

Run it on the bench and measure the fuel consumption. I'd guess that a 6 ounce tank will be more than enough.

>I have to pick a tank.
>
>The MVVS .49 will run, how long on an oz.?
>
>A guess is fine, then I can do the math.
>
>I noticed some tanks are 7.5" long!
>
>CB
>
>

You will need between 75 and 90cc for a stunt run if you use a no-nitro fuel.

Now, how is your math!

>>I have to pick a tank.
>>
>>The MVVS .49 will run, how long on an oz.?
>>
>>A guess is fine, then I can do the math.
>>
>>I noticed some tanks are 7.5" long!
>>
>>CB
>>
>>
>
>You will need between 75 and 90cc for a stunt run if you use a
>no-nitro fuel.
>
>Now, how is your math!

[photo not recovered: sipcof.gif] how many cc to an once?

29.57 cc = 1 oz.

On the standard silencer, my glow 49 used 75 to 80 cc of 5% nitro fuel up here where I live at 5000 ft. ASL. At sea level this would go up to 90 cc. My friends that used tuned pipes use around 110 cc. A 3.5 to 4 oz tank will do just fine. R/C clunk tanks will also work if you set them up properly, so you have many choices. I always used my own metal uniflow tanks that were like the old ones......1 inch thick, with length and width to suit the model.

Uniflow!

Does the tank feed line have to be at the same height as the needle valve?

In all cases?

With a standard tank?

CB

In my experience, it does not matter where the tank fuel feed line is, so long as it stays submerged in the fuel. What is important is where the end of the uniflow line is in the tank. The engine thinks it is sucking fuel from the end of the uniflow and does not know where the fuel feed line is. Again, in my experience, the opening of the uniflow needs to be at or near the same vertical level as the needlevalve on the engine.

Jim,

Interesting!

So my tank can be an inch above the needle valve with no issues if I fly inverted?

You mentioned the uniflow line, didn't you mean horozontal and not vertical?

CB

CB,

Lateral (spanwise) position does have some effect, but "vertical" location has much more. E.g., with the tank shell centered on the engine bearers, both the pickup and the uniflow tube end are outboard of the centerline. That has worked ever since Control-Line negan.

With the model horizontal, wings level, visualize your engine and tank relationship from in front of the propellor. The location of the uniflow tube end inside the tank should be close to the same "height" as the spraybar. If the end is above the spraybar, you get some "positive gravity head" - fuel tends to pour, of its own weight, to the engine. And, of course, vice versa...

(I've done some experiments that strongly suggest this is not a definitive answer for all engines, but it should be close enough to start with.)

Leave some space and access to adjust the tank height to place that uniflow end where the engine runs the same in upright and inverted level flight.

Lou,

What is "E.g.?"

Also, I will have to have a custom tank made or I will have to make one myself.

2.5" long, 1" high, and 2.5" wide. Yes, with a "V" wedge on the outside.

CB

>Lou,
>
>What is "E.g.?"
>
>Also, I will have to have a custom tank made or I will have to
>make one myself.
>
>2.5" long, 1" high, and 2.5" wide. Yes, with a
>"V" wedge on the outside.
>
>CB

"E.g." = "For example..."