I know what I'm asking is akin to "how long is a piece of string?"  So let me elaborate:

I'm building a Legacy.  I'm building from a Brodak kit, and aside from molding the top deck and maybe replacing any really obnoxiously heavy wood, I'm not going to do much to lighten it.  I am going to pay attention to weight during finish as best as I can, but this is going to be my first 'span and dope finish in over 30 years, and my first show-quality one ever, so I can pretty much guarantee that I won't win any prizes for lightness.

To further complicate matters, I may be swapping out engines.  The engine that's going in there initially will be a Byron Barker Magnum 52, but I'll be building the mounts so that if some other nicer engine falls out of the sky, it'll be easy to put it in.

What I'd like to do is plan on putting in a tank that's plenty big enough for whatever I might use, or at least making sure that there's room for such a tank.  I certainly don't want to be caught with my pants down when it comes to flying the entire pattern with this plane.

So -- what tank would be appropriate for a moderately overweight Legacy and a Byron Barker Magnum 52?  How about the same plane and a PA 60 or one of the Eastern European stunt big-blocks (assuming one dropped out of the sky, of course)?

Tim,
6.5 oz will cover most engines through a PA65.  My PA65's use a squeak under 6 oz but if you were to want a larger venturi they could demand a little more than 6 oz...hence 6.5 oz.

Were you to decide you wanted to use a 75 then you're going to need about 7.5 oz or maybe a little more depending on the nitro content and venturi size.  My RO Jett 76 demands about 7.25 oz to run for just over 6 minutes!  This is with a slightly larger than stock venturi and 15-18% nitro.  I typically fly at 2400 ft and higher than most temps.   Oh yeah, this is with all engines on a Smith/Werwage pipe.

If you run a "real engine" you will want to run a pipe!

Your results may vary...but probably not by too much!

Randy Cuberly

Is this tank going to be made out of flattened peach cans again?   Steve

That was funny Steve.  The first time.  Don't you think you should work on fresh material?

I think this plane is going to get a metal clunk tank.  I don't like plastic when I can't see it, and I can never seem to get a fixed-tube tank of any sort to work quite right.

Yes, that's odd.  Maybe some day I'll get this tank stuff figured out.  In the mean time, I'll do what works for me.

I think this plane is going to get a metal clunk tank.  I don't like plastic when I can't see it, and I can never seem to get a fixed-tube tank of any sort to work quite right.

Yes, that's odd.  Maybe some day I'll get this tank stuff figured out.  In the mean time, I'll do what works for me.

   I would expect to not need a lot of fuel with a detuned Magnum 52. I would also suggest that you make sure that a PA/RO-Jett 51/61/65 will fit as well and that will need a lot more fuel - at least six and a half ounces but possibly much more. If it was me I would use either a 7.2 or 7.5 ounce tank, a typical tapered wedge tank will work fine. In any case, don't build it in, make sure you can use all the available space and change tanks easily if necessary.

    Brett

   

The above is good ADVICE, try to follow it, I have seen too many planes ruined by having to cut a tank out of it.
By the way  my Magnum 52s  use about 6 ounces for a pattern.

I'm planning on making the plane so that motor and tank can be replaced -- but I want to start with a tank that covers most of the possibilities, without being absurdly big.

Actually the Legacy is designed with the engine bearers elevated by 1/8" to accommodate pads.  If it hadn't been, I would have carved 'em up.