Hayes 3 oz tank on skyray

[Gordon Tarbell]

Wasn't sure of which heading to post this, so move it if you must. I am doing up a skyray/dirtyDan/BBTU FP20. When mounting the tank inboard does the foot/lip side of the Hayes 3 oz. tank go against the doubler?

[Steve Helmick]

DD changes his tank setup pretty much on a daily basis, but last I recall, the answer would be "NO!".

At first, Dan always said to mount the tank (inboard or outboard) just the way it would be mounted in an R/C plane, i.e., "foot" down. That works awfully well, and is the way I used the 3 oz on my Skyray/.25LA, and also the way I use the 4 oz on my F'Twister/XLS .36, both outboard.

I thought about using the top tube as a uniflow vent, but figured that fueling would be a PITA, because you'd have to stand it on either the inboard wingtip or on the tail to fill it up. I wasn't willing to do either. I do believe that DD is using his Hayes tanks setup this way, regardless of whether they are mounted inboard or outboard. But I can't recall how many NV assy's were considered stylish last season, and neither of us has been to a NW contest yet this year. Next weekend, however, might change that stat.  Steve

[Gordon Tarbell]

Thanks Steve, I will mount it so that the lip or Foot is facing down toward the Wheels instead of against the double . Seems as it would have less head pressure change as it empties this way.

[Tim Wescott]

I run my Hayes tank outboard on my Skyray (because that's the way the plane came to me), with the foot down.  It works great.  The FP-20 seems to really want you to use muffler pressure; at least I get a more consistent run that way.

[Steve Helmick]

I run my Hayes tank outboard on my Skyray (because that's the way the plane came to me), with the foot down.  It works great.  The FP-20 seems to really want you to use muffler pressure; at least I get a more consistent run that way.

I also like muffler pressure on my LA .25, XLS .36, LA .46 and ST G.51. If nothing else, it cures the tendency to go rich/lean as it goes upwind/downwind, and I think it tends to cut down on foaming. I have not tried muffler pressure on my .46VF, PA .51, or DS .60bb, or seen any reason to try it. I will add, however, that if you tend to have various stuff get loose, muffler pressure is not for you.  Steve

[Tim Wescott]

I will add, however, that if you tend to have various stuff get loose, muffler pressure is not for you.  Steve

The first time I had a leak in my fuel line from tank to carb with muffler pressure it took me a while to put short engine runs together with a plane that was drenched with raw fuel.  It was an "OH!" moment when I realized that of course if you have muffler pressure a pinhole leak isn't going to affect the needle setting much -- it's just going to make the plane slobber fuel all over everything.

[Steve Helmick]

If the muffler bolts go loose in flight, the engine goes very lean. With engine parts prices being what they are, that's not good. A consistent leak at the muffler/engine flange isn't a big deal, but it has to be consistent. I wouldn't use a gasket, but would lap the two mating surfaces (not needed on an OS). I don't use any silicone sealer there.  Some may say that muffler pressure will fill your tank with exhaust goop, but they haven't thought out the physics. There's pressure, but very little flow. 

A good fuel filter is important. Most use the Sullivan "Crap Trap".  Steve