Tank Height

[DanielGelinas]

Hello,

I am putting together an arf oriental.
I have always had profiles, so this is my first full fuselage plane.
I have been reading a lot on this forum trying to educate myself as best I can since I am a lonely cowboy... knowone in my area flies control line.

Anyhow, from what I have been reading, it seems like tank height is less critical for a stunt run than in a profile. Is this correct?

If not, how do you go about adjusting tank height? And especially on an ARF oriental where the tank hatch is on the bottom.

Thanks for any hints,

-Daniel

[Steve Helmick]

There are various ways to adjust the "tank height". Shims usually on a full fuselage. However, if you are using a uniflow tank, you can simply adjust the location of the uniflow vent where it ends inside the tank (assuming it's a fixed uniflow vent). If you go with one that is tied to the clunk, then you are back to shimming.

I think you are in Canada? Could you fix your profile to show your location? There are a bunch of guys in Winnipeg and one or two in Saskatoon. If we know where you are located, it might (might not) be of some help.  Steve

[DanielGelinas]

Hi Steve,

I have a metal uniflow tank recommended by Brodak, all tubes forward.
So, I guess I can either shim the tank or open the tank and move the uniflow tube. I think shimming will be more simple. The way to tell how many shims is to fly the plane inverted?
Essentially, the same tank mods as in a profile?

I live a few miles north of Vermont...

Thanks,

-Daniel

[Steve Helmick]

The usual deal is to put the tank about 1/4" high (above the spraybar CL) and shim it down to make it perfect. That's not always easy with a kit, and even harder with an ARF/ARC. Planning ahead is your friend. Da Dirt says it's better to do "lazy eights" to adjust tank height so rpm is same in insides and outsides, and he's usually right. Steve

[Bill Little]

In the arf it is going to be a little bit tougher to shim the tank since being able to move it "up" (with the model on its wheels) is not built into the model.  If you can get mounting pads under the engine, that will give you 1/8" to move "up".  Moving the tank below the engine is very seldom needed.  Usually (depending on engine) it will need to go "up' to equalize the inverted run.  I usually do not have to go much more than 1/8th".  Moving it "up" leans out the inverted run.

When building a model I use pads for 1/8th" and slim down the mounts by 1/8th" behind the first former (in the tank compartment area).  This gives me a 1/4" overall to move "up" but I have never needed to go the full 1/4".  Make sense?

Bill

[Chris Wilson]

Anyhow, from what I have been reading, it seems like tank height is less critical for a stunt run than in a profile. Is this correct?

If you mean is a side mounted engine less critical than an upright or invert mounted engine then the answer is no. Being a profile shouldn't factor into tank positioning here.

They are all simply different in their needs.

With an invert mount engine you could gouge out some of the bearer that the tank rests up against to gain room IF you need to, and its not too difficult to do. Or custom make a thinner tank to allow more wiggle room.

[DanielGelinas]

Hi Bill,

Can you or anyone show me a picture of mounting pads you would use to adjust tank height please?

Thanks,

-d

[jim ivey]

here ya go , simple, no horse apples. wedge or pick point in tank must be on the same center line as the nva for upright  or inverted mount. side mount pick up needs to be on center of thrust or engine if you want it to run the same upside down as right side up. this very important.jim

[Bill Little]

Hi Bill,

Can you or anyone show me a picture of mounting pads you would use to adjust tank height please?

Thanks,

-d

HI Dan,

They are the 1/8th" pads that Tom Morris (and CLC) sell.  It drops the trustline 1/8th" in an arf, but that should not be a problem.  The spinner is not online with out some trimming.  By dropping the engine 1/8th" you give yourself 1/8" of an inch to raise the tank.

Bill

[jim ivey]

how is that going to work on a profile?  and how do you lower the motor imto the mounts on a conventional mount?    like the commercial. why not just put the tank in the right place in the first place? I'm confuzzled <-- conjunction=confused + puzzled  jim

[Bill Little]

how is that going to work on a profile?  and how do you lower the motor imto the mounts on a conventional mount?    like the commercial. why not just put the tank in the right place in the first place? I'm confuzzled <-- conjunction=confused + puzzled  jim

HI Jim,

Dan is working on the full fuselage version ARF.  On a profile it's not a problem to move the tank.

Simply putting the tank flat on the engine mounts in a full fuselage plane doesn't always work with some of (most of) the modern engines.  They will want to run richer when the plane is inverted.  So you have to raise the tank (with the model on its wheels) to even out the run.  It seems to be somewhat a result of uniflow tanks.

Bill

[Jim Thomerson]

In my experience, the level of the fuel pickup is not important, so long as it picks up fuel.  What is important is the level of the uniflow outlet in the tank.  Mine come out very close to the level of the spraybar, maybe 1/16 either way at most, which I ascribe to my inability to remember exactly where the uniflow is in the tank.