As the Hayes 3-ounce clunk tanks have become the defacto standard for many Pukey Profiles, especially those powered by the 25LA and the 20FP, a few comments have come up.

First, availability. I have ordered mine from Hobby People, especially as this is also my source of another defacto standard, Thunderbolt glow plugs. I have also ordered them from a local hobby shop with no problem.

This morning I called SIG Mfg., and while there was a bit of hesitancy at current stock levels ("We've got a few...") they are stocking these tanks.

Another issue is the short, seemingly too-stiff internal feed line supplied with these tanks.

It works just fine. Yes, I know that the clunk will not readily flop to every corner of the tank when the assembly is hand-held and moved around. Don't worry about it. During flight the clunk will readily follow the fuel.

However...

Last night I was going through several tanks in prepping them for the new season. Hmmmm...

The oldest of these tanks has been on my Skyray 20 for almost two years. The feed line in the tank has stiffened to the point of being useless.

We flash back to the VGMC contest of 2005. The 20FP quit prematurely and this should not have been an issue. No way, no how.

Derek Moran and I were flying together, like any Pit Dude who takes his duties seriously, he picked up the model and announced there was still fuel in the tank, certainly enough to have completed the pattern.

The contest was over, I blew it off as an anomaly. And probably didn't have any further problems as I simply made sure to put in a little extra fuel for the next contests.

In looking back the stiffened tubing was quite likely the problem.

Also a "problem" is that these tanks are so reliable one installs them, adjusts the height of the tank and then treats them as bullet-proof.

Don't freak on me, but assuming I cannot find suitable silicone fuel line--and I have not been able to do so in the past--I'm switching over to surgical tubing.

Yeah, yeah, fuel gets to the stuff, turning it to junk. But this does not happen right away; I'm betting a guy could easily get a half-season out of each chunk of tubing.

Being a very conservative sort when it comes to model prep, I have already cut to proper length a dozen pieces of surgical tubing, packed them into my bag of spare tanks and fittings.

Remember, these Hayes tanks are nothing like the ubiquitous Pylon clunkers. There are no screws, plugs, hard-tubing feed lines, vent lines and fill lines to get positioned just perfectly.

Instead, one simply grabs the plastic fitting at the front of the tank, pulls it free of the tank and has ready access to all of the internal plumbing. It is a really simple task to insert a new piece of tubing. Simple enough to do this at every practice session, the morning of every contest.

That should not be necessary, but might be a good idea in the beginning and until one knows more about the effects of his fuel blend on this vital piece.

Incidentally, there is also a 4-ounce version of this tank which might be of interest and which seems to be more widely available. It's only .020-inch taller than the 3-ounce tank; assuming you have any room at all for height adjustment, it will fit.

The 4-ounce units are .120-inch wider and this would not appear to effect the functionality of this tank for our application. They are about .445-inch longer, which means they won't nestle behind the engine on any ARF Flite Streak I have seen.

However, they will easily fit on the left side of a Flite Streak fuselage, an increasingly popular option, even if it looks weird. There is also adequate room for these 4-four ounce tanks to be mounted behind the engine on a SIG Skyray 35.

One of the reason for mentioning the option of a 4-ounce Hayes tank is that I am getting some questions from those flying 20FPs w/BB T-U at high altitude and have suggested more potent fuel with 20% known as working well, 25% being a distinct possibility.

Fuel mileage will of course go down and might get to the point where the 3-ounce tank--which is not actually a full 3-ounce capacity--will not quite deliver a full pattern.

Finally, if you will be trying these tanks for the first time, at least with 20FPs I have found positioning the tank such that the fuel-outlet nipple is 1/8" low in relation to the engine centerline is a good starting point. Be prepared to shim tank up or down with shims of 1/64" ply when getting real serious about it.

Also mount these tanks such that the back end is kicked to the outside of the circle about 1/8 inch.


Dan

Hey Dan,
How about a URL with stock number?

Thanks
Paul

Thanks for the heads up.
I built a tank from dimensions that Charlie Reeves gave me on my FP 20..  It is square (no wedge at all) with a baffle, and I use muffler pressure to even out the final laps.  So far it has worked perfect.  I will get around to ordering a Hayes tank this summer.

One thing I have noticed on these tanks is, the line inside the tank will fold over on it's self. It's a fine line between flexable and too flexable.

Yes, that can happen, but this is also the case with most any RC clunker tank. In fact, the larger tanks such as 16- and 20-ounce units are quite prone to this.

If one has even a sudden-stop landing--not a crash!--it's always a good idea to shake the model to see if one can hear the clunk rattling around free.

Dan