Author Topic: Fuel Tanks (Read 3053 times)

Bill Diedrich · « **on:** July 05, 2006, 06:29:09 PM »

What is the prefered type of fuel tanks for both profile and built up fuselage planes. I have heard and been advised plastic clunk type and on the other hand metal tanks.........What say the experts, inquiring minds want to know.

Paul Taylor · « **Reply #1 on:** July 05, 2006, 06:44:53 PM »

I would say clunk on profiles for sure.

But I am no expert. Guess you will have to wait a little bit for the experts to answer.

Wynn Robins · « **Reply #2 on:** July 05, 2006, 08:00:03 PM »

many schools of thought on this.....a lot depends onth engine you intend to use.

For me and my OS engines.....clunk tanks are the ticket for both profile and built up planes.

Bill Little · « **Reply #3 on:** July 05, 2006, 08:07:17 PM »

Hi Bill,

No preference here. I use both types on profiles. Usually just whatever I have at the time that is the right size. I do tend to use metal tanks on older style engines and clunks on the newer engines, but for no apparent reason.

Also it is somewhat dependant on what size tank I need and the space available to put it in.

Some swear by and/or swear at both types!

Of course, you have to know that I am the proverbial "Blind Squirrell"!

Bill <><

Randy Cuberly · « **Reply #4 on:** July 07, 2006, 10:41:22 AM »

Bill,
Either type can be used successfully.

The important issue with a fuel tank on a profile is to keep the tank and fuel pick up as close to the fuselage (needle valve location) as possible.

Using a fuel tank configuration that is higher than wide is usually the best solution.

Uniflo is mandatory for consistent results, although a few engines will run OK with standard vent set up there is always a constant "leaning" of the fuel mixture due to fuel "head" change without uniflo.

The Brodak medium wedge uniflo tanks will usually work very well, but the "Profile" tanks work best. The profile tanks are higher than wide and concentrate the fuel closer to the fuselage, so that the fuel is closer to the same level as the needle valve. This gives less differential of pressure due to centrifugal force between the tank and needle valve.

Chicken hopper tanks with a small tank outboard of the main fuel tank fed by a uniflo line inside the chicken hopper can give very consistent results and allow the use of a larger venturi if needed. The down side to chicken hoppers is that the needle valve setting required is very different from ground to air. It typically requires a fairly rich setting on the ground and then will give a consistent run for the entire flight after the first lap or so. They have been used almost exclusively on the old AMA slow combat to allow the use of larger venturis for more speed and still get reliable suction for maneuvers.
Usually takes a couple of flights to get the needle setting right.

The inboard mounted clunk system seems to work well with some engines but my personal experience with it was the same as with the chicken hoppers. Takes several flights to get the needle right due to the change in engine speed between ground and air. In this case it usually richens in the air.

Choose your own poison. Personally, I prefer metal medium wedge tanks because they seem to require less "maintenance" and work as well as anything.

The "Profile" tanks seem to be the least critical.

Jim Thomerson · « **Reply #5 on:** July 07, 2006, 12:57:44 PM »

I have to disagree about the superiority of profile type, higher than wide tanks. I have used only one in profile-type stunt. Depending on how I fueled it, it would either run out on me during the latter phases of the pattern, or give me an over run. I have used the flat rectangular tanks ever since with good results. Located outside the fuselage, inset in the fuselage, or stuck all the way through to the inside of the fuselage. No difference that I could see.

I think what happened is that as the fuel runs down, the centrifugal force of the maneuvers would force it to either the bottom or top of the tank and kill the engine. Running enough fuel to keep the pickup covered during the latter maneuvers would give an over run. I might have been able to solve the over run problem by doing some fast loops after completing the pattern, but I did not think to try it at the time.

Randy Powell · « **Reply #6 on:** July 07, 2006, 01:09:12 PM »

Like Bill, I use both, though I have a preference for metal tanks, but that's largely because I make my own and use my own design. When I don't have holes in them (like the new plane had), the work quite well. I've also used clunk tanks, but it seems I'm often unhappy with them for one reason or another. I know others that have great success with them.

I suppose it's a matter of preference, knowledge of the type and execution. I don't think one is inherently better than the other.

rustler · « **Reply #7 on:** July 07, 2006, 01:15:29 PM »

I've been flying a bought model recently. It was a bargain and has got me back in the air after so long away. It has a plastic tank with uniflow set-up, i.e. feed and vent are flex. fuel tube with clunk weights on the end. It's also installed so the greater cross section dimension is vertical! It's more or less o.k. in loops, but speeds up greatly in bunts. I suspect when I alter tank height to compensate it will speed up more on the loops and less on the bunts, but still too much in both. If it could be installed with the smaller dimension vertical this wouldn't happen.

fred krueger · « **Reply #8 on:** July 07, 2006, 02:48:15 PM »

A chicken hopper tank can be used quite successfully in sport/stunt without the extreme ground to air differences. In the 1990s I developed a chicken hopper tank that sticks out only a small amount beyond the needle valve assembly of a sidewinder mounted engine. A number of people use this successfully. Crist Rigotti and John Garrett are a couple notible fliers. An article on this tank was publish in Dec 98 'Stunt News' and later placed on the Tulsa Gluedobbers' website at:

http://www.tulsacl.com/WorkShopFUEL.html

I have built these for everything from 0.049s to .40s. The runs are very consistant and easy to set.

Crist Riggotti posted his new Phacade profile on SSW a couple months ago. The picture of the front end of his plane clearly shows the tank and how far the pickup sticks out relative to the spraybar.

Fred

Fred

Randy Cuberly · « **Reply #9 on:** July 07, 2006, 03:36:01 PM »

Well Bill,
As you can see...you're still getting Yay's and Nay's on both types.

I will say that most "problems" with any fuel tank can be traced to other causes, such as leaks in the tank or plumbing.

Bill Little · « **Reply #10 on:** July 07, 2006, 08:32:08 PM »

Quote from: Randy Cuberly on July 07, 2006, 03:36:01 PM

Well Bill,
As you can see...you're still getting Yay's and Nay's on both types.

I will say that most "problems" with any fuel tank can be traced to other causes, such as leaks in the tank or plumbing.

Hi Randy,

I agree totally with that statement! *Most* of the time, it is a physical problem somewhere, and not the "type" of tank. Heck, Billy W. (and others) have used "soap" bottles for tanks.

"the other" Bill <><

Jim Thomerson · « **Reply #11 on:** July 08, 2006, 11:34:05 AM »

I've not used one myself, but I have see the high profile-type tanks with chicken hopper work quite well.

fred krueger · « **Reply #12 on:** July 10, 2006, 08:37:15 AM »

Here's a couple of pics of the 3oz. chicken hopper tank on my ARF P-Force (Magnum .28 powered). I need to paint mine. Crist Rigotti's look so nice painted.

Fred

Jim Thomerson · « **Reply #13 on:** July 10, 2006, 11:22:41 AM »

Fred, very nice tank. Only thing I would comment on is your use of a bolt to seal the overflow. This is subject to leakage around the threads, although yours looks like the head is sealing. A solid plug, such as a BB or some such is better, I think.

fred krueger · « **Reply #14 on:** July 10, 2006, 12:02:14 PM »

jim,

I usually stuff a short length of 1/8" dia. music wire in the fuel tubing to seal the line. I didn't happen to have any handy when I needed it, so........I found a screw. I blew in the tube real hard to try to get it to leak...nope. I just haven't gotten around to replacing the screw (lazy I guess).

Fred

john e. holliday · « **Reply #15 on:** July 10, 2006, 08:16:02 PM »

I used screws for years with no problem of leakage large enough to even think about. Now converting planes over to a peice of rod epoxied into the plane with a peice of tubing long enough to go from overflow to the rod. I don't remember who posted that idea on the site, but, it works and you don't have to worry about losing the cap for the overflow. DOC Holliday

Bill Little · « **Reply #16 on:** July 11, 2006, 03:27:30 AM »

I like the BBs for the plug. I work them just far enough up into the tube to let the tubing almost close back around them. A 1/4" 4-40 socket head bolt inserted head first far enough that the threads are covered works great, too.

Joe Messinger · « **Reply #17 on:** July 11, 2006, 09:19:54 AM »

Hello,

I was reading the discussion regarding fuel tank set ups and, being relatively new at this, a I thought I would pose this question:

" Muffler pressure in a fuel supply system, or not?"

Perhaps that question has been heavily discussed and debated in the past but I have not been able to find anything written about it.

I'm aware of some of the perils involving pressure use such as a leak somewhere in the system causing a lean run and possibly doing engine damage. But are there enough advantages with pressure to warrant that risk? Do modern engines perform better than vintage engines (do) with muffler pressure?

Seems a good many r/c flyers use muffler pressure on their planes. Maybe that's not relative?

Anyone have opinions that they are willing to express? At this stage of my involvement in c/l flying, I'm just trying to sort out possibilities and make good use of any input someone might care to share.

Thanks,

Joe

Jim Thomerson · « **Reply #18 on:** July 11, 2006, 09:49:56 AM »

If you are running a uniflow tank which requires that it be sealed, except for the uniflow and fuel pickup, for proper operation, even the smallest leak is a big problem. I run muffler pressure whenever I can. I think it helps get a reliable run. I also run crankcase pressure with the TD engines for the same reason. I guess my comment would be you can get a fine run with or without muffler pressure, but I'll use muffler pressure if available. Others will disagree. It is more things which can go wrong.

Bob Reeves · « **Reply #19 on:** July 11, 2006, 10:25:13 AM »

I feel muffler pressure is a good thing.. Ya any leak developed during a flight will result in an overlean run but don't see that as a big problem. The odds are pretty slim and if you are running a modern ABC engine it really won't hurt anything. When we were all running ringed Tigres it could cost you a ring but again the gain in consistent runs was worth the risk. What has surprised me recently was how well it works with a conventionally plumbed clunk tank.