ZoomZoom-RCU

[8D] Got a quick easy question for you 1/4 scale flyers. I am working on a scratch 1/4 scale bird and need a recommendation for fuel tank size. I guess 16, 20, 24, and 32 oz. would all fall in the correct range. If it helps I'm using a converted 25.cc homelite engine as the umph. TIA for your responses.

ZZ.

RK-Aircraft

My Feedback: (81)

Any of those will work. It depends on what flight time you want and how nose heavy it will become when fully fueled unless you can center it on the CG. Also check the cavity size behind the firewall. DuBro and Sullivan have the most variety and shapes.

Dr1Driver

Even at full throttle, 32 oz. will keep you in the air a LOOOOOOONG time. Big gas engines tend to be miserly on gas consumption. However, there are five most useless things to a pilot.

1. Runway behind you.
2. Altitude above you.
3. Airspeed you don't have.
4. A second ago.
5. Fuel in the supply can on the ground.

Dr.1

ZoomZoom-RCU

[8D]Cool! Thanks guys. I'll probably go with the mid 20's size. After all, you dont have to fill it full! As far as room for the tank, its no problem. Its a Fokker type so you've got this big cavernous box to move the tank around in aft of the firewall. Fokkers are always my first choice to test a new aircraft size, or engine. They are great test platforms, and you have a lot of room to move stuff around if you have to. Getting the tank on the CG shouldn't be too tough. Since we're on the topic, do you all know of an easy way to fill a gasser with just gravity. I mean without pumps etc. On aircraft tanks there are no fuel caps of course, so I was planning to use the third line in the tanks stopper, (you know the one that you usually dont use thats not a backfeed or a fuel line) and just run a tube to the exterior of the AC, with a plugged end. That way when It comes time to fill, I just un plug the stopper, link it into an adapter for it on my regular jerry can thats vented, raise the jerry can above the tank level, tilt, and let physics do the rest. Or is there an easier way to gravity fill that I'm missing?

ZZ.

joeflyer

My Feedback: (48)

It's surprising how miserly these gas engines are. I have a 16 oz. tank feeding a converted Ryobi 31 cc. engine in my Extra 300. I can fly WOT for 20 minutes. I've thought of putting a 12 oz. tank in it since I rarely fly for more than 10 or 12 minutes. With a 25 cc. engine you should do better than that.

Of course it depends on how long you wish to fly. I would guess that you could easily go 20 minutes on 12 oz. If you want to fly longer go with 16 oz. In my opinion anything more than 16 oz. would be overkill.

I would expect that trying to gravity fill the tank would take way too long, and how would you empty it? I have the Dubro E/Z Fill Pump, which is a bulb that you put in your gas can line. You squeeze it to fill the tank. Each squeeze is 1.5 oz. If you point one end up it fills, if you point the other end up it pumps the fuel out. They are inexpensive and mine has lasted 5-6 years so far with no signs of wear.

Your local hobby shop probably carries it. If not they are available through Tower.
http://www2.towerhobbies.com/cgi-bin...?&I=LXD705&P=7

Joe

stomper

My Feedback: (20)

16oz is more then enough for a 25cc engine!

ZoomZoom-RCU

Thanks guys!. Now I can make an informed decision. I'll look for a tank in the 16 oz range!

ZZ.