Tank size for 120 4 stroke

[Peter Jenkins]

Bit out of practice in sizing a tank for an OS 120 Surpass. It will be used in a Top Flite Mustang 60 which I estimate will weigh between 10 to 10.5 lb. I'd like a duration of 12-15 mins. My gut feel was around 300 ml tank might be a bit marginal and a 380 might do.

Appreciate some guidance on my gut feeling.

Thanks.

[Jon H]

120 is a little excessive for that model. An 80 or 90 would be a better fit.

If you use the 120, 12oz would be plenty unless you are using shed loads of nitro

[john stones 1 - Moderator]

I had 16oz in mine Peter, I like a long flight and there was always a bit left in.

[Richard Wills 2]

My Hangar 9 Mustang 60 has a 120 Surpass, and a 20oz tank. Depends on how you fly it, mine is definately not flown in a scale manner and I would not want a smaller tank!

[Peter Jenkins]

Thanks for your inputs guys. I get through an FAI aerobatic schedule in 7.5 mins and I cannot see me flying anything as complex as that with the Mustang. Jon has come in with a suggestion between my two tank sizes so I think I'll go with the 12 oz tank.

[Jon H]

I use a 12oz on my laser 155. timer set for 8mins 30 so 10 mins by the time i am back on the ground with probably 5 minutes reserve for aborted landing.

A friend has an os 120 in his kyosho 90 spit, seems very economical once we tuned up the slow run

[Peter Jenkins]

That's very useful info Jon. Thank you.

[Paul Marsh]

16oz. I have loads of SLEC Black 16oz ones.

Ratios I use for engines are:

.10 size: 2 oz
.15 to 25 4oz
.32. to .40 6oz
46 to 53 8oz
60 to 75 9oz to 12
75 to 90 14 oz
120 16 oz

these are for two strokes, but a 4 stroke will give longer flight time

[Bob Cotsford]

I'm pretty sure I used 14oz with my 120s as I had a stock of DuBro 14oz tanks that went in everything, I used to set my timers for 10 mins and never ran out, the OS120 Surpass's seemed to use less than my OS61SFs!

[Former Member]

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[Jon H]

I used a 14oz on my 180 powered stampe. It was good for 15 minutes plus.

20oz on a 120? you will be up there all day! I have 22oz total capacity in my 300v equipped P39 and i barely use 2/3 over a 10 minute flight.

[Bob Cotsford]

Doc, we are talking 4 strokes here. I could see 20oz for a big 2 stroke, my piped OS61SF in my Tornado used to drain a 14oz tank quicker than I liked and I landed on fumes a few times but the same size tank with a 120 4 stroke was another matter entirely.

[Peter Jenkins]

Thanks again chaps. I've gone for a 12 oz tank. If I remember to, once the aircraft has flown, I'll report back on what happened!

[Former Member]

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