BritishCubBloke
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Not selling the cub are you? I’d be more worried about the headwinds on the way back.
Rowly
How is your cub configured now? Do you have a cruise prop you can use?
What belly tank are you looking at? What flight duration/speed are you seeing now
with standard tanks?
Have you run this Cub? I have a PA-18-160 with 26 tires. I can run 85KTs TAS with with a 74-56 on 7.7 gph. I just figure 8 gph with a climb. I know you want to be conservative, but a 12% over burn on a 17% underspeed is a lot. I think you want to nail it down a little closer to determine your needs accurately. Do you have an EGT gauge on this plane?
They say that you can't go to Lord Howe unless you have enough fuel for a return so that rules out waiting for a tail wind.
How Sir Francis Chichester did it in a Gypsy Moth on floats is beyond comprehension.
Yes, owned it for 16 years. It always seem to burn more and go slower! Haven't flown it a ton since it had an engine rebuild to 160HP at the end of last year, though. It is better than I'm saying, but I don't think it does anything like 85kts TAS on 7.7GPH and I want to be really conservative. It would get a fuel flow computer before it did the trip, which is essential.
If it did 80knots on 8 GPH you could do it with a standard belly tank, but you'd still be very at the mercy of oceanic winds. How Sir Francis Chichester did it in a Gypsy Moth on floats is beyond comprehension.
It would be fun though to have a Cub in NZ.
Goodluck.
Yes I would get an Insight G2 or an EPI and get some good numbers. Per Lycoming you can run peak EGT at 75% or less. 75% is 9.2 GPH. At 7.7 gph you are at 62% and I get 85 kts TAS there. It seems to be the "sweet" spot for a 160 You can get more range out of it going slower, but you drop down on the L/D curve so quickly getting there will drive you crazy.
Do not forget the most important overwater range question. Oil consumption. Make sure you know that one cold.