Endurance design spec? - help please!

Hi all,

I'm looking for a motor/prop combination that will give me good endurance (over 45 minutes flying times) on my model. It seems like something along the lines of a relatively low KV motor (maybe this 400 KV one: http://www.rctigermotor.com/html/201...r_0910/40.html) and a larger prop with a 6S battery would be quite efficient?

The table shows that with a 15 x 5 prop I can generate 2620g of thrust at 100% throttle, drawing 18.7A for a strong take off (about 1.25:1 thrust:weight) and can hopefully cruise on something like 50% or lower throttle, drawing 5.7A which would allow for a long flight time (provided I used a large enough battery).

I guess my question is: am I missing anything here? Obviously there are a lot of variables in calculating flight times but it seems like this would be a reasonable option for me? Is there something I'm missing like this prop isn't suitable as it would take an age to spin up or something like this?

If it's of use, there's a little more info about the plane below:

Weight: 2100 g / 74 oz
Wingspan: 2000 mm / 79 in
Wing area: 60 dm2 / 930 in2

I've run this through WebOcalc and it seems to agree that the plane will fly ok but suggests a different propeller (13 x 6.5). In reality I need a folding prop and am restricted by what's manufactured so maybe something like a 14 x 6 would be a good compromise?
I've found a good website that has quite a few options for props here: http://www.gliders.uk.com/PROPSSPINN...departments/6/

Thanks for taking the time to read through this and any advice would be much appreciated.

Cheers, Tom

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