Calculating Power to Weight Ratio - IC

I can calculate for electric stuff but looking for petrol engine formula. Have two engines in mind, one developes 5.5hp and the other 4.8hp. The engine is going into a 16lb approx, scale aerobatic plane but not being intended for use in 3D, just general sport stuff. I am hoping the 4.8hp is strong enough.

Maybe not the ideal way to look at it but 4.8hp would be (electrically speaking) 228 watts per pound whereas the 5.5hp would be 261 watts per pound. All this also depends on best prop of course!

Phil, completely off topic but I had to let you know how much I enjoyed your new profile image, only temporary of course but very topical!

Reminds me of my 92 year old cousin who had a hip replacement under epidural anesthesia and, being wide awake throughout her op, claimed that the surgeon's running commentary and all the sawing and hammering which really helped to pass the time!

Have a good rest and a rapid recovery.

David

Thanks David. Just got a call from the hospital at 1800. Admission been put back 5 hours from 0700 to 1200. I think they are trying to string me out... :lol:

Hope they don't use string Phil - You'd be far better off coming out of hostpital with balls made of stainless steel ! (in your hip joint of course)

But seriously - Hope all goes well. Then when you get out of hospital you might get a sensible answer to your original question.

Phil - Wishing you all the best for your op and look forward to seeing you back in action.
Regards
Colin.A

This might be of some help Thrust Calc

Although I haven't used it in anger, feeding in some sample figures for my OS 22 seemed to give believable results.

Top Tip: Check your feet point in the right direction before they sign you off