power/weight ratio?

bartley · 06-04-2005

Hi all, do you know if there's a power/weight ratio guide anywhere which, depending on type of plane, build etc. will provide info as to what will actually get off the ground?

I know that I could just have said that my Nieuport 11 has been scratch built as acurately as pos. with a 4' wingspan and has an OS 25 glow engine and may well come in at 4 or 5 pounds all up, so will it fly?, but I'd be interested to know, for present and future reference, what the weight limits are.

Incidentally, the slower the Bebe flies, so long as it does fly, the better as I wouldn't want it whizzing around like a Spit on Speed!

Thanks,
Steve.

Greyhead · 07-04-2005

Weight isn’t the most important factor, especially in the case of these old biplanes, what really “soaks up the power” is drag.

Obviously the wing has to produce enough lift to overcome the effects of gravity or you end up with a RC car but once again with biplanes there’s loads of wing area so that’s not usually a problem. All the flying wires, interplane struts and dummy guns etc. soon add copious amounts of drag but without the use of a wind tunnel it’s pretty much guess work.

As an example, using a Laser 70, my 62” span Elf flies quite happily on ¼ throttle but my 54” span Albatros DVa certainly wasn’t overpowered and both models are about the same weight.

All I can say is that if you’ve gone to town on the scale additions, in my opinion the power may well be marginal, especially if it’s an OS 25 Four Stroke.

bartley · 07-04-2005

Quote:

Originally Posted by Greyhead

Weight isn’t the most important factor, especially in the case of these old biplanes, what really “soaks up the power” is drag.

Obviously the wing has to produce enough lift to overcome the effects of gravity or you end up with a RC car but once again with biplanes there’s loads of wing area so that’s not usually a problem. All the flying wires, interplane struts and dummy guns etc. soon add copious amounts of drag but without the use of a wind tunnel it’s pretty much guess work.

As an example, using a Laser 70, my 62” span Elf flies quite happily on ¼ throttle but my 54” span Albatros DVa certainly wasn’t overpowered and both models are about the same weight.

All I can say is that if you’ve gone to town on the scale additions, in my opinion the power may well be marginal, especially if it’s an OS 25 Four Stroke.

Thanks for that, I'll go easy on the 'extras' 'till I see how she goes.

Steve.

**Bluewavestudios** · 08-04-2005

Steve,

The OS25 should be fine for that one, I had an own design which weighed in at 3 & 1/4 pounds on a PAW .19 Diesel. At first I thought it was heavy for that engine but it was extremely quick !!!. Mine was a single wing design too....but as Grey has stated above ..drag factor comes into it with Bipes but I think you will find that the OS25 should be more than fine due to the extra wing area. (Presuming it is the 2 stroke engine that is !!)

Regards..........Mark.

**wonwinglo** · 08-04-2005

Quote:

Originally Posted by bartley

Thanks for that, I'll go easy on the 'extras' 'till I see how she goes.

Steve.

*** Steve you are getting some good advice here about biplanes in particular,one thing that will help is not be afraid to experiment with different propeller sizes and pitch,these type of models benefit from larger torqy props rather than screaming away with a small one which are more suited to fast models,also the large frontal area can sap a lot of the useful pitch,so as I say just experiment,you will be surprised what a difference the correct propeller for the application will make.
You will be ok,your Baby Nieuport will fly fine.