power for 100cc size plane

[Franz2002_01]

I am thinking of converting a 100cc size plane (~106in. ~28lbs). Tyically these planes are flown with a DA-100 gas motor which products 10-11hp. (=7.500W). If I go with the rule of thumb of 200W/lbs for 3D performance then I would arrive at a motor requirement in the 5.000-5.500 Watts range. What do you all think would a 5KW motor be enough for 3D type performance or should I go to a 7-8KW electric motor?

[treehog]

Predator 15KW with 14s2p and suitable solution in a CAP normally for 100cc motor uses ~ 10kw from memory
There is a link from a few years back when Predator motor first came out to be found in the search option

a replacement for 200cc is done with Wolfe in this link and I think he did the 100cc CAP Predator version

http://www.rcgroups.com/forums/showthread.php?t=776635

Ralf

[Jocke]

With my 36% scale katana, that is for 100cc engine i used the Predator 30/8, on 7kw it had nice power for both 3D and pattern, i used 15s2p but i would use 14s today, to power a 100cc plane with good performance i would start with 30/8, SPIN200 (22timing8khz), 14sxp 25-30c 7000-9000mAh 28x12" 2 blade Mejzlik, if needed with good cooling one can go up to 30x12". I guess other motor on the market that is to compare with the 30/8 would be Hacker A150 on 14s, with the Predator 30 you can get 10kw, so a larger motor like the Predator 37 or A200 would be way overpowered.

[Franz2002_01]

Is the reason why you chose more output power than a DA-100 because of the additional weight or because you feel that the 27 lbs planes are underpowered at 10 hp?

[Jocke]

At the time i was testing the powersystem, thats why i went over 7kw, ofcorse it all depends on the flying style and how much power one wants, i felt 7kw is enough for my flying style, but for the most crazy 3D power pilot might feel they want more, maby 8-9kw. Going with 11kw in the Katana i only used full power a few sec in vertical uplines and sometimes pulling out of hover at flight events to demonstrate the power.

My final setup was with the EVO25 15s2p 7400 batterys and a 27x12 3blade TH Mejzlik prop, this gave 11kw, and abit more with newly charged packs at a good temperature. With 14sxp and same prop one would land around 9-10kw i think, thats also a good max level for the controller and motor in terms of eff/ heat.

[Franz2002_01]

Jocke, Thanks for the answer. If I understand you correct then you feel that 7KW would be ample power for aerobatics unless one is into heavy 3D. One option that I am also considering is going to 5.5KW instead of 7KW. At that point I could drop weight by almost two pounds for the plane by using a smaller motor and less batteries. Usually planes fly much nicer with lower weight. However the plane might be underpowered if I drop power by 20% and weight only by 5-10%. On the other hand I could also prop for more thrust and lower pitch speed since lift goes with the square of velocity and a 10% drop in weight would equal a 20% (1.1*1.1) drop in required flight veloicty - any thoughts