Prop pitch speed for Sea Duck?

[fahrvergnuugen]

I built a FT Sea Duck and powered it with some motors and props I had left over from an old 450 sized quad copter. The plane barely flies, and now I have a question about motor & props because it seems the recommended powerpack C is only a tiny bit faster pitch speed then what I'm using. This is my second airplane ever so please bear with me, maybe I'm missing something basic

I understand the basic idea of calculating the wing loading to get the plane's stall speed. I read that you need a prop pitch speed thats 2-3x the stall speed in order to have good performance.

I have a pair of Tiger MS2208-18 1100kv motors turning 10x4.7" props. With this setup, the plane can barely climb and you absolutely have to fly at full throttle.
Power Pack C comes with Emax GT2215/09 1180kv motors and the same 10x4.7" props.


Here's my problem (I think):

• My calculated stall speed of my sea duck (confirmed by ecalc) is 21-24mph depending on weight (1300 - 1600 grams). Mine weighs 1600 grams with gopro and fpv gear.
• My pitch speed with the tiger motors is only 34mph and my stall speed is 24mph, or 1.4x
• The Power Pack C from FT only has a pitch speed of 39mph, or 1.6x.

I can't believe that that this tiny difference of 5mph pitch speed is really going to make that much difference.
Am I missing anything? Is my sea duck simply too heavy for the recommended power pack?

If yes, I guess I need to find a higher KV motor capable of swinging the 10x4.7 prop?

 

[FlyingSparky]

I'm fairly new as well, but fortunately I just bought the Sea Duck and it flies great.

All I can say is I use a 4S battery, and 9x4.5 props. Sorry if this doesn't help at all!