Sizing plane after motor?

[FiberToast]

Hi everyone!

Would much appreciate if anyone could help me.

I plan on building a Spitfire for FPV and want to make it a bit larger. Im going to try to follow something like these plans http://www.outerzone.co.uk/plan_details.asp?ID=824 but will build from a mix of foam board and other materials.

Now i have a Rimfire .25 (42-40) 1000kv motor new in box that found in my rc pile and would like to build the plane around this, so is there a way to determine what size the plane should be for a well over powered build?

Want to run this on a 4s 2700mh 65c as i have about 15 of those and a 80A Futaba esc

Maybe this is completely off but since i have all the bits laying around and its dark and winter i thought i build something.

By the way that page i linked is great for drawings for scratch builds.

 

[RAM]

If you know the weight of the plane rather than the size you could use the watts per pound method.
Can you find the specs on your motor?? Prop size range etc??

 

[FiberToast]

Diameter 42mm
Längd 40mm
Axeldiameter 5mm
Axellängd 17mm
kV 1000 varv/V
Vikt 125gram
Spänning 3-4S Li-Po
Ström 45A kont./50A max
Effekt 666W kont./740W max
Rekommenderad propeller 10x5 - 11x7

Sorry the text is in Swedish but i think you find the info there.
The motor is recommended for sport flyers up to 2000 grams or 3d up to 1350 grams.

 

[pgerts]

It says .25 motor, but the power is more like twice that.
You want well over powered - aim for a spit with 120 cm span and not much more than 1 - 1,2 kg flying wieight.
The spit is a fast plane - go for a prop with high pitch and smaller diameter. 9*8 to 9*10 carbon fiber prop.

 

[FiberToast]

Ok tack pgerts.

Printed these plans today http://www.outerzone.co.uk/plan_details.asp?ID=5502 and lay them out on the floor, wow it´s a 56" monster. This would be my first build from scratch, been doing multirotors for the last few years and are a real looser at LOS flying so this will have to be FPV.

But if you going to do it why not do it big. More space for working with and i have been building things (but not planes) since i can remember.

So would it be better to start from a profile and put the formers around that and then covering with 3mm foam board or start from a box type fuselage like David´s spit and add the formers to that. The last option would give moor space inside for battery and electronics.
Or maybe a mix of both with a box shape in the middle section and profile in nose and tail.

Im also thinking about the wing spar, i think it will need some wood or carbon since it´s so large. David´s 200% spit snapped the wings due to being in moist air i think so a foam spar feels a little weak.

Forgive me if my terminology is wrong since this is my first scratch build. Have done some FT planes and arf´s before.
The plan have all control surfaces with hidden internal "controls". Is maybe foam board to soft for that and would need a lot of reinforcing or would it be easier to just do it with external control horns even if it will be less slick looking.
I saw someone did it with a Z shaped music wire going from the ailerons inside the wing to the center fuselage and using one servo for both ailerons looked kind of neat.

What are people recommending for glueing? I was thinking of using hot glue for tacking things down and polyurethane glue for strength.
Will be removing the paper from most of the foam board and later covering with craft paper and polyurethane laqouir.

Questions questions questions.

Hopefully this will turn in to a build thread at some point, if i havet bitten of more than i can chew.

Now over to write about my new ground station build.