F3P plans - Page 15 - RC Groups
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May 15, 2010, 06:58 AM
Registered User
bluey1982's Avatar
ok guys i have hit a problem.
Was sent a motor that despite being advertised as 16g it actually comes out at 27.5g and it will put the model over auw.
i am looking at some other lighter motors but have a question about prop sizes. if a 9.5g motor can produce 180-200g of thrust but on a tiny 4x2.5 size prop, does the smaller prop size matter?
cheers
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May 15, 2010, 06:08 PM
OSMBuddha
nagayama13's Avatar
kv has alot to do with it.....what kv is this 26g motor?
May 16, 2010, 01:57 PM
Registered User
Aio_1's Avatar
Yes, the prop size matters. The characteristics of the prop effect the speed, acceleration and braking of the plane. It also effects the airflow over the planes control surfaces. I'd recommend aiming for an 8" prop with a pitch of between 3" and 4.5" such as an GWS 8x4.3 or APC 8x3.8. However most props from 7" to 9" diameter with pitch around 40% to 55% of diameter should be fine on a typical sized F3P plane.
Because the swept area of a 4" diameter prop is much smaller (4 times less than an 8" prop) the speed of the airflow from the prop will be much faster. This will make the speed of the plane harder to control in addition to which you'll have much less braking effect in dives. You would almost certainly have very little aileron control in high angle of attack or hovering flight.

If you want to keep things simple and be sure of decent performance I'd suggest you stick with a motor that weighs 15g to 20g and will provide at least 200g thrust on say an 8x4.3 prop on 2s. The Hacker A10-15s is a good choice.

Aidan
May 17, 2010, 08:01 AM
Registered User
bluey1982's Avatar
Thanks guys, i think i am going to have to bite the bullit and get another motor. The turnigy 2204-14 looks ok and cheap.
whats the good watt range for say a 150g model? im thinking about 50-60w?
just weighed the model now painted and the bare airframe is 69g with the total electronics at 68g although i will be shortening all the wires etc. im frustrated because the all up weight on your index plans say 140g max and im gunna go at least 16g over that with the motor. i just can not see any way of building it lighter.
have seen some very light batteries on
http://www.alebproducts.com/index.php
does anyone know if he is still trading because i cant get through?
Aio, sorry this is not exactly on topic for the thread,
May 18, 2010, 02:15 AM
Love the sport, not the plane
Did you mill it?
May 18, 2010, 03:32 AM
Registered User
Aio_1's Avatar
Quote:
Originally Posted by bluey1982
Thanks guys, i think i am going to have to bite the bullit and get another motor. The turnigy 2204-14 looks ok and cheap.
whats the good watt range for say a 150g model? im thinking about 50-60w?
just weighed the model now painted and the bare airframe is 69g with the total electronics at 68g although i will be shortening all the wires etc. im frustrated because the all up weight on your index plans say 140g max and im gunna go at least 16g over that with the motor. i just can not see any way of building it lighter.
have seen some very light batteries on
http://www.alebproducts.com/index.php
does anyone know if he is still trading because i cant get through?
Aio, sorry this is not exactly on topic for the thread,
That Turnigy motor should be fine. My planes weighing from 115g to 135g have max power of about 40W or 45W. I reckon 50W should be enough for F3P at the slightly higher AUW.
You're a bit overweight on the bare airframe. If I remember correctly I got a little under 55g for the airframe (depron, carbon and paint) before starting radio and motor installation on my lightest un-milled Index. Your extra weight could be due to the specific foam you're using, excessive adhesive or paint or a combination of the 3. I wouldn't worry about it too much for your first one. It'll fly faster than a lighter version but should still fly well and slower than most typical foamies.

It would be best to continue this discussion in the Index 2 thread rather than here. I'll leave this discussion up for a few days and then delete the off topic posts if no one has any objections?

Aidan
Last edited by Aio_1; May 18, 2010 at 03:44 AM.
May 21, 2010, 06:23 AM
Registered User
bluey1982's Avatar
Aio, you are probably right i suppose i was hoping for too much for my first attempt!
However, she has flown and i can report that i am slightly in love! what a cool style of flying! couple of cliks of rudder and she was hands off will try n get a photo of the little beauty on for all to see.
Even with my limited experiance of this type of model the index flew SUPERB! well done on a great design and thankyou!
(indoor masters here we come!)
May 22, 2010, 12:52 AM
Thanos Papantonopoulos
pappy69's Avatar
hi all,

First of all congratulations to all of you guys building those nice f3p planes and sharing all those nice plans.
i have some questions which i believe you as specialists would easily answer. I am planing to build moreback and i was wondering what size of depron should i use?
6mm or 3mm with light FC enforcements as shown in the majority of your photos?

Thanks in advance
safe flights
Pappy
May 22, 2010, 10:21 AM
Registered User
bluey1982's Avatar
Hi pappy, although i am in no way a 'specialist' i think the morback is an all 3mm design. that will be my next project after i have thoroughly flight tested the index 2.2 i just completed (as soon as i get hold of more depron!)
good luck!
May 24, 2010, 12:03 AM
Thanos Papantonopoulos
pappy69's Avatar
Thanks bluey1982.
May 24, 2010, 07:35 AM
Thanos Papantonopoulos
pappy69's Avatar
It took me 6 hours to build this wonderful moreback and now it's done.
Another question is if there is a right and down thrust setup for this plane.
Does anybody have any idea?
As for the CG it's already answered (i believe the answer is to start it's 1 cm in front of the wing CF spar line).
Final weight is 88gr which i believe is not bad for a first time ever attempt to build a 3d depron plane.
May 24, 2010, 08:57 PM
Love the sport, not the plane
Did you build it with the VPP?
May 25, 2010, 01:05 AM
Thanos Papantonopoulos
pappy69's Avatar
nop! I used Depron
May 25, 2010, 01:40 AM
Phlathead
ToxicToast's Avatar
Quote:
Originally Posted by pappy69
Did you build it with the VPP? nop! I used Depron
OMFFF! This gave me a smile.

VPP=Variable Pitch Propeller



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