RC India

RC Models => Gas/Glow/Nitro Planes => Topic started by: carloz on February 27, 2011, 08:57:16 PM

Title: Pro and Cons of overpowering
Post by: carloz on February 27, 2011, 08:57:16 PM
hi all,
saw these posts , how smart or safe is this? apparently a lot of ppl seem to be doing this

www.rcuniverse.com/forum/m_7912128/anchors_7912189/mpage_1/key_/anchor/tm.htm#7912189

www.rcuniverse.com/forum/m_7912128/anchors_7922376/mpage_1/key_/anchor/tm.htm#7922376

so according to the above posts, can we put a lets say 90 4stroke on a 46size yak 3d? has anyone here done something like this?
your views plz

regards
carloz
Title: Re: Pro and Cons of overpowering
Post by: carloz on February 27, 2011, 09:16:12 PM
googling a bit more shows that using a 61 engine on a 46 model for 3d is common
Title: Re: Pro and Cons of overpowering
Post by: anwar on February 27, 2011, 09:18:04 PM
I have a 55 2 stroke on a .46 size profile Yak 54.  Overpowered, but not to the scale being discussed in these threads.

Remember that 4-stroke engines for equivalent 2 stroke ones are always higher displacement.
Title: Re: Pro and Cons of overpowering
Post by: Rajib Samadder on February 27, 2011, 10:06:55 PM
Mr. Anwar may I know what size of propeller you are using for your Yak 54 with 55 2 stroke engine? I am asking you because I have same thing but because of my accident I didn't get chance to fly it yet. I think you're talking about the model which is on your profile picture, if yes then I also have same model with same engine setup.
Title: Re: Pro and Cons of overpowering
Post by: anwar on February 27, 2011, 11:14:51 PM
12x3.75 currently. I can go a bit higher, but this seems to be more than enough for now.
Title: Re: Pro and Cons of overpowering
Post by: Rajib Samadder on February 28, 2011, 12:04:22 AM
12x3.75 or APC 12.25x3.75 Sport Propeller?
Title: Re: Pro and Cons of overpowering
Post by: anwar on February 28, 2011, 12:05:52 AM
The APC one. 
Title: Re: Pro and Cons of overpowering
Post by: flying doc on February 28, 2011, 12:11:26 AM
It is 12.25 X 3.75. U can also use a 12 X 4 and u'll get the same performance.
I have a ASP 91 on a 60 size plane. Am flying it with an 14 X 6 prop, but will soon try and change it to a 15 X 4 and try some prop hangs.
Just saw a beautiful plane at Amby Valley with a set up most will frown upon.
A 46 size high wing trainer with a 91 4 stroke engine. It does a prop hang just after take off and maybe u could just take ur thumb off the throttle and it would hang on its own.
Doc
Title: Re: Pro and Cons of overpowering
Post by: PankajC on February 28, 2011, 09:46:02 AM
apart from increase in weight, wing loading and probably shift in CG, any other cons of overpowering?
Title: Re: Pro and Cons of overpowering
Post by: carloz on February 28, 2011, 09:48:11 AM
another con i think would be to keep a firm hand on the throttle, improper or full thrttle would obviously result in losing the model..

regards
carloz
Title: Re: Pro and Cons of overpowering
Post by: flyingboxcar on February 28, 2011, 05:21:05 PM
Yes the biggest con would be the increased probability of structural failure in case VNE for the aircraft is exceeded
Title: Re: Pro and Cons of overpowering
Post by: anwar on February 28, 2011, 05:23:11 PM
VNE ? :) 

http://www.rcindia.org/rc-general-topics/rc-jargon-the-mega-list/ :headscratch:
Title: Re: Pro and Cons of overpowering
Post by: carloz on February 28, 2011, 06:06:57 PM
en.m.wikipedia.org/wiki/V_speeds?wasRedirected=true

heres a more detailed explanation

regards
carloz
Title: Re: Pro and Cons of overpowering
Post by: flyingboxcar on February 28, 2011, 06:41:30 PM
In simple terms VNE = Velocity Not to be Exceeded