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-   -   nose length? (http://www.rcuniverse.com/forum/scratch-building-aircraft-design-3d-cad-174/10462536-nose-length.html)

flybyjohn 04-14-2011 10:45 AM

nose length?
 
I have a question on engine prop position in front of a wing. If a plane is known to come out tail heavy, is it acceptable to cut the nose of the plane shorter to balance the model or does this affect the flying characteristics of the plane? In the process of having to cut the nose shorter, the fuel tank would be closer to the center of balance of the plane creating a better balance through out the tank of fuel. So is there ever a problem with doing this practice or is a plane designed to have the thrust point at a certain distance from the point of balance?

smithcreek 04-14-2011 10:52 AM

RE: nose length?
 
To start, do you mean nose heavy?

BMatthews 04-14-2011 10:55 AM

RE: nose length?
 

ORIGINAL: flybyjohn

......If a plane is known to come out tail heavy, is it acceptable to cut the nose of the plane shorter to balance the model ?......

Errr.... you got that backwards. A tail heavy model needs to have the nose be made LONGER to get it to balance in order to avoid having to add unwanted nose weight.


In terms of how this all affects the model for flying if by some chance a model comes out nose heavy then shortening the nose instead of adding tail weight means that you're both keeping the ends of the model lighter as well as slightly shortening the moments. So making the nose shorter without needing to add nose weight means that the rotational mass moments are smaller so the model will rotate in pitch quicker for a given elevator deflection. Alternately making the nose longer makes the inertia moments higher so the model will be less "perky" in response to elevator in puts.

But all in all you'd have to have a really keen eye to see these changes or be a high placing precision aerobatics pilot or judge with a keen eye for what to look for in terms of overshoot wobble in pitching maneuvers and other things. On the whole if a model isn't a scale design and it needs a big hunk of nose weight to balance then making the nose longer to lose most or all of that nose weight generally is a good thing that has only minor bad side effects that most would not notice unless the increase in nose length was taken to extremes.

Dsegal 04-14-2011 12:24 PM

RE: nose length?
 
1 Attachment(s)
You can do some chopping and the plane will still be OK. I built a Blitz from Aspect Aviation and it was wildly nose heavy. I moved the fuselage mounted servos behind the wing and even reconfigured the receiver pack to fit at the rear of the fuselage. Still no good. So I held my breath, took out the razor saw and whacked off one inch of the nose and reset the firewall. (This was a .25 size engine.) The plane flew great.

The attached photo is my later redesign of the fuselage which kept the shortened nose and it also is a wonderful flyer.

flybyjohn 04-15-2011 05:06 AM

RE: nose length?
 
Yes, Nose heavy is what I ment. The info I have been reading about it is that you will need to add tail weight, plus I was going to add a bit larger engine. I have moved my battery back in some planes to the rear of the fuse but I would think that would place the weight farther from out from the CG causing slower rotational movements. Moving the engine back .5 to 1 inch seemed to be a better fix for the problem. Thanks for the replies.

beepee 04-15-2011 06:52 AM

RE: nose length?
 
John,

I did it and was very successful. Had a Balsa USA EAA Bipe that I was putting a gasser in and was coming out nose heavy. I shortened it by 3" and everything worked out well. Whether you can or not depends on the airframe. The EAA Bipe is long nosed and could afford the adjustment. Roughly speaking, as long as it looks about right you should be OK.

Have fun!

Bedford

Lnewqban 04-15-2011 09:13 AM

RE: nose length?
 


ORIGINAL: flybyjohn

If a plane is known to come out tail heavy, is it acceptable to cut the nose of the plane shorter to balance the model or does this affect the flying characteristics of the plane?
Balancing is the main reason for airplanes to have a nose; flying wings don't have a nose and fly OK.

Do a simple calculation before cutting the nose off, and the amount of extra weight will be minimal if any.

dreadnaut 04-15-2011 05:28 PM

RE: nose length?
 
Without getting into scale theory, smaller engines tend to have better power to weight ratios than larger engines. In the early days, when almost all model engines were lightweight two strokes, it was given that weight would have to be added to the nose of a scale plane. This produced a tendency for a lot of designers of non-scale models to use similar moments out of habit. One of my first R/C models, and Midwest Little Stick, required nose weight. As I got more experienced, I would extend the noses on kits I got so that they would need little to no added weight. They flew fine as far as I could tell.


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