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Author Topic: Why did fuselages trend from rectangular to square that taper down to the fin  (Read 920 times)
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wmazz
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« on: April 12, 2018, 10:16:56 PM »

I am used to rectangular fuselages. I have mainly built Sal Taibi models like the Orbiteer.

But many newer plans, like AstroStar, Time Machine, etc have square fuselages that taper
down to the rudder.

The square fuselages look lighter, but not as strong as a rectangular fuselage?

Is the rectangular fuselage to heavy for a 55% tail moment?

Does a square fuselage recover faster after a stall or the power pattern?


thanks!

Bill M.
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flydean1
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« Reply #1 on: April 12, 2018, 10:30:17 PM »

To take your first question, they are definitely lighter, and are no stronger than needed.  All that beef back there accomplishes little except require more weight in the nose, or a longer nose.

Don't know what you mean by 55% tail moment.  Tail moment is usually measured from the CG to the 1/4 chord point on the stab.

Your third question is quite to the point.  With less weight some distance behind the CG the airplane will recover faster, and respond quicker to the stabilizing effect of the stab.

I'm sure some of our more learned participants will do a better job explaining  this than a Redneck Flight Instructor from Lower Alabama (Roll Tide)
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lincoln
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« Reply #2 on: April 12, 2018, 10:43:31 PM »

I don't fly power ff, but it seems to me that the biggest stress on the fuselage is usually a cartwheel. Therefore you need a certain amount of width. In the RC world, the Chrysalis glider has a fuselage that's actually wider than it is high.
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wmazz
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« Reply #3 on: April 13, 2018, 12:17:54 AM »

I started working on my own design again (after visiting the local club), and decided
on changing it to work for AMA A, B, C, and Electric A, B.

I am trying hard not to create a perfect model, but instead something that will work
well initially with low powered (stock) engines and motors. I am also trying to make
the design to be easy to trim and forgiving. Then as I improve, I can make small changes
to accept other engine sizes and motors. Then finally get to the stuff I really like, engines
with more HP Smiley Smiley

Is the rectangular fuselage to heavy for a 55% tail moment?


Don't know what you mean by 55% tail moment.  Tail moment is usually measured from the CG to the 1/4 chord point on the stab.

Sorry if I seem to be misusing the terminology. I have always used the article from
the 59' to 61' Zaic yearbook. "Tail volume & CG location" (Bill Bogart & Bud Rhodes).

So, I am in the habit of comparing the wing span to the wings mac leading edge, to
the 1/4 cord of the stab Smiley


Bill M.
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flydean1
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« Reply #4 on: April 13, 2018, 10:14:51 AM »

Bill, where are you located?  There may be other modelers nearby.
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wmazz
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« Reply #5 on: April 13, 2018, 02:18:35 PM »

I live in Riverside, CA.
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wmazz
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« Reply #6 on: April 13, 2018, 05:07:29 PM »

I started working on my own design again (after visiting the local club), and decided
on changing it to work for AMA A, B, C, and Electric A, B.

I am trying hard not to create a perfect model, but instead something that will work
well initially with low powered (stock) engines and motors. I am also trying to make
the design to be easy to trim and forgiving. Then as I improve, I can make small changes
to accept other engine sizes and motors. Then finally get to the stuff I really like, engines
with more HP Smiley Smiley

My goal is to change the fuselage slightly (pylons and rudder height) for different engines
and motors, but  use the same wing and stabilizer.

Bill M. 
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flydean1
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« Reply #7 on: April 13, 2018, 11:18:25 PM »

It would be wise to join the National Free Flight Society if you are not already a member.  This will connect you with a network of fliers, some of which are in your area.
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danberry
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« Reply #8 on: April 13, 2018, 11:27:14 PM »

You are 18 miles from Perris, Ca. There is a field with a regular group of VERY good flyers there.
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Starduster
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« Reply #9 on: August 21, 2018, 04:01:14 PM »

As usual, I'm late for the party, but I've never been able to master the art of building a fuselage that has a taper. Mine always look like a banana.
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