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<P>Lance</P>
<P>I think my numbers went over most peoples head. None the less once they spend the time and money to build / design a competative pattern airplane they will come to the same conclusion that I have. wing loading not weight limit is the limiting factor and I believe that even if we removed the weight limit entirely pattern design would would not see radical changes with the 2 meter size limit we now have.</P>
<P>Buddy <BR><BR></P></DIV>
<DIV></DIV>
<DIV></DIV>>From: s.vannostrand@kodak.com
<DIV></DIV>>Reply-To: discussion@nsrca.org
<DIV></DIV>>To: discussion@nsrca.org
<DIV></DIV>>Subject: Re: Weight Limit
<DIV></DIV>>Date: Mon, 11 Nov 2002 12:38:06 -0600
<DIV></DIV>>
<DIV></DIV>>Buddy,
<DIV></DIV>>I like opinions that are backed up with data and not just perceptions. My
<DIV></DIV>>experience as a designer, like yours, leads me to the conclusion that
<DIV></DIV>>there is a limit on how much airframe volume can exist in a 2m box and
<DIV></DIV>>still have a precision aircraft. This limit may be larger than what we
<DIV></DIV>>have today, but not much larger. A cubic airplane will not have the same
<DIV></DIV>>stability as a monoplane or biplane. Also, a heavy plane with a bigger
<DIV></DIV>>engine won't necessarily fly better either. As you state, there is a wing
<DIV></DIV>>loading target that must be maintained.
<DIV></DIV>> The cost of "exotic" materials in an airframe is not the expensive part.
<DIV></DIV>> Too many people focus on this and forget where their money really goes.
<DIV></DIV>>AeroSlave has carbon fiber planes for the same price or less than other
<DIV></DIV>>manufacturers glass planes. I think the prices paid for carbon fiber
<DIV></DIV>>exhaust systems have much more of a price premium than the premiums
<DIV></DIV>>assessed on airplane kits. The emergence of digital servos has also upped
<DIV></DIV>>the ante.
<DIV></DIV>>
<DIV></DIV>>Thanks for the numbers,
<DIV></DIV>>--Lance
<DIV></DIV>>
<DIV></DIV>>===============================
<DIV></DIV>>Ron and Georgie
<DIV></DIV>>Good point! Except before any conclusions can be made reguarding weather
<DIV></DIV>>raising the weight limit while keeping the 2 meter size will result in
<DIV></DIV>>larger airplanes and increasing cost you must first study the limitations
<DIV></DIV>>of a high performance pattern airplane.
<DIV></DIV>>
<DIV></DIV>>If you accept the fact a high performance pattern plane will have a wing
<DIV></DIV>>loading of 100 sq. in. per pound then a 13 lb airplane will have a 1300
<DIV></DIV>>sq. in. wing area . Lighter loading will result in less than acceptable
<DIV></DIV>>fligh charesticts especially in higher wind conditions and I think that we
<DIV></DIV>>will all agree that heavier wing loading will degrade performance.
<DIV></DIV>>
<DIV></DIV>>Adding a fatter and taller fuse and larger wings will certainly add
<DIV></DIV>>weight.If you run the numbers this will be about a 15% increase in
<DIV></DIV>>airframe weight for the 1300 sq. in. size.
<DIV></DIV>>
<DIV></DIV>>I personally think that increasing the airframe size/ weight 15% will have
<DIV></DIV>>little effect on cost.
<DIV></DIV>>
<DIV></DIV>>Now if you increase size (Keeping the Maximum 2 meters limit ) you may
<DIV></DIV>>need more power! and that will possibly result in engine design changes
<DIV></DIV>>or the ability to adapt gasoline engines to pattern. If a gasoline engine
<DIV></DIV>>can be used then it's a no brainer the cost of flying will be reduced .
<DIV></DIV>>the more you fly with gas the more the average cost of pattern is lowered.
<DIV></DIV>>If you fly 8 flights per gallon @ $16.00 per gallon the cost is $2.00 per
<DIV></DIV>>flight. Gasoline @ $2.00 per gallon 25 cents per flight a savings of $1.75
<DIV></DIV>>per flight. The savings there could reduce the cost of flying pattern by
<DIV></DIV>>30%
<DIV></DIV>>
<DIV></DIV>>As a designer and builder of pattern airplanes given the current 2 meter
<DIV></DIV>>limit I think the only reason for me to consider a larger design would be
<DIV></DIV>>to cut my cost since I can find no other reason to go larger. If anyone
<DIV></DIV>>has a valid reason speak up I am listening.
<DIV></DIV>>
<DIV></DIV>> And we have the age old argument that raising the limit will make
<DIV></DIV>>many of the current near 2 meter size ARF's legal for pattern and bring
<DIV></DIV>>more people into pattern at a reasonable cost. I think that may be true,
<DIV></DIV>>and once they are hooked they will opt for a true pattern design.
<DIV></DIV>>
<DIV></DIV>>Buddy
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