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Old Jan 31, 2009, 12:09 PM
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Geode's Avatar
San Jose, CA
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Project QR-1 - Rutan Quickie Racer

Thanking about kick off a PSS project for the upcoming slope soaring season.

Quickie is the choice - I love the streamline body shape and the challenge of of Tandem wing design.

A few question before I jump ahead. Your inputs are greatly appreciated.

- What's the target wind loading?
I fly at ~15 mph wind on a "OK" slope (most of time) or within 1 hr driving distance from SF Bay Area (occasionally).

- Wing span - shooting for 48 in (would consider 60 in if necessary)

- Construction - is "molded fuse + bagged wing" a good choice? Will I run into "repair for every landing"? Are the "narrow chord" and landing gear on
the win a headache down the road? Is the EPP a better bet?

Thanks in advance for your comments/inputs,
Geode
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Last edited by Geode; Feb 08, 2009 at 01:17 AM. Reason: Tile modified
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Old Jan 31, 2009, 12:11 PM
Composites Kid
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Lima, Peru
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Make an EPP version first, test it, if you like it a lot, go molded ?

Alex
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Old Jan 31, 2009, 12:20 PM
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I imagine it will fly alright, but youre going to hammer that LG/canard every time you land.
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Old Jan 31, 2009, 12:25 PM
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Why not go for one of the other Rutan shapes - the Long Eze would go really well off the slope
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Old Jan 31, 2009, 12:52 PM
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San Jose, CA
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Alex/slopememo, sounds like a good plan to go for EPP first. It's a "quickie", isn't it ?

Long EZ looks great and goes EZ on the slope. Another great Rutan design. Thanks for your input.

Is a 20~30 oz a good target weight for a 48 in PSS Quickie?

Geode
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Old Jan 31, 2009, 01:33 PM
Composites Kid
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Lima, Peru
Joined Jul 2008
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If you use good airfoils that give you lift but little drag, it might be a very nice PSS sloper.

Ive heard of biplane PSS and it always went wrong because the airfoils were too draggy. The extra wing provides extra lift, but also lots of extra drag ..

Go for it! Id like to see a plane that nice flying as a sloper.
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Old Jan 31, 2009, 03:41 PM
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San Jose, CA
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Good point. Airfoil is everything for tandem wings.

From the three view, the airfoil looks very different for the forward wing (FW) and main wing (MW).

Wondering what's the requirements for airfoil selection in FW and MW?

A few modern airfoils under consideration ..... MH3x, MG06, PWxxx (not sure if this one fits ), AGxx (can't leave my DLG root behind ) , S606x (too fast for me to handle ). Any recommendations?

Geode
Reading "The basics of R/C model aircraft design" right now.
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Old Jan 31, 2009, 03:57 PM
Deniable plausibility
Shedofdread's Avatar
Derbyshire, UK
Joined Aug 2008
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IMHO a good idea when thinking about something a bit odd is to make a balsa chuck glider. Make it big enough to be representative (>18" span). That way you can find the C/G etc. and if it is generally a good idea without braking the bank.

As for the section, nothing with too low a camber. With all that fuselage it won't be quick and modern low camber sections rely on the airframe being low drag to give an efficient overall aeroplane.

S
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Old Jan 31, 2009, 04:34 PM
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Geode's Avatar
San Jose, CA
Joined Jan 2007
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That's right. A chuck glider Quickie is something can't be ignored.

As for airfoil, I really try not to compromise on this front. But what you said is very true. May be I could streamline the fuse a little bit to make it less draggy (more compatible to modern airfoil and still look like a Quickie) . Good inputs . Thanks.

p.s. The book says ....

Two requirements are critical for stable flight:
- The front wing must stall before the main wing stalls
- The main wing must arrive at it's angle of zero lift before the foreplane achieves the zero lift

The search for airfoils start ......

Geode
Good book, will stay in my library
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Old Jan 31, 2009, 04:59 PM
gizzo don't tweet
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Adelaide, Australia
Joined Jan 2008
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Biplane PSS work ok, they are just slow. But thats ok, they fly at a scaleish speed. A few bipes have rectracts or are seaplanes so no landing gear to smash off. Getting off topic, just a point of interest.
cheers, s
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Old Jan 31, 2009, 05:11 PM
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Nice to hear that. Thanks Gizzo.

For some reason, my perception of PSS is sort of equivalent to led sled. And that really limits how often (or where) I could fly during season.

A quick search on RCGroups, I think I find some guidelines in this link ..... http://www.rcgroups.com/forums/showp...40&postcount=5

Geode
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Old Jan 31, 2009, 05:12 PM
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Nice to hear that. Thanks Gizzo.

For some reason, my perception of PSS is sort of equivalent to led sled. And that really limits how often (or where) I could fly during season.

A quick search on RCGroups, I think I find some guidelines in this link ..... http://www.rcgroups.com/forums/showp...40&postcount=5

Basic Rules of Thumb:

Big Slope, Big Lift - Thinnish section, low camber, loading around 18oz+

Moderate Slope, OK Lift - Thicker section (maybe 9%), higher camber (maybe 1.5%), loading around 12 - 16oz

Little Slope, Little Lift - Same as above, but loading around 9-14oz


Geode
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Old Jan 31, 2009, 10:46 PM
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A few hours of CAD work .....
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Old Jan 31, 2009, 10:58 PM
It was just a flesh wound!
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San Diego, CA
Joined Sep 2007
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Definitely true about A LOT of drag on PSS biplanes. Probably a lot less drag on the Rutan model than on my Beech Staggerwing.

http://www.rcgroups.com/forums/showp...postcount=1294

Sounds like a great project.

Dale

Quote:
Originally Posted by Alex.Schweig
If you use good airfoils that give you lift but little drag, it might be a very nice PSS sloper.

Ive heard of biplane PSS and it always went wrong because the airfoils were too draggy. The extra wing provides extra lift, but also lots of extra drag ..

Go for it! Id like to see a plane that nice flying as a sloper.
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Old Jan 31, 2009, 11:03 PM
Embrace the suck
nauga's Avatar
Joined Nov 2004
4,269 Posts
It warms my heart to see all the unusual PSS stuff people are coming up with these days. Great subject, good luck with it.
Slopemeno's right, the canard is going to take a beating, so you might want to go with low wing loading and/or coupled flaps and canard to get the landing speed down.
Personally, I wouldn't prototype anything in EPP before doing a glass version -it's just too much work and a chuckie give you enough of a clue about functionality. I'd do (and am doing now on other models) a lost foam fuse and foam wing, and if it flew well I'd use the original fuse as a mold plug.
I still build EPP occasionally, but not as a 'glass prototype'.
The original Quickie was 'moldless composite', basically glass over hotwired foam, so lost foam is almost scale. "Found Foam" would be true scale, I guess.

Too much drag on a PSS'er? I hear your words but I know not what they mean? The S stands for "Scale", not "Slick"

Nauga,
Onan Onan on.
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Last edited by nauga; Jan 31, 2009 at 11:33 PM. Reason: someone took a P
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