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Old Dec 11, 2007, 09:46 PM
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Sailaire Airfoil Mods

Has anyone tried Phillips entry on their Sailaire wing? How did you like it? I know it has been done on Paragons for years, but I've never heard of a Sailaire with that mod and they both have very similar airfoils.

How about flaps on the inboard pannels in place of the stock spoilers? Anybody tried that with a Sailaire? My PIK 20 has flaps only for glide path control and they work much better than spoilers, but that is a completly different airfoil from a Sailaire. I'm currently building a Sailaire and thinking about these mods, but don't want to mess it up, so any comments would be welcome.
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Old Dec 11, 2007, 10:26 PM
Jackass of many Trades
USA, UT, Pleasant Grove
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I have wondered the same thing, as I too have a Sairaire kit in the que.

It has also been suggested that I add carbon fiber caps to the top and bottom spars, as well as wrap the spar with carbon tow.

Any one care to elaborate? Share your Sailaire mods?
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Old Dec 11, 2007, 11:29 PM
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MichaUT,
I've made and plan a few structural changes so far. My kit had a big block of balsa that went in the vertical stab for the bellcrank to fit in. That had to go, I don't see how one could get a very accurate stab arrangment with it. Replaced it with a 1" wide strip of .060 ply on each side of the fin with the crank hanging from a short piece of tube inside another tube. That worked out real well. I'm also going to add carbon to the inboard spars and extend it about six in. into the tip pannels to beef up the dihedral joint. Those wire dihedral braces will also be replaced with ply too. The spar webs look light too and ought to be wider with carbon spars. I guess I should to cover the tail boom with some light glass too. This one is going to be an e-Sailare with an Hacker B50S/12/6.7 so it shouldn't end up tail heavy.
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Old Dec 12, 2007, 07:04 PM
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The Sailaire modified airfoil with phillips entry sanded in works very well. In the early 80's, the MOSS club from Columbus OH used a modified Sailaire in the Great Race cross country contest in Chicago to complete a 46 mile course non stop. Team Airtronics was the only other contestant to finish using a brand new design called the Sagitta XC with Skip Miller at the controls.
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Old Dec 12, 2007, 11:35 PM
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I'm not sure why anyone would want to modify the existing airfoil with all the terrific airfoils we have available today. Why not set up and make a set of 3014 0r 3021 ribs?

Just my thoughts on it.

Jack
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Old Dec 13, 2007, 08:32 AM
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Jack,
I agree that would be the best way to go. But I already have the kit with all the ribs and all I have to do is raise the LE and sand in a little lower camber on the ribs. OK, I'm lazy.
Bill
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Old Dec 13, 2007, 01:59 PM
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I have been flying Sailaires for 30 years and never found need for any modifications. If I need speed, I fly one of my more modern designs. My wife thinks watching my Sailaire floating in a thermal is much more beautiful than my other gliders scooting around the sky.
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Old Dec 14, 2007, 10:50 PM
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Need some help figurring out just how to cap the spars with carbon, let alone wrap them.
Looking at the plans, the spars sit flush with the sheeting. Inlay them deeper? so the balsa sheet covers the carbon?

M.
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Old Dec 15, 2007, 08:48 AM
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Sand a relief into the back side of the sheeting. Apply the sheeting and if necessary sand the top of the sheet to blend into the rib notch.
Bob
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Old Dec 15, 2007, 09:40 AM
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M,
Looks like the notches in the ribs for thr spars will have to be deepened enough so the sheeting can extend over the spars to cover the wrap. My plans show a .75" wide spar on the bottom and a .5" one on top. If carbon is added and webs are also .5", the same size spar on the bottom should be fine. Then you could wrap the spar w/o any problem. The airfoil is plenty thick, about 12%, so you can move the spars closer and still have good seperation for strength. A Sailaire is not the type to do much of a zoom launch, so I wonder how much this is needed. I still would like some carbon in the dihedral joint and some carbon wraps over the wing tubes. 150" of wing is a big lever on that area. Anybody have problems with the stock Sailaire spars?
Bill
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Old Dec 15, 2007, 10:27 AM
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Quote:
Originally Posted by ChuckA
I have been flying Sailaires for 30 years and never found need for any modifications. If I need speed, I fly one of my more modern designs. My wife thinks watching my Sailaire floating in a thermal is much more beautiful than my other gliders scooting around the sky.
All Phillips did for me is reduce the amount of ballast needed by about 20% on the Sailaire and Paragon. Truly, maintaining the blunt entry of the original profile already raises entry somewhat.

The Sailair is surprisingly fast, just limited in wing loading because of size. Size also makes it appear slow; however, response to stick informs you that big and beautiful is not sluggish!
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Old Dec 15, 2007, 02:07 PM
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It isn't necessary to deepen any rib notches or trim any shear webs. Just get a couple pieces of aluminum identical in thickness to the original spar and at least as long. Screw them to something like a scrap 2x4 a spar's width apart and attach something at one end to serve as a stop-block. Laminate your carbon to the spar, let cure and then slide it into the jig carbon-side-down. Then simply plane/sand the spar to the correct thickness. Simple, neat and works with tapered carbon strips, too!
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Old Dec 15, 2007, 06:19 PM
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Quote:
Originally Posted by MichaUT
It has also been suggested that I add carbon fiber caps to the top and bottom spars, as well as wrap the spar with carbon tow.

Kevlar tow is easier to work with and a better product for wrapping spars. See:

http://www.rcgroups.com/forums/showthread.php?t=587629

for a post by Little Flyer with photos. The thread is closed, but he has lots of Kevlar (and Carbon tow) available.
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Old Dec 16, 2007, 09:29 PM
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Quote:
Originally Posted by MichaUT
Need some help figurring out just how to cap the spars with carbon, let alone wrap them.
Looking at the plans, the spars sit flush with the sheeting. Inlay them deeper? so the balsa sheet covers the carbon?

M.
Spar design has become somewhat retarded. Common practice is to make the cap stock larger in cross section, top and bottom.

In the age of high tech design it is somewhat silly to design wings for bi-directional loading. Spar failure is generally identified as a compression failure to the upper cap. The major lift force occurs at about 60% of each half of the wing, with the pressure of compression constantly increasing to the wing root. One can increase spar depth by simply rotating the upper spar cap 90 degrees while securing it to a plane of sheeting so that the sideway resistance to spar motion is improved (plate wing concept).

Laminating top spar from the region of maximum lift to root, making it square in cross section, is another simple technique to intensify spar incompressibility.

The bottom spar is attached to the top spar by a web of vertical material typically. A fancier construction can use a horizontal grain for the base web core material while using vertical grain front and back laminations for the area of greatest stress (balsa plywood). This tapers the laminated spar with its web transfer to match the build up of compression stress.

As the upper spar is deflected, the tension buildup in the lower spar increases with web coupling reinforcing straightness, thus a bit of stable film on balsa is a zealous overkill. If curious, take a strip of 8 lb balsa and attempt to pull it apart you will be amazed at its strength; whereas, pushing it together - it will snap easily.

Obviously I am using a wood standard, however the phylosophy is adaptable to exotic materials. Have fun making lighter wings this way.
Rib height can reduce spar material as proved by the old (extremely strong) MB 253515. [Mine was built with balsa spars for super light.]
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Old Dec 17, 2007, 10:37 PM
Jackass of many Trades
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Thanks for all the input!!

MayFly, Thank you for tolerating the hijack of your thread, I hope you found it as useful as I have.

Micha
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