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Old Aug 07, 2014, 08:00 PM
Stealth Plane Works
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USA, MA, Stow
Joined Sep 2004
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Congratulations

Greg,

Just noticed your blog. Beautiful work. Next time we should discuss cutting a spar channel instead of cutting the cores apart and having to rebuild the top surface.

Happy to have made a small contribution to your efforts and thanks for the good press!

Anker
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Old Aug 08, 2014, 12:40 PM
Master of the Wind
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United States, CA, San Jose
Joined Sep 2008
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I thought about doing that but at the time I had not made the spars and was not exactly sure what the final dimensions would be. I also used the thickness of the core to make the final adjustment on the shear web thickness. Perhaps with the data I got off this one I could predict the spar thickness next time before they are made.
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Old Aug 12, 2014, 06:13 PM
Master of the Wind
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Joined Sep 2008
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I just picked up a T3000 to install. I took a walk down to the corner with it live in my hand and just that demo convinced me that we got beat by this toy (and some good piloting) not by the planes. Now I need to run more data through my course model to see what it will take to beat a loaded J plane. How much higher start, what speed to fly, do I really need to ballast to the last gram, etc. my plan:

Model a J plane. Royale more or less will do since I can guess the planform and the foils are published.

Get the speed to fly and visibility numbers nailed down.

Remember how I did the graphical model and run my #11 vs a 4m J plane and see if the delta in start height is enough to beat the higher top end.

This will be an interesting exercise, kind of like going back to school but more fun.
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Old Aug 12, 2014, 07:15 PM
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Quote:
Originally Posted by G Norsworthy View Post
I just picked up a T3000 to install. I took a walk down to the corner with it live in my hand and just that demo convinced me that we got beat by this toy (and some good piloting) not by the planes. Now I need to run more data through my course model to see what it will take to beat a loaded J plane. How much higher start, what speed to fly, do I really need to ballast to the last gram, etc. my plan:

Model a J plane. Royale more or less will do since I can guess the planform and the foils are published.

Get the speed to fly and visibility numbers nailed down.

Remember how I did the graphical model and run my #11 vs a 4m J plane and see if the delta in start height is enough to beat the higher top end.

This will be an interesting exercise, kind of like going back to school but more fun.
Greg,

All four J teams at Montague were using the T3000. I was skeptical at first due to John sort of down playing the advantage of this telemetry system but after experiencing it first hand I had to agree with Philip Kolb who was convinced he was knocking 15-20 minutes off his time on an average race due to the many advantages of flying with this system.

I'm now a true believer. The T3000 (or other similar telemetry) and the high wing loadings made possible by the smaller J wings (17-21 oz) change everything. I remember all those years we were preaching CHORD for visibility and altitude.... 12" absolute minimum, etc.. But at the same time John was always telling me he wished he could load up his MXC several lbs more than the FAI limit so he could make it go faster and handle wind better. I think the days of scary high flying are over for me.

Cal Valley is going to be an interesting test with the inevitable wind we will see.

Steve
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Old Aug 12, 2014, 08:35 PM
Launch high, go long
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Boise, ID
Joined Sep 2006
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Originally Posted by TrekBiker View Post
I'm now a true believer. The T3000 (or other similar telemetry) and the high wing loadings made possible by the smaller J wings (17-21 oz) change everything. I remember all those years we were preaching CHORD for visibility and altitude.... 12" absolute minimum, etc.. But at the same time John was always telling me he wished he could load up his MXC several lbs more than the FAI limit so he could make it go faster and handle wind better. I think the days of scary high flying are over for me.

Cal Valley is going to be an interesting test with the inevitable wind we will see.

Steve
Steve - Granted I have very limited experience in XC but I really saw an advantage using the T3000 system. There is even more to be gained if you use multiple display units in the vehicle all tuned to the same channel as the plane. The pilot has one and the spotter with at least one display unit. More is better from my experience with John and Rick.

And don't believe for a second that - "the days of scary high flying are over for me" - is true. We were constantly battling visibility of the plane. At a 1100 meters that 4M Xplorer was difficult to see and we were always on a "short leash". Meaning the plane wasn't to far afield to either side or in front.

The higher transit speeds give you the opportunity to move between thermals at lower altitudes.

Mike Grindle
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Old Aug 13, 2014, 12:04 AM
Master of the Wind
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OK I got a generic 4m J plane that is probably pretty close to an X2 in XFLR5. I'm stuck on the polar conversion to a,b,c speed to fly coefficients. Magnitude and sign are way off. I need to get this documented here so I can find it in the future. Notes are not clear. I suspect I need to turn the graph upside down but maybe there is more to it than that.
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Old Aug 13, 2014, 12:18 AM
Master of the Wind
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OK two things I had forgotten. I have all this in a writeup if anybody wants it. One, invert the Vz axis because XFLR5 plots it upside down compared to the speed to fly convention. Two, use the Vz by Vx polar for both the min sink and speed to fly calculations, and delete the points around the min sink to get a better fit if needed. For future reference the document that describes all this is in the folder Papers for course model.

Also note that a in Zunzun is c in my model so they have to be switched.
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Old Aug 13, 2014, 03:56 PM
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United States, CA, Granite Bay
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Originally Posted by LostVisual View Post
And don't believe for a second that - "the days of scary high flying are over for me" - is true. We were constantly battling visibility of the plane. At a 1100 meters that 4M Xplorer was difficult to see and we were always on a "short leash". Meaning the plane wasn't to far afield to either side or in front.

Mike Grindle
yes. Probably wishful thinking on my part.

you are right about the short leash. Unfortunately wind has this way of lengthening that leash. Also the T3000 lets you cut corners much more accurately in certain places but that also means you can get pretty far off the road if you're not careful. We got into trouble three times during the event that I can remember due to wind blowing us away from the road in thermals we badly needed. Even though you can still see the glider doesnt mean you can clearly see what its doing while circling in thermals a mile away. "Larry, I think you are upside down...!!! I don't got it!!!! no... wait"

These smaller J planes can turn into specks pretty fast.

Steve

ps. Greg, nice to see you sprung for the T3000, not exactly a cheap setup. I think we will be using two of the ground display units at Cal Valley after watching Philips team in action. I'll bet Rolle and Dudley end up with them as well
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Old Aug 13, 2014, 04:47 PM
Master of the Wind
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OK I cleaned up the model and ran it with XC11 vs a generic 4M J plane using the Supra foils, which is about as good as anything out there. Area was within a few cm2 of the advertised X2 wing. Experience tells me I can fly 200m higher than a plane with a 10 5/8" chord. If we assume there is a bump in thermal strength at 1200m, which I have some data to support, and I can exploit that from 1200 to 1300m, then XC10 beats the J plane by about 5 minutes on a 50 mile, 90 minute course. Real values will be slower because this analysis does not include the fuse and tail, which are now about equal or at least close to the J fuses.

Next step will be to try and model the school and back course from the last day atMontague and see if we can do better with a higher start. I will dig through the threads for the data since we saw repetitive thermal locations and this would make a really accurate model to play with.
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Old Aug 17, 2014, 05:46 PM
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Greg,
Awesome work. I know the latest trend is to go with a "J" bird as it certainly does have some advantages over a typical XC design. In all of my years of flying many aspects of soaring I see the same pattern over and over. There is no "One" best sailplane design. Every design has come from many compromises. In the end, the design is biased on what the designer is leaning toward. the newer "J" planes are good but so are the XC planes too. Both have their pluses and minuses and both have to be flown in a different way to make the best of "their" performance. Even in TD, many swing to the "model of the moment" when it comes to purchasing / building a new glider. Thanks for your work and I hope that the results show that both are still very competitive and we just have to be aware that with the design differences, so is the flying style.
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Old Aug 21, 2014, 12:39 AM
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United States, CA, San Rafael
Joined Jun 2012
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Back building

I am finally back to building after moving and getting settled in. We had to move. It was not totally unexpected, but sudden enough.

After reading all about the "J" planes one would think of scrapping plans of an seemingly older gen design, but I am going ahead anyway. I am not in a rush so I am going to take a leisurely pace. I also think I was drawn to cross country because of the large size of the sailplanes.

Anyway, it appears Greg is not quite ready give in, well, in wing cord anyway.

And a fuselage in hand is better than one on a design board.
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