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Old Aug 30, 2010, 11:22 PM
launch low, fly high
New Zealand, Hawke's Bay, Havelock North
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SD7003... I give it low odds of working well for XC. This airfoil does not respond well to camber. For that matter, at thermal type Re, it doesn't respond well to Cl! It does go fast though.
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Old Aug 31, 2010, 12:18 AM
Master of the Wind
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United States, CA, San Jose
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Kinda figured, and the RG14 on my Opus does not give me a good feeling for low saves but if you start with a premade planform and airfoil set it doesn't take much time to run it through.
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Old Aug 31, 2010, 09:27 AM
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If you want a fast glide with a section that responds well to camber look into the MG06. Have fun with that layup schedule to sustain over 100 mph.
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Old Sep 04, 2010, 09:11 PM
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Hn-990

Took a good look at the HN-990, my notes say it is the airfoil with the lowest Cd at Cl .20 out of the published ones meaning it should favor the speed end, if I can get it to thermal. Did the most complex analysis yet on this one, taking the Supra planform and optimizing the break by Re, making sure the tip has a broad enough peak to be forgiving in the thermal turns. This was the hardest one yet to get it to play along but in the end I came up with something I was happy with.

Performance is good, comparable to the Supra in most conditions. The problem is to get the sink rate, it needs 3 degrees of camber, and the airfoil has a sharp peak at min sink. Could I make this work with snap flap? Maybe. Would it be worth changing the tooling and trading for the Supra, no way.

Where we are at here is that the AG40 series foils somehow respond well to thermal camber, and also have a tail out at STF 20-22m/s in the polar that is really hard to beat. Some of the HN series that are a generation or two old can match it, depending on the day, but nothing stands out as an improvement that would justify changing the tooling from something that I flew with my own hands and really performed well.

Got a few things on the list to go over just to satisfy the curiosity, blown up Fletcher, MG-06 and DS-19 again now that my bag of tricks is bigger. HN-354 and HN-483 again to see if I can do a better job of optimizing. Got one more person who may take a look at this who knows more than I do. After that we build another Supra.
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Old Sep 07, 2010, 02:01 PM
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the question is, can the Supra be further optimized for the requirements of XC? We know the scaled up Supra (#9) flies very well at the higher wing loading, wider planform and lower AR. But I'm starting to wonder about the ideal wing loading after flying it. It definately seems to thermal better and generally handle better at less than max 11 lb wieght. Not much less, I think we have it trimmed out at just over 10 lbs but ideally we should be able to use the full 11 lbs. It's possibly the best XC thermaller in tight small thermal situations I've flown yet but does that mean we could give up some of the thermalling ability for more speed by tweaking the airfoils (thinning/de-cambering)?


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After that we build another Supra.
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Old Sep 07, 2010, 03:12 PM
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Or make it bigger and use the full 11 lbs. I already scaled it down I think to 94% and it got faster at the expense of a little min sink. I would not rule it out at 11 lbs until we spend a little more time trimming.
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Old Nov 07, 2010, 03:12 PM
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New developments

I looked at the HN-990 and HN-483 as root airfoils and you can make a pretty good plane out of either one. You can also scale the Supra up and down and improve some races at the expense of others. I was about ready to build my own Supra when via Roydor I had the good fortune to contact Philip Kolb, who has an interest in the event and was looking for some practical feedback for a design. The end result is I have something to try. The design is locked and construction is proceeding full speed ahead with the intent of getting some stick time on it before next season. I'm tied up on the airfoils and planform but I can say that it is a slightly smaller plane, designed to outrun my previous designs yet not give up anything on the climbout. It will probably be more challenging to fly but on paper the performance is worth it. Thanks to my employer I have two extra weeks of "rest" this winter and will put the time to good use.

Materials are all bought. Joiners and boxes made. Working on spar caps. Next step is to block and cut foam.
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Old Nov 07, 2010, 11:48 PM
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Looks like we pulled it off. Got 4 spar caps out of the fixture. This method is super slick and I will use it again. On to blanking foam, working on the sketches now.
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Old Nov 08, 2010, 12:16 AM
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That graphlite spar cap looks awsome!
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Old Nov 08, 2010, 10:34 AM
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What airfoils/planform did you decide on? And most important, what kind of hot-sauce is that in post 82.
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Old Nov 08, 2010, 10:48 AM
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Span?

Chord?

T-tail?

X-tail?

GJ fuse?

RES? full house??

airfoil coordinate files?(maybe reaching a little on that one)

inquiring minds must know....
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Old Nov 08, 2010, 11:17 AM
yyz
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Quote:
Originally Posted by dbaya View Post
That graphlite spar cap looks awsome!
Absolutely! Nice work, Greg.

If you look in the EB29 thread, I held the Graphlite rods together with blue masking tape while I bonded them to the webs with thickened (West bonding compound not microballons) epoxy.

Once they were dry, I removed the tape, sanded the spar assemblies and then socked them and put them in the bag. Would save you a step and possibly a little weight.

Mike

ps: Nice surprise seeing you guys at the F3B TS last weekend.
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Old Nov 08, 2010, 11:49 AM
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Mike,

I saw how you did it and really liked it but since I was fighting with 14 skinny rods instead of 4 fat ones I was afraid I would not be able to get them to all behave in the working time of the epoxy. The channel fixture turned out to be really easy, even easier with epoxy than on the dry run. I just dropped them in, clamped lightly, packed them with a mini screwdriver, and tightened the clamps. Easy release with a bit of car wax.

I'll probably assemble the spars in the beds, then bag the sock, but that must wait for the cores.

Airfoils are proprietary, the span is about 153" and the chord is about 12". GJ fuse, T-tail, full house. The MXC, Supra, and #8 were playing around in the big plane, good visibility design space. This one is an experiment in the other direction. No turning back now.
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Old Nov 08, 2010, 11:59 AM
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interesting.... max wingloading at 11 lbs? (probably wont load to 11 lbs?)

12" is still good (SBXC)

I think I saw somewhere that Graphlite is made in rectangular cross section

Steve


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Mike,

I saw how you did it and really liked it but since I was fighting with 14 skinny rods instead of 4 fat ones I was afraid I would not be able to get them to all behave in the working time of the epoxy. The channel fixture turned out to be really easy, even easier with epoxy than on the dry run. I just dropped them in, clamped lightly, packed them with a mini screwdriver, and tightened the clamps. Easy release with a bit of car wax.

I'll probably assemble the spars in the beds, then bag the sock, but that must wait for the cores.

Airfoils are proprietary, the span is about 153" and the chord is about 12". GJ fuse, T-tail, full house. The MXC, Supra, and #8 were playing around in the big plane, good visibility design space. This one is an experiment in the other direction. No turning back now.
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Old Nov 08, 2010, 01:25 PM
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United States, CA, San Jose
Joined Sep 2008
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Weight depends on the day but the intent is to fly at full all the time if we can.

Graphlite comes in a variety of shapes but the large roll under my bed for 10 years was round .060. And I still might have enough left to finish off the F3F cores sitting on my kitchen floor. I used it to make a DS plane and it was super stiff. I learned a lot from that plane but a bad receiver killed it.
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