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Discussion
Montague 2014 - T3000 and the rise of the "J" planes......
A few thoughts from my observations at this years Montague event.
There were four teams using modified F3J planes for this event. X2xc - John Ellias John started it all with his 4m Explorer2 he built as an experiment last year. He ordered a stronger wing and joiners and extended the boom 7" for more directional stability. His ballast system consists of brass tubes in the center wing section fitted just behind the spar. The entire tube is removeable and was filled with lead shot which was then melted with a torch resulting in lead extending about 20 inches or so from the center towards the end of the panel on each side. He slides the entire tube into the wing and secures it with a piece of plywood in the flap servo bay. The wing tip panels serve to hold it in place from the ends. I think he told me the unballasted wieght of the X2 is low 90 oz range so he is putting around 80 ounces ballast into the wings. It did not give up anything in lift. The advantage of placing the ballast in the wing is in freeing up space under the wing saddle. John put a 2S2P Lithium Ion pack under the wing good for 4600mah I think. The 4m X2xc is pretty well proven now and was very impressive in the high winds we experienced at our Davis XC race. Wing loading is 19oz at full 5kg. John's build thread on the X2xc: https://www.rcgroups.com/forums/show....php?t=1962639 Royale - Dean Gradwell Unfortunately this one crashed out of the race and we did not really get a chance to see how it performs. 4m span with the wieght built into the wing by Don Peters close to the root. There is no provision for reducing ballast (ballast permanently glued into wing root) but after this contest I'm not sure we would ever need to fly below the max 5kg. So far no one has flown below 5kg so it remains to be seen what kind of conditions would require this, certainly not wind or strong thermal days. Time will tell. I noticed Dean had the boom wrapped with carbon fiber. The boom on the Royale is very long and did not require modifications to lengthen it. My flying partner Bill Curry flies a stock Royale for TD and what I have noticed about this design is that 1) that boom seems awfully noodly weak when compared to a Supra/Maxa boom, and 2) if anything the stock Royale is too light. But the wing seems very fast. I forgot to ask Dean about the wingloading but I suspect that at 4m it is the same as the X2xc, 19oz. at max 5kg. Pretty sure we will get to see it perform this fall at Cal Valley, wing and stab survived the crash, just needs a new fuse. AspireXC - Larry Jolly Larry joined my team last year for Cal Valley and has flown with Bill and me at Davis and Montague so far this year. We crashed our primary ship, Super Supra just one week prior to Montague and lucky for us Larry barely managed to finish his modified Aspire in time (we test flew it the Saturday prior to the event). He extended the nose 2.5" and the boom 5" and had Lubos Pazderka build a double carbon wing with doubled joiners. This turned out to be a wise move as we severely tested this wing during the races, one time losing sight and a couple times losing control at extreme distances. But we are rapidly fine tuning this new plane and performance is VERY good. Ballast for the AspireXC is six 1" diameter x 1.5" long tungsten slugs fitted in the fuse under the wing, each slug weighing 11.3 oz. We thought by doing this the majority of the wieght would be concentrated close to the aerodynamic center but now we are not so sure this matters so much, especially after watching the performance of Philip Kolb's Prestige. The problem with fitting so much ballast (68oz) under the wing like that is it takes up valuable space in these skinny little fuselages. There was so much stuff crammed in there that Bill told me he saw Larry using a hammer to make it all fit. Larry was only able to fit a 2300mah 2S1P battery pack in the nose. At the end of one days racing, I think it was Thursday, he put 2000mah back into the pack. Thats cutting it a little close. Perfomance of the Aspire is excellent but tip stalls, especially at long distances can be a handful to recover from. Tip stalls were no problem as long as it was close enough to clearly see what it was doing. But this is all getting sorted out and I was surprised how fast I was getting comfortable flying her. Moving the CG forward a little also helped. The first time I picked it up it was hard to believe something so heavy could fly just like the unballasted TD version, just faster. The AspireXC wing is 3.8m, wing loading is 20oz, the second heaviest loading at this event. I think any future version of this racer will have the ballast fitted into the wings, that seems to be the general consensus among the "J" teams at this point. Prestige - Philip Kolb This was a very impressive sailplane, just a beautiful design and workmanship is top notch. Not for sale, not anywhere. Philip told me he only builds them for himself and the national F3J team. Bill tried to convince him to sell him one but no luck. I told Philip if he would sell me one I would not even fly it, I would hang it on my living room wall as a piece of sculpture. The ballast system was similar to John's X2. Philip glued in carbon ballast tubes while the wing mold was open (one in each wing behind the spar) and he uses 4 brass rods in each wing end to end extending the full length of the center panel. The wing and fuse were also beefed up with extra carbon. Roll response does not seem to suffer at all. I took some measurements and the boom on this model is 4 inches longer from TE to front of fin than the stock Aspire boom so Philip saw no need to lengthen it like Larry did to the Aspire and John with the X2. The fin/rudder on the Prestige is also very large. Stab is mounted in front of fin on boom like a Perfection or Maxa, not full flying but uses stab/elevator configuration. 3.65m span, 21oz wing loading. This was the smallest most highly loaded sailplane at the event. Sure wish I could have got my hands on the sticks for a little while. RC Electronics T3000 - Rick Shelby (USA distributor) This device was a revelation for me and offers a lot of advantages. After using it I believe it will also help make XC safer. The airspeed is a very nice feature, especially when combined with the sinkrate (m/sec) during the glide between thermals or the final glide to the finish . We still have a little bit of a learning curve to figure out how to best use this on my team. I think this can result in a better idea when to use cruise or reflex and aid in final glide calcs. The T3000 telemetry also gives a constant direct line to the next turnpoint. You can use this to increase the efficiency of the glide direction by not wasting potential energy (altitude) trying to follow the road and sort of guessing the right direction like we've always done in the past, with the T3000 you know exactly the right direction. So for instance if a turnpoint is 6 miles away you might save a half mile in actual air miles by flying a truer path. The screen shows the glider in the middle and the course rotates around depending on direction flown so the spotter can constantly update the pilot as to degrees off course and see exactly when the pilot is on the correct heading. This greatly minimizes the tendency to S turn your way down the course. Maintaining a straight and accurate heading is one of the more difficult skills in XC and the T3000 makes it easy. One thing to watch out for is that if you simply stick to the indicated heading it can lead you out over terrain you might want to avoid or result in cutting a corner deeper than you should. Another big advantage was the ability to see the turnpoint cylinder on the screen from nearly a mile away. The TP cylinder has a 0.2 mile radius. Normally we have to drive to the TP and then stare up at the glider to make sure we have entered the cylinder. Flying thru and too far past the cylinder is very common. With the T3000 we can be situated well before the turnpoint and know exactly when we have entered it. In one race my team hit a very good thermal about 3/4 mile from the turnpoint, we were parked on the road by the thermal and simply made a dash to the TP, flew our glider to just within the TP circle and returned to the thermal while parked the entire time next to it (this was a goal and return TP at one end of the course). This is a big improvement and advantage to the way we used to hit turnpoints. There are also some strategies that the Prestige team employed that have to do with how the winscore program calculates average speed from distance flown that can be used to advantage thanks to the T3000 (I'll let John or Philip explain that as my team is still too newbie at this strategy). Same is true for the start /finish line. You know exactly when you cross it. If you start and hit a good thermal within say 1/2 mile to a mile from the start you can tank up then make a dash back to the start to restart the clock and come straight back to the thermal at good altitude the whole time while sitting out on course near the thermal. Used to be you would need to turn the vehicle around and drive back to the start to make sure you crossed the line then drive back to try and relocate the thermal. For the finish line the T3000 allowed us to hit 90+mph airspeed on the final glide and let the glider outfly us while still knowing exactly when we crossed the line to hit our stopwatch. This is not critical as the Winscore program sees this but the stopwatch is our backup in case the gps fails (which happened to Rolle's team). I think as we get better at calculating final glide we wont be flying so fast. 90mph means we basically blew our final glide calculation and should have left the last thermal much earlier than we did. The Germans proved to be masters at this which is one reason why (of many) they beat us like they did. Another neat thing about the T3000 is the visual variometer on the screen that tells you the strength of the thermal as you circle in it. This helps to core it and also is a big help in letting you know if you are wasting your time in weak thermals. I primarily use the vario tone but noticed that in some weak thermals when we thought we were slowly gaining altitude we were in fact just maintaining altitude and wasting a lot of time. This was a revelation to me that I have been getting fooled sometimes by the vario tone in weak thermals. Rick Shelby is the RC Electronics distributer for the US. Rick's thread on the T3000: https://www.rcgroups.com/forums/show....php?t=1964230 XC has always been a great adventure and it just got even more interesting Steve |
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Last edited by TrekBiker; Jun 19, 2014 at 09:28 AM.
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Hey Steve,
Cal Valley is certainly close to me. I am not in Paso anymore but I am still on the central coast so it is still my "home" field The Maxa XC would be pretty straight forward. I was thinking of buying a Maxa with the new storm layup and then extending the boom. The fuse is skinny but also quite long. Moving the ballast to the wings would leave a good amount of room for electronics. -Aaron |
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I think the Maxa 4m "long tail" with the "storm" layup would make an excellent XC glider. The fuse is already 73" long so I don't think you need to extend it. John |
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How do you lengthen the tailboom of an F3J glider?
Does this involve cutting the boom and inserting a section of carbon tubing? Thanks in advance. |
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Described in detail here: www.rcgroups.com/forums/showthread.php?t=1962639
It's a bit of work, and it might be worthwhile to look for J-birds with long fuses to begin with. Indeed, Jiri Baudis' new Skywalker may be a good candidate. Dieter Mahlein, ShredAir |
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Quote:
Steve |
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Steve,
I spliced a Icon II nose and tailboom to the Royale center section completing the project about the same time a new fuselage showed up. The new fuselage has double the amount of material normally used. It is very strong and better looking than my repair so that is what I went with. The new fuselage came painted red. I wanted to try something darker so I went with a very dark blue removing the mold line in the process. Shows up very well at altitude. Dean |
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Last edited by DEAN GRADWELL; Aug 13, 2014 at 12:11 AM.
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