ORIGINAL: Art ARRO
Hot Spot Drivers,
I have the Graupner Hot Spot and it calls for 8-10 mm of uptrim on the elevons. This is due to the non-reflex airfoil on this version. I understand that later versions utilized a true reflex airfoil which is required on tailess delta planform aircraft. A forward canard may eliminate the need for this uptrim.
Using engine thrustline changes to compensate may only work at certain airspeeds, typically low speed where the aerodynamic forces are miminal. As the airspeed increases these forces dominate which may help in the overall flying characteristics of the Hot Spot. I don't like the use of elevon uptrim but will live with it on my model. Further discussion on this would be appreciated.
Art ARRO
Hey Art,
If I can offer some advise, the jet may look a bit unconventional with the offset elevons, but it works very well and does not seem to change vs. airspeed. Don't over think the aircraft. Many of them are still flying after this many years due to the robustness of the design. After your 1st flight, any concerns about the reflex will be a distant memory. If you fly it hard and fast, concentrate on the stiffness of the fin mounts to avoid flutter, regularly check the bonding quality in the aft underside skin, and use extra hinges. I flew mine at the rear end of the CG range in the Wilcox instructions for every flight.
Mine lasted for 10 years + 1 week, but it went down last September in a flame out just after lift-off, not much I could do to save it unfortunately. Bummer, but I'm hoping to get another. My last one has a PST-1300R on it, and it was clocked at 249mph via eagle tree (in Canada.....). I swapped that out for a P-120SX, and it was noticeably more powerful. I never tested the top end on the 120SX, but 249 in the older PST was plenty fast already and the 120SX would break 200 very easily. With ~3.25L on board, the 120SX will also make it go vertical forever immediately after lift-off.
Here's a couple video links from before the 'expiry date' was reached...
([link=http://www.youtube.com/watch?v=g6ERzZP3b8A]Vid 1[/link], [link=http://www.youtube.com/watch?v=_Eymah8ZPT8]Vid 2[/link])
Kelly