Hey Art,
The pressure will still build in the back, even with sealed wheel wells, its a common fluid dynamics principle according to the Bernoulli equation. Where the wheel wells will help is with regards to stabilizing the leading edge of the rear skin, if the pressure starts to push it out - the wind can't grab it, tearing it and the rest of the skin off! If I get another though, I'd do the same as you or add gear doors to cover it up entirely. On mine, I sanded the structural former and skin immediately after the gear opening, and laid in a good thick Hysol fillet, nothing more.


A few other thoughts, for anyone out there still lucky enough to have a kit to build;
On the fins, I had 2 sets. I made the rudders rather large on the 1st set and almost lost the jet due to flutter about 3.5 years ago now. I had Volz Wing Maxx servos in it, and the plastic servo arm split and stripped on one, followed by flutter, followed by the other stripping and fluttering as well due to the vibrations of the 1st (or at least that's what i figure happened.) I just happened to buy an extra set of untouched fins and wings on RCU 6 weeks prior! I retired the old fins immediately, and built a new set with smaller rudders, maybe 1.25" chord, and 2/3rds length from the bottom up to the tip. The rigid trailing edge in the tip area will help to stabilize the flow, and it allows an integrated servo to be mounted a bit lower (less pendulum mass, and stiffer skin). The smaller rudders were still responsive enough for cross wind. The servo I used in the 2nd set was the [link=http://www.horizonhobby.com/products/ds398hv-hv-digital-precision-mg-thin-wing-servo-JRPS398HV#t2]JR 398HV[/link], and I wouldn't hesitate to use it again. I don't know of a better servo choice for the HotSpot fins. The heavy duty plastic JR servo horns are a perfect match for this setup.

My elevon servos were Hitec 5945MG's with the stock aluminum arm, and the speed brake was a 645MG - no need for a digital on the speed brake...

Construction wise, I used 7 Robart large hinge points per elevon, and 5 per rudder. When I cut out the hinge line, I cut back 5/8" and capped the section with hard balsa. Prior to bonding the cap strip on, I also mapped out each hinge location and sunk a hard balsa block behind the strip on both sides of the hinge; lots of meat for the hinge to grab with Hysol. On all surfaces, I oriented the servo linkage about 1/4" offset from a hinge, just to support the torque better, and I used 4-40 threaded rods with [link=http://shop.dubro.com/p/4-40-safety-lock-kwik-link-qty-pkg-12/aircraft_kwik-links-clevis?pp=12&pp=12]DuBro Kwik links[/link] everywhere.

Once built up, I glassed the wings and fins. The wings had 2oz cloth with the strands 45 degrees to the leading edge. That allowed a thicker glass to go seamless around the LE and cover the entire top and bottom easily with 1 sheet. A few cycles of sanding and skim coats of finishing resin gave a smooth and very robust wing surface but it took a while. This was good for 9.5 G's according to the eagle tree.

The fins were a different story. It's known that fin flutter is a failure mode on this jet, so stiffness and mounting technique are critical if you want to push the speed envelope. I've even seen it on a Hotspot with a P-80 at less than full power. I coated each side of the fins with the same 2oz cloth as the wing, sanded, then coated each side again with 3/4oz cloth rotated 45 degrees from the 1st. The fins will turn our brutally stiff, and the 3/4oz cloth is easy to finish up for primer. Mounting the fins - I went overboard there too. I bonded a thick plywood doubler on the inside of the wing root wall inside the fuselage, ahead and behind the internal formers, allowing for hard points. I had 3 countersunk screws per fin going into brass inserts in the fuse, 2 in the rear and 1 in the front. Then, I had 2 allen head cap screws inserted from the underside of the fuselage, through the already mounted fin, and into the wing, effectively sandwiching the fin onto the fuse with 5 screws per side. (see images below). Every time I met another Hotpot pilot, I checked his fins to compare stiffness. The only stiffer set I came across was permanently bonded to the fuse! Take it or leave it, but this system worked pretty good and I'd probably do it again the exact same way.


Flying, I've witnessed the deep stall issue but never had it happen myself. If the CG is rearward, keep the speed reasonable and it won't be a problem from what I could tell. The instance I witnessed was when my flying buddy was trying to do a slow rolling circle... I can agree that the solution to the 'chicken flop' is NOT to power your way out - it will not happen. Pull off the power, let the nose drop, and fly it out if you still have altitude. The erratic flight path in deep stall may be a result of gyroscopic effect of the engine, which gets worse with more RPM as you try to power out of it![:@]

Speed wise, I'm really curious to see what sort of hardware was used to measure the speeds claimed earlier in this thread. I had to push mine really hard to hit 249mph, and did not use a 'stock' 1300R to get there. (I use to be a service rep, mine was cranked up to 127k, stock is 120k...). I found that atmosphere conditions actually did very little with respect to top speed, possibly since the air density that effects the engine performance also effects the drag, and drag is a squared function vs velocity... You will probably notice better verticals near sea level though! The 120SX was stock, and essentially new. I'd love to see what a 140 or 180RX would do. I don't know of many other turbines that would work well if you want to overpower it, since anything over 1.2lb of residual thrust will make a power on landing much more difficult IMO. When the PST 1300R was 1st introduced it had an idle speed of 40k, on a 66mm exhaust turbine platform that equated to around ~2lb +/- of idle thrust and it was a bi&#$% to get down without a 'roo hop'. I lowered the idle to 34/35k and it became much more reasonable. The 180RX appears to have a really good residual spec according to the last RCJI I just read, so that would make a seriously exciting model, but holy cow would you ever need to practice good energy management with the left stick. (imagine accelerating up at what would be normal gravity acceleration down, ~2:1 thrust to weight! )

Below is a series of photos showing how I mounted the fins and wings. It was a lot of work, but it was wickedly strong. Hope this info helps someone out there if they need a hand.

Kelly