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MikeS -> Hanger9 P-47 Thunderbolt 150 assembly notes. (3/14/2006 8:03:02 PM)
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I got my Giant Scale P-47 Last Thursday and am as far as I can go at the time being, so I thought I'd post a few quirks and problems. I have 5 peeves and only one real problem, but thought it would good to post my probs, maybe someone will have a solution I have not thought of.
General - The fit and finish of the airplane is superb. It is designed very light, with lots of attention to detail and good thought into how to equip it with standard high-torque servos throughout.
Problems - Only one and that is a material problem. The retract mechanism is oleo strut ready, meaning you don't use music wire into the strut and retract. The size control of the struts and the drilled holes in the mechanism are not very precise. One strut is so tight it will barely allow itself to be forced into the hole, the other so loose that the the retract can't be tightened enough to hold it in place. The result, a retract that is not usable. It seems to me that the struts are slightly different, and onme is too small. I called Horizon Hobbby, and they do not have the struts in stock, so I may have to wait until they are available before my airplane is redy to fly.
A word on the retracts. The instructions say it is designed around a low-profile retract servo and recommends the JRPS791. I had Hitec 77's on hand, but they won't fit so I had to order the JR servo. Horizon only had one in stock between their Midwest and California facilities, so that is on backorder, too. Another delay.
Here are my peeves. None of these are problems, just my preferences.
1. Pushrods are 4-40 metal rods in plastic tubes. The tubes are already glued in the fuselage. I prefer carbon fiber pushrods, but it would take extensive modifications to use anything other than the metal rods.
2. The plastic tubes only allow one location for the servos in the fuse. While there is lots of room, the servos are on rails with pre-drilled holes in locations where the plastic guide tubes come out. The problem? The elevators use one servo per side and both guide tube runs are on the outside of the fuse, on opposite sides. You need either an extra receiver slot, a JR Matchbox, or a a reversing y harness to get the servos to push'pull in the same directions. In fact, this occurs not only with the two elevator servos, but the retract servos and the flap servos as well. You need either a 9-channel radio, three reversing harnesses or three matchboxes to get them to work correctly. That's too mych. It would take so little design to put route the elevator rod to the other side of one servo, or put the flap hatches slightly offset so the servos could be mounted so they operate alike to relieve this problem.
3. All the pushrods use, on one end, a 90 degree bend and plastic snap keepers. I can't seem to get a good enough bend that they work without forcing them onto the rods. That's especially so when you have to make a tight bend while the metal rod is rigidle locked into place inside the fuse. I replaced these with silver-soldered clevises.
4. The top hatch is huge, taking up the entire canopy and going all the way to the firewall. The problem - when the cowl is in place, the hatch can not be removed. I think I can change that with a little filing on the aluminum posts that secure the hatch onto the fuse.
5. The flaps use robart hinge point like hinges. One one flap, the holes were drilled so that the flap was 1/4 inch lower than the top surface of the wing. I saw this, but went ahead gluing thinking I could jam it in a little further and achieve a match. Wrong. I shouold have redrilled the hinge holes.
6. Using the Saito 180 four stroke, the throttle arm is right up against the firewall and the pushrod is very tight. This causes binding, making the throttle operation very hard. I think a cable will do better than the pushrod provided.
7. All of the control horn installations have wood screws screwed into hardwood, except the elevator horns, which screw into balsa, using #2 by 1/2 inch wood screws. The instructions have you put thin CA in the screw holes. I would have preferred holes that go all the way through and are captured by a plate on the opposite side, but with thick wood, the standard three-hole control horn is hard to install. I did it their way to see if it works, and I will go to a type of horn that goes thru the control surface if I find any sign that the wood screws are coming loose. I don't see it failing in mid air, but I am a little uncomfortable with it.
All things considered, this is a very good airplane that is well designed and supplied with lots of hardware that should work fine. Once I get the new struts, I will let you know how it flies, but at a calculated 31 ounces per square foot wing loading, it should fly really nice.
Oh yeah, ever have screws and other things left over? There are two four inch long metal bolts with 1/2 inch 4-40 (i think) threads on one end and 1/2 inch wide knurled knobs on the other. They do not show up anywhere in the instructions. Anyone know wjat they are for??
Mike
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