Setting up the gear doors on the P-51 for the first time isn’t that difficult assuming you are given some ground rules. I’ve been building for many years, but never set one up with the scale features as on the CARF P-51. The P-51 has outer doors attached to the retract struts and inner gear doors that articulate open/closed in a sequence with the retracts. Of course, a special retract air valve (Ultra Precision 2) is needed to control all this action (installation should be similar using electric retract system as well). All these functions operating together can be quite intimidating to think about the first time you are going to take it on. I felt the same way as just described when I bought the CARF P-51, and this was the part I was least interested in building up. Lucky for me, a fellow RC Club member, Jack H, loaned me his CARF P-51 wing half for me to look over and use as a work guide. He also had some basic words for the proper installation of the outer doors that I somehow failed to put into practice the first time thru. Only after Jack looked at my work did he tell me I failed to listen to his instructions! Well, I was glad to hear what I did wrong, and got it right the second time around.
Here is the basic rule Jack gave me that you must get correct for the outer door hinge: “You MUST get the outer door hinge (pin) aligned EXACTLY parallel AND in the SAME plane as the axis pin of the retract! ”
Failing to do this will mean you will get a close fit of the outer door, but it will never be EXACTLY right! By this I mean the other end of the door will be off by some small margin, one direction or the other. Try as you will, it won’t go up/down with the retract as it should unless you get that hinge down correctly.
Jack felt it necessary to abandon the CARF method of installing the outer doors and used some of his own ideas instead. After looking at the factory setup, I was in agreement with Jack and followed his lead. He used a small hinge from the hardware store which made the whole outer door hinging a lot easier. The first photos below describe how the small brass hinge is set in place against the base of the retract.
In the middle of the door, you must add a turnbuckle attach bracket to pull the outer door up/down with the retract. I made this out of some steel sheet metal from the scrap box. Don’t use aluminum or brass – too weak. It is fairly obvious where it mounts, but you will likely have some trial and error getting it positioned correctly – hinge must be installed first.
Next to discuss is the inner gear door sometimes called the clamshell door. This door opens AND closes on every gear cycle so it gets a lot of use. It must be installed with absolutely no binding. On the CARF P-51, the hinge is factory installed. However, on mine, the hinge on one wing-half was deformed at the factory and I had to take it apart and reglue to make it correct. The air cylinder has to be installed inside the wheel well to open/close the door on each cycle. It must be mounted/epoxied securely at the base as well as on the door itself. There are two places to mount the cylinder – on either side of the tire. I chose to mount the cylinder at the leading edge of the door to put as much pressure on the door at the forward edge. This is where the air pressure will try hardest to lift it open when closed. But keep in mind, the scale location is to the aft of the tire.
TEXT & PHOTOS BY LANE CRABTREE; OPENER PHOTO BY NANCY ABBY