Hello,

I would like some assistance installing a set of Spring Air retracts with Robart struts in a GSP Spitfire. On this Spitfire, and most Spitfires from what I am told, the gear must be canted forward. That is, the retracts must have a bend to accomodate the location of the retract mount and the wheel wells, i.e., the center point of the wheel is more forward than the retract mount. Thus, I cannot simply cut the strut to length and attach it to the retract because the wheel would be behind the wheel well, i.e., too far back. How do people handle this?

One possible solution is to bend the wire that connects the strut to the retract. Any suggestions would be greatly appreciated. This is my first experience with retracts and I would like to do a good job.

Travis

here's a few thoughts (My winter project is the now discontinued Spitfire 40 from Great Planes).

Firstly, the real spitfires have the retract mechanism close to the fuselage, and the wheels retract toward the wing tips.... This means that the real spitfire landing gear has a narrow "stance". This is only good if you have really good ground handling because otherwise you will keep tipping over when taxiing. To counter this, most spitfire kits coe with instructions to put the retract mechanism toward the wing tip, and the wheels retract toward the fuse, meaning the plane has a wider, more stable stance.

So, given the above, you must decide how close to scale you want to be.

The engines on the spitfire were heavy, and the landing gear mechanism never really changed it's location in any of the spitfire "marks". but, as the engine weights changed, they cantered the gear forward or back to prevent nose-overs on the ground.

If you choose to have the wheels retract toward the fuse for ground stability, you can set the camber angle by installing the whole retact mount with a 20degree or so angle of incidence relative to the wing's angle of incidence. Doing this means that the wheel will not line up perfectly flush with the wing when it is retracted, but this can be rectified by having a scale-like strut cover, or by simply ignoring it.

A picture is worth a thousand words .... so, have a look at the following:

Some guy's yellow aircraft landing gear installation....
http://www.homestead.com/evoshangar/spitfire.html
see how the retracts are done in the correct direction at least. When retracted, the wheel will not be parallel with the wing surface. Further, he has made it retract at the scale like angle relative to the wing spar (swept back in the wing). This woks by giving the wing the riht canter when extended.

If you want, and is easier, you can have it retract parallel to the wing spar. If so, you need to canter the whole retract mechanism so that it angles forward (like I described above).

I am going with the second method for my spit.

gus

Yep - I had the same problems working this out on an old Sterling kit ... 63" wingspan. Pretty much only used the wingribs as templates, and redesigned the whole wing for flaps and retracts. As Gus says, first you have to decide if they retract in or out. I went with the scale option, just to torture myself. I have to tell you, when the wheels are down, you look at it and say, "No WAY!". They are very close together, and I am looking forward to a season of ground loops.
If you go this way, the key is in setting the angles of the retract assembly itself, first with respect to the long axis of the wing, then how much you rotate it about that axis. I found that the wheel struts on mine needed to be 19 degrees canted back with respect to the spar. This allowed the wheel to clear the spar when raised. In order to get the strut oriented properly so the wheel was in the right place when down, I found I had to install the retract assembly tipped forward 15 degrees WRT to the chord. I have some good photos of a spit in flight - amazingly, the real wheels are canted in the wells just like mine when up.
I used Dave Brown retracts on this eight pound airplane - flying off grass, and no, it hasn't flown yet. The real hardpart for me was accepting the reality that I was going to have to install the retract mechanism where there ought to be spar ... I had to fabricate a "carry through" bulkhead in the wing to allow the spar to be interrupted at the retract mechanism. The spar is glued to this bulkhead. It was a lot of effort, but works well.