Just ordered Robart Retracts for my SBD a couple days ago and I'm studying the plans to get my ducks in a row for installation. This is my first retract job and the plans are designed for mechanical/servo gear so I need some help with what may seem obvious to most of you...

The SBD has a one-piece wing and I'm assuming that I'd want my air system & cylinder all to be in the wing??? I don't think that you'd want to connect & disconnect air lines between the fuse and wing every time you flew... seems like potential for wear & leaking. Likewise for fill valves, pressure checks, etc.

I think that my system comes with the Medium size air cylinder, which is 8" long by 2-1/4" diameter. This size will require a good bit of cutout in my 85" wing, which concerns me from a structural strenght standpoint.

Any advice??

Thanks!

Neo

It is common practice to mount the air tank, as well as the servo/valve in the fuselage and use quick-connects between the wing and fuselage.

If you have a retractable tailwheel, you'll need to have lines between the fuse and wing either way you approach the problem.

I usually put the air tank, valve/servo, the schrader fill valve, and retract-tail plumbing in the fuselage.
I then have two hoses that exit the fuse going to the wing via qd's........

What is above the wing where it mounts on the fuse? Perhaps you don't need to fully bury the tank in the wing. Maybe it can sit on top. In my (deceased) Pica FW190-D9 I had the tank fitting between some ribs (lengthwise not crosswise) and about half buried into the wing.

As to quick disconnects I have used them for some time without any problems so putting it in the fuse should work as well.

cheers

Jeff

Thanks guys... great info.

No retract tailwheel, so that's not an issue. I guess I was looking for opinions on using the quick disconnects. I do have room above the wing to bury the cylinder partially in the fuse and partialy in the wing.

I don't think I can go lengthwise vs crosswise without hitting the wing tongue or the flap & dive brake servos. I'll have to look at that when I'm back in the shop. If you think the quick disconnect is a safe setup, then I'll probably go that route to avoid cutting up my ribs too much.

Neo

Don't compromise your wing structure for the sake of not having to connect/diconnect two "quick disconnect" fittings. These are used exclusively by all of the jet pilots. I have never seen a tank mounted in or on top of the wing on a jet. I have used them on every plane I have ever equipped with retracts and I can say I never had any problems related to the quick disconnects.

GP Patriot
GP F-4
Trim Acft F-86
JMP Starfire
Hangar9 P-51
BVM T-33
BVM Ultraviper
Planes Plus F-86
JMP T-33

On the jets, I have two sets of quick disconnects due to the pneumatic wheel brakes.

I have had occasional air leaks but never at the quick disconnects. Mount your valve and tank in the fuselage where you have plenty of room.

aptar,

Thanks for the info.

If I can find room in the fuse, close enough to the CG, then that's where it will go. (Complete scale cockpit & gunner are eating up a lot of space)

I just want to make sure I don't have to shove it back towards the tail any to find room... she'll be tail-heavy enough on her own.

I'm glad you've calmed my concerns on QD's... I feel much safer now!

Thanks,

Neo