hessian123

John (or whoever knows the answers), I am seeking information about the retracts shown here: http://www.nitroplanes.com/prmerore.html

Who makes them and what size plane (how heavy) are they intended for?

Why are they called "pre-installed"?

Are they an appropriate size for the 71" CMP hellcat (http://www.nitroplanes.com/hellcat120.html)?

How much modification to the wing (especially the spar) is needed to install retracts into the above hellcat?

Finally, when are you going to have these retracts in stock?


Thanks!

opjose

They are too small for the Hellcat. These retracts are better suited to 40-.60 sized planes.

You want something with thicker wires at the least... at best more scale like retracts.

hessian123

What size wire would be sufficient? I'm not as worried about scale and I'd rather not spend $200 on a set of retracts for a plane that only cost $200 itself.

opjose

I have one of these bad boys...


5/32nd wire is rated for UP TO 10lb airplanes.

This plane comes in around 11-12lb AUW and more when fueled.

Manufactures are a bit "optimistic" in their ratings, and 5/32nd gear will bend easily on this size aircraft.

Unless you grease in every landing, you want to avoid wire gear.


You really need to go with struts, preferably shock absorbing type struts. or at the least shock absorbing wheels.

Unfortunately doing so puts you around the $200.00 mark for landing gear.

It is not unusual for the gear to cost almost as much as the plane.

hessian123

And here I was thinking that I got a sweet scale Hellcat for cheap. . . If I'm going to spend that much, I think I'll go with the Lado's, but they don't come with struts. Any recommendations for the struts and/or wheels?

opjose

You could do with the wires if you act to keep the plane light...

e.g. Maybe a 2C engine or something like a Saito ( which are very light ) 4C, and throw the batteries on the mount to get the C.G. right.

Don't go overboard on the battery size as well ( I know I do ).

If you get it to come in around 9-10 lbs they will work, but harden the mounting area as much as possible too.

Mine came in much heavier ( around 13-15lbs ) but I went with struts, scale changes, etc... as were suggested in the rather huge CMP Hellcat thread on the Warbirds forum.

hessian123

I'm planning to throw a converted Ryobi 32CC engine on there, so the weight will surely be an issue. My brother is a machinist, so maybe I'll try to work something out on the cheap through him.

Since you've built one of these, perhaps you can answer this: If I build the plane with fixed gear initially, would it be difficult to come back later and add some sort of retract mechanism after a few flights? (Assuming I can keep the plane intact that long of course.)

opjose

If you install Air retracts after the fact and not install the wheel well cups, you may be able to do it with the caveat below...

However installing the fixed gear means that you are to epoxy a wooden block in place for the fixed gear.

This wooden block fills the area normally inhabited by the retracts.

You would have to plane ahead and probably modify the mounting a bit to be able to later change the gear.

The 32CC Ryobi is relatively heavy compared to say a Saito, so I would not go with the spings with that engine in place.

With struts the biggest problem is that unlike the wire gear, they do not "give" when lateral forces are exerted on them.

This tends to cause the gear to rip out at the mounts when a lot of lateral force is imparted, e.g. a rough nose in landing or when transitioning from asphalt to grass, or if you hit a bump on grass while the plane is landing.

The wire gear bend at the loop preventing damage to the mount.

Struts on the other hand tend to rip out... which is one reason I suggest struts with some sort of shock absorption, etc.

Make the mounting area as beefy as possible and re-inforce when you can.

I'll add extra wood strips along the strut blocks, making them as long as possible to help spread out any torsional forces.


Of course you can only do this up to a point, and beyond that it is best to improve the pilot not the plane... heh.

hessian123

Sounds like I'd be better off just waiting for the Lado's before maidening it. There's plenty of room to improve this pilot, so we'll see what happens.