Author Topic: Sterling Corsair/ Robert's Corsair (Read 2729 times)

dankar · « **on:** February 24, 2008, 04:28:59 AM »

I have one of each and want to make the Robert's a class 2 and Sterling a class1. No sliders and classic old school Carrier. I will use the new bellcranks as they look much better. Hopefully down the road I can get a few other flyers in Tucson to do some old school Carrier. I have a nice full body Skyraider with ST .40R just needs some final detailing and markings. She is a beauty and make a MO-1 look like what it really is-one UGLY plane!!
Cheers,Dan

Joejust · « **Reply #1 on:** February 24, 2008, 08:56:35 AM »

Dan, loved your thread! nearly every word speaks of F U N !!

Keep us informed.

Joe Just

The attached picture is of an entry level (spell that FUN) proile carrier ship. This plane and attending article is a proposed new article for a future issue of CLW.

Balsa Butcher · « **Reply #2 on:** February 24, 2008, 12:10:01 PM »

If this catches on-count me in. I wrote an article for the Carrier Newsletter on this topic. That was about 10 years ago. It featured my "Buster-Cat" w/OS-35FP power. Both my son and I flew that plane to many victories in local contests. I guess what I'd like to see is 10% nitro limit, no line sliders, limit on prolonged flight attitude (so no prop hanging), plain bearing engines to encourage FP's, LA's, etc. that are cheap, easily accessible, and easy to make work. If you are going to have extra points, make it for full bodied carrier planes to encourage those designs but not have to have a separate class for them. Make it a .40 max engine size since .40 engines are easier to get than .35's these days. Oh, yea, muffler required. BUT since a new class is not going to happen - I will go along with the old school proposiotion as originally posted.

john e. holliday · « **Reply #3 on:** February 24, 2008, 02:16:08 PM »

Dankar, I had a Sterling Corsair years ago with a K&B 40 rear intake that I flew. The last contest it flew in was one of those days that was perfect for the Corsair. I was concentrating on low speed so much I forgot what lap I was on. I looked at the officials and everyone had their back to me. I yelled and asked what lap I was on. That is when it ran out of fuel. Seems I flew about 15 laps afteer low speed I was having so much fun. Talk about being disgusted I rolled up lines and put every thing in the car and have not been back to that meet since. By the way it got me a third place in scale carrier the first year they had carrier. Didn't even get scale points as my three views were at home on the bench and nobody would loan me a set. May build another one with a Fox this time as I have a kit in the basement.

I still say do away with sliders and MO-1's. DOC Holliday

Chris McMillin · « **Reply #4 on:** February 25, 2008, 02:07:23 AM »

They have, in Nostalgia.
Let's just talk about Nostalgia and old kits, designs and engines we can use.
Are the old JRoberts bellcranks OK with a Corsair with an ST 40? Strong enough?
Are the new Brodak bellranks better?
Chris...

Mike Anderson · « **Reply #5 on:** February 25, 2008, 07:19:37 AM »

Quote from: Chris McMillin on February 25, 2008, 02:07:23 AM

They have, in Nostalgia.
Let's just talk about Nostalgia and old kits, designs and engines we can use.
Are the old JRoberts bellcranks OK with a Corsair with an ST 40? Strong enough?
Are the new Brodak bellranks better?
Chris...

"They have, in Nostalgia.
Let's just talk about Nostalgia and old kits, designs and engines we can use. "

Good idea (but unlikely) -

"Are the old JRoberts bellcranks OK with a Corsair with an ST 40? Strong enough?"

Probably -- The JRoberts cranks have been used in some very heavy, very fast
(and now, very old) planes - I've never had a crank fail in any plane - but I had
one in my pocket for about a couple of days one time, and when I pulled it out,
the brass bearing in the slot had come apart --

? I also think the aluminum/brass
slider tends to gall a little bit and get kind of sticky, sometimes. I only use JRoberts
on .15 planes, anymore.

"Are the new Brodak bellcranks better?"

If they are still making them the way Leon did (and I think they are still using
parts that he had made), then yes they are much better, strengthwise. The cranks
are steel, not aluminum and they are quite a bit stronger. They are also a bit
bulkier and take more room to mount.

They are not optimized for JRoberts handles however. I don't know if everyone
is aware, but the LR (Brodak) handle has more throttle line movement then the
JRoberts did. This makes for kind of an odd feel to the throttle trigger, if you
try to use a LR/Brodak Handle with a JRoberts bellcrank. If you mix the other
direction - a JRoberts handle with an LR/Brodak bellcrank - you just never use
all of the available throw, which you can work around by changing the throw
somewhere else - like at the carb arm itself.

Mike A

don Burke · « **Reply #6 on:** February 25, 2008, 09:27:33 AM »

The is a dangerous side to mixing Brodak handles with J Roberts bellcranks. Since the Brodak has a longer thow all the airplane weight MAY be on the throttle line at full throw. The elevator lines go slack.

Mike Anderson · « **Reply #7 on:** February 25, 2008, 09:49:25 AM »

True - it can happen if you set up for a "Pull" on the throttle
line to be high throttle. Also, that would put an awful lot of force on
the pushrod to the carb - could actually loosen the screw and
have the carb arm come loose.

Personally, as mentioned, I only use JRoberts on .15's. Even there
it is only the handle, anymore. Mostly I use homemade bellcranks
(I like to use two fox cranks because the bearing is very low
profile). I don't think I've ever owned an LR/brodak bellcrank,
though I've got a few handles.

Chris McMillin · « **Reply #8 on:** February 26, 2008, 12:26:40 AM »

Thanks men,
I have both types, handles and bellcranks. Just more JRoberts bellcranks than the later stuff. Good info, especially to keep in mind for the direction of wide open throttle and which line gets the tug!
Chris...

john e. holliday · « **Reply #9 on:** February 26, 2008, 09:31:51 PM »

How did we ever get a complete flight in with the Roberts bellcranks. I remember before the 4 pund weight limit pulling my Sterling Gaurdian to 118 pound pull test in 1970 NATS at Glenview NAS. Then there were all the guys using Rossi's and Super Tigre 60's. At the 70 Nats Bill Johnson clocked in practice at 130+ mph high speed. But, the low speed would flame out. When he backed off the high speed he was able to get full flights. I don't think I ever seen a J-Roberts system fail. DOC Holliday

eric conley · « **Reply #10 on:** February 27, 2008, 11:55:04 AM »

Boy I guess I have lots of company with the worry of these bellcranks failing. Course Ive never had one fail in flight. I did see a Brodak 3-wire BC fall apart on a training plane (MO-1) but it must have had hours and hours on it and had become very loose. It fell apart while being readied for a flight thank goodness. Its best to check these things once in a while and maybe a little more if they have high time on them. They can get very loose which means "keep an eye on me".
Ive never seen a early bellcrank get real loose but I think its because the ones Ive seen were never used much. With the newer rules the carrier planes can last a long time (they don't get crashed at the end of each flight) so they can have many hours on them. eric

Mike Anderson · « **Reply #11 on:** February 27, 2008, 04:25:53 PM »

I certainly never meant to give the impression that I didn't trust
the JRoberts units - (I DID say that many fast, heavy OLD models
have been using them for years). I was only trying to point out
that there is a difference between the JRoberts and the LR/Brodak
handles and cranks.

I did say that I only use them on .15's - because all my other
stuff is set up for the LR handles. And I seldom use anything but
homemade bellcranks anymore - because I'm cheap, not because
I don't trust them. Whatever you use, install it carefully, set it
up so it can't jam and it will probably last for years.

I also don't think that the comments about the possible hazards
of mixing the different makes was meant as a safety warning - it
was just something to think about. The reality is, if you use a
pull for high speed (most don't) then you could possibly be putting
all the flight load on one line, but if that line should break, the
engine would immediately go to low throttle anyway.

Mike@

eric conley · « **Reply #12 on:** February 27, 2008, 08:30:07 PM »

Hi Mike, I must not have worded my post all that well. I agree with you completely on what you have posted about the bellcranks. I was thinking outloud about how I feel about the 3-line bellcranks as a whole. I look at all the parts and how they are held together and wonder how the things ever hold together. Your right about the strength of the earlier ones as they took a harder beating from those 130mph planes than the present day bellcranks and planes do.
When I first started competitive flying I noticed a lot of people were having trouble getting there throttles to work properly. Mine seemed to work just fine as I had bought them from Brodak's and they were built to work together. When I would go over and look at these planes that were having trouble I found that the bellcranks looked different than mine. Thats when I found out that there were many different bellcranks and also control handles that were being mismatched and the result was that some of these mixes did not give the pilot much throw to the carburetor arm. When I questioned about this the flier would pull out a couple more handles and say they must have hooked up the wrong handle. It didn't look to me that any of there stuff matched and it was apparent that they had never questioned this fact. This didn't happen just once this happened several times.
Up until then I had thought they would all work together but they sure don't. Your right its not about safety, it is they dint give you the throws that you would expect. eric

Chris McMillin · « **Reply #13 on:** March 10, 2008, 12:51:08 PM »

I have received some older NOS bellcranks lately and find them much more lightly built than the later JRoberts I first got as a kid and later. These have a thinner stock and MUCH softer than the later versions. Once mounted and under tension i think they are plenty strong, but I can tell that they are different.

I am giving one to my son to install in his scaler, so I'll see its operation first hand for a few dozen flights at least this summer.

Chris...

Chris McMillin · « **Reply #14 on:** March 11, 2008, 07:06:34 PM »

Does anyone know the size of the swage collets and what tool is necessary to make those cables like the JRoberts kit had included?
Chris...

dankar · « **Reply #15 on:** April 18, 2008, 05:11:36 AM »

For whats its worth I called a excellent 70's flyer about old Robert's bellcranks and he never has a problem. He ran ST G.65's on 65% nitro. Even today its a kick butt engine. I woulf feel better with Bordaks modern version but class 1 on problem with older B/ cranks.
Dan

Peter Mazur · « **Reply #16 on:** April 18, 2008, 02:10:33 PM »

In the old days Bill Johnson sold a beefed-up version of the J-Roberts bellcrank that was recommended for Class 2. I believe the Class 2 MO-1 plans even had that specified on the plans. Back then we tended to build a lot smaller and lighter airplanes, even in Class 2, which is one reason they went so much faster. A modern 4 1/2 pound (flying weight for high speed with fuel) at 110 MPH pulls harder than a 3 pound model at 130 mph, so the stress on the bellcrank today can be pretty serious.
The GS/LR/Brodak bellcranks are a lot stronger, I believe. The only catch is that the Brodak assembly procedure does not always insure low operating friction. And the GS/LR/Brodak handles often had the leadouts at seemingly random lengths as Eric mentioned. I went through a bunch of mine some years ago and replaced the leadouts on many of them so they would be uniform. I used heavy-duty Sullivan leadout material with the copper tubing and crimp tool that came with the leadouts and have not had a failure. (It's still a good idea to inspect the leadouts where they attach to the metal parts of the handle occasionally and look for broken strands.)
Pete

Chris McMillin · « **Reply #17 on:** April 20, 2008, 12:51:28 PM »

Thanks for the good info, Pete.

dankar · « **Reply #18 on:** May 12, 2008, 07:36:53 PM »

Yahoo, finally have a good kit of Sterling Guardian. Have one OK kit another kind of rough. Going to need some serious mods. I want to be able to change out tank if needed. Flaps/ Rudder/ tail hook will need some fail safe effort..
Cheers,Dan

Mike Anderson · « **Reply #19 on:** May 13, 2008, 07:00:03 AM »

Quote from: dankar on May 12, 2008, 07:36:53 PM

Yahoo, finally have a good kit of Sterling Guardian. Have one OK kit another kind of rough. Going to need some serious mods. I want to be able to change out tank if needed. Flaps/ Rudder/ tail hook will need some fail safe effort..
Cheers,Dan

I had one a long time ago (It was a hand-me-down, so I didn't build it and don't know a lot of the internal details) that had a removable tank - it had a regular 3 or 4 oz. tank ( I also don't remember if it was a rectangular or wedge tank). I only remember that is slid in on the engine mount rails, through a matching hole cut in the first plywood former. It had "ears" soldered to the tank near the front so that when it was almost all the way into the hole, the ears were up against the bulkhead - a wood screw or sheet metal screw through each ear into the plywood bulkhead kept it from sliding forward again. I THINK that the fill and vent tubing must have come out the front of the tank and gone straight down - to exit the cowl on the bottom.

It also had no operational flaps and if I remember, the tail hook had a music wire arm up through a leadout eyelet that trapped the rudder (spring loaded) into the "high speed" position.

Mike A

dankar · « **Reply #20 on:** May 16, 2008, 03:42:16 AM »

The plans and set up for this ship are at best quite amusing. Still this was a very good ship. Stock L/G wire is just bad news. / going to 1/8" wire. It may bend but will not take out wing supports.
Dan

Balsa Butcher · « **Reply #21 on:** May 29, 2008, 11:50:42 PM »

Uh Oh, I'm confused (easily done)

We jumped from the Sterling/Roberts Corsairs to the Sterling Guardian. Did I miss something? FWIW, I vote for the Guardian, a much more competative plane than the Sterling Corsair. Dan, is the Roberts Corsair you are referring to the profile one or the carved fuselage one that was a companion to the Roberts Mauler? If so, I believe it is a pretty rare kit.

On another note: I use the modern Brodak bellcrank/handle on most of my planes but keep a few older ones and an original handle for future nostalgia carrier projects. The older ones are much more compact and I think would fit inside the wings/fuselages of the old Class I designs that I like a lot easier than the larger current ones. No issues personally with the strength etc. They are pretty well proven.

Mike Anderson · « **Reply #22 on:** May 30, 2008, 11:21:31 AM »

Quote from: Pete Cunha on May 29, 2008, 11:50:42 PM

Uh Oh, I'm confused (easily done) We jumped from the Sterling/Roberts Corsairs to the Sterling Guardian. ....

Whoa - I didn't notice that Dan was talking about a Guardian kit (& changing out tank, etc.) I was talking about a hand-me-down CORSAIR in my reply to him. Sorry if I confused anyone besides myself ...

dankar · « **Reply #23 on:** July 05, 2008, 04:29:04 PM »

Sorry for confusion,I also have the Guardian. the Robert's Corsair is full body version with formed fuse sides.
Dan

Author Topic: Sterling Corsair/ Robert's Corsair (Read 2729 times)

Joejust