Ground Fault - Commodore

[Ian Hewitt]

Hi folks,

Just thought I'd share my latest build.

A Ground Fault merged with a Claus Maikis Commodore fuselage outline dressed up like a T38.

I had a brief flight earlier today - despite the fast controls it handled well but I learned that the Irvine 25 is completely worn out - felt good cold but no compression after the flight.

Have now re-engined with a new ASP 25A and hoping that this will be a good practice plan.

The other model is a Thunderbolt from 1955 by Bill Morley - 50 years between these two designs.

Best

Ian

[Gerald Arana]

Nice! I like them both Ian. I believe in the K.I.S.S. technique....

Cheers, Jerry

[Ken Culbertson]

Curious as to your reason to split the controls.  I think it is a good idea.

Ken

[Ian Hewitt]

Thanks for the comments.

Jerry, yes KISS is a good principle!

Ken a short question which might involve a lengthy answer..   I built the major components of the Ground Fault in 2016 but they lay on a shelf until recently - the controls may have been a contributing factor. I have ventured into the use of ball links on my Trophy Trainer build and wanted to try to use them to help complete the Ground Fault.

The one piece elevator meant that a metal control horn was unnecessary and I was reluctant to use nylon RC horns as per the plan. I also wanted the flap/bellcrank horn to be normal to the pushrod. Having built a Pat Johnson Ringmaster 576 I quite liked his control system design using bushed ply horns and split pushrods.  The split push rod allows the two horns to be shaped to suit and keeps the ball links out of the way of each other.  I confess to taking the horn design directly from the Pat Johnson plan - if it ain't broke don't fix it.. .. and it has stood up to a lot of use on my Ringmaster.

Hope this makes some sense.

Ian

[John Park]

If there's anybody out there who's a connoisseur of typographical errors, here's one I treasure: the Thunderbolt article in AeroModeller stated that the fuselage sides should be held together for glueing "w banith rubberds".  Geddit?

[Tim Wescott]

I need to get hold of Pat's plans, to see how he made the flap controls -- I'd be concerned about getting differential action on the flaps.

One other advantage you didn't mention is that tweaking the flaps for roll is just a matter of adjusting a ball link on one side or another -- no trying to bend the flap joiner and praying that you bent it just enough, and if you want to go back to exactly where you started it's just a matter of counting turns.

[Dennis Leonhardi]

Nice!

[Ken Culbertson]

I'd be concerned about getting differential action on the flaps.

My initial reaction was the same.  One of the things I learned early in building a lot of the sterling profiles was to put the controls on the inboard side.  That is where I got used to having the up line in front.  With a flap mounted horn you will get some twisting and as a result some roll.  Best that roll was to the outboard.  I am not sure that this arrangement doesn't contribute to that problem. Or not...

Ken

[Gary Mondry]

One other advantage you didn't mention is that tweaking the flaps for roll is just a matter of adjusting a ball link on one side or another -- no trying to bend the flap joiner and praying that you bent it just enough, and if you want to go back to exactly where you started it's just a matter of counting turns.

I don’t see that.  It looks like the bellcrank drives the left flap, which drives the right flap through the joiner, and the right flap drives the elevator.

[Tim Wescott]

I don’t see that.

I wouldn't expect it -- Pat knows how to design a good plane.

[Gary Mondry]

No doubt about that, but I have RM 576 plans, and there’s nothing fancy apparent going on with the flap horn.  It’s depicted as a single L-shaped horn joiner.  That gets the 90 degree pushrod angles, but no way to individually adjust the flaps without tweaking the joiner. 

[Ian Hewitt]

Thanks for the further responses.

As Gary says the layout of the flaps/horns on the Ringmaster 576 is straight forwards and ball end links are not shown.

The 576 has small flaps and a strong wire joiner - 3/32 or 12 SWG. By contrast the Ground Fault has big flaps! I have used a similar sized joiner but I guess the torsion will be bigger.

The bellcrank is reversed and operates on the inner flap so I guess the worst case scenario will see some differential flap at least operating as per Bob Palmer.. .. and the elevator drive may be diminished.

I will try not to think too much about this next time out, but it will no doubt be at the back of my mind. Currently the main issue is to break in a new motor.

The 576 did need a trim tab on the outer flap to reduce hinging.. .. wonder if this may be connected?

Thanks again.

Ian

[Gary Mondry]

Ian,

Thanks for the clarification. That’s what I thought I saw.
It’s a handsome model.

Gary