All moving tailplane linkage

[Amy flygirl]

Hello Guys and Dolls,

I'm going to be building a EDF Folland Gnat soon around 1/5 scale and of course it has an all moving tail plane so I have been looking for a linkage to use for the purpose.

Do you think I can find one, I've seen people using them in their builds in magazines so i know they exist. there usually made of aluminium and carbon fibre which would be great as I I'm going to push the Gnat to the limit.

Any help will be greatly appreciated.

Amy xx

[McG 6969]

Hi Amy,

The 2020 PSSA Mass Build Sabre also uses an all moving tailplane.

It uses a 105° plastic bellcrank (SLEC) but is only 1:10 scale.

It was designed by GM Models, so you could send Martin Gay a PM asking for some further info.

Cheers & stay safe

Chris

[Mike Etheridge 1]

On a simple very old glider a Micro Mold Sprite, the all moving tail plane is provided in two halves linked with two lightweight metal rods. The rods are secured in one half of the tail plane and push fit into the other half of the tail plane having passed through the fin first. The forward rod passes through a tube sleeve that the rod can swivel about and the other rod passes through an arc cut through the fin. Does this make sense.?-Obviously your set up would need to be more substantial.

[Murat Kece 1]

Hi Amy

Here's an example from the Phoenix100 glider I am building currently. I revised the pivot point of the bellcrank and moved it towards the leading edge of the fin.

[Murat Kece 1]

See Sigma_RC_oz12150.pdf at Outerzone for this example..

[Alan Gorham_]

Amy it seems as though most respondents so far haven't quite grasped the requirements.

You could try and make contact with Russ Delaney of Thorjet who modified the old John Carpenter designed Gnat from IC DF to small turbine. He used linkages very close to what you describe: IE 6mm diameter carbon rods in the tailplane running in alloy bearing blocks with alloy horns and carbon pushrods (one servo per surface). There used to be pictures on another uk based forum of this setup, but while the thread is still there the pics were all lost some years ago.

Similarly, the Thorjet facebook page has some pics of the Gnat, but not the part you need. A message to Russ might bring you the exact solution you need?

[Wilco Wingco]

I have a 40" PSS Hawker Hunter that has an all moving tailplane. The linkage is the same as the Phoenix and the Sigma above. It flies perfectly with no special bits just a bog standard control line bellcrank.

[Simon Chaddock]

Amy

I had the same problem on my Hawker P1121 a dihedral all moving tail.

I solved it by using a fixed single glass fibre tube with the necessary dihedral included and had each the tail plane half rotate around it. It required two bearings to be built into each tail plane.

A small 'pip' pin retained the tail pane at the outer bearing.

It required a positive pull to remove the tail plane. A force it would never experience when in flight.

Note the servo mounted in the fuselage with a short vertical link to the horn in the tail plane.

A bit of an engineering solution but it works well.

Remember all moving tail planes are pretty sensitive so only need a small movement and with no linkage slop!

Just an aside the Gnat has big elevator trim tabs. So big in fact that the event of hydraulic failure they could be connected directly to the stick and used as simple elevators. For simplicity the Gnat did not have hydraulic redundancy. As my Gnat has no hydraulics I just avoided the problem of the all moving tail plane and used the trim tabs as elevators. They are surprisingly powerful.

[Mike Etheridge 1]

Whilst I was in our loft I took some pictures of the old Sprite all moving tail plane, as shown below. As you can see the brass tube sleeve through the fin has needed a bodged repair. The plane has been used as a slope soarer and has flown from a bungee so has been roughly treated but somehow has survived..  

Edited By Mike Etheridge 1 on 15/12/2020 11:52:37

Edited By Mike Etheridge 1 on 15/12/2020 11:54:40

[Martin McIntosh]

I fitted an all flying tail to an F3A model in the 70`s, hoping to smooth out the elevator response since expo had not been invented then. It was simply made from pieces of brass tube which fitted inside each other (don`t use any piano wire because it rusts and binds up). The centre piece went into each tail side with a brass horn soldered in the middle then fitted with brass strips glued to the ribs, the outer piece being glued to each tail side. Simple to make and it worked well. No carbon available in those days and even now if you use it you will need an adhesive promoter to glue on the horn etc.