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John A's Sabre build

PSS F-86F Sabre build blog

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John A H10/12/2019 17:33:07
138 forum posts
173 photos

22. Position and glue in the rest of the outboard ribs and R1.


23. After putting on the spar shear webs remove the wing from the wing jig and cut out and open up the slots in the lower wing skin.

Finally you can slot in the pylons and see if it all work. If the release wire is tight when the pylons are in open out the holes in the pylons a little at a time until it slides freely and spring is able to close it. If the pylons end up a little loose it is not an issue as this can be sorted when the weapon load is built onto them.

The next step is to make up a custom servo horn. If you don't install the "2 stage" release option then a standard horn will do the trick (as on the A4 Skyhawk).

If you managed to read all that then I hope it makes sense and is useful to someone. Hopefully haven't put anybody off adding drop tanks, it looks more complicated than it is when written down and only using drop tanks will reduce much of the "fiddly" steps.

Steve McLaren10/12/2019 20:07:54
249 forum posts
260 photos

Very impressive work again John. But It's too late for me, I've already added the top wing skin. So where did I put those magnets?

Peter Garsden15/12/2019 14:50:47
1729 forum posts
1301 photos

Agree completely with Steve, very impressive. As I am going to attempt fuselage speed brakes, I will run out of channels on the receiver as it is as I am also going for flaps. I also worry about panicking on landing trying to drop 2 lots of munitions before I touch down. Can't wait to see it working in flight. Presumably, though it doesn't require a high torque servo to operate it as it is simply sliding a loose fitting wire out of a hole?

John A H17/12/2019 03:14:54
138 forum posts
173 photos

Peter, both lots of munitions can be dropped at the same time if required. On the A4 Skyhawk I used a Hitec MG65 for the release and on this model have a Savox servo of similar power. The Sabre release drop has a bit more "work" to do as it is pulling against the spring, otherwise it just needs to overcome the friction of the wire in the slots/pylons.

Phil Cooke12/01/2020 10:06:20
2591 forum posts
1824 photos


A while back in your blog you stated 'I will make up a custom servo horn out of glass fibre so that the opposite wing release has as straight a pull as possible'.

Will this be bolted to an existing servo horn with splines and fit tailored to your servo? I need to do something similar on mine, as the supplied Hitec HS-85 servo arms are tiny and its clear with my set up i need longer arms at a specific angle to equal out the pushrod throws. Was planning on bolting a home made arm to the Hitec arm - is that what you're doing too?

John A H12/01/2020 12:50:05
138 forum posts
173 photos

Hi Phil, yes I was going to bolt a oversize fibreglass plate to the servo horn (on the HS85 perhaps use the circular horn so you can have 4 attachment screws). Test out the position required for the wire attachment and drill holes in fibreglass plate then you can shape/cut down the plate around the attachment holes (if that makes sense).

John A H12/01/2020 13:05:16
138 forum posts
173 photos

The lack of larger horns for the HS85 is why I ended up using a HS65 on the A4 Skyhawk. With my Sabre needing even more travel, due to the two stage/inner outer munitions drop, non of the standard servo horns were big enough. Also a custom horn means you can line up the holes for the best “straight pull” without been stuck with the standard horn geometry.

Phil Cooke12/01/2020 13:29:38
2591 forum posts
1824 photos

I've just discovered that Futaba servo horns fit Hitec splines - so I've made one from a larger Futaba output arm - sorted!

N Pritchett15/01/2020 23:06:30
21 forum posts

Great work.

Don’t want to be a party pooper but: I believe you need to clear it with the CAA to have permission to drop anything from a flying object!

I know this used to be the case years ago when, in a previous existence, I ran a company manufacturing sports kites here in the UK. At the festivals some display teams needed to get this permission/license to drop small quantities of sweets from kites as they were covered by the same laws.

Martin Gay16/01/2020 09:16:58
396 forum posts
255 photos

Hi Neil,

We fit releasable underwing stores so that we can clean up the bottom of the wing just before landing. Otherwise the drop tanks can catch in the grass and make the model to cartwheel causing lots of damage.

Much safer that way!


Andy Meade16/01/2020 09:56:07
2772 forum posts
717 photos

I've never known anyone need a "license" for dropping anything from an RC model - from toffee bombers at shows, to bomb-drop competitions. The ANO states that nothing should leave the aircraft in flight unintentionally (they are dropped as required), and of course to never endanger anyone with an aircraft (risk assessment on what you are dropping covers this well).

Tally ho, bombs gone! cool

John A H23/03/2020 23:15:34
138 forum posts
173 photos

The Sabre build was on hold over Xmas and new year period due to a few other projects needing to be completed.

Over the last few weeks I've got back to work on the Sabre.

I lined the inside of the servo bays with fiberglass so that when the hatches are cut out they have some strength and retain their shape.


I am mounting the HS65 wing servos so that the control rod will be at right angles to the trailing edge. I have created 3D printed mounts for them.

On the right is the servo mount (that will be up against the top wing skin, centre is the hatch cover support frame work and left is a template to cut the hatch out of the lower wing skin.


Below shows the same but with HS65 servo inserted.


John A H23/03/2020 23:24:39
138 forum posts
173 photos

The servo hatch supports slot between the relevant ribs. Pins are pushed through the mount holes and bottom wing skin.


The hatch template is then slotted onto the pins protruding out of the bottom wing skin


I then cut round the outside of the hatch templates and the hatches can be removed.


and the hatch frames can be glued in.


John A H23/03/2020 23:29:40
138 forum posts
173 photos

The servo mounts can then be glued in position - hopefully flush with the top of the ribs.


How it looks from below with one servo in position. The string is for pulling servo wires through the wing.


and servo hatches in position


John A H23/03/2020 23:41:33
138 forum posts
173 photos

Before gluing on the top wing skin I needed to make sure I could find the correct position to create holes for the wing munitions release cable controls to exit. By laying a sheet of clear plastic over the unskinned top of the wing I could draw the position of the holes related to the root rib and leading edge. Once the top wing skin was attached I used the plastic sheet template to cut the initial holes



and then used small files to carefully open up the holes to the required sizes. The ball connectors are not yet glue to the control cables which made glueing the top wing skin on a lot easier.


Phil Cooke23/03/2020 23:48:52
2591 forum posts
1824 photos

Wow! Those tailored servo mounts and hatch frames are pretty cool John - excellent stuff! Presume you've seen we've had to push our event back to later in the year from our planned June date! keep well!!

dirk tinck24/03/2020 00:01:18
628 forum posts
861 photos

Very nice servo-mounts John!! They won't get any better !!

John A H24/03/2020 00:50:34
138 forum posts
173 photos

Hi Phil, saw that - now it's in September (hopefully) even I won't have an excuse if I'm still trying to finish the model the night before. The only thing that maybe a show stopper on the build is not been able to get hold of paint if everthing is closed down. I've also remembered that I haven't yet ordered the canopy so will have to contact Steve at Vortex to see if he is still working in the present situation.

Dirk, I don't think drawing up and 3D printing parts is as impressive as the artistry involved in producing your fiberglass speed brakes.

I've just started planking the fuselage so that has sorted out the social isolation requirement for the next week.

Hope everyone is well and "enjoying" the home schooling.

Edited By John A H on 24/03/2020 00:53:47

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