Simon's F-86 Sabre of the Patrullia Ascua.

Had a look through everyone's chosen scheme's and couldn't see this one, so I'll give it a whirl.

It's a bit 'flashy', maybe not in the same league as Martyn K's though!!

Very nice Simon,

Shouldn't be too difficult to mask up for painting!

martin.

My thoughts exactly Martin.

I've not finished an aircraft in paint for a long time, so this is a great opportunity to have another go.

Simon.

Well, finally managed to get round to starting the build.

I like building wings, so decided to make a start on the wing jig. Once the ply parts had been fettled a bit, I dry assembled the structure. At this point I noticed the port side of the jig was a little 'off' compared to the other. Not a problem as I'd decided to use Martin's trick of adding in some triangular fillets to 'lock' the structure in place.

However, at the last minute I remembered a rather solid piece of MDF in the shed, which I could utilise as a base board, sticking the whole jig to it. This has the added benefit of really locking the jig in place, as well as allowing me to move the whole structure if needed. The building room doubles/triples as a 'pain cave' and a music room.

So at time of writing it looks like this:

Next job is to sort out some suitable wood for the skins and then decide what wood to use for the spars. I'm leaning towards hard balsa, as the final finish is hopefully going to be glass/epoxy, which should add a little strength to the structure.

Simon.

'Pain cave'?

No, I am not going to ask!

Wise man .

Well, I did make a start on the wing skins this week and I decided to go with hard balsa spars.

So at present the lower skins look like this, with the hard balsa spars glued up:

Hopefully tomorrow (Sunday) I can crack on with the glueing the ribs on. I've decided to leave off the flaps, I'd already pondered on this and then saw Peter's post in Danny Fenton's build and that was the clincher.

Looks like I will also go with 2 centrally mounted servo's. I always like to try and keep the weight out of the outboard portion of the wings if at all possible. The 2 servo's will still allow me to use the ailerons as spoilers.

Simon.

Sounds like a sensible plan to me Simon I will follow you with balsa spars.

I can see you have a bottle of titebond will you use that for the wing construction? I usually use thin CA but I know that will penetrate through the sheeting and stick the wing skins to the jig So may use an aliphatic or pva.

Cheers

Danny

Hi Danny, good to speak to you.

I used Titebond to glue the spars down, but to be honest I use a mixture of glues. As it's the wings, I tend to steer clear of superglues as I've found the joints to be a little brittle over time. I'll probably use aliphatic on the ribs and then Titebond on the shear webs. I have used super'phatic before and this speeds up construction quite a bit. Regarding the shear webs, I'm using 1/8th hard balsa between the spars to form an I section. I've found this reduces weight (less glue) as well as increasing the strength. Win, win.

Cheers,

Simon.

Managed to get the ribs glued up yesterday. In the end I used Super'Phatic for the most part. I did 'cheat' a little and used Zap-a Gap to bond the front 1/4" of rib R1 to the lower skin, just because I wasn't able to weight the rib down to conform to the jig. Once R1 was in and stable, I was able to weight subsequent ribs and just used Super'Phatic for the remainder of the ribs.

Need to add the false LE next and then it's onto the right wing panel to get it to the same stage. That's probably going to take me the rest of the week!!

Cheers.

Simon.

Hi Simon,

Following your build and learning a lot...

... and I really need that.

Cheers

Chris

Hi Chris, following your build too.

Harry's advice is spot on regarding the top skins, much easier to make all 4 skins up now.

Cheers,

Simon.

Well, progress has been a little slower than anticipated, but I have managed to find the odd 5 minutes here and there. The false LE was added to the left panel, followed by the webs, in my case some very hard 1/8" balsa between the spars:

The webs were levelled using a Permagrit spar slotter before the top spar was bonded in place:

Next job I tackled was making up some torque rods for the ailerons. I saw on another post a discussion on the merits of wing mounted servo's vs. a centrally mounted servo using torque rods.

My own take on it, is that a lot of the time, it depends on the model and the type of performance you're after. When I used to fly aerobatics in the late 90's, the accepted method for aileron's seemed to be wing mounted servo's. I know this method is really popular today, with cheap, high powered servo's, not to mention the speed of construction in the ARTF world. A friend of mine just recently finished an own design pattern ship and he's opted for torque rods. As far as I can tell, his reasoning is to remove as much weight from the wing structure as possible.

So when I first looked at the plan, my initial thought was to go with a single, centrally mounted servo. After a bit of cogitating, I opted for 2 centrally mounted servo's. The other plus, is that there's no control horns/rods hanging out of the bottom of a low wing fighter aircraft, that's hopefully going to fly off the Great Orme!!

Here's the torque rods being made-up:

I've used some pretty heavy gauge wire for the torque rods and used some pretty hefty ball links, as there is rather a lot of sweep on the wing panels. You can see from the above pics, the amount of twist the ball links have to accommodate and I'm pleased to say, they are smooth running and slop free.

I'm a little further on from this stage, but I'll update again when there's some more tangible progress.

Bye for now.

Simon.

Simon,

A very tidy build. Nice to see personal touches like two centre mounted servos for the ailerons.

I think the different ways that various people are putting the Sabre together is fantastic and I am learning a lot from it all!

Keep up the great work,

Martin.

Edited By Martin Gay on 11/12/2019 23:07:21

Hey Simon,

Even being a bit slower than you thought, glad you made some nice progress.

I noticed you had your 'I' -beam shear web interrupted after R10. Am I seeing this right?

If so, aren't you creating a weak spot by interrupting the shear web so 'suddenly or abruptly'?

Keep it up.

Cheers

Chris

It's common practise on wings built in this manner.

The lifting force will diminish towards the wing tips (not least because of the wings taper) and thus the bending moment on the spars is less towards the tip.

Hi Chris and Alan, thanks for dropping by.

Alan's spot on regarding the stress on the wing towards the tips. Especially this type of wing. I have to confess that my initial thought was to omit these outer webs, but in the end, I bonded on some medium grade 1/16" balsa onto the rear of the spars. It shouldn't be necessary, however the 'weight' penalty is pretty small. Guess I was getting a bit paranoid about wing flutter!!

Hinge reinforcements added, as well as a small amount of balsa at the root TE, to allow the torque rods to notch into the wing without weakening it too much. Also managed to get the servo mounting plate bonded in:

The plate is an off-cut from a previous build and is made up of 2 pieces of 1/16" ply, with 400gm carbon cloth sandwiched in the middle, all glued up with ZAP laminating epoxy.

Cheers guys.

Regards,

Simon.

Hi you both,

I totally agree with the wing loading decreasing towards the tips, Alan.

But, my comment was about the 'sudden' interruption of the shear webs instead of an evolving decrease, ie. from 3mm to 2 and finally to 1mm web.

Unfortunately, whatever your type of wing, it's always seriously 'not done' to have those forces interrupted at 1 single point.

But no point as Simon decided to resolve it.

Cheers

Chris

Edited By McG 6969 on 12/12/2019 20:31:05

As I said, it is quite common to stop the shear webs at the point shown in Simon's picture. Due to the decreasing bending moment as you move out towards the tips I mentioned previously, what actually happens is a more graduated reduction in bending stress along the spar and shear web. I've seen it done on literally dozens of model wing plans and have probably done it a dozen or more times on my own models. I'm totally happy with it as a method and I've never had structural failure on a model.

So perhaps it is not so bad as you think Chris .

Managed to get a little more done to the left wing panel this morning, also started work on the right one.

Bonded the top skin to the left panel and made a start on the webs for the right panel.

Pulled the left wing panel off the jig this evening and I've got to say it felt very light and very rigid. No doubt due to a great design and construction method from Martin and co. Excellent .

I started another project, rather stupidly, just before the mass build start date. It's going to be a PSS, but progress won't continue until I've got the Sabre somewhere near completed. Thought you might like to see a couple of pics, as the wing shape, thickness and taper are very similar to the Sabre, with just a slightly longer span. It's getting a balsa skinned foam wing, so I'll be able to compare weights once completed:

Cheers.

Simon.