Pitts Special S1 - 1/3 scale

[Herri]

This is going to be my winter project:

Pitts S1-S 1/3 scale. Wingspan 1725mm

Weight +- 8.5 kg

Motor 62cc Zenoah

Kit from Toni Clark Practical Scale in Germany.

**LINK**

This has been on my wish list for almost 20 years. I saw one way back then and it was way out of my budget. Since then, I gave up on models for a while, been back 3 years so decided it was now time.

I had a stroke of luck back in June as there was an unbuilt kit advertised for E400.-. At that time the kit was still E750.- (it has since gone up to E899.- !)

[Herri]

The kit is fantastic. Everything is included except the covering (and engine of course)

The wood is all bundled, all the screws, bolts, bits of metal, even an allen key driver.

The plans are really well drawn with lots of detail.

It’s a real trip down memory lane as this was how kits used to be.

Herri

[Herri]

Radio etc

I have decided to use S-Bus servos for the first time as a: I want to try them out and b: it should make the cables neat. I have the Futaba 6308SBT receiver, so I may well try the telemetry (cylinder head temp?).

I am going to use S3071HV servos, except the throttle, which will be an S3072HV.

A Jetti Max BEC will regulate the two LIPO receiver batteries and a Power box spark switch will switch the ignition, also from a LIPO.

Engine.

A Zenoah 62cc with the Toni Clark stainless steel exhaust mounted on their Hydro Mount and a 24x10" Super Silence 2-blade prop.

Herri

[Herri]

As I am going to start with the wings, the tips need to be laminated.

There is even a form included, made of chipboard.

This is nailed to the board and the balsa soaked in water to make it bendable.

There are 4 laminations but a fifth strip is fixed (but not glued) to stop nail damage when the tips are done.

The top wing also has a similar but tighter “round bit” (technical term), which is made in the same way after the correct radius is penciled onto the building board.

Here the protecting strip should have been on the inside, as that is what is later visible – oh well, nobody’s perfect.

[Herri]

Forgot this one'

Herri

[Herri]

The main spars are made up of laminations of hard wood. The laminations get shorter towards the tip

These are then sanded to give a smooth joint.

I used my favorite piece of kit here – my proxon sander after protecting the spar with tape. I think the photos explain better than words.

Herri

[Herri]

The wing ribs come in a big pack. Unfortunately they are not numbered so it took me an hour to match them up with the drawing, mark and bundle them for each wing.

[Herri]

The trailing edge is also a lamination of 4 pieces of wood with a hard wood center. Looks like a neat idea as later, when sanded the edge will be hard wood.

I am already enjoying this build as its so well thought out and I can imagine why it will be relatively light, even with the 62 Zenoah.

Herri

[Herri]

That seems to be most of the prep for the wing. I shall start on the lower wing first as suggested in the booklet.

Here two building boards are joined with the correct dihedral. As my building boards were the wrong size anyway I treated myself to two new ones. They will do nicely later, when flat, for the top wing as well.

Watch this space.

Herri

[Steve Hargreaves - Moderator]

Just adding a post so I can follow along Herri......I love the Pitts Special..great aeroplane.

Your kit looks fantastic...I'm sure it will make a great model.....

My ARTF Pitts is a good bit smaller than 1/3rd scale at 42" but still great fun to fly......I do need to be "in the mood" though....

Here she is....

[jeff2wings]

Oh ! you lucky,lucky man ! my fav aerobatic bi-plane ,did you ever see the film Cloud Dancer ??

[Herri]

Nice looking model Steve.

No, cant say I did Jeff. Just looked on Amazon. Its listed as a VHS, but not avaialable.

My wife has just found it on YouTube.

cheers Herri

[Bob Cotsford]

it's one of those films I have to dig out every now and then. I can't remember whether I've got it on VHS or DVD now, I thought it was DVD.

Try here

I've just aquired a 1.20 size 61" (1550mm) Flair(?) Christen Eagle and it seems a big lump at that size, so a 69" Pitts must be humungous.

[Herri]

Thanks for the link.

I didn't realise Flair did a Christen Eagle.

I did a bit more today:

Set up the two building boards to the correct angle. I screwed them to the table to make sure they dont go walkabouts.

I then cut out the lower wing from the plan, dont usually like doing that but hey it looks the easiest way.

I then fastened the lower spars down useing steel pins with the heads cut off, so that the wing can later be pulled off and the pins pulled out from underneath. The spars rest on a pre-shaped bit of balsa to gine the correct angles.

The center join was expoxied and the ribs glued in with aliphatic.

I'll leave them overnight now.

Herri

[Bob Cotsford]

It was made by CMPro but sold under the Flair banner in the UK. Unfortunately spares are no longer available so I'm trying to save the existing covering and cowl. If it survives I can give it a proper makeover during next winter. The wings weigh a ton so I'll see how it behaves before commiting too much time or money on it.

Think you might need a bigger bottle of glue Herri!

[Herri]

Did a bit more to the bottom wing:

Joined the center and added the top spars.

Then inserted the web peices between the spars. This was somewhat different to what I am used to as they are glued between the spars as opposed to gluing to the front or rear.

This obviously gives a nice H-section.

There were a few more strengtheners where the flying wires would normally be fitted.

I will not be bothering with these, saving myself some work at this stage.

The end rib is then glued in with a small piece under the spar to get the correct angles.

Cheers

Herri

[Herri]

Here I have added all the shear webbing. Quite a fiddly job as basically they all have to be fitted individually.

I was reading a piece on RC Model design last night:

(**LINK** )

Here it states that this H-profile is much stronger than just gluing to the sides of the spar.

Considering, that the designer of this Pitts Kit (Gerhard Reinsch ) has his degree as an Aircraft Designer, I shouldn’t be surprised.

These small pieces were fitted to the tips and the false leading edge glued on.

Next is the trailing edge and the tips.

I think I might make it with my glue bottle

Herri

[Martyn K]

Looks like this is going to be a great build blog.

Following with interest

Martyn

[Biggles' Elder Brother - Moderator]

What a stunning kit! And taking shape nicely. Here is my long lived, but sadly no more, Pitts S2.

Photographed by Mr Bott at the very first RCM&E Greenacres Fly in 3 years ago. One day I'll have another - great aeroplane to fly - but fly it you must - 100% of the time!

BEB

Edited By Biggles' Elder Brother - Moderator on 03/09/2013 15:29:23

[Herri]

Looks nice BEB, I may go for the classic red but my wife prefers the green one we saw at Duxford in the summer.

Today's progress - trailing edge:

I very carefully lined up the edge which had been laminated earlier and filed the slots.

I then measured the height of the rib ends

Then glued the trailing edge on making sure the measurment was the same.

Look ok to me

Herri

[Herri]

Help,

I am now getting a message saying I cannot paste my text in this box due to ny browser settings!!

I am using word on a macbook.

Anyone know the reason. It worked ok at the begining.

Herri

[Pete B]

Hi Herri,

I've no experience of Mac but we've had a new text editor installed a couple of weeks ago which has caused a few problems in Windows. The solution is to clear the internet cache from your particular browser as explained if you follow the link in the first post here.

I don't know if this will work - can you let us know?

Pete

[Herri]

Panic over chaps, I restarted the whole lot and it looks like it works again.

I obtained these beautiful aluminum servo holders at North Weald (Kingfisher Aviation) They are threaded and really look the business.

The bellcranks were assembled as per plan, sandwiching the ball joints between two, so as to eliminate play.

I made a small jig to get the angle right and epoxied them in with some 6x6 mm strengtheners.

I made this servo holder using M3 blind nuts for easy accessibility later.

This was epoxied in to the center of the wing. The wing will only have one servo each This not only saves work and expense but according to the designer, it will improve roll rate.

The ply aileron hinge strengtheners are pre cut and pre drilled. This is good as I cant make any mistakes here. They were glued in place. The ailerons will be hinged with wire.

As you can see the holes for the wire hinges are pre-drilled. I like this idea as they fit beautifully and lessen the chance I will make mistakes.

The wing tip is next. They were formed a while ago. I decided to get the main shape before gluing. I marked the center and sanded the half round profile.

The finished tip was then cut to size and glued into place. This was followed by various strengthening pieces.

First determin the center

Its still 30C plus in my room, so thats it for today

Herri

[Herri]

Posted by Pete B - Moderator on 06/09/2013 18:25:03:

Hi Herri,

I've no experience of Mac but we've had a new text editor installed a couple of weeks ago which has caused a few problems in Windows. The solution is to clear the internet cache from your particular browser as explained if you follow the link in the first post here.

I don't know if this will work - can you let us know?

Pete

Thanks Pete,

I will try that next time I get problems. I have had some other problems involving the cache trying to log into hotel Wifi services.

I was under the impression you then loose all your passwords, which are stored, so I have been wary.

Thanks

Herri

[Lindsay Todd]

Excellent build, you can't beat a Pitts, i have had three or four now all sizes and all great fun to fly. Linds