Hanno Prettner Magic

[Sam Wragg]

Re Snap-Flaps

Yes that's what Hanno called them, I read the reason he developed the flap system was for the T.O.C. He states that he was aware the judges were looking for tight radiuses on square loops etc.............. Typical Hanno always ahead of the game.

Reason I lost Curare was simply due to sloppy workmanship / poor linkages at the time (Lesson learned, still learning my trade) and not the design of the snap-flaps. if I was to build another Curare/Magic I would fit them as per design.

Sam

[Martyn K]

I cant believe that it is 7 weeks since I last wrote on this blog.

No real excuse, I ran into a couple of problems (3 actually) and it seemed advisable to put it aside while I took time to have a think. It was also during this time that problem 3 manifested itself. I committed to build a Precedent T240 as a club trainer and it simply filled my shed space to the extent I was risking damaging things tried to work around it. It was safer to build and get rid of the T240 to get my space back.

Back to the Magic

Things were progressing well. The wing had been glassed and sanded and I was pleased with it.

I carefully fitted the ailerons. I am using the Kevlar cloth as the hinge material so the ailerons are laminated.

The aileron ends are capped with 1/32 ply to keep nice sharp edges.

Then I came to fit the flaps. I cut slots for the torque rods and laminated them with ply.

So far so good. These were slotted to accept the Kevlar cloth, the rods epoxied into place then capped with ply/balsa. They were not going to fall off.

All I had to do was finish off sanding/carving to shape in situ and I broke one of the blooming things.

I was also checking the fit of the wing with the flap servo fitted - and it wouldn't. The torque arms were binding against the elevator servo (which I had anticipated) but even worse, the wing wouldn't fit with the flap servo in place.

Basically, the flap servo was locked against the rudder servo...

What I had done was transposed the position of the flap servo in the wing. Not a huge problem but my patience was diminishing and my temper rising so it was a good time to put it aside to have a think. Nobodies fault but my own.

Now fast forward 5 or 6 weeks..

The flap has been repaired...

The battery and flap servo has been swapped round

The elevator push rods have been lowered

And everything how fits (although it is very tight for space).

The last 3 evenings have been spent fitting the wing fairings and carving and sanding to shape. A bit frustrating, the plan says refer to the cross section for the shape of the fairing - but there is no cross section..

But - they look OK. Still need a bit more work to complete though. I have also fitted the wing bolt mounting plate.

Once done, it will be time to fit the rudder and the top of the fin and then glass the fuselage..

Then painting and trim then maiden then crash

More to come.

Martyn

Edited By Martyn K on 20/03/2014 22:02:49

[Martin McIntosh]

Looking good Martyn. Just tell me about the interference of the flap servo and the rest of it. Been there. The wing plate on the Curare caused the biggest problem. What are the elevator and rudder servos? Not MG16R`s I hope.

[Martyn K]

Hi Martin

MG996. They seem quite fast and centre well. Much better than the junk MG995 they replaced.

M

[Willyuk]

This may be well known to all, but there is a document created by hanno of the set up for the new artf curare. In it he discusses how he uses the snap flaps. A link here

http://www.der-schweighofer.at/artikel/91653/bk_hanno_prettner_curare_60_ep_gp_arf_blau_gelb_orange_1640_mm

look under the pdf documents and you will see the hanno tips pdf

it is in German but Jon wold has produced a short translation, it can be found on rc universe.

He also shows all the rates etc he used on the artf, lots of expo!

[Martyn K]

Thanks for that. I have worked out what most of the words are in the table.

Here is a link to the document (pdf) Curare Setup instructions

II'll make up the aileron and elevator gauges. They look really useful.

Martyn

[Willyuk]

This is what Jon posted on rc universe.

Hi, I'm sorry I won't have time to make a translated PDF, but I can post some key point here.
(Here's the link to the German PDF: http://www.aerowold.com/wp-content/u...elltipps-1.pdf )

Teil 1 (Part 1) is an introduction. It states that Hanno has test flown and tuned the Schweighofer Curare perfectly so that with these templates and tips, any pilot can achieve the performance the Curare as 8 times TOC champion is capable of.

To measure the correct CG without having the wing attached, you can balance the plane at 58 mm behind the fuselage former as shown in the picture. Regardless of equipment in the wing, this will provide the correct balance point.

"Einstellwerte für Quer, Hoch, Seite, Flaps an CURARE-E" means settings for Aileron, Elevator, Rudder and Flaps, specifically for the electric version, and using the CG point described earlier.
You must add a 1,6 mm shim to the upper part of the engine mount to achieve the proper motor thrust for this CG setting. (With the CG this far back, this is essential for proper performance)

Notes for the the table showing all the different rates: The Capital letters L, R, and so on mean the stick direction on your radio. L (Links) is Left, R (Rechts) is Right, H (Hoch) is Up, U (Unten) is Down.
Aileron differential is 35 % less down than up.

There are three dual rates or flight modes set up. Gros (Very sensitive, big throws for show flyging) Mittel (Normal throws for F3A) and Klein (Small throws, 3 rolls in 5 seconds).

There are also various rudder/aileron and elevator mixes as well as the flap settings. The key point here is to acheive neutral knife edge and proper trim when using flaps for landing. The settings speak for themselves, provided you know what is what in German:
Quer/Querruder: Aileron
Hohenruder: Elevator
Seitenruder: Rudder
Gas: Throttle
Leerlauf: Idle
Rechts: right
Tief: down

Example: Landing setting: 13 % up for both ailerons, 30 % down flaps, 4 % down flap->elevator mix.
Throttle (K1) mix is 1 % down elevator from half throttle to idle.

The templates should be printed, cut to shape and glued to depron plates. As an indicator guide, you tape a 15 cm long and 1 mm thick steel rod to the control surface and it will allow you to accurately measure the correct throw.

Not stated in the manual, but noted by Hanno, is that for the glow-powered version the wing dihedral is correct, but for the electric version without the heavy tuned pipe and with the battery high in the fuselage, it needs a very slight increase in dihedral. This is achieved by adding a very small wooden shim to the bottom of the wing joint when joining the wings.

Using the dual rates in different flight modes:

- High Rate for AIL/ELE/RUD for show flyging
- RC1/F3A precision flyging: AIL middle rate, Elevator low rate, Rudder High rate
- Square manouvers: AIL middle rate, Elevator low rate, SnapFlaps active
- Spin: Ail middle rate, Elevator middle rate, Rudder low rate
- Avalanche and snaps: Aileron middle rate, Elevator Middle or low rate, Rudder low rate, Snap Flaps active
- Landing: Aileron Middle rate, Elevator Low or middle rate, rudder high rate, Ailerons up and flaps down as pr. the table of throws and mixes.

I find these settings too sensitive on the ailerons, but that is a matter of personal taste.

if anyone can inform what why and when the K1 mix is used I would appreciate it,.

rgds

Al.

[Martyn K]

A brief update but no photos.

The fin tip has been added - it looks lovely..

I have glassed the fuselage and fin (using epoxy resin and 60g cloth). Just waiting for it to cure for a couple of days before I start sanding it down. One irritating area is still a bit sticky, left it leaning against the heater in the shed - hopefully that will sort it. When sanded smooth, I'll add a couple of coats of water based varnish to make sure that it is properly sealed then a final rub down with very fine wet and dry and then we are ready for paint.

[David Foley]

Wondering why you used 60g cloth ? I have only ever used 15g for this, found it easy to apply and finish.

Edited By David Foley on 01/04/2014 14:13:06

[Martyn K]

Hi David

You made me go and check, I thought that I had got it wrong when I typed it in.

I had got the units wrong, its actually 0.6oz, 24g cloth that I have used.

The resin has now hardened and I have been sanding the fus (using 800 grit wet and dry - used wet) to a smooth shape - added 1 coat of interior varnish last night - more sanding to follow, but it's getting there.

Martyn

[Martin McIntosh]

I am rather more aggressive when sanding gf. I start with 180 production paper (the grey stuff from Wickes), then 320 followed by 800 and 1200 wet. I now only apply the cloth using peel ply where possible which reduces the sanding stage by 90%. Floor varnish added midway also works for me. This method is the result of much previous hard labour now reduced to a simple job.

[Martyn K]

Thanks for the guidance Martin. I am now back using 400grit wet and dry..

Just a couple of shots..

This was the fus last night after the first sanding down exercise. I added a coat of Antique pine water based varnish. Looks quite nice

This evening I have spent an hour with the wet and dry.

The dark areas are where the varnish sits in pits

and

Its actually nowhere near as bad as it looks. Using the fingertip test you can't actually feel the pits although shining a light down the fus will show them up. However, I think that it is ready for high build primer. Halfords here I come...

Getting there..

Martyn

[Martyn K]

I managed to get down to Halfords this lunchtime and bought some rattle cans.

A light coat on the fus and the underside of the wing. I am really very happy - there is not much more reworking to do and only a couple of spots that will need a little filler.

No close- ups just a bit of "White Magic".

and

Only the lower side of the wing has been painted. It started raining before I could do the upper side.

I also need more paint..

Martyn

Edited By Martyn K on 03/04/2014 22:26:36

[Martyn K]

Still working on this Up at 06:30 this morning when I remembered that I hadn't built the short fairing that sits under the wing leading edge.

This evening is the first time that the model has been fully assembled. Still lots to do though but I am getting there.

And

More White Magic to come

Martyn

[Martyn K]

I cant believe that it is 4 moths since I last updated this.

I have been working on the model during moments of spare shed time and the model is now 80% painted. A great deal of time has been spent trying to remove dings and blemishes - and in the processes usually adding new ones.

However, I have been very worried about the weight but (as most people do when faced with bad news) I have been putting off weighing the model.

I had the fright of my life last night when I eventually weighed the wing - painted but waiting for fuel proofer:

Wing: 2.7kg !!!

This morning I weighed the rest of it:

Fuselage - including cowl, tunnel, tail and almost finished painting - 3.7kg

Add to this:

Retracts and legs: 330g

Engine: 656g

Pipe: 133g

Flight batteries and radio gear: 400g

Final finishing (say): 250g

Fuel: 400g

AUW - approx 8kg

Shall I just set fire to it?

I am considering a new wing - I know I didn't use any oak in the current wing though, but I would hope that I can save at least 700gms.

I can also strip off the glass cloth and paint on the fus and recover in film, but to be honest, I am not sure its worth the effort.

Any suggestions?

Martyn

[Bob Cotsford]

at 8kg I think I would be reaching for a sanding belt to get that glass cloth off! I thought my Blue Angel heavy at 8LBS! It's got to be the finish, surely the bare airframe can't be that heavy? Nearly 6lbs for a wing? Sure your scales are not set to lbs after all? My 'Argos' kitchen scales are easy to switch to imperial by mistake.

[Martyn K]

Bob - you are a genius (I have just run to the shed and checked and reweighed it)

Scales had reset to lbs and I hadn't spotted it..

(and I nearly set fire to it this morning, I was so despondent).

I owe you a big beer and a half..

(It still feels heavy though!)

Martyn

[Bob Cotsford]

yes, it's still heavy at 6lbs for the airframe but not disasterously so. 8, maybe 9lb all up? If the 250gm allowance for final finishing is the remaining paint and fuel proofer then I think I know where you are going wrong 10oz is a LOT of paint. Don't include fuel in the auw and it sounds better already!

[Martyn K]

Now I feel a bit better here are a couple of Paint in progress photos:

Masked up Fus

Top deck/tunnel.

And the wing. Contrasting colour scheme underneath. (The blue is the same shade by the way - just different lighting)

Hopefully it will be ready for Shrewsbury.

Martyn

[Martyn K]

Hi Bob,

I have used a lot of paint. I have also sanded a lot of paint off. I have even managed to sand through the glass covering in the wing in two places (which was another delay while I repaired that).

This has been a very time consuming model - aggravated by the fact that I have to wait for the right conditions to paint the model outside.

Thanks again

Martyn

[Bob Cotsford]

I found the same with the painted finish on the Skybolt, I seemed to be sanding off more paint than I was putting on but the weight still kept creeping up. It's worth it though, it's hard to beat a paint finish. I like your colour scheme

 

ps - for future reference, get some Tamaya masking tape for defining the lines, use the 'ordinary' tape to backfill from the Tamaya, it gives a much cleaner line with less chance of the paint bleeding underneath it so less time spent on rectification.

Edited By Bob Cotsford on 05/08/2014 11:59:11

[john stones 1 - Moderator]

That looks well Martyn, nice job

John

[Martyn K]

Cheers Bob

Just googled it - I could do with some slim stuff for curvy lines.. I am using Frog low tack masking tape - which is a lot better than the usual pound shop paper stuff. Any bleeds have mainly been my fault not sealing the edge properly before painting.

M

[Andy Green]

lbs / Kg That made me laugh.

Do you need anymore UKCAA stickers cutting?

Andy

[Andy Green]

My next build will be the DSM Saphir and the instruction say all up weight 9.5 lbs, so you are not far off I'd have thought.

Andy