Hanno Prettner Magic

[Martyn K]

Hi Danny

Thanks for that. The reason I used a ply subframe on the cowl was in case I had to split it to make 2 paired moulds. I am hoping that I can do it in one piece...

It has sanded OK, it just needs final sealing and finishing before I worry about the mould.

Many thanks

Martyn

[David Foley]

Hi Martyn,

A two piece mold will make it easier to make a cowl of that shape.

There is very good info on the net on the subject.

Enjoying your build.

Dave

 

Edited By David Foley on 25/09/2013 00:35:21

[Martyn K]

Thanks David.

My thoughts as well. I am taking the plug for the cowl down to a local specialist this morning to see what they suggest

Martyn

[Martyn K]

I visited my local G/F supplier and specialist. He thinks that with a bit more work, the cowl plus can be made in one piece as it tapers towards the nose in all directions.. We will see. I am now £50+ lighter after buying cloth, matting, tissue, resin (epoxy and polyester), release agent and gel coat.

So, still working on the plugs. Both have now been coated in resin and I am currently 'flatting' them ready for mould making. The man in the G/F shop said make sure that the casts (his words) were 100% non porous or it won't work

 

Some photos:

The front end of the top cowling has been extended using balsa so I have an extended flange that will be cut back. This has subesquently been covered in 60gm cloth and resined.

I bought a Wirebender - it took 2 minutes to make this noseleg from 8g piano wire. An absolute bargain.

The original stub for the nosewheel was 5mm. 8g plus a brass tube sleeve (as suggested by Bob) was 4.9mm, Its a bit sloppy. The original stub was swaged to prevent it falling out. I put an additional brass tube collar over the sleeve brass tube and soldered the whole lot up. Because of the bend in the leg, it had to be done in situ, but it isn't going to fall out (in a hurry).

Started installing the radio gear in the fus. The servo tray is 1/8 birch ply with beech cross bearers and 1/4" sq hard balsa longerons.

Front noseleg i psition - retracted. I had to move the retract unit forward about 10mm to get it to fit, which means that the motor for the retract is slightly in the engine bay. Nothing that can't be resolved with a bit of spruce and ply to form a cover.

 

The wheel extended. Note the slight caster angle bent in to get the wheel to track properly and also to fit cleanly into the bay

 

And another shot.

As videos are in vogue at the moment, here is one showing the retract working..

 

 

Magic!

 

More to come.

 

Martyn

 

Edited By Martyn K on 01/10/2013 09:30:58

[Martyn K]

OK - video not there at the moment - still processing according to YouTube

 

edit - just finished..

Edited By Martyn K on 01/10/2013 09:28:28

[Steve Dunning]

Nice work Martyn.

[Martyn K]

Thanks Steve

Hopefully, I'll get the moulds completed this week, if they are any good, I'll bring them to Retford.

Look forward to seeing you there.

Martyn

[Danny Fenton]

Looks great Martyn, a lot of trouble and expense if it turns out to be a one-off. However a very useful skill to have!

If you do it in one piece, make sure you use the release agent, and a blast of air between the mould and part may help seperate them. Two part would be more trouble, as you would need a parting plane, but give another level of knowledge and parts would come out of the mould easier....

Cheers

Danny

[Martyn K]

Thanks Danny

I have to admit that I am a bit nervous about this, I keep putting it off - hence the distraction by fitting the radio gear...

I will bite that proverbial bullet this week though. (just a bit more flatting to do)

Martyn

[Bob Cotsford]

It's coming along well Martyn. As for the retract protruding into the engine bay, I had to do the same on the Blue Angel as the original used a bulkhead mount mechanical unit which seems to have fitted into a shorter bay.

Once you have the moulds you might find that putting a post on the Classic Pattern forum on RCG will find someone willing to 'share' the costs in return for a deck and cowl.

[Martyn K]

Cheers Bob

One of thre reasons why I want to make moulds is so that I can make a spare cowl and deck for myself and hopefully encourage anyone else to make one. If I get a few shillings back as a contribution that would be great, but TBH, it's more important to me that the models are getting built.

The F/G man reckons I should get 4 out of each mould - possibly a couple more. We will see...

BW

Martyn

[Rich too]

Fantastic - you have a lot of patience!

Rich

[Martyn K]

Thank you Rich.

I said at the start of this blog that this will be a long (for me) build, however Danny Fenton is the man who *really* has patience. Mine is simply a battle of taking on new challenges. For the record these are (for this model)

1st model with flaps and air brakes

1st model with retracts

1st model with home made G/F mouldings.

1st model with rear exhaust and tuned pipe.

Got a few more things to sort yet, but hopefully it will be flying shortly after Christmas.

Martyn

[Martyn K]

Not much progress this past few days. I am still working on the plugs for the cowl and the upper deck, However, I have decided that tonight I have wet and dried them enough. I'll have a practice making a mould of something that doesn't matter if I get it wrong, possibly a tapered drinking glass or similar before I risk my precious plugs..

A bit more work on the fuselage though.

I have used goldenrods for the elevator linkages, one for each elevator.The outers are terminated on a lite-ply bulkhead , the inners on a brass plate soldered to an 18swg piano wire linkage that goes to the elevator servo and back through the bulkhead. This will allow me to adjust either elevator separately - the piano wire rod prevent the plate from twisting - i.e. it moves linearly. There is also another intermediate lite-ply bulkhead half way down the fuselage to stop the rods from whipping. It looks very neat.

There is a hook that supports the rudder goldenrod outer - screwed to the throttle (middle) servo securing screw.

Because the rear fuselage is so narrow, the goldenrod outers exit underneath the LE of the tailplane. Again, to keep them stiff, they have been glued (epoxy) to a balsa fairing. This keep the outers nice and stiff and hopefully, there will be no slop. Note the rudder outlet and rod - waiting for the rudder which will be a good while yet. I am a bit too clumsy to put the rudder on at this stage..

I am using these rather elegant Tornado arms for all the primary functions. They are rock solid and the clevis is actually screwed into place - through a ball race. Very smooth, but not cheap.

And the engine goes in - so I can set up the throttle linkage. The engine has a slide carb - I have never seen one before on an aero engine

Finally, a test fit for the tuned pipe. Brackets will need to be made to hold it in place.

I am not totally happy with the elevator linkage yet. There is a tiny bit if binding somewhere with full up elevator which I would like to get resolved before I put the bottom sheeting in.

More to come

Martyn

[Steve Dunning]

Dynamix carb Martyn, once set up, nothing better.

[Martyn K]

Thanks Steve.. It's very impressive..

I am really looking forward to getting this airborne,

See you Sunday.

Martyn

[Concorde Speedbird]

I like this plane, keep at it! It will be fantastic when done, is the tuned pipe going in the tunnel?

CS

[Martyn K]

Hi CS

Yep, the pipe is totally enclosed apart from a 4mm gap at the front of the tunnel to let cooling air in. Slow progress, but I got the rear lower fuselage sheeting done tonight. Just needs letting dry and then trimming and sanding back.

Big problem though, my camera has died..

Martyn

[Martyn K]

As implied, a little bit of progress this week. Work and family commitments tend to get in the way, but these are more important.

The bottom sheeting has now been added. The binding problem was simply I had more throw than the elevators could handle - fixed by moving the servo linkage inwards one hole. I tend to cut my sheeting oversize and trim back when dry. Note that the grain is across the fuselage.

The other time consuming activity - I have practised making a mould before I do it for real.

I actually used a small plastic sauce pot (free with fish from Asda) - which I use for mixing glues.

The process that I followed was,

1. Plasticine on work surface and rolled out.

2. place dish onto Plasticine and remove excess around the edge using a scalpel

3. Add PVA release agent using a sponge (no brush marks) - let it dry

4. Mixed Gel coat on scales (I mixed about 50gms with 0.5gm of hardener (100:1) and apply (I actually used a spatula - a brush would have been better). Let it harden overnight

5. Apply 100gms polyester resin over 1 layer tissue, 2 layers of matting. One thing I learned was that it is much easier to use small pieces than big pieces - just keep overlapping them. I used a brush and just kept dabbing until it was all covered. Let it harden overnight

6. Pop it off the work surface  - a sheet of polycarbonate 'glass' 

7. Remove the Plasticine

8. Trim the flange back

9. Pop out the master - took a bit of effort but I managed to do this without damaging it..

Voila!

Quite pleased with that

 

More to come..

Martyn

Edited By Martyn K on 11/10/2013 14:02:27

Edited By Martyn K on 11/10/2013 14:02:56

[Danny Fenton]

Well done Martyn

[Martyn K]

Cheers Danny, it was easier than I expected. I'll try the tunnel tonight/this weekend.

The only other thing that has been suggested was to wax the plug before the release agent goes on. I have some beeswax at the ready.

Martyn

[Danny Fenton]

Somebody said hairspray works too, never tried it so before you risk anything valuable do a test

I use Maquires Mirror Glaze relase wax

I love all the experimenting and learning new skills, brilliant fun!

[Martyn K]

I think I'll stick to Beeswax.. My wife hasn't missed that yet. She would miss her hairspray though.

Martyn

[Martyn K]

Two weeks since I last updated this blog. Sorry about that.

Progress has been a bit slow, a new job plus being away last weekend has slowed things down a bit.

However I have been working on the Fibreglass bits.

I have created moulds for both the cowling and the tunnel. I didn't get photos of the cowling because the camera phone managed to get resin all over itself, at which point I banned it from the workshop until it learned how to keep itself clean

The tunnel glued down on a bed of plasticene - that in itself was an evenings work as the plasticene was not very pliable in the cool conditions.

Laid up with 1 coat of release agent (1 evening) and allowed to dry, 1 coat of Gel (1 evening), then 1 layer of tissue and 1 layer of strand (1 evening) and allowed to harden.

I had great difficulty getting the plug out of the mould, it had attached itself in one place which resulted in destruction of the plug.. However, I am very pleased with the mould.

The same process was repeated for the cowl - which also only came out after destroying the plug - again the mould looks fine.

Next task was to make the real tunnel. 2 evenings applying wax polish then release agent (lots) followed by the gel coat. I used epoxy resin with 130gm cloth for the tunnel - doubled up at the front rear and along the edges. The resin then failed to go off, so then I read the instructions and found that I had got the mix wrong, so ripped the cloth out - it was only tacky and redid it again last night.

Overnight, the resin hardened and I tried to release it today. Once again, the tunnel and the mould were stuck together again with one area about 2" long where the gel coat stuck had to the mould. I managed to separate it and I have a light and flexible tunnel that is definitely usable although it will need a bit of work to get it ready for painting. Note that the blue release agent hasn't been cleaned off yet. The tunnel is back in the airing cupboard while the resin hardens further. Getting the tunnel out of the mould has caused a few hairline cracks in the resin and I may stiffen it up a bit using some carbon fibre tows that I have.

Outside of mould and the tunnel, It needs polishing!

Can anyone suggest what I am doing wrong please? I don't want to attempt the cowl until I can be sure that I will be able to separate the cowl from the mould. That will be a very tight fit!

 

Thanks

Martyn

Edited By Martyn K on 25/10/2013 14:36:11

[Nigel Dell]

Hi Martin

 

Just read the thread, nice build, I was going to do a Magic build but other thing of interest have side lined it!

I have been moulding things for a long time now and a couple of things that I have learnt over the years that might help.

When I make the plug, I mount it onto 6mm paper faced foam board (I have easy access to this)  about 20 - 40mm wider all round than the part, keeping it square/ rectangular  and glue a 20mm lip at 90% around the edge once the mould is made this gives the mould a lot of torsional strength so you don't mould in a twist.

Re your cowl mould the only way I do these now after making 2 even 3 piece moulds in the past, is( as long as they slightly tapered), one piece, if you visit your local friendly tyre centre and ask for a handful of the old valve stems they cut off the wheels, they get thrown away, on cowls I mount one of these on the spinner plate of the cowl or the hole where the crankshaft will go through, after you have waxed the plug, I also use PVA release agent, clean the rubber stem with thinners or similar the glue into position with some 5 minute epoxy, make your mould as normal paying attention around the stem I normally use a mix of resin and Micro Balloons or Thixophic agent ( similar to Micro Balloons) to thicken up the resin to a paste, this helps maintain the gap for the cloth to attach itself to and avoid air voids and strengthen the joint, should also use this method for corners in the mould, I usually use 3 layers of 160gsm twill weave as I found this is ideal for me at this sort of size mould.

Leave for a couple of days to completely cure, don't be tempted to do this any earlier as you don't need too much flexing in the mould for the next bit!!

Get an airline, this only works if you have got a compressor! and attach the airline and blast it out!

When you come to make the moulding just put a Plasticine bung in the hole, about 3mm thick will do it and lay up you part in the normal way.

Experiment with the psi for the part say start at 20 psi, I normally find that 40 psi works for my mouldings, I have found if the part is made with lightweight cloth you can destroy it with too much air! but on the whole it takes the stress out of the release process.

 

I hope that helps.

 

I might get my Magic done at some point in the future I do have the ST X 61 earmarked for it although the Chip Hyde Webra is very tempting.

 

Keep up the good work.

 

Regards

 

Nige.

 

P.S. You don't need a valve in the stem for this to work.

Edited By Nigel l Dell on 27/10/2013 18:07:17

Edited By Nigel l Dell on 27/10/2013 18:08:49