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Spitfire by Cambrian Funfighters Electric Version


Peter Garsden
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Have not been modelling for a while because I have moved workshops - what a marathon - years of stuff to throw away and box up. Is there a thread for showing your workshop, which I know would interest me. I have had a double garage built which is 2 thirds workshop and 1 third office. Might be of interest?

 

When I moved, I was part way through redoing the balancing of the hybrid slope soarer and power model. Stupidly I thought I could just fill one spinner with lead for soaring until I realised that for power I could not do the same as the spinner would ping off under load - what a twonk!

 

So I set about working out how much lead I would have to squeeze inside the cowl and it was huge - more than I can fit in without fowling the motor, so.. here are the pictures of the removed cowl and the amount of lead needed

 

large.1643987483158-244351594.jpg.17482ecafc1af2ac9f41fa49aeae7c24.jpglarge.16439875108401480820287.jpg.988aabfbbc63704a77ebc92c6bf1bf81.jpglarge.1643987532075399663514.jpg.07596e676eef5b6edf4e724ac4375f8c.jpg

 

I am going to make a lost foam cowl out of fibreglass. I can then much more easily remove the cowl with screws and glue in strips of lead. I figure it won't be too difficult.

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1 hour ago, Peter Garsden said:

Have not been modelling for a while because I have moved workshops - what a marathon - years of stuff to throw away and box up. Is there a thread for showing your workshop, which I know would interest me. I have had a double garage built which is 2 thirds workshop and 1 third office. Might be of interest?

 

When I moved, I was part way through redoing the balancing of the hybrid slope soarer and power model. Stupidly I thought I could just fill one spinner with lead for soaring until I realised that for power I could not do the same as the spinner would ping off under load - what a twonk!

 

So I set about working out how much lead I would have to squeeze inside the cowl and it was huge - more than I can fit in without fowling the motor, so.. here are the pictures of the removed cowl and the amount of lead needed

 

large.1643987483158-244351594.jpg.17482ecafc1af2ac9f41fa49aeae7c24.jpglarge.16439875108401480820287.jpg.988aabfbbc63704a77ebc92c6bf1bf81.jpglarge.1643987532075399663514.jpg.07596e676eef5b6edf4e724ac4375f8c.jpg

 

I am going to make a lost foam cowl out of fibreglass. I can then much more easily remove the cowl with screws and glue in strips of lead. I figure it won't be too difficult.

Hi Peter,

It is indeed a tail heavy beast! As we discussed, I had similar issues getting the thing to balance; there's just no room to add ballast without causing some other issue (cooling!), I managed to get some lead inside the motor box using a team of trained mice...

 

The cowl is a good idea. that will at least free up some clearance for both lead and cooling air.

 

Graham

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  • 2 weeks later...

Thanks for the workshop thread Early Bird. Will post when I have done some photos. Nearly finished now.

 

Back to the cowl. I made a start on a blue foam inner mould today using a combination of my foam cutting pen, Model Belt Sander, Japanese Pull Saw, Permagrit Rough File, and Sanding Disc with holes which is brilliant. Here are the pictures

 

large.16451121617441840955199.jpg.b336961b04d3ef6804ce7d7af329ae43.jpg

 

I drew round the existing cowl then sliced bits off with the Japanese Saw

 

large.1645112187515-516436418.jpg.eab5ebd4c48b898c80c1dc3f95627fe1.jpg

 

I had to cut out an internal hole for the engine mount so marked up the foam

 

large.16451126605361403479070.jpg.f414b1a264f1ba24c869691627f7e87d.jpg

 

I used my home made foam cutting pen which is 2 pieces of wire bound with tape between a piece of balsa capped with 2 inserts from a 13A Plug and some nichrome wire inserted in the tip.

 

large.1645112682025-1189216399.jpg.6e173ec2feacc3edda18d29ba2c6a887.jpg

 

Wires connected to the ends then attached to the transformer - 

 

large.16451127174582056995082.jpg.b1bccca8bc936d933a02664fdd81be2a.jpg

 

large.1645113340176-1630624991.jpg.9dce77265b375a234ba1d7d460ab5995.jpg

 

large.1645115060862-2264728.jpg.01f93a7ff1921dfd6a17d1d9e665d2e2.jpg

 

Fashioned with the Permagrit file

 

large.16451150890161513830388.jpg.759438d6617831a7626d6fa94190cc40.jpg

 

large.1645115111332-1691021020.jpg.5b1e4126cabc629a45df5b07e65ef5f0.jpg

 

Next job is wrap it in Parcel Tape, and wax it, and mount on something suitable to wrap around the fibreglass bandage and resin. Watch this space.

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Well, the blue foam shape is now wrapped with brown parcel tape, which I then ironed down flat with my Solarfilm Iron. The plan is then to add a layer of wax, but when I got out the tin it had dried out, so I have put it on the radiator to thaw out. No doubt there is a fluid you can add to moisten it up? Turpentine apparently but not so straight forward - https://gillysaustralia.com.au/blogs/gillys-blog/how-to-soften-up-hardened-furniture-wax

 

large.1645289883744-558783826.jpg.5f80ac724a3ed43fb57426bfac31874a.jpg

 

You can see here the finished mould sitting on a support. When applying the fibreglass you have to have 360 degree access with the brush, so I made this balsa stand which will be clamped to the bench. The cloth will be in strips on the sides with a disc on the top and overlap. It will drape over the bottom edges then be trimmed when dry with a Dremmel.

 

large.1645289840354528305874.jpg.6f39a4f501ba6bed8e4c4d2594df052c.jpg

 

Obviously I used 3mm balsa scrap which I wedged into the receptive hole for size

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Well 3 layers of 160 gram fibreglass cloth later it was time for a final coat of resin and micro balloons mix. I find that it is important to coat the mould first in resin before applying the cloth, and dabbing resin on top with emphasis on the dab. If you try to brush it will disturb and drag the cloth out of shape.

 

The coat needs to be thick enough not to run when applied but not too thick to prevent spreading over the cloth.

 

large.1646256248960-1978359431.jpg.3d9aecbe525c0dd20381c5acdfa8fa80.jpg

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27 minutes ago, Peter Garsden said:

Well 3 layers of 160 gram fibreglass cloth later it was time for a final coat of resin and micro balloons mix. I find that it is important to coat the mould first in resin before applying the cloth, and dabbing resin on top with emphasis on the dab. If you try to brush it will disturb and drag the cloth out of shape.

 

The coat needs to be thick enough not to run when applied but not too thick to prevent spreading over the cloth.

 

large.1646256248960-1978359431.jpg.3d9aecbe525c0dd20381c5acdfa8fa80.jpg


The Paul Janssens method (he was famous for this technique for PSS models in the 90s) utilised the old formulation 3M77 spray to attach the cloth initially. It had the perfect amount of “tack” for the job without affecting how the cloth wetted out with epoxy. Unfortunately environmental regs meant the propellant was changed sometime in the early 2000s, and the new version was too prone to gloving up to be appropriate.

 

https://pjmodelclassics.weebly.com/about.html

Edited by MattyB
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2 hours ago, MattyB said:

...Unfortunately environmental regs meant the propellant was changed sometime in the early 2000s, and the new version was too prone to gloving up to be appropriate.

 

... or even globbing up! ?‍♂️?

Edited by MattyB
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5 hours ago, MattyB said:

 

... or even globbing up! ?‍♂️?

Absolutely Matty, it all started for me with a Paul Janssen plan of an Alpha Jet, and I did indeed use the spray, but only for the first layer methinks. The problem is wetting out the cloth enough so that it sticks, and avoiding the cloth underneath the fuselage from dropping off. As the bottom of the cowl is open this isn't fortunately a problem for me hence why I didn't use that method.

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I have sanded off the excess microballoons and smoothed down the outside of the canopy, then the dreaded job of the Acetone to scoop out the blue foam and pull off the parcel tape. Much easier with this small mould than a whole fuselage from the inside, I can tell you. Came out easily leaving a smooth inner surface

 

large.16464958707381305085802.jpg.be4230b69134a4d430b72cf609f93e15.jpg

 

I then had to cut a circle out for the motor and spinner. I matched up the old cowl, and drew a line round the hole as a guide, then used these router tools in the dremmel/Proxxon

 

large.1646495916070-322916191.jpg.fe0d75a13f9979eda7a7e230f3b9853a.jpg

 

I finished off with the round Permagrit file which worked a treat.

 

large.1646495894057357492740.jpg.c565fb273e5cf7303c743d13fcef1cc8.jpg

 

I usually used 2 layers of 160 gram then a final layer of 80 gram, however as this part is likely to take some hammer I went for 3 layers of 160 gram. After all I only have to add lead round the inside of this, so?

Edited by Peter Garsden
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  • 3 months later...
  • 1 month later...
  • 4 weeks later...
  • 1 month later...

Well a bit of news - I took the completed Spitfire to the PSSA meeting at the Orme with a view to flying it on the Friday. Conditions were ideal with a 20mph wind on the tank tracks slope if slightly Westerly.

 

I duly assembled everything. I had a switch to turn the motor off with the Failsafe set to 0%. All good so far. I switched on and went to put the model down, by mistake switched the switch off and the motor revved up to full speed - no prop on as it was set up for sloping. I couldn't stop it and had to disconnect the battery. By this time it had pulled the cowling and the motor box off the firewall. I was so annoyed. I really don't know why this happened. Al suggested it was because on Futaba Transmitters the motor reverses itself so 0% was 100%.

 

I had weighed the model at 3.4 lbs so it would have flown fast, but none the less I was annoyed, so back in the bag it went.

 

large.16662599769662567077373660087566.jpg.ca07616de671d02b27de0a6813949f11.jpg

 

So I decided to make it a PSS model only, took the motor out, replaced the fibreglass cowling I had made with the original balsa cowl, balanced and weighed at 1lb less ie 2.4lbs - more like it. I took the LIPO out and put an NImh battery in its place. I had to cut away some ply to make a battery box slide in.

 

large.16662598360516230981140190522686.jpg.19b8c67bd6d476bb37ff185c1597e7e5.jpg

 

And I bought a magnetic switch so I don't have to remove the hatch to switch it on.

 

large.16662600176311256789205373690359.jpg.b212cdd9c8863a0ed0ab574b5ce26a8e.jpg

 

Finally an underneath shot showing the airbrush shading I did.

 

I am planning to fly this, wind permitting, at the LMMGA Club PSS competition a week on Sunday - https://www.lmmga.co.uk/2011-08-18-13-54-36/277-power-scale-club-competition

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  • 2 months later...

Thought I would report on an unfortunate smash at the last PSS event, which looks awful but was actually repaired and back to flying condition within a couple of hours on the bench.

 

 

The event was an impromptu meeting of the PSSA at the Great Orme on 29th December 2022. The winds were 55mph on the edge and with compression, but only 35mph where we stood, or rather kneeled as the gusts kept blowing you off your feet!

 

I was looping the Spitfire across the slope, but the winds were so strong that I was being blown back towards the slope. Gradually the loops got closer.

 

I pulled up elevator to bring the plane round then to my horror saw the Spitfire hit the ground in front of me. The compression had sucked the plane into the ground. If you look carefully, you will notice that it nearly made, hence getting away with little damage.

 

It looks dramatic because the elevators and rudder were ripped out on impact and the  weighted cowl sheered off.

 

Stevie Kemp was videoing Phil Cooke's A4 Skyhawk, which you can just see in the distance when the Spitfire suddenly crashed right in front of him. A true "You've been framed" moment. Steve's daughter cleverly edited it into slow down mode, hence the strange audio.

Edited by Peter Garsden
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