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Engine Doctor01/04/2018 11:41:51
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Posted by Chris Barlow on 31/03/2018 02:12:28:

So a frustrating but productive couple of days which at one point had me gripping the nose between my legs and pinching the sides to the formers with my right hand and left wrist whilst trying to apply drops or runny cyano with my left hand! Oh and I dropped the fuselage twice creating a dent in the side that will have to be filled! surprise

You can remove most dents in balsa simply by wetting the dent and applying heat from a covering iron . The steam generated swells the fibers back to their normal shape. It saves a lot of filling and sanding plus no filler to fall out later.

Have don similar contortions holding bits with knees hand and applying cyano ! Have been stuck firmly to fuselages in past blush on a couple of occasions !

Trevor21/04/2018 12:23:28
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Having ordered my short kit from Sarik yesterday, I’m re-reading these threads with renewed interest! Rather than struggle to distort the 1/8 sheet sides, is there any reason why one shouldn’t plank the more curvaceous sections? I’m not saying it would be quicker but I think, for me at least, it might be less stressful.

Trevor

Levanter21/04/2018 13:20:41
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Trevor

​I would definitely think about planking as an option as it does seem to be a bit problematical.
​A couple of things to consider maybe:
​If the planking has to finish at 1/8" to match with sheeting and for strength you may want to plank a bit thicker as you will need a sanding allowance.
​You will use more glue and the planked section may end up slightly heavier.
​With planking you don't want the balsa too soft. It is better that it wraps around the curves without buckling. On the other hand you don't want it to hard or that will make sanding more difficult.

Levanter

Chris Barlow21/04/2018 18:38:12
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1747 forum posts
1192 photos

Trevor, I'd recommend having a look at how Phil has done his fuzz and go with that method of external molding formers. There aren't really enough formers down the fuselage for planking, just the 2 immediately behind the cockpit.

Chris Barlow23/07/2018 03:00:39
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1747 forum posts
1192 photos

So, you'd think that having a few weeks off from the build would put me quite behind and as such I wouldn't be faffing around with trivial scale detail that adds days onto the job....

Finally got started again yesterday since my car was in for it's MOT and I couldn't go to Wrexhams' fly in. Hammered out the wing ribs, cut the 1/16 sheeting and stuck it all together.

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OK so not all that was done in a day but I did make sure I had all 3 panels glued up and pinned to the bench to dry overnight. Stuck the 3 sections together this afternoon and added the leading edges and wing tips.

I also got started with the tail feathers this afternoon. The rib and canvas tail is quite distinctive of the Hurricane so I wanted to replicate it and also keep everything light, in view of the occasional windless PSSA meetings.

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Yep, that's going to add plenty more time to the build for me, hence the 2am finish. crying

Andy Meade23/07/2018 09:05:42
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2359 forum posts
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Nice work Chris, looks like a great lightweight back end yes

Alan Gorham_23/07/2018 09:46:22
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I'm liking that Chris!

Chris Barlow30/07/2018 01:12:50
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1747 forum posts
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Thanks Andy, Alan. Not sure how much good it'll do r.e. balancing though.

A bit more done today as the DVMFC fly in was postponed for the weekend after strong winds stopped play!

Ailerons cut and twisted with ammonia to match the wash out. My ailerons are 3/8 ths thick as I added 1/16th strips to carry on the rib and fabric theme.

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I have also added the switch gear for the landing lights. Just a 5g servo and 2 micro switches to select either left of right lights. You can see the pull through for the wires.

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I have drilled the hole for the wing bolt using this nifty sharpened M6 steel bolt wound into the captive nut. Just insert the wing via the dowel and push it onto the wing seat & the sharpened bolt marks the position of the hole! I think it was Peter Millers idea I nicked!

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After covering the tail surfaces, gluing the fin/rudder and hinging the elevators I have had another look at the balance. Hmmm.

So, with the tail, wings and Fuzz assembled the required nose weight is approximately..........9oz! That's after planing loads off the underside rear fuselage and heavily sanding the sides and curves at the rear!. The nose is approx 250mm ahead of the CG and the tail seat is 650mm behind the CG point. Using the CG as a fulcrum the difference front to rear is a factor of 2.6. To avoid having to add any nose weight at all I would have to remove approximately 24 oz from around the tail seat! The entire tail section doesn't weigh that much!

Weighing all the bits my projected weight is looking like 2lb 9oz plus another 9oz of dread in the nose.AUW looks around 3lb 2oz, probably more like 3lb 8oz after filler!

Excuse the mess, I'm in a rush! laugh

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Trevor30/07/2018 08:50:37
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289 forum posts
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Wow, that's really coming along well Chris. In view of your weight figures, I might try something similar with the tail surfaces. If I read your picture right, the tailplane is a 3/16 framework with 1/16 'ribs' laid on the top only and the fin is 3/16 with 1/16 ribs either side. Is that right?

Trevor

Andy Meade30/07/2018 08:57:06
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2359 forum posts
614 photos

I don't think the weight is anything to worry about chaps. I'm sure Phil will be along later to clear things up, but I believe the 2.5lb AUW was a red herring. I mean, look at the size of the aircraft. You'd struggle to get a JP in at that weight.

Great progress btw Chris yes

Chris Barlow30/07/2018 16:16:13
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1747 forum posts
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I agree Andy. Even if you build the tail extremely light you're still going to be adding some nose weight to balance. Anything 3 1/2 lb to 4 lb would be "normal" I think.

Trevor, 3/16 would be ideal. I used 1/4 but sanded it down a lot after building up the surfaces before adding the 1/16 x 1/8 "ribs". It creates a nicer finish but I wouldn't worry too much about the weight saving as mentioned above. Nose weight is unavoidable.

Phil Cooke30/07/2018 19:31:21
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2110 forum posts
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We never quoted 2.5lb... I've checked back and talked with Matt - the prototype was 3lb BEFORE the additional nose weight was added - I'm not sure of the resultant ballast needed but Matts model now, fully painted and detailed on top of the original covering is 'pushing 4lb'

Again, as stated in my reply on Petes' blog, we really don't need to worry too much about the AUW - the model is lightly loaded as PSS models go...

Love the way the tail looks with the covering on Chris - very scale like!! thumbs up

Nick Cripps30/07/2018 22:45:43
37 forum posts
16 photos

Actually, Chris, you've got your moments the wrong way round . You'd only need to remove about 3.5oz from the tail to balance without the 9oz noseweight.

Nice build, by the way.

Chris Barlow02/08/2018 22:31:15
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1747 forum posts
1192 photos

You're right Nick, I've "worked" it the wrong way! Still equates to around 100g and the entire tail plane and rudder is only 57g!

Getting on with the wing fairing and final sanding before covering. Tonight I had a go at making the famous landing lights!

Going back to some old methods I drilled a hole in a scrap of ply slight smaller than a 5/8th glass marble

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Then clamped a scrap of acetate sheet over the hole

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Heated the sheet over the hole with a hobby heat gun

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After approximately 10-15 seconds the acetate started to "move" so I removed the heat and pressed in the marble

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and allow to cool, roughly 1 minute

20180802_213626.jpg

I removed the marble and acetate from the ply former and drilled a 5mm hole to accept the LED

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Then cut it out in ever decreasing spirals until it looked about right

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Using a scrap of balsa to save my finger tips I sanded the cut edge carefully to get it flat and even

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Poked a white LED through

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Then painted the back of the reflector and LED with Humbrol silver

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A quick test on the breadboard (which also makes a great stand whilst the paint dries)

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I can't remember what this technique of moulding is called but I haven't done it for at least 30 years. Forgot how easy and quick it was.

Phil Cooke02/08/2018 22:34:59
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2110 forum posts
1470 photos

Impressive Chris thumbs up

... makes my internet purchase look awfully lazy - I bet I spent more time perusing and choosing what I needed than you did making it from scratch!!

Chris Barlow02/08/2018 22:38:48
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1747 forum posts
1192 photos

One of my favorite phrases Phil. "Made, not bought" wink

john stones 102/08/2018 22:53:39
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9666 forum posts
1435 photos

Like it. idea

Alan Gorham_03/08/2018 00:21:56
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506 forum posts
46 photos

It's called crash-moulding or smash-molding if you are an American!

Mark Kettle 103/08/2018 06:49:00
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2117 forum posts
1289 photos

I'm another Chris - "I Like It" idea -

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