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dirk tinck14/12/2019 22:56:33
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628 forum posts
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20191214_220251.jpg20191214_215319.jpgThe idea is to make the doors in epoxy.

To protect the fuse ,i'm covering it with plastic foil.Then a few layers of epoxy resin is applied together with cloth.I'm using 4 layers of 200gr.

To press the whole down i'm using another plastic foil and some balsa strips and pins and leave it to dry.

This should be my first speed brake !The surface won't be 100% but good enough after some sanding.

Good thing is that i can still see the outlines i drew on the fuse.When dry i can copy them on the epoxy part and cut it out.

Tha plan is to make a complete ''insert'' for the brakes ,meaning they must be fully oprational before mounting them in the fuse.20191214_213220.jpg

Peter Garsden15/12/2019 00:19:34
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1729 forum posts
1301 photos

Very very interesting Dirk. I too am doing the speed brakes but will use a fibreglass fuselage so should be easier. Am very interested how you are going to hinge and operate. Very useful to have a top designer ahead of me. Great blog by the way. Very intriguing, like a mystery novel!

Edited By Peter Garsden on 15/12/2019 00:20:07

McG 696915/12/2019 10:02:26
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3249 forum posts
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Great job as usual, Dirk.

I wouldn't even try to dream about that 'drooping hinge system' but totally convinced that if somebody can handle it... it will be you. wink

I already answered to your 'MB Weekend Attenders' post.

Cheers

Chris

Peter Garsden15/12/2019 15:03:02
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1729 forum posts
1301 photos

I agree with McG - drooping hinge would be a nightmare because it would touch the ground on landing and get ripped off.

I notice that you are using 4 sheets of 200gm fibreglass. All I use for the fuselage will be 2 layers of 150gm then a layer of 80 gram followed by some splurge of resin and microballoons to finish. Since you are the master of fibreglass I am sure you are right but I worry about weight particularly in the rear of the fuselage.

Also, presumably you are going to make holes in the flap servo support pieces afterwards when you make the hole for the servo arm - I would use a small needle file, I think? I was thinking one had to make holes before putting on the top sheeting, but perhaps it is not necessary?

dirk tinck24/12/2019 15:39:06
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628 forum posts
863 photos

Hi Peter ,you're right about the thickness of the panels. layers of 200gr. will be enough,even 2 layers i guess...

As for making the holes in the servo supports :You can do this anytime with a needle file !

Back to the airbrakes : When you look closely to the real sabre you see the panels ''drop'' when they open. IMO the upper hinge must be situated deeper in the fuselage than the lower to get this result so i tested it15349169153_18d69a7e20_b.jpg

dirk tinck24/12/2019 15:41:20
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628 forum posts
863 photos

20191216_221412.jpg20191216_221355.jpg

dirk tinck24/12/2019 15:45:41
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628 forum posts
863 photos

The first pic in the previous post shows the right angle for the panels , the second pic shows that the panel dusn't drop enough in ''open''position, capiche ??

dirk tinck24/12/2019 15:49:18
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628 forum posts
863 photos

So, with the drop angle sorted first thing is to put the laminations back in their position on the fuse and copy the panel lines on them20191215_205306.jpg

dirk tinck24/12/2019 15:52:14
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628 forum posts
863 photos

For long time i tought that the angled part of the hinge cover had something to do with the complex hinge system but it seems a printing error20191215_205730.jpg

dirk tinck24/12/2019 16:03:13
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628 forum posts
863 photos

As this is only a test i ''guessed the shape of the hinge parts. I made them out of epoxy plate, a bit to big just in case...They were gleued in place with Z poxy . Then sanded them with a dremel tool as much as possible to save weight ....yes allways ! The hinge pin holes were pré drilled again guessing their position. Looking at it after, they were spot-on !20191218_220418.jpg

dirk tinck24/12/2019 16:08:21
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628 forum posts
863 photos

Next job is to get the panels ''boxed-in" with 3mm balsa .This is going to be the outline of the brake-insert and needs to be perpendicular to the panel20191218_220435.jpg

dirk tinck24/12/2019 16:33:41
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628 forum posts
863 photos

20191219_224945.jpgThen added a dubbler on the back side for the panel to rest on .Also added a former just behind the hinge line to support the hatch and to accept the hinge supports later.All in place in the next pic.

The most dificult part is to get the hinge holes and pins in the right place .As they are pré drilled in the epoxy hinge-parts it's like a darts game here.

Once i was happy with this i could "test" the brake opening it.To my surprise it went very well !

With the pioneer hole in the right spot it's time to enlarge it to the diameter of the brass tube i'm using to "hinge" the two parts.20191219_224932.jpg

dirk tinck24/12/2019 16:37:05
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628 forum posts
863 photos

20191219_224953.jpgHere and there i forgot to take pic's but if any explanation is needed please ask20191219_234440.jpg

dirk tinck24/12/2019 16:39:50
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628 forum posts
863 photos

20191223_223905.jpg20191223_223839.jpg20191223_223803.jpg20191223_223748.jpg20191223_221201.jpg

dirk tinck24/12/2019 16:42:06
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628 forum posts
863 photos

20191223_224604.jpgMounting them on a piece of cheese it looks like this :20191223_224546.jpg

Martin Gay24/12/2019 16:53:03
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396 forum posts
255 photos

"Cracking job Gromit" as Wallace would say!

I think you could sell a few sets of those Dirk.

Chris Barlow25/12/2019 16:30:29
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1904 forum posts
1308 photos

Genius Dirk, right up to the part where you used a block of cheese, then it got weird! laughsurprise

dirk tinck25/12/2019 17:11:22
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628 forum posts
863 photos

Hi Chris , i was just playing along with some crazy lawyer on the PSSA facebook page who asked me why i used a block of cheese to present the speed brakes.....wink 2

dirk tinck25/12/2019 17:33:33
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628 forum posts
863 photos

20191225_181358.jpg20191225_181351.jpgReading this blog myself did me realize there's something important missing.

For the builders here who want to make speed brakes: Be sure you place the hinge supports perpendicular to the hinge pin ! If not , the brake will touch the sides in the area of the hinge-covers. For the good order i'm showing the LEFT brake here.20191225_181426.jpg

McG 696925/12/2019 17:47:20
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3249 forum posts
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Splendid engineering, Dirk.

... even the 'cheese' part... wink

But I think that I'll be sticking to my Dog-fuselage which is complicated enough for me. blush

Zalige Kerst

Cheers

Chris

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