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Scratch built Pilatus B4 to 1/4 scale.

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B Sharp
Posts: 718
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Scratch built Pilatus B4 to 1/4 scale.

Post by B Sharp »

As I recently posted on the "who's building what" thread I am about to scratch build a Pilatus B4 to 1/4 scale. Why do that when there are lots of kits about I hear you ask. The answer is "just because I can and I want to". This will be a relatively slow build as my name isn't Williams but I hope to fly the model later this year. The build started with drawing the plans (old school pencil and paper) and there should be a couple of pictures attached. Other than the plans the only part of the model which is complete is the retract mechanism which I built a couple of years ago.
The first real construction job will be to produce all the fuselage formers. These have been designed with Devcad and the printouts are currently being attached to ply sheet ready for the jigsaw.
Brian. :)
Attachments
This what I am setting out to achieve.
This what I am setting out to achieve.
The fuselage plan and elevation.
The fuselage plan and elevation.
The wing plan.
The wing plan.
My home build retract gear.
My home build retract gear.

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VinceC
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Re: Scratch built Pilatus B4 to 1/4 scale.

Post by VinceC »

You can do it Brian - go go go

roo Hawkins
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Joined: 18 Mar 2015, 20:12
Location: Northamptonshire

Re: Scratch built Pilatus B4 to 1/4 scale.

Post by roo Hawkins »

looking forward to this. thinking I may what to build a pilatus or salto one day??? will be following. :D

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B Sharp
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Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: Scratch built Pilatus B4 to 1/4 scale.

Post by B Sharp »

Thanks guys for your comments. I am sitting happily with a cup of coffee in the workshop as the snow comes down outside. My fingers are gently vibrating as I have been cutting formers this morning with my dremel jigsaw. I do so much love cutting wood!
Brian. :) :) :)

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B Sharp
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Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: Scratch built Pilatus B4 to 1/4 scale.

Post by B Sharp »

As it was a lousy wet, snowy day I spent the best part of it in my cosy little workshop. The results of my labours can be seen in the attached photo - all but three of the fuselage formers and all of the up-stands for my fuselage jig. The remaining three formers will be cut from the 1/4 birch ply which will be arriving from Balsa Cabin some time this week. You might notice that I have added temporary horizontal reinforcement to three of the formers to stop then bowing inwards during construction and before the planking is added.
Brian :)
Attachments
Fuselage formers from 1/8 birch ply.
Fuselage formers from 1/8 birch ply.

Nigel Argall
Posts: 141
Joined: 20 Mar 2015, 18:26
Location: Cornwall

Re: Scratch built Pilatus B4 to 1/4 scale.

Post by Nigel Argall »

Brian, I'm trying to send you those canopy pix and dimensions but struggling with the message system. PM an email and I can get them to you.

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B Sharp
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Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: Scratch built Pilatus B4 to 1/4 scale.

Post by B Sharp »

I said this wasn’t going to be a fast build! While I waited for my timber and other materials to arrive I set up the fuselage jig. There was lots of measuring and re-measuring and adjusting before I got it all right. :)
I increased the thickness of former 6 to 5/8 inch with balsa both sides of the plywood as this would be the point where the rear sheeting would join the front planking. And once the carbon fibre arrived I cut the 14mm main spar tube and the 12mm Joiner bar to lengths. Then I did the same with the 6mm incidence tube and the 4mm incidence rod. The boxes for the joiner and incidence tubes were the formed onto formers 7 and 8 with 1/8 ply and balsa reinforcement. :) :)
Finally this afternoon I was able to get all the formers mounted on the jig and the spruce longerons all glued in place to form the fuselage skeleton. :) :) :)
I started work on the fin, mounting the rudder post and attaching some of the internal bracing. I was feeling pretty good about the progress when I took a couple of check measurements and discovered that the rudder post was set at the incorrect angle to the fuselage. After a few minutes and several choice words the embryonic fin was deconstructed. I will start afresh later in the week. :( :x :x
Brian. :)
Attachments
The fuselage jig set up.
The fuselage jig set up.
Former 6 with balsa packing to support sheeting.
Former 6 with balsa packing to support sheeting.
All the carbon joiner pieces.
All the carbon joiner pieces.
Formers 7 & 8 with joiner boxes.
Formers 7 & 8 with joiner boxes.
The fuselage skeleton
The fuselage skeleton
The fuselage skeleton
The fuselage skeleton
The fin in build before I had to deconstruct!
The fin in build before I had to deconstruct!

Jolly Roger
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Joined: 30 May 2015, 20:35
Location: Sutton Bank, North Yorkshire

Re: Scratch built Pilatus B4 to 1/4 scale.

Post by Jolly Roger »

Sorry to hear about your fin Brian. This kind of thing happens!

Build looks good - following with interest.

Rog

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B Sharp
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Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: Scratch built Pilatus B4 to 1/4 scale.

Post by B Sharp »

Despite all the care and attention things do go wrong. I had been congratulating myself that the basic structure had gone together rather well till I noticed the lines round the middle of the cockpit area. The culprit was former 4 which was drawing the longerons inwards a little too much creating a coke bottle effect. After checking and rechecking I realised that my drawing (CAD) was a little out. I redrew and cut a replacement former, which when fitted, still wasn’t correct. I then repeated the process once again and thankfully the third former appears to be just fine and the flowing lines are restored. Anyone want to buy a couple of slightly used plywood formers?
I made up some stiff cardboard templates from the fin drawings and used them as I rebuilt the fin inner structure. This time I also remembered to punch holes in the ribs for the elevator servo cable as the servo is going to reside in the top section of the fin.
Brian. :?
Attachments
Former F4 version 3 finally fitted.
Former F4 version 3 finally fitted.
The embryonic fin, now the correct shape.
The embryonic fin, now the correct shape.

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B Sharp
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Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: Scratch built Pilatus B4 to 1/4 scale.

Post by B Sharp »

I completed the fin basic structure and sheeted one side then began the elevator installation in the uppermost bay. I soon realised that in order to make the elevator linkage to the correct length I would require a tailplane. A couple of days saw a tailplane constructed but I soon realised that I also needed the elevator. One thing led to another and I ended up with a fully finished, covered, hinged and with a control horn, tailplane assembly. However that allowed me to set up the push rod geometry and check that the elevator surface movements were going to be sufficient. It was then a simple task to sheet the other side of the fin. You will notice that I built in an access hatch for the servo as well. This will have a little moulded cover over the servo when complete.
I was very happy to find that the finished tailplane sits at -3 degrees to the proposed wing datum line. :) :) :)
The next job will be to start on the fuselage sheeting and planking.
Brian. :)
Attachments
Elevator servo snug in its little home.
Elevator servo snug in its little home.
The basic tailplane construction.
The basic tailplane construction.
The finished tailplane and elevator assembly.
The finished tailplane and elevator assembly.
The fin sheeting finished and the little servo hatch.
The fin sheeting finished and the little servo hatch.
Fin and tailplane in perfect harmony.
Fin and tailplane in perfect harmony.

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