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ASK13 1/3 Scale

Let us all watch your new project progress.
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Trevor
Posts: 124
Joined: 19 Jul 2016, 16:29
Location: Hampshire
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Re: ASK13 1/3 Scale

Post by Trevor »

Whilst I too am a fan of Aliphatic glues, mainly for their superior sanding qualities, I'm also very happy to use PVA for internal joints. As for its longevity, I have several models over 30 years old, all built using PVA, and the glue joints still seem pretty sound to me. I've had at least three PVA-built models take serious duckings at some stage or other. They've all dried out perfectly well without falling apart.

That said, if I'm building a model nowadays which is intended to fly off water, I'll usually use a water resistant Aliphatic in preference!

Keith
Posts: 101
Joined: 07 Jan 2019, 18:18
Location: Lincolnshire

Re: ASK13 1/3 Scale

Post by Keith »

Ok thanks for the replys guys.

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: ASK13 1/3 Scale

Post by Peter Balcombe »

The wing structure is more or less complete now apart from the TE and brakes.
The drawing shows a balsa core TE which is sanded to profile & capped with 0.4mm ply skins.
However, I am going to try an alternative approach of using a ply core as the jam in a balsa sandwich. This will give a hard (& hopefully straight) TE.
So.. currently I am making up a 2.5m long TE strip, ready to notch to accept the ribs.

Meanwhile, I have started on the airbrakes which are standard top & bottom Schemp Hirth types, installed in two brake box sides glued directly to the wing ribs. The plan shows the brakes being actuated in the normal way via a pushrod from a nearby servo, but Cliff is developing a ‘direct drive’ arrangement which I will be trialing on this build.
The brass brake arms are replaced by 3D printed alternatives, but the twist is that one of them has a square drive shaft connection to a close coupled servo who’s shaft is on the same rotational axis.
All this should become clearer over the next couple of days, but in the meantime, I have assembled the 1st pair of blades and fitted the 3D printed arms with bushes & checked they all have the same centres etc.
You should be able to see the square drive shaft in one of the photos below. This rotates nicely in a 5mm brass tube.
Attachments
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: ASK13 1/3 Scale

Post by Peter Balcombe »

As there is no airbrake box structure as such on this design (front & rear faces only mounted directly to rib notches in the brake aperture) I decided to check out the brake operation in a standalone box assembly before committing to wing installation.
Thus I made a simple Liteply box with the same internal dimensions as the final brake blade aperture & same pivot hole centres. The box was stiffened by edgewise strips of liteply along top & bottom edges of front & rear face.
I also fitted the four 3/4” x 3/16” vertical stiffeners - one at each main pivot hole on each side.
I fitted 5mm brass tubes in the arm centre holes in order to bush the 1/8” square brass drive tube at one end & 4mm pivot pin at the other (3/16” tubes used normally, so not much different.
I also fitted short 5mm bearing tubes in the box walls at the driven end to act as bearings for the square tube.
The blade fitting were 5/32” tube& 1/8” rod as per drawing.
The pics below show the LH box fitted with blades from both front & rear.
At the driven end, the 1/8” drive tube is fitted with a compatible servo-like disc, which can then be driven from any servo/arm using a simple twin peg coupling.
A small servo is mounted so that it’s shaft/servo disc axis is on the brake arm/coupling disc centre.
The servo is a K&S PDI-HV0903MG which has 2Kg torque at 6v, 2.6Kg at 7.4v.
I tested using a 5 cell NiMn pack.
Hopefully, Cliff will be able to put up a video clip of the brakes driven from a servo tester in cyclic mode.

I’ve also fitted a section of my sandwich TE strip to the outer wing section. (I had forgotten the taper break at the inboard end of the aileron, so could have made the TE unit in 2 shorter pieces) 😏
Attachments
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3F5FF738-6C63-4115-A1F6-3E1B3973566C.jpeg

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Cliff Evans
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Re: ASK13 1/3 Scale

Post by Cliff Evans »

Here is the video of said air brakes.

Laser Cut sailplanes

SedB
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Joined: 14 Nov 2019, 09:17
Location: Netherlands

Re: ASK13 1/3 Scale

Post by SedB »

That runs very smooth by the looks of it! Nice to see how i's constructed, thanks for sharing!!

Dan

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Cliff Evans
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Location: Bristol
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Re: ASK13 1/3 Scale

Post by Cliff Evans »

3d printed arms and drive wheel.
Laser Cut sailplanes

Keith
Posts: 101
Joined: 07 Jan 2019, 18:18
Location: Lincolnshire

Re: ASK13 1/3 Scale

Post by Keith »

That would save some time a effort, some pre assembly pics would be helpfull.

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: ASK13 1/3 Scale

Post by Peter Balcombe »

Which bits do you mean Keith?
The blade units or assembly to arms etc?
Peter

tjarko
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Joined: 08 Dec 2019, 16:56
Location: Netherlands

Re: ASK13 1/3 Scale

Post by tjarko »

Very neat solution.
With a strong servo with good ball bearings, the brake arm might be directly bolted to the servo arm even.
This avoids the need for carefull alignment of servo and brake axes.

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