1/5 Scale Slingsby T51 Dart 17.

Let us all watch your new project progress.
User avatar
B Sharp
Posts: 580
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp » 07 Jul 2019, 08:16

Rog, what I think I will do is to extend the hinge line of the fin rearwards by 23mm and remove the top of the fin and replace with the correct shape. This will give a final shape which is much closer to scale and increase the tail volume at the same time. This is illustrated in the image attached.
A check of my scale drawings shows the full size Dart 17 fuselage length from nose to rudder post to be 7.0 metres as near as I can make out. At 1:3.5 scale this equates to 1.40 metres (which is pretty much the length of my 1:3.5 model by CW). The glass fuselage is 1.255m which scales up to 6.275m, 0.725m short or 0.145m at 1:5 scale. As I intend to add a further 23mm to the rear of the fin this will make the finished fuselage length 1.485m which equates to 122mm shorter than scale.
Now I suspect that the fuselage has probably been shortened by this amount in order to cut down the amount of lead that is required to balance the model. I know that in my CW Dart the majority of the nose cone is either lead or filler which makes it a bit of a lump.
However I am not sugesting in any way that a Dart built to the plan and unmodified will not fly well. All of Pats aeroplanes fly well. It is just my tendency to be finiky that leads me to make these proposed modifications.
Brian. :)
Attachments
Dart 10.jpg
Proposed extensions to fin.

User avatar
Barry_Cole
Posts: 1225
Joined: 10 Mar 2015, 09:30
Location: Hampshire UK

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by Barry_Cole » 07 Jul 2019, 08:57

Pat's ??

User avatar
B Sharp
Posts: 580
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp » 07 Jul 2019, 16:03

Yes Barry. This fuselage dates back to West Mendip Sailplanes (Pat Teakle) as I have flown a couple from that era. Granted that these are now produced under the ownership of our own Cliff Evans. Can anyone correct me on this?
Brian. :D

User avatar
Cliff Evans
Posts: 1593
Joined: 13 Mar 2015, 10:32
Location: Bristol
Contact:

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by Cliff Evans » 07 Jul 2019, 16:39

No Brian, you are absolutely correct.

User avatar
B Sharp
Posts: 580
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp » 09 Jul 2019, 17:40

Before I do any work on the modifications to the fin/rudder area I need to get the equipment bay sorted out. I need to be able to locate a servo and pushrod so a servo/Rx tray has to be installed. However before that I have to install the wheel well and axel supports. These were made out of ply and were glassed into place.
The servo tray is also made of ply and fitted just above the wheel well once again glassed in place. All very easy-peasy.
Brian. :)
Attachments
Dart 11.jpg
Wheel Bay.
Dart 12.jpg
Axel supports.
Dart 13.jpg
Servo/Rx tray in place.
Dart 14.jpg

User avatar
B Sharp
Posts: 580
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp » 11 Jul 2019, 17:21

Having sorted out the wheel and servo arrangements at the front end its now back to the tail end again.
This afternoon I have built the tailplane halves. Due to the shorter than expected tail moment arm I have increased the area by 10% to retain the stability factor. You can see that the blanks have a very simple structure which mirrors the construction used by CW in his plans. I will leave these to set up solid for 24 hours before sanding them to section tomorrow.
I also constructed the all-moving-tailplane horn using epoxy board and brass tubing.
Brian. :)
Attachments
Dart 15.jpg
Tailplane blanks ready for sanding to section.
Dart 16.jpg
Tailplane crank.

User avatar
B Sharp
Posts: 580
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp » 13 Jul 2019, 16:27

The tailplane is now finish sanded and weighs in at only 1.4oz or 42 gm with which I am very pleased.
The fin was carefully drilled and the actuation slot formed. The slot allows for a little more up elevator than down. The elevator crank fitted in perfectly and the tailplane now sits neatly in place.
The next task will be to manufacture and fit the pushrod before finally fixing the crank into place.
Brian. :)
Attachments
Dart 17.jpg
The finished tailplane.
Dart 18.jpg
The fin drilled and slotted and with the crank in place.
Dart 19.jpg
Tailplane fitted and sitting pretty.

User avatar
B Sharp
Posts: 580
Joined: 19 Mar 2015, 17:18
Location: Perthshire

Re: 1/5 Scale Slingsby T51 Dart 17.

Post by B Sharp » 16 Jul 2019, 15:24

A nice 6mm carbon fibre tube has been formed into a pushrod with clevises at both ends and the tailplane crank swivel tube has been glued in place. The tailplane now sits absolutely square with a long baton sitting across the wing seat.
The fin extension pieces have been manufactured out of ½ inch balsa sheet (stiff but light) the front edged of which has been grooved to allow the balsa to sit inside the moulding by 6mm. I cut the top off the fin and a balsa substitute will take its place.
This has increased the width of the fin considerably and the height by about 30mm.
The next job will be to “pretty up” the whole assembly.
Brian. :)
Attachments
Dart 20.jpg
The fin extension components.
Dart 21.jpg
The components dry-fitted to the fin.

Post Reply