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John A's Sabre build

PSS F-86F Sabre build blog

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John A H03/12/2019 18:14:27
138 forum posts
173 photos

For a change I though I would start the PSS build in good time to attempt to avoid the "still painting the night before the PSS meet" scenario again.

Colour scheme I'm thinking of is this one

sabre.jpg

John A H03/12/2019 18:23:13
138 forum posts
173 photos

As we have so many blogs I'll just post where I have used a method that I haven't seen anybody else use.

To build the wing jig I pushed the boat out and dedicated £4 worth of plasterboard to the job. I lay a set of overlaping pieces of A4 Blue Handcopy Carbon Paper over the plasterboard, ping the wing plan over the top and then draw over all the wing jig, spar, wing rib lines and you end up with this :-

sabre1.jpg

Then build and glue the wing jig onto the plasterboard. This method saves having to make gussets to keep the jig assembly square and also means you don't need to worry about sticking it to your plan.

sabre2.jpg

John A H03/12/2019 18:26:30
138 forum posts
173 photos

I used the same carbon paper method to transfer the plan (spar and rib positions) onto the wing skins.

To get the leading/trailing edge angles on the wing ribs I measured the angle and then used my Lidl mini bench sander to sand the ribs, sanding a little at a time constantly checking the fit.

sabre3.jpg

John A H03/12/2019 18:37:24
138 forum posts
173 photos

I created riblets and pylon keels for the releasable wing stores (drop tanks and bombs). The release slot is made from 1/16th balsa riblets with 1/32nd ply facings on the inside faces and a 1/8th ply spacer glued to create a slot. The pylon keels are made from 1/8th lite ply.

Drop tanks position is between ribs 8-9 and the inner weapons on is between ribs 5-6 (for true scale the bomb rack position should be further out but I thought it looked more balance with them further inboard.

Parts laid out :

sabre4.jpg

riblets glued together :

sabre5.jpg

and with pylons slotted in (fillet of 1/16th balsa used to take into account the lower wing skin when drilling holes for release rod.

sabre6.jpg

John A H03/12/2019 18:41:00
138 forum posts
173 photos

The inner pylons need to have a slot cut out so that the release wire for the drop tanks can pass through it without stopping it releasing. The inner release is done using a short wire soldered to the main release wire going through the second hole

sabre7.jpg

John A H03/12/2019 18:55:53
138 forum posts
173 photos

Here is the release slot positioned on the wing skin

sabre8.jpg

And how it looks when setup. The inner release wire stops the main wire been able to rotate so if the servo was connected directly to it the arc of the servo horn would cause it to bind or put stress on the servo. To solve this the servo is connected to the release by a ball link and short pull cable. There is then a spring between ribs 6-7 that pulls the release closed. This also has the advantage that when closed there is no load in the servo.

sabre91.jpg

The wires are setup so that with the servo in the mid (neutral position) the bomb release is "open" but drop tanks still attached :

sabre92.jpg

and on full travel both releases are open - so with half travel you just release the bombs and full travel will release both bombs and drop tanks. Releasing one set at a time might make them easier to find in the all consuming gorse bushes !

sabre93.jpg

I will make up a custom servo horn out of glass fibre so that the opposite wing release has as straight a pull as possible.

John A H03/12/2019 18:58:56
138 forum posts
173 photos

Here's how it looks from the wing underside with the release mechanism slots :

sabre94.jpg

and with the pylons in ready to have the drop tanks and bombs attached to them once they are built :

sabre95.jpg

John A H03/12/2019 19:14:58
138 forum posts
173 photos

I forgot to say at the start ….. when I build my wing jig I realised that the R1 level did not line up with the rest of the rib jigs, I think Harry mentioned this on his wing build. I glued a 1/16th balsa shim to the plasterboard under the R1 positions before glueing the jig down and it then lined up perfectly.

Steve McLaren03/12/2019 19:33:15
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248 forum posts
257 photos

Wow! Does carbon paper still exist then?!

Very clever approach John! And fantastic progress for 1 day!

McG 696903/12/2019 21:08:33
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3177 forum posts
1199 photos

... wooow, indeed very impressive, John AH.

... and welcome to the Sabre 'insanity'... wink

Cheers

Chris

Danny Fenton03/12/2019 22:28:29
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9496 forum posts
4312 photos

Cracking start

Phil Cooke03/12/2019 22:42:20
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2551 forum posts
1796 photos

Good to see you up and running so early John - looks like im the last to launch this time round!

Andy Meade04/12/2019 09:10:12
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2764 forum posts
717 photos

Heyup John - good to see your build on here yes

Neat work as ever sir!

John A H10/12/2019 17:19:27
138 forum posts
173 photos

Slightly more than a days work in the wing build due to the convoluted release mechanism smiley

While building up the release mechanism in the port wing I took pictures of each step I used to attempt to make the action as smooth as possible.

Warning reading this might put you to sleep as it's a bit long winded - much like myself. I actually wrote out the steps before I started so that I could glue things in the right order.

To make it easy to mark holes in the ribs for the release wire run I add them individually, by pushing the wire through from the tip end you can mark the hole positions on each one in return. It does increase the wing build time by a factor of 4 but means you don't have to slot the ribs to drop the wire in after the ribs are glued.

Edited By John A H on 10/12/2019 17:36:46

John A H10/12/2019 17:20:34
138 forum posts
173 photos

1. Mark the path of the main release wire onto the wing skin (as I already had the release servo in the other wing I could put both wings into the wing jig and check the servo horn position).

2. Mark the position of the wire in the outer release slot riblets, measure the angle between the riblets and wire, set the angle on the pillar drill and drill through the riblets with 1/16th shim and drop tank pylon inserted.

3. Mark the position of the wire onto rib 4 and use pillar drill still set at an angle to put the hole in it. This will be used as a guide for the release wire as we build up the wing so should be as accurate as possible.

4. Pin the outer release slot (riblets) and R3 onto the wing skin (while it is pinned to the wing jig) and feed the wire through both along with a carbon guide rod. Check it is free running and then use SuperPhatic glue to glue the slot riblets into position. DO NOT GLUE R3 AT THIS POINT - LEAVE IT PINNED IN POSITION.

5. Use Epoxy mixed with Micro Balloons to "pot" the carbon rod into place (I actually use Fibreglass flocking because it adds a lot more strength to the join). Before it sets check that the wire is free running and does not baulk when pulled out/pushed into the slot.

Note:- in the picture you can see I initially accidentally used R4 instead of R3 !

sabre951.jpg

Edited By John A H on 10/12/2019 17:33:53

John A H10/12/2019 17:22:48
138 forum posts
173 photos

6.Once the epoxy has dried and the carbon rod is held firm drill R5 to fit over the carbon rod, make the hole oversize so there is no chance that it effects the rods position and glue it in, using epoxy around the rod.

7. Position R7 and by feeding the wire through the slot riblets and carbon rod from the tip and mark the hole position and drill it. Glue in R7.

8. The release spring is anchored on R7. Make up a 1/32nd ply doubler for R7, drill hole and glue it in place (keep checking that the wire runs freely when threaded through the installed ribs and R3. Bodge up the spring anchor by gluing a short piece of piano wire that passes through the spring to the doubler - photo shows what I mean. The release wire runs through the middle of the spring.

sabre952.jpg

sabre953.jpg

John A H10/12/2019 17:24:25
138 forum posts
173 photos

9. Pushing the wire from the tip end mark up and drill the hole position on R6. DO NOT GLUE IN R6 AT THIS POINT.

10. Mark and drill hole position into the inboard slot riblets using the pillar drill. Also drill a second hole in the slot riblets about 20mm to from the first. While drilling the holes have the bomb pylon inserted with the 1/16th shim.

11. with the guide wire inserted glue in the slot riblets.

sabre954.jpg

12. Now comes the tricky bit - the picture explains it better. Make up the short "inner release" wire with initially the one bend in it, thread carbon guide rod onto it and using pins/balsa jig it in place to run parallel to the main release wire. Glue the carbon rod to the riblet..........check the wires run smooth. Both the inner and outer release wires are still over length at this point to allow for trimming.

sabre955.jpg

John A H10/12/2019 17:26:23
138 forum posts
173 photos

13. Once the carbon rod joint has dried mark, drill and glue in R5. Now put the second bend to make a large Z bend) in the inner release wire so that it sits on top of the main release wire and cut it to length at the join. Do not make the length of the solder join too long as it should allow the required movement for release of inboard and outboard munitions before the joined wires strike R3.

sabre956.jpg

14. Solder the wires together while they are in position. At this point because R4 is not glued in you can still remove the release wire.

sabre957.jpg

sabre958.jpg

John A H10/12/2019 17:27:23
138 forum posts
173 photos

15. Now you can trim the release wires to length, I put a slight point on the end to help it them centre/feed through the holes in the ply slot doublers. The inner release wire is just long enough to pass fully through the inner release riblets slot when the Z bend is against the carbon guide rod. The outer release wire is long enough that when the inner release wire clears the inner slot the outer is still fully through the outer release slot. This allows the outer drop tanks to be retained while dropping the inner munitions (If you only want to be able to drop all munitions at once you will only need half as much servo travel which might help with servo horn geometry).

16. Mark and drill holes in R4 and R2. The hole in R4 needs opening out into a slot so that the solder join between the inner and out release wires can pass through it.

17. On each of the release slots prick through the bottom wing skin with a pin in each corner of the slot to mark it for cutting out later. Make the holes obvious (wobble the pin about a bit to enlarge them) so they are not confused with the various pin holes created when pinning ribs/skins down earlier !

John A H10/12/2019 17:28:27
138 forum posts
173 photos

18. The release spring is now attached to the release wire. The hole in R6 needs to be opened out to allow the spring to have enough movement, as it is a large hole I put ply doublers both sides.

19. After this next step the release wire cannot be removed from the wing so the ribs need to be in the correct order on the wire (but not glued yet). Slide R4, R3 and R2 onto the wire. Slide the wire through R5 and inner slot riblets. Slide wire through R6 (do not glue R6). Slide wire through the MIDDLE of the spring along with R7, R8 and outer slot riblets.

20. The spring anchor on the wire is a balance between just enough tension to hold the mechanism closed while not too strong for the servo when pulled open. The anchor is just a piano wire hook soldered to the release wire.

21. R2, R3, R4 and R6 can now be glued in position ...... check wires are free running still.

sabre9591.jpg

sabre9592.jpg

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