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F-86A Sabre Montana Air National Guard

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Harry Twist29/10/2019 22:23:38
333 forum posts
246 photos

Hi All, Firstly - thankyou to Martin Gay and Gordon Studley for the planning, design, production and general "effort" that has led to us obtaining our F-86 PSS kits. Also many thanks to Phil Cooke for his detailed work in supporting and promoting this mass build 2020 project.

I've decided to attempt the scheme shown below for my F-86. Its a USAF F-86A of the Montana ANG, target tug, circa 1955 at Nellis AFB.

 

Profile view:

montana ang f-86.jpg

Model kit (not by me!)

sabre2.jpg

Edited By Harry Twist on 29/10/2019 22:25:31

Phil Cooke29/10/2019 23:07:59
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2281 forum posts
1550 photos

very nice scheme that Harry! The silver and yellow and blue do go well! I look forward to seeing your Sabre develop - Nearly time to get going!

Andy Meade30/10/2019 09:00:38
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2671 forum posts
681 photos

Yellow and silver, looks familiar Phil wink

Nice variant Harry, not long before you start now!

Harry Twist02/11/2019 00:14:14
333 forum posts
246 photos

Off we go! Its Nov 1st, so, being a miser I've turned over my piece of plasterboard building board and rescrewed it down on the other (clean!) side. I've then spent a little time making a start on the F-86. I started by fettling the wing jig sub pieces, just minor trimming needed. Then I cut up the wing plan sheet and then added extended lines for the ribs and wing spars. Once done I assembled the wing jig sub pieces and then finally assembled the wing jig, on the covered plan, carefully ensuring it all sat square and flat on the bench. I did add some triangular support as suggested by Martin in his gamma build.

Couple of shots...

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Harry Twist03/11/2019 23:54:02
333 forum posts
246 photos

Hi All, got a little more done over the weekend. Once dried, the wing jig was carefully removed from the plan and stored. Right and left lower wing sheets were then made up. Careful cutting gets one wing panel from 2 x 3"x 36" lengths. These were joined by the "tape on the back, fold along the tape line, glue in the fold, then unfold, wiping any excess away and adding weights to the new panel whilst drying" method. Once the panel was dry the rib and spar locations were added and the lower spruce spar cut and glued in location. Finally, I looked at a method for adjusting the spar slots in the ribs to get the correct spar/rib angle at the base. A simple jig to hold the rib made from scrap balsa and two clothes pegs helped! Photos below...

img_20191102_171338705.jpg

img_20191103_114412370.jpg

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Edited By Harry Twist on 03/11/2019 23:57:11

Mark Kettle 104/11/2019 02:56:10
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2471 forum posts
1492 photos

Lots of good tips Harry cheers.

Andy Meade04/11/2019 09:06:55
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2671 forum posts
681 photos

Nice little jig Harry, good work yes

Harry Twist05/11/2019 22:13:48
333 forum posts
246 photos

Hi All, Over the last couple of nights I have pushed the wings on a little more. Both lower skins now made, with centre spars and false TE's added - and whilst drying I sat them, with weights on, in the wing jig to "train" the balsa to the anticipated curve. Each rib was them trimmed to the correct angle for the top and bottom spars and the false TE, simple angle jigs helped this. The wing jig was then relocacted into position over the plan on the building board and although square, it was lifting a little in places - so the solution involved a few moulding pins and a small hammer and then gently nailing it to the building board!

With the wing skin sat in the jig I did notice that there was a gap between the underside of the wing skin and R1 - whereas all the other ribs sat neatly. To force the skin down onto R1 would have created a largish step form R1 to R2. So to remove this step/gap I glued a piece of scrap wing sheet balsa over the top of the twin R1 centre braces in the jig - this took up the gap and the wing sits much better now at the root.

Next stage was to locate the ribs in their final position and glue them. (the false TE was located prior to any ribs going in). To keep the skin "in the seat" I sat weights between each rib as I glued, and finally placed a piece of waste spruce in the slot on the top of the ribs and weighted down on this.

So as of tonight - I have located all the ribs on the right wing apart from R1. As an additional aid to keeping the rib leading edges located on the sheet I wedged a piece of 1" triangle below the front of the sheet.

Photos....offer better explanations than my words!

 

Additional strip over R1 area- indicated by blue pen

img_20191105_175013810_hdr.jpg

 

Weighted between ribs

img_20191105_181434037_hdr.jpg

Right wing ribs glued in situ

img_20191105_192727229_hdr.jpg

 

Rib leading edge trimming jig

img_20191105_200234654_hdr.jpg

Edited By Harry Twist on 05/11/2019 22:17:00

Steve McLaren09/11/2019 10:45:34
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226 forum posts
242 photos

Nicely done Harry. I'm hoping to catch up to this stage today. I made the wing skins last weekend, but no progress during the week.

I can see that they're useful, but why do you have so many lead/acid batteries??

Harry Twist10/11/2019 15:35:55
333 forum posts
246 photos

Hi Phil, I think the lead acids came to one of our model club meets, they were tired out but I saw them as weights! Just a bit of "repurposing" really! I've got 4, they're approx 2lbs each in weight so are quite useful.

Harry Twist10/11/2019 23:31:21
333 forum posts
246 photos

Really enjoying reading all the F-86 blogs, it's great that some people have started wing first and others fus first. Bit more progress on wings, false leading edges and hinge blocks added. Main work this weekend however has involved cutting, sizing and fitting the shear webs.

Enjoying the build, thanks again Martin and Gordon

img_20191110_214843667_hdr.jpg

Chris Barlow11/11/2019 01:53:23
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1858 forum posts
1266 photos

Good progress there Harry.yes

There's a lot of shear webs! Cyano or aliphatic?

Harry Twist11/11/2019 10:17:50
333 forum posts
246 photos

Hi Chris, 48 shear webs, each lovingly cut and trimmed, done over 3 sessions. Aliphatic all the way. Nice progress on your fuselage and thanks for sharing the 10 planking tips!

Steve Houghton11/11/2019 12:56:43
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540 forum posts
367 photos

Harry, another meticulous build on its way, I see. Thanks for the R1 tip, to be noted when I start my wings.

Harry Twist18/11/2019 19:55:00
333 forum posts
246 photos

Hi All, I have been slowly inching the Sabre along a bit more.

After a bit of thinking and head scratching I've decided that the drop tanks are so much a feature of the Sabre that I wanted to try to incorporate them into the build. Since they would be damaged easily on landing I'm planning for them to be jettisonable. So using a 1:72 Airfix model I have tried to scale up the location on the wing and the size of the tank and pylon to suit a 1:10 model. Disclaimer(!) - these are my kitchen table/ pen and pencil numbers and may not be 100% scale accurate! I reckon the tank pylon sits midway between R8 and R9, or 30cm from the centreline. The tank itself is approx 34.5cm long and 6.5cm in diameter at its widest. (its basically a torpedo shape with fins and a flattened top, although there is more than one tank type!).

So leaving the tank detail and construction until later, I have added the first part of a delivery system to the wings (basically I have copied John Heys proven method from the PSSA A4 mass build - thanks John!). Its a central servo driving a piano wire pushrod to the chosen location, the end of the rod push/ pulls through a hole in the pylon/keel of the tank. It did take some time to set it up - and you need to put holes through all those lovely ribs, it has also meant chopping away a portion of the front of the two R1 ribs to accomodate a servo location.

The wings were then planed and sanded to approaching a near finish state, although the top skins have not yet been added. I have now set them aside temporarily and moved onto the fuselage.

Drop tank location and size - ( ignore right hand location/ image of tank- I had a plan and elevation view on the same piece of paper and simply laid it below the wing, left hand tank drawing is "in location" between R8 and R9).

img_20191112_162620722_hdr.jpg

Tank delivery system- straw for support, plastic tubing either end, slightly larger internal diameter than piano wire diameter- sliding fit.

img_20191117_175503095_hdr.jpg

Alan Gorham_18/11/2019 20:01:08
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1069 forum posts
129 photos

Excellent Harry! Watching with interest.

McG 696918/11/2019 20:12:21
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2714 forum posts
1017 photos

This is indeed excellent engineering, Harry.

Watching with interest. yes

Cheers

Chris

Harry Twist18/11/2019 20:54:58
333 forum posts
246 photos

So, taking a breather from the wings, it was time to make a start on the fuselage. First job was to tickle all the surfaces with fine sandpaper removing any loose particles and hopefully create a slight key for surface jointing. I then laid out each piece with its partner and checked for symmetry ( I also went a little over the top and labelled, in pen, all the left pieces with a discrete little "x" and all the right with a little "y". In addition I measured the longitudinal parts for equal length for left and right sides (F14 and f15). All was good here.

I then dry fitted all the parts I could, a little work was needed here and there to ensure a good fit on some slots but no great issues were found. Subsequently I have started to assemble of some of the "sub structures" ( the central overwing block of three formers and F14, plus the tail block of F9, F15, and F10, they're all basically 90 degree joints.

Once all the sub assemblies are complete, I'll locate all on the plan, add the keels and do a full fit before gluing.

Some progress shots below.

 

Parts laid out - I subsequently turned the upper fuselage plan around 180 degrees to be the right way up, so now building both halves the right way up ( I could'nt cope with upside down and reversed, I was bound to make a mistake!).

img_20191031_131643021.jpg

 

Sub assembly 90 deg jointing, left side shows central crutch, F7 previously jointed at top, F4 under weights, F6 not yet glued in position. Right side shows rear sub assemblies F9 previously jointed, F15, F10 under weights.

Clearly they're not sat in situ on the plan (!) since they're 90 degree joints I chose to sit the former flat on the build board  and build upwards ensuring 90 degree joint with the longitudinal formers F14 and F15) and adding weights to the laid flat former. Then once dry turn the whole thing over ( like an egg timer) to glue the opposite former. They will be located  on the plan later.

img_20191117_163912902_hdr.jpg

Nose area - a sub assembly in itself

img_20191118_181305120_hdr.jpg

 

 

Edited By Harry Twist on 18/11/2019 21:22:58

Steve McLaren19/11/2019 21:11:53
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226 forum posts
242 photos

Nice work Harry. I'm interested in the tank drop mechanism. What size servo do you plan to use? and does 1 servo do both tanks? I'm trying to visualise the geometry of pushrods meeting the servo.

Martin Gay19/11/2019 21:26:55
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260 forum posts
230 photos

Steve,

here is the original blog by John H:

**LINK**

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