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Phil W's Sabre Build Blog

My dodgy attempt at building the F86!

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Phil Willett11/02/2020 18:58:37
17 forum posts
42 photos

Hi Everyone, this is my F86 Sabre Build Blog.

Although I have been building and flying RC gliders and sailplanes for many years now off and on as time has permitted, now recently retired I have more time on my hands and have started building and flying again. I'm relatively new to the sport and have previously only built one PSS model before, however I find PSS a fascinating RC discipline as I really enjoy the building part of the hobby as much as the flying bit.

So I am participating in the 2020 Sabre mass build this year.

I know I'm a bit slow to start the build but I figured that it would be best for me to fall in behind the obviously many experienced PSS builders and take advantage of the extensive advice and tips from the many bloggers on this site.

Now I'm no build expert at all, so the purpose of this blog is to show how I am going on and to invite anyone to comment or add advice as they see fit.

So having read the articles in the 2 RCM&E mags and the advice/debate on the many brilliant build blogs in here I am going for 4 servo wing and a fixed rudder. I don't see the need for a working rudder on a model like this; I don't expect to do many stall turns and take offs and landing will be on rough grass so I'll manage without a rudder. I do however think I would need some means of slowing the Sabre down during landing so I'll fit flaps and utilise crow braking which I've used successfully on previous slope soarers and like the extra control it gives. This will also enable me to switch a bit of trailing edge camber to help with take off and when lift fades away. I would dearly have liked to fit the fuselage airbrakes to this model but I'm afraid the extra skill and work involved would be a bit too much for me, so I look forward to seeing them fitted to others in June.

I chose to build completely from plan so have cut all parts by hand! (maybe this was a mistake!!)

So I'll post some pictures next.

Can anyone tell me how do I insert an image into a thread as the forum doesn't seem to allow me to browse my computer?

Pete B - Moderator11/02/2020 21:23:59
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Moderator
7674 forum posts
734 photos

Welcome, Phil!

Easiest way to insert pics is to upload them to an album here and use them as you wish. Full instructions here - any problems, just askthumbs up

Pete

McG 696911/02/2020 21:30:23
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3359 forum posts
1279 photos

... and welcome to the 'mad' Sabre Club here. wink

Cheers

Chris

dirk tinck11/02/2020 23:08:12
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654 forum posts
922 photos

Welcome and good luck Phil ,

Phil Willett12/02/2020 12:52:24
17 forum posts
42 photos

Thanks for the instructions. Here are some early photos;

I started out by cutting & building the jigs and ribs.

sabre1.jpg

Phil Willett12/02/2020 12:53:40
17 forum posts
42 photos

Then I prepared, joined and trimmed the lower skins

sabre2.jpg

Phil Willett12/02/2020 13:06:57
17 forum posts
42 photos

Then I glued the ribs R1 together and then spruce wing spars onto the skins. Here I found an error on the wing plan which states that the spars are 1/8 x 1/4 inch but the cut-outs shown on the ribs on the plan are actually deeper; they are actually 3/16" x 1/4", but too late I cut the ribs out before I spotted this! So given that I used spruce for the spars I decided to press on and add small 1/16 balsa packing pieces to each rib joint slot top and bottom, and hope this will be strong enough!. Lesson to be learnt; always check dimensions before you cut out!

I also decided to add a small 1/4" ply wing joiner across ribs R1 to R2 to strengthen the joint (its under the tape measure and shown on the next photo)

sabre3.jpg

Phil Willett12/02/2020 13:15:46
17 forum posts
42 photos

Then I glued the remaining ribs and top spar omitting the ones affected by the wing servo hatches. I designed hatch supports from 1/32 liteply and cut recesses from the se ribs before fixing in place.

sabre4.jpg

Phil Willett12/02/2020 13:19:39
17 forum posts
42 photos

Next glued 4 servo hatch supports, and all remaining ribs, followed by the spar shear webs.

sabre5.jpg

Phil Willett12/02/2020 13:33:04
17 forum posts
42 photos

At this point I looked at fixing the aileron wing servos in position using two Futaba micro servos I had from a previous model. I really wanted to install a mainly internal linkage to the aileron like that shown in the RCM&E article written by Gordon Studley for the second build. But I couldn't see how to fit the servo and internal linkage into the thin space available in the wing. So I decided to use an external linkage for the ailerons and fit some form of fairing to protect it against damage (does anyone have any ideas how to do this?) I decided to fit servo fixing plates across the adjacent ribs on the top to allow me to fix the servos onto without touching the top skin. I used 1/8" liteply for these. The flap servo space is more generous and I will use flat wing servos so I am hoping to use a top exit linkage the flaps when I get round to this later as the flaps linkage will probably be more prone to damage when landing ?. I was tempted to have a go at an RDS system but the design of the aileron/flap sliding box seemed like a challenge too far. There must be a better way for internal control linkages for PSS models?

sabre6.jpg

Phil Willett12/02/2020 13:34:16
17 forum posts
42 photos

Now I started to cut out the fuselage formers etc from a big sheet of 1/8th Liteply (should keep me busy for a few weeks!!

sabre7.jpg

Andy Meade12/02/2020 14:03:04
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2780 forum posts
717 photos

Proper scratch building, good work yes

Phil Willett16/05/2020 21:55:44
17 forum posts
42 photos

Now onto the fuse assembly in two halves followed by the dreaded planking.

.planking.jpg

.fuse assembly.jpg

I pondered for a while how best to ensure an accurate fit of wing and fuselage, so I decided to leave the drilling and fixing of wing dowels and wing bolts until the skinned wing and fuselage were built sufficiently with fuselage wing seat cut outs done to enable them to be offered up together and holes marked out before final drilling. To enable this I omitted some planking on the top and bottom of the fuselage till after the wing has been mated to the fuz.Then the two fuselage halves were joined together.

.fuse joined.jpg

.img_1337 (1).jpg

.At this point I fitted the stabiliser servo plate. I deviated from plan here and located the servo behind former F6 as there seemed to be plenty of space there.

elevator servo mount.jpg

Phil Willett16/05/2020 22:05:57
17 forum posts
42 photos

Whilst the fuselage was in two halves I attempted to fit and mount the elevator snake to the bell crank. Whilst testing this linkage I experienced problems with the snake bending under stress. Also the snake anchoring lugs on the formers tended to cause the linkage on the servo to pull to one side. It may be because I used a snake diameter a bit small for this job. So after some though I decided to do away with the snake and go for a good old fashioned push rod. This fitted nice and centrally down the fuse and works well.

.push rod and crank.jpg

.Getting back to fuselage building, the nose was then crafted with scrap blocks and fitted carved and sanded. Fairly straightforward me thinks.

Next up was the exhaust, which I built from scrap block and cut, sanded. As you can see I haven't bothered trying to cut a scale hole for the exhaust; it looks good with a plain curve.

.exhaust.jpg

nose.jpg

dirk tinck16/05/2020 23:06:09
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654 forum posts
922 photos

Good progress Phil !Any idea for the sheme yet ?

Phil Willett18/05/2020 09:14:14
17 forum posts
42 photos

Hi Dirk,

Yes, I have settled on this scheme which is FU-661 (S/N 24661) of 50th FBW Squadron USAF. I particularly like the USAF schemes and I like the fact that it comes from an operational squadron. Its not too complicated to paint and the flashes of yellow should help it stand out in the sky. I hope this doesn't clash with anyone's scheme. If so let me know.

My intention is to cover the wing and tail planes, and rudder in film, and glass and paint the fuse. Not sure about the fin yet; could do either. Covering the wing in film should be easy and I hope will save a bit of weight. I happen to have a role of film waiting to be used up as well!. The fuselage obviously needs some strengthening and glassing will do this nicely. No one else appears to be proposing this approach but I'm assuming this will work ok.

sabre fu661 jpg.jpg

.

Bye the way, thanks for your excellent build blog which I have followed throughout. Keep up the good work!

Phil

Phil Cooke18/05/2020 09:45:47
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2645 forum posts
1850 photos

Hi Phil,

I think we've done very well in trying to manage scheme clashes this time round - the forum has really helped! Not easy with so many models being built in parrallel - but it really doesn't matter if we do get the odd duplicate!

You've chosen a great scheme, and you are right the yellow banding will really stand out well! Yellow is one of the very best colours to aid vis and orientation.

Film on wings and tailplanes combined with a glassed fus and fin will be fine, I think most will glass the whole airframe once they've got their glassing kit out and in use. Over the years I've found this to be the most robust way to maintain the models appearance. My film goes on well, but after a few sessions with the model sat in the pits in the sun you soon have to start a continuous programme of maintenance with the heat gun, which doesn't go hand in hand with vinyl decals or paint details. The glass finish is so robust and the models only need a dusting between events!

Horses for courses I guess.

Phil Willett18/05/2020 10:05:46
17 forum posts
42 photos

Further photos of my build;

I moved onto cutting out the wing seat from the fuselage. I decided to fit two sheets of 1/32 ply as the wing seat supports. I notice from full size photos that there is very little in the way of a wing fillet between wing and fuse on the Sabre. I thought without a fillet it didn't look quite right (with a sharp acute angle) so I have given it a very small thin fillet on the outside which will blend into the leading and trailing farings.

wing seat ply.jpg

.Masking tape on the wing top skin to protect from glue, then tacked the 1/32 ply to the fuse with CA. Then dry I packed the gaps with balsa pieces (see photo) and glued. This ensured the ply is a neat fit on the wing top skin and no gaps.

.wing seat ply packing.jpg

Next I fitted a fillet onto the gap using 1/4 soft triangle which was shaped to follow the contour. It needed a little coaxing by wetting it and bending until dry. The ply acts as a support for the balsa now. Once glued on and dry, it was carefully sanded and the ply edge trimmed to give a small fillet.

wing fillet sanding.jpg

.Next job was to offer up the wing and fuselage for final fitting of dowels and wing bolts.

The gaps left in the fuselage allowed me to accurately mark the location of the holes for the wing dowels and the wing bolts by prodding a screwdriver/allen key with paint on the end to make the position of holes as follows.

wing dowel marking.jpg.wing bolt marking.jpg

.Once the wing was sitting straight and level, I marked both were drilled and dowels fitted/glued and wing bolt holes drilled. This ensured the two mated perfectly.

.wing fixed.jpg

I also fitted a triangular sheet piece behind the wing bolts to fill in the space.

.wing fitted.jpg

Now the remaining fuse planking was finished off.

Now I fashioned a belly pan onto the wing using 6mm balsa soft sheet.

.belly pan.jpg

Next jobs were to fit small farings on leading edges and training edges of the wing root to blend in with the wing fillets.The front ones required a bit of reinforcement to prevent damage so I used a 1/16 ply plate. When sanded this looked quite nice.

.front wing faring.jpg

.Then onto the rear faring.This involved a sheet of 6mm balsa glued and carefully sanded to blend in with the fuselage.

.wing rear faring finished.jpg

.rear wing fillets.jpg

Finally two small farings added to allow the wing TE to fare into the rear wing faring.

The cockpit floor panels are added. I'm afraid I don't have the skill or the time to produce a scale like cockpit like many of you expert PSSA'r are doing, I'm quite satisfied with a basic pilot and cockpit outline shape W/O detail which is painted grey to blend down behind the canopy. Talking of which, I have not been able to procure a canopy from Vortex Vacforms as they have not responded to my requests or emails for the last 2 months. I'm assuming they are closed due to the Virus and very much hope they will reopen soon as I cannot complete the fuse build until I get a canopy. Failing that you may see my Sabre pilot flying around the Orme "Al-Fresco"!

.

.The fin was finally glued in place having carefully checked that the bell crank is moving freely. A little packing was required between the formers. The dorsal fin added also.

.fin and fillets.jpg

This part is quite tricky to get right in terms of the positioning of the tailplaneand shaping of the fillets . Careful sanding produced a reasonable finish.

.fin fillet finished.jpg

So its coming together now.

cheers Phil

Phil Willett18/05/2020 10:36:43
17 forum posts
42 photos

Hi, a bit more progress this week,

.cockpit floor.jpg

.The fuselage is more or less finished now awaiting the cockpit detail and canopy. I think I'll glass the fuselage and add the canopy afterwards. I'll use any spare time waiting for a canopy to add cockpit detail.

.Back onto the wings now. The 4 control surfaces need completing. This involves fitting the hinges, linkages, horns and testing control throws are ok.

hinges.jpg

I've tried three different arrangements of hinges now and settled on centre mounted Robart hinges, with rounded LE on flaps and ailerons, and convex TE on the wing. The gap is minimal and I can get quite a good downward drop on the flaps of around 70 to 80 degrees. To get a convex TE I added two small triangle strips to give a V shape then filled with filler and sanded.

.Servos hatches look like this. The hatch covers are 1/32 ply sheet with 1/32 balsa frame (1/16 sanded). My intension is to tack glue them in place with CA. If I ever need to remove them I will prise them out thus breaking the balsa frame and replace/repair and reglue.

flap hatch.jpg

The only downside of modelling the Sabre for slope flying is the low wing position and its susceptibility to damage on landing (or in my case ditching)!I The control linkages are particularly prone to damage. I therefore favoured a top exit linkage for the flaps and ailerons to prevent damage on landing as per the design on the second Sabre RCM&E article. However, I had the devil's own job getting the geometry for a top actuating aileron linkage to work due to the wing thickness being quite slim at this point. Probably down to my limited experience I fitted the servos a little too central in the wing? So I've ended with a conventional bottom hanging wing linkage as per the prototype. I'm not happy with this arrangement due to the exposure to damage on landing, but I will fashion a small cowling onto the hatch covers to protect the linkage a bit (like that used on the prototype Sabre). However, I have gone for a top exit flap linkage which is a better arrangement on these al least.

That's my progress up to date. With the fuse and wing now practically built, I'll move on to finishing now. I'm only glad the event has been postponed to September as it would have been a mad rush to get it ready to fly by next month! Should have started it earlier I hear you shout!!

Cheers,

Phil

Phil Willett07/06/2020 19:25:26
17 forum posts
42 photos

A bit more progress on the wings. I have now covered the wing with silver film. This was easy to apply and the finished article looks great!. I covered the wing with five pieces of film; belly pan first, two bottom surfaces and two top surfaces last.

.wing film covering.jpg

.The finished wing looks like this.

.finished wing covering.jpg

Now onto the fuselage. This is my first time at glassing a fuselage! so I read up on some written articles I have from various sources and of course the excellent guidance given on this sabre build blog. Advice does differ slightly between modellers so you have to go with the method you think should work for you, and try it and see what the outcome is.

I have glassed the fuse using 25g/m glass cloth and the Aeropoxy epoxy resin system.

I carefully cut the glass cloth to shape the fuse including the fin with sharp scissors (it helps if you wear tight rubber gloves during this process to stop the glass cloth snagging on you fingers). Once placed over one side of the fuse, I mixed a small amount of resin and carefully poured and spread it over the cloth starting at the centre just enough to wet the cloth. when spread I used a soft brush to brush it smoothly over the cloth. I continued to mix more small quantities until the whole side was done taking care not to spread over the openings or sides. This was left to cure. When it was dry but still bit tacky, I used a razor blade to cut and shave off the excess cloth from the edges. I did end up with a few runs when it was cured by a careful sanding with fine wet/dry paper soon cleaned them up.

.fuse glassed.jpg

.When dry I repeated the other side using the same process.

When this was cured, I lightly sanded the fused using fine paper, then applied a flow coat of resin over the whole fuse using a brush. When this dried it gave a nice smooth glossy surface over the whole fuse.

The next job is to sand the whole fuse using fine paper to prepare it for spraying with primer.

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