Phil W's Sabre Build Blog

[Phil Willett]

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]

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 ask

Pete

[McG 6969]

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

Cheers

Chris

[dirk tinck]

Welcome and good luck Phil ,

[Phil Willett]

Thanks for the instructions. Here are some early photos;

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

[Phil Willett]

Then I prepared, joined and trimmed the lower skins

[Phil Willett]

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)

[Phil Willett]

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.

[Phil Willett]

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

[Phil Willett]

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?

[Phil Willett]

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!!

[Andy Meade]

Proper scratch building, good work

[Phil Willett]

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

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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.

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.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.

[Phil Willett]

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.

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.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.

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[dirk tinck]

Good progress Phil !Any idea for the sheme yet ?

[Phil Willett]

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.

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

Phil

[Phil Cooke]

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 Willett]

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.

.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.

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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.

.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.

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.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.

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

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Now the remaining fuse planking was finished off.

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

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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.

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

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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"!

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.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.

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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.

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So its coming together now.

cheers Phil

[Phil Willett]

Hi, a bit more progress this week,

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.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.

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.

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 Willett]

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.

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.The finished wing looks like this.

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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.

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.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.

[Phil Willett]

A bit more progress for me...

The fuselage is now sanded and primed.

. Im still waiting for Vortex to supply me the canopy so I cant really move further forward anymore on the fuse because there is still some balsa work to do the fit the canopy. So I've started to finish the stabilisers and wings. Here are the finished stabilisers.

Covered in film and sprayed yellow/black stripe.

I made 4 servo hatch covers using ply sheet with a plastic tube cut and glued over a slot for the linkage, and reinforced with glass/epoxy then sprayed silver to match. Couple of mini screws used to secure it down and it looks ok and should protect the linkage quite well.

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[Phil Willett]

And the wings now finished, with ailerons and flap hinges glued in final place and linkages adjusted to suit.

The wing is covered in grey film with yellow/black stripes sprayed over. The USAF star has been home printed on sticky back vinyl with my ink jet printer, given a thin coat of clear lacquer (I used Halfords automotive clear lacquer) and then stuck in place. I next plan to add panel join lines with a permanent marker pen and the give the wing a thin coat of clear varnish over the lot to waterproof them.

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I have also made a simple cockpit arrangement seat and pilot. sprayed and ready to fit when I get my canopy.

On the delayed Vortex canopy problem, I have had no response from Vortex to my many emails, so I wrote a letter to them last week and received a reply by email from Steve. He tells me they are having problems sourcing the thin plastic material used for the canopy as the supplies have been gobbled up by the NHS for use in making the visors for covid NHS staff. Hence the delays. He hopes to get a supply soon and will make the canopy for me as soon as he can. So as far as I'm concerned the plastic is being put to a more important use than my canopy and I am happy to wait until he can manufacture it.

Cheers,

Phil

[McG 6969]

Great job, Phil.

I wish I was that far with my progress...

I've been reading that Steve/Vortex had now just received a new stock of PETG.

I guess you will have your canopy soon now.

Cheers & keep safe

Chris