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Avon Sabre Spirit 78

CA-27 Sabre of Indonesian Airforec display team

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Steve Houghton04/06/2020 23:26:51
592 forum posts
442 photos

Pushing On

The wings are now sheeted and joined. Foolishly I sheeted the left panel before joining them together. I feared a poor join coming up, but thanks to the fabulous G&M wing jig I was able to pin and weight the panels into the jig absolutely flush together whilst the epoxy set, without being able to clamp the two R1s together:


Straighten up the Ply Right!

Having completed the remaining wing sheeting, I trimmed the wing seat in the fuselage to see how well the leading edge fitted against F4 before fixing the 5mm ply facing. It was a poor fit, and rather than sanding away at the wing I glued a shim of 1/16" balsa behind the ply. I could then dry fit this and sand away at the balsa shim to level it up against F4. When satisfied, I finally glued the ply into place. The shim is just visible here, needing about 1/16" on one side and virtually nothing on the other. This is the bottom of the wing:


Fattening Up

I bought 3/8" thick TE stock but found it to be slightly undersize for my wing. I laminated a layer of 1/32" balsa to the underside of the TE, where it wouldn't show. I then sanded the top of the TE to fit, rather than risk thinning the lamination to nothing and leaving a thin glued edge that would probably lift in places:


What, no torque rods?

The torque rods will need to be flush with the lower surface of the wing to cope with the bottom hinged flaps. I thought it best to fit the root TE first, and then cut slots underneath for the full length torque rod tubes afterwards. That way I was more likely to get the TE correctly aligned with the wing profile, having the full depth of TE to glue on. Here's the top view:


The slots have not yet been cut, until I finish the wing seating area.

(is it June already?!!)


Edited By Steve Houghton on 04/06/2020 23:27:34

Steve Houghton24/06/2020 23:30:10
592 forum posts
442 photos

Ah, The Torque Rods!

Nothing very exciting tonight. Just trying to convince myself that I am progressing. The flap torque rod slots were gouged out on the bottom of the wing using the traditional sharpened brass tube, plus a round file:


The ends of the root TE were reinforced with 1/32" ply for ding-resistance, and to support the torque rods:


The torque rods had full length plastic tube bearings which were buried just below the surface, allowing a finishing filler of 1/32" balsa to be inserted to cover the slots, after the application of a smear of vaseline to the sensitive rotating areas:


Chiselled ends to the rods, to minimise the risk of bursting out of the flaps:


Ball links on the rods, and kwiklinks to be used on the servo end, although not yet trimmed to length and fitted. I noted Phil's comment about possible trim changes from the horns rotating, but mine are far too stiff - would need brute force to twist them round.


Steve Houghton20/07/2020 23:08:15
592 forum posts
442 photos

Make Way

F6 has now been trimmed back to make way for the flap torque rods. I added a cross-brace after the hatchet work, to compensate for the removed rigidity:

2007_1701 f6_trimmed.jpg

Are you Seated Comfortably?

I followed other builders' suggestion of lining the wing seat. In my case I cut the fuselage sides back by 3/32" above the wing using Steve McLaren's idea of pinning strips of balsa to the wing to act as the trimming guide - not shown here. I in-filled the missing corners of the F14 keels to make them up to full height, to support the seat sheet:

2007_1702 wing seat.jpg

A little tirimming of the wing bolt plate to clear the torque rods, then I chamfered the bottom of F7 and added a 1/32" ply facing plate to protect the balsa fuselage planks:

2007_1703 bolt_plate_trimmed.jpg

Put on a Happy Face

Despite lagging behind most builders, I thought I'd put on a happy face with a cunningly shaped 1/16" ply load spreader plate under the wing bolts. I made mine the full width shown on the plan, aware that other builders have narrowed theirs down to fit within the under-wing fairing, still to be added:

2007_1704 bolt_spreader.jpg

I left a small gap at the back to allow for the addition of a final 1/32" ply facing when the fairing is complete:

2007_1705 wing_fairing_gap.jpg

The top side is left with a small shelf to be filled:

2007_1706 bolt_spreader_top.jpg

A single piece of 3/32" balsa filled the ledge nicely and didn't interfere with the wing seating:

2007_2001 rootinfill.jpg


I borrowed Dirk's idea of circular stand-offs on top of the wing bolt plate to prevent wing crushing:

2007_2002 boltstandoffs.jpg

I angled the stand-offs to suit the concave shape of the top of the wing:

2007_2003 boltstandoffs.jpg

Congratulations to those of you who have already finished (and flown!). I'm relieved we have been given a little more time, so I'm still hoping to see you up the Orme with a finished Sabre in due course!

McG 696921/07/2020 07:02:41
3450 forum posts
1319 photos

Very neat and tidy build, Steve. yes

... and no worries, I'm way behind you with my Dog build progress...

Cheers & keep safe


Steve Houghton21/07/2020 17:50:04
592 forum posts
442 photos


Thanks for looking in. I would say we're roughly neck and neck, although you've done more on the tail section of the fuselage.

Trying to keep safe - just ordered 200 face masks from Sarik, ready for the new rules for shopping only with a mask - bang goes the budget for my next balsa order!

Steve McLaren26/07/2020 20:54:34
265 forum posts
277 photos

Lovely neat building Steve. It's good to see so many different ways of doing things. Now that's a better way to do the wing seat. I should have done that! Have you created a little fillet fairing at the same time?

Steve Houghton28/07/2020 21:43:01
592 forum posts
442 photos

Hi Steve,

Thanks for you inspiration on this one, for using a template strip on the wing.

Yes, I followed other builders' fairing advice (Phil and Dirk, I think, but may have been others too), and left a lip over the rear 3 inches of the fairing to allow the building of a fillet. I've struggled to get my head around what shape each part of the wing fairing and fillets should be. It seems to take a long time for little progress, so will be glad to finish this bit.

Slight delay to the build at the moment, due to house decoration taking priority. My eldest daughter is assembling her first Ikea flat-pack tonight, so I'll try to encourage her to progress to model building if I can!

Phil Cooke28/07/2020 22:04:38
2666 forum posts
1858 photos

Steve - no probs with your build lag, between you and me we will be putting the Sabre Mass Build back into 2021 - I will be going to press shortly on this - a tough decision but with the current second waves brewing across Europe and such uncertainty still about travel its just not right to run the event half cocked and not enable a number of over seas flyers the chance to join us. There are a lot of builds still at risk of not being completed in time, myself included if im honest, so you are not alone!

Nice progress on the wing seat and fillets, yes they are quite tricky mine took far too long too!

Hope the Ikea work goes well!

Steve Houghton28/07/2020 22:54:39
592 forum posts
442 photos

Phil, Thanks for the rumour - I look forward to the public announcement!

Who knows, with even more time to build, and more builders able to participate and finish, this could be the 'massiest' mass build ever. I hope you bring your wide angle lense for the group photo!

Ikea desk now completed and looking good - ready for her 'not going' to University in the Autumn, and having to study her degree online from home.

Steve Houghton30/10/2020 20:53:26
592 forum posts
442 photos

Now, where were we?

After a short delay, work is continuing. I struggled with the shape of the underwing fairing and had to remove my first attempt, leaving some of the wing sheeting a little scratched. However, I ended up with this, complete with rust marks from the pins (which don't appear to be rusty!):

2010_3003 wing fairing.jpg

The Blender

To blend the wing trailing edges into the fuselage I inset a couple of triangular(ish) pieces of 1/16" ply, sitting flush with the fuselage planking. From the few underside photos I've seen of the Sabre, the outer edges of fairing pieces meet the trailing edge at roughly 90 degrees:

2010_3004 wing fairing.jpg

The ply pieces are level with the bottom of the wing, and roughly continue the underside profile of the airfoil:

2010_3005 te fairing.jpg

The plan is to build up the fairing on top of these ply platforms, and to bridge the step up to the 3/32" balsa wing seat, which I left oversize for cutting down later:

2010_3007 te fairing step.jpg

Hopefully, progress will be a little more rapid over the next few weeks.

McG 696930/10/2020 21:12:58
3450 forum posts
1319 photos

Hi Steve,

Glad I'm not the only one... angel

Struggling at the wing seat fairings and the TE fairing as well at the moment.

Quite a lot of sculpting/sanding for not to much satisfactory result... frown

But then, we'll get there, young man.

Cheers & keep careful


Phil Cooke30/10/2020 23:49:43
2666 forum posts
1858 photos

Yep, the little wing fillets are tough features on this one for sure, they've had a few of us scratching our heads and pondering... keep up the good work Steve - great to see you updating the blog!

Stay safe and well,


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