Breguet Fauvette

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StephenB
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Re: Breguet Fauvette

Post by StephenB » 02 Mar 2019, 15:49

Wing ribs have been cut out after a false start whereby I realised half way through the starboard wing batch that my printer had produced them at it's default setting of 97%! Half a day and a bit of balsa wasted. Spruce spars and trailing edge spliced and all ready to go.

Dry fitted lower spar and ribs on the plan to check fit and now ready to start glueing up but I'm dithering over the build sequence which I think goes like this:

Glue ribs on to bottom main spar and lower aileron spruce spar, glue false leading edge and spruce trailing edge which will be packed up to suit.

Glue top balsa trailing edge in place, slot out root ribs and epoxy in place the wing joiner box, glue top main spar in place.

Webbing around the wing joiner box - epoxy in place at same time as the box goes in?

At around this point I need to remove the wing to get the bottom sheeting on but doubt it will be very stable so do I web the whole wing prior to removing and sheeting?

At which point should I seperate the aileron?

Wing dry fit.JPG

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RobbieB
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Re: Breguet Fauvette

Post by RobbieB » 02 Mar 2019, 16:28

Stephen,

It is preferable to get to the stage where you can add the top sheeting - that obviously includes all the false LE stuff, webbing etc while the structure is still on the board. This ensures the spar remains straight and doesn't bend.

To do the bottom sheeting the wing will, of course, have to come off the board and you will probably be quite alarmed at how twisty is is. This is quite normal and will be remedied once the lower sheeting is added. To do this, the wing must be placed back on the board, upside down and the structure supported with the correct incidences while you add the lower sheeting so you don't introduce any adverse twist into the structure. You can either do this by making full profile supports for the appropriate positions or use a wedge system as I usually do as shown below - just make sure the blocks and wedges are well secured and don't move.

top_sheeting.jpg
Once it is all dry the wing can finally be removed from the board.

It is of course, not actually necessary to buid a wing on a board at all:

wing_jig.JPG

StephenB
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Re: Breguet Fauvette

Post by StephenB » 02 Mar 2019, 17:04

Thanks Robbie. So, don't remove from the board untill the whole top surface is complete - sheeted, brakes installed, capping strips in place, leaving only the lower sheeting and cap strips to be fitted?

Then cut the aileron out?

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RobbieB
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Re: Breguet Fauvette

Post by RobbieB » 03 Mar 2019, 10:36

Just the top sheeting and as much of the TE as you can do with the wing on the board. Don't start cutting out for brakes and stuff until the lower sheeting is fitted and the wing nice and torsionally rigid. Detail like cap strips can be left until the wing is off the board.

The important thing is to ensure the wing is well supported once you have turned it over to do the bottom sheeting - once that is added the relative incidences along the wing are more or less set in stone.

How are you going to glue the LE sheeting on?

StephenB
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Re: Breguet Fauvette

Post by StephenB » 03 Mar 2019, 11:02

I would normally use PVA for the sheeting, pinning and taping to hold it in place, although in this instance with a spruce false LE I may have to fit the balsa LE prior to sheeting to give me something to pin to.

I like to use CA for the cap strips as I can hold them to the curve of the rib for the few seconds it takes to set - quick and simple.

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RobbieB
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Re: Breguet Fauvette

Post by RobbieB » 03 Mar 2019, 14:50

Stephen, to either glue down your leading edge sheeting with no false LE sheeting or the finished LE in place is not the best way to do it. You are likely to end up with wavy sheeting.
I would seriously consider a 1.5mm false LE glued on the nose of the ribs with the spruce reinforcing piece behind it. Sand the 1.5mm flush with the top of all the ribs and you are left with a nice straight gluing edge for the sheeting. You can then add the LE proper and plane and sand it to profile and the same to the underside of the wing when you turn it over. The LE proper doesn't need to be added until the wing is off the board with all sheeting added.

You can reduce the thickness of the LE by that extra 1.5mm if you want to but to be honest, I wouldn't bother (Scale Police alert!!!).

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Peter Balcombe
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Re: Breguet Fauvette

Post by Peter Balcombe » 03 Mar 2019, 16:15

Stephen,
I can’t recall what I did with mine, but agree with Robbie.
The plan shows a Spruce horizontal dummy LE spar, so if you have fitted that, just add a vertical balsa dummy LE on the front & sand flush to tops of ribs to give a glueing land for your top sheeting.
Once top sheeting fitted, turn over, support & sand lower edge flush prior to fitting lower sheeting.
Once top & bottom sheeting fitted, you can cut/sand sheeting back to the balsa dummy LE & fit the real LE.
Plane/sand the LE to profile. I generally do this by eye, but you can also use cardboard/thin ply LE profile templates.

BTW, I tend to use Aliphatic glue wherever I might need to sand the joint as this dries hard & is better to sand than either Cyano (too hard) or white glue (too gooey).

StephenB
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Re: Breguet Fauvette

Post by StephenB » 03 Mar 2019, 16:28

Thank you Robbie and Peter, that makes sense and I'll proceed on that basis.

StephenB
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Re: Breguet Fauvette

Post by StephenB » 23 Apr 2019, 16:32

The onset of fine spring weather severeley cut in to my build schedule (such as it is) as attention was diverted to non-modelling jobs outside, but the nagging thought of a partially finished wing eventually lured me back in to the workshop.

Spruce false LE fitted:

Spruce LE (1).jpg


Followed by the 1/16" upper trailing edege, and as advised I glued a 1/16" dummy leading edge on to the false LE to give the sheeting something to "land" on. The ply and balsa bracing was glued between the spars before the top surface sheeting was added along with cap strips:

Bracing.JPG
Topside.JPG


The airbrake aperture was then cut out and blade fabricated along with it's fibreglass control horn before mouting the servo in the in the D box After running the cables and checking the operation the servo was hot glued in position prior to sealing up with the lower sheeting. Aileron servo was similarly mounted:

Brake servo.JPG
Aileron servo.JPG
Underside.JPG

The underside was then sheeted, cap strips added, 3/16" sheet leading edge glued on and shaped before giving the near complete wing a sanding. Finally the ply root rib was fitted leaving only the wing tip to be shaped prior to glueing on, followed by the removal of the aileron.

Root ribJPG.JPG

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Peter Balcombe
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Re: Breguet Fauvette

Post by Peter Balcombe » 23 Apr 2019, 17:38

Looking very nice Stephen :)

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