Help ! tailplane attachment

[jantar]

ZS-UDT work continues well but I have met a problem--can anyone help ?
Drawing no 7 (fuselage attachments) by nipper kits etc shows the three attachment points along the tailplane spar. The arrangement drawn DOES NOT WORK !!
Central attachment shows ( top to bottom) tailplane,F1093(what is this?) rubber pack E443 , fuse bracket,rubber (circular) packE442, washer? and stiffnut. Strut outer attachment shows (top to bottom) tailplane,rubberpackE442,washerF121NI and stiffnut. When you assemble like this there is a 9 mm gap between the tailplane and the rubber pack E443 !!! at fuselage... If you assemble with strut attach rubber pack BELOW the strut lug the gap mentioned above reduces to 2mm and looks more realistic. Is F1093 therefore a 2 or 2.5 mm pack of alloy ? and is the second assembly correct and the drawing wrong ? or am I going nuts? Whats all this rubber for?
Next I cannot differentiate between the top and bottom of my refinished tailplane ( nor can Alan Ayles) so have assumed it to be structurally symetrical and may be fitted either way up. Front attach bolt fits slightly better one way and I have treated this as a clue-----any views ?
Finally WING main attach bolts show 2 no 5/16 thin nuts locked. Seems a bit iffy. Would a nyloc or castle + cotter be better? and can I use them to hold down the instrument panel instead of original sticky foam? Help me sleep nights ! Jantar

[Pat Blenkinsopp]

Jantar
I dont have the drawings handy . I agonized over which way up the tale plane goes, when I recovered my nipper
but if my memory is working OK (less frequent these days!!!) I think there is a very slight greater curve on the forward
edge, ie aerofoil on one side than the other. This goes on the underside, ie like an upside down aerofoil.
Thats how I mounted mine, as most aircraft have a positive downward force on the tail plane.
Hope this is of some use.
What does everyone else think?
My tail plane fits OK as per the drawings ???
All the best,
Pat

[G-BLMW]

Hi Jantar

Don't panic, the tailplane is symetrical in section, I have a copy of an original Fairey avions tailplane assembly (sorry l'empenage)and shows it symetrical and that is how I built mine. The spar faces are plywood with the grain at 45 degrees so it does not matter which way up it goes. The aerodynamic bit (angle of incidence) is adjusted by the front mounting block and should be set to give 0 degrees 30 minutes positive incinence. In the pilots notes (maintenance section) there are a couple of drawings showing the assembly. I can PDF the info and send it to you but it shows the same assembly as Nipper Kits drawing. PM me your email address. I used the Nipper Kits drawings and if my memory serves me right I didnt have a problem. F1093 is a thin piece of Aluminium with a joggle and a couple of slots so you can slide in the underside tailplane to fuselage fairings. Question, is this an all new or a rebuild? Are the struts too long?
As to the spar holding down bolts and nuts again don't panic yes, two locknuts are correct, just make sure they are AGS and torque to 1.15 to 1.60 kgm (100 to 140 in.lbs). My wing hasn't fallen off yet I wouldn't recommend holding the instument panel with these bolts either their function is simply to attach wing to fuselage as designed. I attached the instrument panel brackets on strips of rubber araldited in place and that was 23years ago

Hope this all helps

cheers

Stuart

[G-ARBG]

See photos attached
David G-ARBG

[G-ARBG]

Another photo - do you have any witness marks from the top forward fitting to help you?

david G-ARBG

[G-ARBG]

Jantar,

Hope the pictures above help;

The assembly drawing is correct but if yours will not assemble as shown maybe you should measure your struts for comparison with others. The rubber is about 4mm thick (I use tap washers for the round ones-they don't need cutting out).

Have you any witness marks on the top of your tailplane to show which way up it was? the front fitting often leaves a mark or you may see the screw holes previously used for the fitting.

Wing attachment as drawn is correct (unless you have the later rolled threaded stud type).

The panel should be resiliently mounted on rubber strips. Do you have the panel brackets, and which panel are you fitting (there are two original types). Do you need any details?

david G-ARBG

[jantar]

Thanks to all you guys for the prompt replies. ZS-UDT is a rebuild of a slingsby T66 mk 3. Yes the struts are obviously too long to assemble as drg. Two solutions exist 1/ put the rubber washers below the strut lug also insert an extra 2mm pack on fuse bracket or 2/ (with hindsight) insert a 7mm pack on fuse bracket , a 5mm pack under the incidence block and the rubber washers (5mm) above the strut lug. Because hindsight never comes first I have used method 1 . The fit is perfect and there is enough flexibility to adjust the incidence. I am inclined to think the rubber is to allow incidence adjustment as I cannot identify any structural logic. Have fitted (again) all today and adjusted the incidence by ingenious means to 30 sec dead. I am now quite confident with this lot and am now puzzeled as to the fixing of the rear end of the lower alloy fairings--- I just cant see any ! Again thanks for the help and if anyone disagrees with my method 1 with sound reasons tell me before the accident !! No there were no witness marks at all---thick finish. Had my brain boiled getting my Hayes hydraulic cycle brakes to work until I had a revelation---but thats another story. Jantar

[Neil Spooner]

Hi,

Just a thought.....if the holes have been drilled slightly out of position thru the tailplane spar then that will give rise to the problems you have. On my a/c I have rubber washers above and below the tailplane spar, but to a thickness of about 8mm to make good the fitting. They are also not symetrical in order to level the tailplane with the mainplane, one side is about 6mm, the other about 8mm.

I would definately NOT use the wing bolts to mount the instrument panel. My a/c has wooden blocks glued to the main spar, then a rubber mount on that which attaches the inst' panel. Depending on the wing bolts you have, (some are studs with nuts both ends, some are bolts with nuts only one end, and some are drilled for a cotter pin. If you don't have a drilling for a cotter pin then a counter-lock nut is fine, but don't overtorque, and for "belt and braces" use a drop of locktite. These photos are pre-restoration, but I didn't change them much other than improved brackets.

Inst panel (2).JPG (829.72 KiB) Viewed 10248 times

Inst panel (6).JPG (827.01 KiB) Viewed 10380 times

To attach the front end of the panels around the tailplane I used an alloy bracket that was attached to the front of the wooden fwd tailplane mounting block. The bracket extended out to the sides, just two screws hold the top cover and the lower panels at the front. During the restoration I welded a couple of tabs onto the upper longeron for the rear lower screws.

Neil

[jantar]

Thanks Neil your replies are always informative. Found v.small hole under paint in rear ends of lower tail fairing plates so these were for a no6 woodscrew into tail soffit and I have done this. The tailplane fit now seems a very good fit so the mystery of the drawing remains. Slingsbys most certainly had jigs so differs in production see unlikely. Delusional draftsmen are more likely I will take measurements and publish them here so comparisons can be made. Your panel is well attached --- mine is not---yet. Tom H

[G-ARBG]

Jantar,

Should have included this with earlier shots above - shows fairings slotted in to 'joggled' alloy plate (F1093). Top and bottom fairings are secured at front with single self tapping screw each side into metal hoop. As a gliding person you will probably see that adding wing tape to front edge makes a nice secure finish.

Regards,

david G-ARBG