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Joining the wings sig 1/4 scale cub


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Hi,i am building a sig piper cub 1/4 scale now got as far as joining the left wing to the centre section,problem is there is a gap at the back between the two wing ribs i am about to glue ,and the wing looks flat , not much dihedral, should i use epoxy resin araldite to fill in gap or put some balsa in there and block the wingtips up for correct dihedral

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Danny,i believe the model cub flies better with a bit of dihedral.I did take some photos but couldnt get them off my iphone on to here,will try again,much easier on my laptop.

John ,im still at it still building,that sounds a better idea better than filling it with araldite,should i join the left hand wing to centre section with my wood glue (green bottle) or araldite,doesnt seem strong enough to me,needs strengthening,i suppose the struts may help a bit.

Hows your cub coming on?

Chris

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IIRC the dihedral is 1 degree but there is definitely some on both the full size and this model. The Sig online instructions (.pdf download) confirm this and the method by which the angle is set:

Slide the W1/W1A rib back onto the Center-Section. Now place the Center-Section against the end of the wing panel by inserting the tip of the Front Dihedral Brace into the opening in the rib W2 and setting the W1/W1A rib onto the bottom spars and sheeting. Note that the center-section should not set flat against the building board - the difference between the openings in the W1 and W2 ribs automatically sets the proper dihedral angle. Once satisfied with the fit, glue the bottom of the W1/W1A rib onto the bottom spars and sheeting. Leave the Center-Section in position while the glue dries so that it holds the W1 rib at the proper angle.

It isn't immediately clear on a quick scan of the instructions how the ailerons articulate - my 1/4 scale Cub has Frise ailerons like the real thing and needs surprisingly little rudder to co-ordinate turns.

Edited By Martin Harris on 30/06/2018 10:27:00

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Thanks John I shall probably stick with the wood glue,I think the dihedral was 1 1/2 inches under each wingtip.

Thanks for the download instructions Martin not sure if I have got this wrong,both wing ribs for joining are at 90 degrees,should the wing rib w1 have been glued later,got a photo now at last not sure how I got it here though.image.jpg

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I believe that one wing is permanently joined to the centre section and the other plugs in when assembling for flying?

I think what they are saying is that the dihedral brace is a tight fit in the holes in the ribs and the dihedral is self-jigging...i.e. if you hold the centre section down to the board, the tip should be clear of the board and will just need supporting at its natural position while the glue is setting. I would measure this "natural" position and double check that it is the same for the other wing before gluing the permanently joined wing.

I'm lucky with my Cub as the struts are fully functional and set both the dihedral and wash-out.

Edited By Martin Harris on 30/06/2018 20:35:27

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I have pushed the wings up tight to centre section,put some heavy batteries on the centre section,which gives me just under 1/2 an inch under each wingtip,will block up wing tips at 1/2 inch before glueing.

so that works out at 1 degree of incidence according to my calculator.will get my evostick wood glue out tomorrow and glue it up.

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