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Outdoor Free Flight Forum => Proven Techniques in building, trimming and flying models => Topic started by: MentalDekay on April 30, 2014, 05:26:54 PM



Title: Building Undercambered Wings
Post by: MentalDekay on April 30, 2014, 05:26:54 PM
So I was thinking I might try to build a KK Senator, based on the universally positive reviews/opinions I've seen on it.  However...

The wings have an undercambered shape that doesn't look like it lends itself to how I've usually built flat-bottomed wings.  So the question is: How would I do it? Do I get the ribs perpendicular to the board, attach all the top longerons (I don't think that's the right name for them, but I can't put a name to it now) then flip the wings over and do the bottom ones?  Is there a better way??

-desmond


Title: Re: Building Undercambered Wings
Post by: billdennis747 on April 30, 2014, 06:03:57 PM
Slot and pin down the TE
I think you can pin one of the lower spars flat to the board (no pins through the spar though!)
Add the ribs
Use a straight edged piece of eg 1/4" sheet to push the LE into the front of the ribs and glue (keeps it straight)
Add the top spars then remove and add the lower spars
Tip up the centre section the right amount and build on the tips.
How do others do it?


Title: Re: Building Undercambered Wings
Post by: applehoney on April 30, 2014, 07:39:09 PM
Kind of similar though I do not lay down the bottom spar first.

A piece of 1/4" pinned to plan at LE - on the middle line that denotes the top of such.
Pin down slotted TE
Insert ribs, front up to the 1/4", rear fitted into TE slots.
When dry, slot ribs for upper spars (some may pre-slot ribs but I never so so)  using steel straightedge and new razor blade and glue spars in place
Pin panel end ribs to board at point of contact, remove 1/4" and glue LE stock into place in notched ribs, secure in place with pins against it
When dry, unpin, turn over and using steel edge, slot ribs and  add lower spars

has worked fine for a half dozen Senators over the years


Title: Re: Building Undercambered Wings
Post by: gossie on May 01, 2014, 12:56:47 AM
I've built five of them and they have all flown off the board, and even flown away.......under DT, so make sure you either tip the stab. down 80 degrees or use a tip up at the front wing.

Built much the same as Bill and Jim.

 I make all the ribs ready to go.  I slice light 1/16th well sanded, to the thickness or is that width? of the rib, then cut the strip off to the exact length......don't forget to include the little bit extra that slots into the TE.  Pin the required number of blanks together, then carve to shape with a very sharp pocket knife.  Sand to exact shape.  Mark where the 1/16th square spars go, and with a 1/16th thick file, file into the ribs 1/16th deep.  Pins out and the ribs are ready for use.

TE is shaped when its on the sheet, then stripped off to the correct width, and slots put in with a 1/16th thick file.    LE is easy.  1/16th spars I suggest from hard springy sheet.
I make the flat center section first, slot in the top spars, lift it off the board/plan next day when it's all dry and slot in the lower spars.  Then build the tips.   Center section held down with not too heavy weights, then tips glued at the dihedral angle. Add gussets etc.

Stab. is built as per the wing.  Fuselage sides first.   Build a little down thrust and right side thrust into the front of fuselage when putting it together.

Hope that helps a little. :)


Title: Re: Building Undercambered Wings
Post by: billdennis747 on May 01, 2014, 01:42:54 AM
I've built five of them and they have all flown off the board, and even flown away.......under DT, so make sure you either tip the stab. down 80 degrees or use a tip up at the front wing.

Does nobody use the tip up fuselage, split behind the motor peg, as described by Ian Davitt?


Title: Re: Building Undercambered Wings
Post by: gossie on May 01, 2014, 03:40:55 AM
I've built five of them and they have all flown off the board, and even flown away.......under DT, so make sure you either tip the stab. down 80 degrees or use a tip up at the front wing.

Does nobody use the tip up fuselage, split behind the motor peg, as described by Ian Davitt?

I'm sure some do, but I prefer the tip down tailplane.  I guess to each his own.

As mentioned I did lose two of them, but since using plenty of angle they have come down okay.


Title: Re: Building Undercambered Wings
Post by: MentalDekay on May 01, 2014, 10:44:04 AM
Thanks for the advice everyone.  I'm confident that it will help me greatly.  And who knows maybe, by the time I've built 5 of them, one will go OOS.

-desmond