marcov

Hmmm, best study aeronautical engineering before messing with wings. Extending wings will significantly change spar loads, drag, stall speed, Vne, and importantly the pitching moment of the wing which can result in reduced or insufficient elevator authority at various speeds. Roll rate would reduce and rudder size may no longer be appropriate as differential aileron drag on outer wings is higher and requires greater rudder force to balance (note large rudders on gliders). So the risks are: damaging or breaking the spar, not having enough power from existing motor to have sufficient climb rate to safely depart(due to increased drag), structural damage from unknowingly exceeding a now reduced Vne, and not having elevator authority(usually as speed increases), yaw instability plus maybe more.

 

Shortening wings can have similar and unexpected side effects, surprisingly it can increase drag for a given airfoil as a higher angle of attack is required to generate sufficient lift. This will bring the wing further up the L/D curve into an unsafe zone- as you noted increased stall speed. Increased cruise speed would only occur if you have sufficient HP from the engine as power requirements increase exponentially with speed.

 

Do lots of study or hire a professional- I have studied this extensively as I am designing a similar change. I am not a qualified engineer and there may be additional issues not noted. Tread carefully.

 

 

The flaperons were set incorrectly, with some downward droop. When he got the ICP jig to set them properly, all came good.

Great news. Thanks for letting me know.

 

 

Today the weather was good and we were able to fly the Savannah VG.Previously, we had set the flaperons with the ICP tool.

The change in the plane is great, now it flies perfectly level.

 

Many thanks to all, especially to John Gilpin.

Hi, Id be very interested to discover what the problem was and how it was solved. Thank you in advance. Cheers

 

 

As a textbook warrior, I would expect that removing slats and installing VG's may move the centre of lift of the wing slightly rearwards. I would start with basics. recheck CG, as it may have been near forward limit which worked OK with slats, but now with CL moved rear, may be out of CG range. As you suggested other culprits could be flap setting, elevator trim/incidence setting or engine incidence. Running out of elevator authority at low speeds could be serious. Good luck and please tell us what you discover.

 

 

Hi Marcov, I see we are Neighbours in a sense.I fly out of Lismore and are you flying at the moment ?

I have not flown GA for many years. Last in the air in paragliders and hang gliders last year. Looking for something with stronger landing gear Lol. My project will likely fly out of Lismore or Evans Head. Im based near Alstonville.

 

 

if you've got the skills, wouldn't you be better off buying an incomplete project?

Yes, maybe, but the aircraft I'm considering has been written off by hail damage(dented upper surface of wings). I was "simply" going to build new wings. Someone suggested I cannot re-register because it has been written off. I just want to check. Price, aircraft type and equipment levels are unbeatable.

 

 

My Savannah S model rebuild Blog this one didn't look very pretty on the trailer on it's way to it's new home, BUT now starting to breathe again. Take a look at this thread Marco and welcome to the forum. You could message Mark about his experience.

Thank you for the lead. Has anyone done a composite craft repair?

 

 

Hi All,

 

Like many, my dreams are bigger than my budget. There are many damaged aircraft for sale on the market here and overseas.

 

I have an engineering background and a machine shop with composites experience.

 

Is it possible to repair /rebuild and more importantly re-register a written off ultralight or light aircraft in Australia? Id be happy to have it as experimental under the 40 hour test rule.

 

Cannot seem to find reliable information on the subject.

 

Any reliable comments with references or direct experience are greatly appreciated.