Rans S6: 390kg to 450kg upgrade

[Bill Scott]

Being a simple soul, I don't understand the need to change the flaps & ailerons on my S6 as part of the upgrade.

The upgrade requires replacement of the original flaps with a broader chord towrds the wing root, for the later constant chord type.

The original flaps on my aircraft would(?) be more effective as they must have almost twice the surface area.

I thought that the stronger struts would have been sufficient and that the new narrow chord flaps are not going to make a major difference.

Perhaps somebody can explain the aerodynamic rules that dictate this?

[gasax]

I'm guessing - it could be that the imposed loads from the larger surfaces impose just a bit more force than the spars can comfortably withstand - given that they are carrying more weight from the uprade.

[Bill Scott]

Thanks Pete, I did think it might be along those lines. However, I can't see why the flaps have to be operating, rather than fixed? I can imediately think of at least one other 450kg microlight which has no flaps.

[gasax]

That option would I guess have to go to Francis, but with them locked in the up position you would think all should be well.

[Tony Harrison-Smith]

Bill, usually the only reason for the flaps on a microlight is to get the stall speed down to the maximum specified (35 knots if I remember correctly). When you enable the Rans to fly at it's new all up weight, the stall speed might be too high without the flaps.

[Bill Scott]

Cheers Tony,
That indicates that keeping the original flaps & ailerons would mean the stall speed would be ok so far as microlight requirements go.
Then we just need to know if there is any specific reason for fitting the narrower constant chord ones instead.... Wing loading?