Pilatus B4 build started

[chiloschista]

Hi ensemble,

I did start the build of a 1:4 Pilatus B4, but am blocked at a stupid detail, so let ideas flow, please.

General geometry is already done and airfoils selected. It is planned without spoiler and with ailerons and flaps. So this is not in question.

The problem arise because the original airfoil is a Ritz3-30-14 (so 14%) and the selected airfoil is at 10%: a huge difference.

The first 10cm of wingspan are devoted to match the Karman. Now if root and tip airfoils of the first 10cm are set with the chords at same level I get a straight leading and trailing edge, but with some problems to position the spar and the wing joiner. The top  of the wing is not straight instead. Not very beautiful, but not so noticeable and of secondary importance.

If the tip airfoil of the first section is raised to have a straight top of the wing and an easier work related to spar and wing joiner, I get an inclined leading and trailing edge, which force to start flaps at 10cm and is not beautiful either. Probably more noticeable.

I would not increase the span of the first section, if possible.

I planned a fiberglass joiner of 16mm, but at this point am wondering if it would not be easier to swap to 14mm steel or titanium. I guess 14mm fiberglass could be at the limit, for hard aerobatics.

As a comparision I have a Salto of 380cm with a 12mm steel joiner which never showed any sign of stress, even after a crash (yes it is still flying ...).

Thanks for any ideas!

Ric

[oipigface]

Hi, Ric!

When you say the original airfoil is Ritz3-30-14 do you mean full size, or have you bought a fuselage with moulded karman with this section? If the the former, why not just modify the design of the karman to match the 10% airfoil? If the latter, then some surgery may be an alternative to trying to match two unmatchable sections.

 

[chiloschista]

Hi John!

Yes, the airfoil is referred to the model. The original was a five digits NACA.

I did not even think at your idea, thanks for posting it!

That could work, but I'm worried reducing a 14% airfoil to a 10% one, with a completely different shape. There are 5-6mm to remove, both top and bottom, but the wing would be totally clean. I'm worried because it is a very beautiful Rosenthal fuselage, so no room for experimenting.

Ric