A little science from English researchers in 1957 http://naca.central.cranfield.ac.uk/reports/arc/cp/0323.pdf but I'm sure there must be more recent published findings from elsewhere.
This suggests that a solid airbrake produces a bubble of reduced airflow behind the brake with airflow velocity fluctuations occurring around the edge of the brake which may cause vibrations to the structure. Perforations in the airbrake reduce this effect and were found to be more effective towards the centre of the plate than around the periphery. >From the Pprune forum, this explanation was offered: "Perforation reduces buffeting downrange of the speed brake, and reduces its interference with flying surfaces or the fuselage or wing or horizontal stab. Remember, the speed brake is there to create drag, but not undesirable flight characteristics. A perforated brake doesn't create nearly the airflow disruption, pitch change, or load on the surrounding and supporting structure that a solid brake might create. The number and placement of holes are important considerations, and part of the design. Holes permit a lighter structure that takes less of an airload, reducing not only the weight of the brake assembly but the force required to actuate it and the structure around it that must support the load. Remember that much of the time, that speed brake isn't anything but dead weight." Mike Mold Devon, UK. -----Original Message----- From: KRnet [mailto:krnet-bounces at list.krnet.org] On Behalf Of Mac McConnell-Wood via KRnet Sent: 31 December 2014 10:35 To: Herbert F?rle; KRnet Subject: Re: KR> Bellyboard The RAF Vulcan bomber had solid airbrakes-no holes (which enabled this 90 ton delta to descend vertically-..been there..) Mac On Wed, Dec 31, 2014 at 9:51 AM, Herbert F?rle <krnet at list.krnet.org> wrote: > > ....any Test,however it is performed,gives a lot of informations! The > aerodynamic principles are always the same ,also in the case of the hot" > bellyboard -drag" discusion.For me it's important the location of the board > and I think the place underneath the rearspar is very well chosen ( far > enough behind the CG ,to give the Kr a small amount of direction stability > like a dragchute and the waketurbulences does'nt hit the HS !) I 'm > convinced,a board without holes are more effectiv ( one big waketurbulence > produce more drag compared to many small ones). > I'm also think,a big advantage of the bellyboard is the fact ,that you can > lower the nose of the Kr on final for better sight( wether you have to push > or pull the stik )! > Herbert > German Kr builder . > > > Von meinem iPad gesendet > _______________________________________________ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options > _______________________________________________ Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org please see other KRnet info at http://www.krnet.org/info.html see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options
