Mike - Perhaps you can explain why in the report the term, "/normal to the airflow/" rather 'than parallel with', or 'perpendicular to' the airflow is used. Is that a common reference in the UK? It just seems a little nebulous to me in understanding immediately upon reading the report, and it would seem sensible to think that normal would be in line with airflow . . . but then ours (US) is a lower grade society, after all !!
George ------------------------------------------------------------------------ On 12/31/2014 6:19 AM, Mike via KRnet wrote: > 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 > > > _______________________________________________ > 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 --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com
