orion
R.I.P.
One of the drawbacks of curiosity is that it can lead you down tangential paths, distracting you from the work that you should actually be doing. We touched upon Jerry Blumenthal's Raspberry in the Facet Opal thread - the subject sort of struck a curious chord with me so I decided to follow this investigation a bit further in order to see if the idea can be expanded upon and maybe configured in such a way that it could make for a small, fun and well performaing airplane.
Like the Opal, the Raspberry is a flying wing, sort of configured like a planck but complicated a bit by the extensive forebody, which provides a significant amount of lift during cruise and the more unpredictable vortex lift, at higher angles of attack. To the best of my knowlege, there has been no real design work done on this layout and as such, the isometric drawing is the only basis that we have for any level of investigation.
While certainly attractive, the drawing does have a number of items that could be considered problematic and as such, need to be addressed in the derivation of what is hoped to be a viable configuration. The first of these is the location of the prop - it is rather high on the body and so it would be expected that the airplane's trim would be significantly affected with changes in power. The first configurational issue therefore is to lower the prop so that it sits somewhat nearer the mass center.
Given also the issues of disturbed air flow and propeller behavior, it will be beneficial to move the prop aft a bit so as to sepeate it from the effect of the wing and/or fuselage. This also introduces a secondary issue, cooling air - for best prop performance it would be best if the cooling air exhaust would not impinge on the prop. This means that the cooling exhaust (as well as engine exhaust) will most likely have to be ducted out the bottom of the fuselage, below the prop disk.
The body volume is also of issue. Although the layout looks sufficient, trying to draft a shape using the iso as a guideline quickly reveals that the body may lack cockpit volume for reasonable accomodation. If the body is shallow on the bottom, this would require that the pilot sat in there more like in a go-cart, with his butt and heels at the same level. This is extremely uncomfortable for any length of time. Ideally, the butt should be at least six inches higher than the floor. Given the floor's structural and geometric requirements, the body will need quite a bit of depth by the time it reaches the cockpit.
Another problem encountered in the attempt at configuring this airplane is that the iso is more of an artistic interpretation rather than a technical one. Although basic proportions can be picked out, no direct correlations can be made and so the derivation of the configuration needs to be approached with only the most basic guidelines.
So, for those that haven't seen it, below is the original drawing, copied from Jerry Blumethal's page at the TWITT (The Wing Is The Thing) web site.
Like the Opal, the Raspberry is a flying wing, sort of configured like a planck but complicated a bit by the extensive forebody, which provides a significant amount of lift during cruise and the more unpredictable vortex lift, at higher angles of attack. To the best of my knowlege, there has been no real design work done on this layout and as such, the isometric drawing is the only basis that we have for any level of investigation.
While certainly attractive, the drawing does have a number of items that could be considered problematic and as such, need to be addressed in the derivation of what is hoped to be a viable configuration. The first of these is the location of the prop - it is rather high on the body and so it would be expected that the airplane's trim would be significantly affected with changes in power. The first configurational issue therefore is to lower the prop so that it sits somewhat nearer the mass center.
Given also the issues of disturbed air flow and propeller behavior, it will be beneficial to move the prop aft a bit so as to sepeate it from the effect of the wing and/or fuselage. This also introduces a secondary issue, cooling air - for best prop performance it would be best if the cooling air exhaust would not impinge on the prop. This means that the cooling exhaust (as well as engine exhaust) will most likely have to be ducted out the bottom of the fuselage, below the prop disk.
The body volume is also of issue. Although the layout looks sufficient, trying to draft a shape using the iso as a guideline quickly reveals that the body may lack cockpit volume for reasonable accomodation. If the body is shallow on the bottom, this would require that the pilot sat in there more like in a go-cart, with his butt and heels at the same level. This is extremely uncomfortable for any length of time. Ideally, the butt should be at least six inches higher than the floor. Given the floor's structural and geometric requirements, the body will need quite a bit of depth by the time it reaches the cockpit.
Another problem encountered in the attempt at configuring this airplane is that the iso is more of an artistic interpretation rather than a technical one. Although basic proportions can be picked out, no direct correlations can be made and so the derivation of the configuration needs to be approached with only the most basic guidelines.
So, for those that haven't seen it, below is the original drawing, copied from Jerry Blumethal's page at the TWITT (The Wing Is The Thing) web site.
