Low pitching moment NLF airfoil with low sensitivity to bugs and dirt

Here is the Honda’s tech paper about the SHM-1 airfoil (which was designed for the Honda-Jet). The airfoil includes features which are not important on low speed low Reynolds number flight but it also has features which makes it ideal for lower speed concepts:

http://hondajet.honda.com/pdf/tech_papers/Journal_of_Aircraft_Vol40_No4_P609_P615_SHM_1_NLF.pdf

SHM-1 could be a good starting point for an airfoil for GA-use. The Re area for the SHM-1 is a lot higher than needed by GA, so it may not be directly applicable, but the ideology in the SHM-1 seems just what would be needed for also high speed high efficiency, long endurance GA aircraft, which in addition to having low drag and high Clmax also exhibits good behavior.

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    • everard
    • January 2nd, 2009

    Hi Karoliina,

    I stumbled across your blog on aircraft design and I recognised your name from another aircraft forum post – I think you were looking for Vari-Viggen plans – no, I only have a three-view which I can email if you’re interested?
    The main reason I’m writing is that I too am collecting design information and your reference to the Honda jet airfoil piqued my interest as I am attempting to design a cranked delta ultralight (to meet Australian CAO 95:10 MTOW 300kg min 10 sq mtr area, single seat) and am looking for a low pitching moment airfoil. In the past, I have dismissed laminar flow aerofoils as they tend to be unforgiving of imperfections and roughness – in particular insects accumulated on the leading edge.
    The wind tunnel results do fall roughly within the range I’m looking for (700,200 at tip – 4,700,000 at root @ approx 30 mph (48 kph) target stall speed).
    As I have only Windows O/S I will miss out on your design software 😦
    Anyhow all the best for the new year!

    Cheers
    Greg Everard

    • everard
    • January 2nd, 2009

    Hi Karoliina,

    I stumbled across your blog on aircraft design and I recognised your name from another aircraft forum post – I think you were looking for Vari-Viggen plans – no, I only have a three-view which I can email if you’re interested?
    The main reason I’m writing is that I too am collecting design information and your reference to the Honda jet airfoil piqued my interest as I am attempting to design a cranked delta ultralight (to meet Australian CAO 95:10 MTOW 300kg min 10 sq mtr area, single seat) and am looking for a low pitching moment airfoil. In the past, I have dismissed laminar flow aerofoils as they tend to be unforgiving of imperfections and roughness – in particular insects accumulated on the leading edge.
    The wind tunnel results do fall roughly within the range I’m looking for (700,200 at tip – 4,700,000 at root @ approx 30 mph (48 kph) target stall speed).
    As I have only Windows O/S I will miss out on your design software 😦
    Anyhow all the best for the new year!

    Cheers
    Greg Everard

    • Karoliina Salminen
    • January 2nd, 2009

    Hi,

    I have the Vari-viggen plans nowadays, I have also Long-Ez and Cozy MKIV plans. I am no longer that interested in them. The technology (box-style composite construction instead of thinking the structure as a monococue), philosophy of the construction method (only basic tools needed, easiness when there are no tools available) etc. is not very up to date these days (when the tools are not the problem, but rather time is) and that information is not very useful these days to a new design, and especially not useful if the original intent of Rutan is not followed – i.e. one is not supposed to do airshow quality with moldless composite method, I saw for example Burt Rutan’s handwork in Defiant which is in Hiller Aviation museum. It was a kind of eye opener. I realized what was the intent behind this method. It really shows what the moldless composite is – you are not supposed to spend your life with sanding it to perfection, you just finish it quickly and then move to the next project. That is the only way this method pays of in time, in all other cases (when better quality is targeted) it is very slow method.

    The plans are good educational material though even if I will never build any of the abovementioned designs, for e.g. how to do controls etc. But for construction method vacuum bagging, RTM infusion etc. is more like today’s composite technology and I mean high vacuum here, not lo-vac. I did not know that it is so easy and so inexpensive to do until I attended one course where we did that. The only part which is more expensive is the special sealant tape which is not available elsewhere than from composite suppliers.

    I am not sure how a laminar flow airfoil works in delta wing because the laminar flow is achieved best when the wing is a straight line rather than angled a lot (like on delta), might be that you would not be getting the full benefits. Anyhow, the SHM-1 seems to have good features also when contaminated with insects etc., it has good design philosophy for GA use.

    You can install VMWARE player to your Windows machine, get Ubuntu image built on it on one free online service and you can run the Ubuntu in a window and run the software there. It does not cost anything else than takes couple of gigabytes from your hard drive space.

    Cheers,
    Karoliina

    • Karoliina Salminen
    • January 2nd, 2009

    Hi,

    I have the Vari-viggen plans nowadays, I have also Long-Ez and Cozy MKIV plans. I am no longer that interested in them. The technology (box-style composite construction instead of thinking the structure as a monococue), philosophy of the construction method (only basic tools needed, easiness when there are no tools available) etc. is not very up to date these days (when the tools are not the problem, but rather time is) and that information is not very useful these days to a new design, and especially not useful if the original intent of Rutan is not followed – i.e. one is not supposed to do airshow quality with moldless composite method, I saw for example Burt Rutan’s handwork in Defiant which is in Hiller Aviation museum. It was a kind of eye opener. I realized what was the intent behind this method. It really shows what the moldless composite is – you are not supposed to spend your life with sanding it to perfection, you just finish it quickly and then move to the next project. That is the only way this method pays of in time, in all other cases (when better quality is targeted) it is very slow method.

    The plans are good educational material though even if I will never build any of the abovementioned designs, for e.g. how to do controls etc. But for construction method vacuum bagging, RTM infusion etc. is more like today’s composite technology and I mean high vacuum here, not lo-vac. I did not know that it is so easy and so inexpensive to do until I attended one course where we did that. The only part which is more expensive is the special sealant tape which is not available elsewhere than from composite suppliers.

    I am not sure how a laminar flow airfoil works in delta wing because the laminar flow is achieved best when the wing is a straight line rather than angled a lot (like on delta), might be that you would not be getting the full benefits. Anyhow, the SHM-1 seems to have good features also when contaminated with insects etc., it has good design philosophy for GA use.

    You can install VMWARE player to your Windows machine, get Ubuntu image built on it on one free online service and you can run the Ubuntu in a window and run the software there. It does not cost anything else than takes couple of gigabytes from your hard drive space.

    Cheers,
    Karoliina

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