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  1. Peter V

    Freewing construction

    THere's a new article you might be interested in: http://spratt.103.free.fr/images/medias/p9-13%20pdf%20Rev2.pdf Geffray hopes to sell plans by summer this year.
  2. Peter V

    34-50 hp Engines

    The JC Whitney one is a pretty cheap and basic example. If you were to spend some time investigating the options for your particular application you'd come across many different designs (there's a bunch here), as these things have been around for decades and are the standard way to alleviate...
  3. Peter V

    34-50 hp Engines

    If you don't want you exhaust breaking, try one of these: http://www.jcwhitney.com/webapp/wcs/stores/servlet/Product?storeId=10101&Pr=p_Product.CATENTRY_ID%3A2006251&productId=2006251&catalogId=10101 Flexible stainless exhaust tubing. :)
  4. Peter V

    34-50 hp Engines

    Outboards are ideal. Gobs of torque at low revs. Big job to convert though. Motorcycle engines are good in terms of technology and weight, but they tend to need high revs and the engine designs focus more on horse power instead of torque, especially the smaller displacement ones.
  5. Peter V

    Freewing construction

    But, if you do resolve to move the wings fore and aft during flight, what about the struts? I think the 103 has been designed around a very restricted performance envelope. The engine might be your only form of trim.
  6. Peter V

    Freewing construction

    Thanks for that report Duncan. Nice summary :) I've given a bit of thought to trimming a freewing ultralight. I was actually serious about moving the pilot seat back and forth :para::ponder: The pilot is by far the heaviest part of the aircraft, so employing a skulls boat sliding seat...
  7. Peter V

    Freewing construction

    Well, I'm no expert on freewings, just someone with an interest. Unfortunately, there arn't too many people with any expertise in the area. I'd talk to Bernard Geffray (spratt103@gmail.com) he designed the Spratt 103 and with 5 prototypes under his belt, he should be of some help, espcially if...
  8. Peter V

    Freewing construction

    That article was based on a study of the Spratt 107 and is particular to its 23112 airfoil. As long as the 103 has the same wing and hinge point, the article may apply. :nervous:
  9. Peter V

    Freewing construction

    Unless you're making a Spratt 107, that data won't be any help to you. You'll be needing the original NASA studies: Evaluation of the gust-alleviation characteristics and handling qualities of a free-wing aircraft http://ntrs.nasa.gov/search.jsp?R=733626&id=2&qs=N%3D4294919817 Investigation of...
  10. Peter V

    Freewing construction

    But how do you propose to move the pivot point? That diagram is intended to show where the best position is for your pivot point in relation to your maximum airspeed (plus you'll need some torsional resistance on the pivot to increase incidence and low speed performance). A freewing is very...
  11. Peter V

    Okay, new discussion: welding

    Oh no, now you've done it. :rolleyes: the two camps were at peace for months, and now you had to go and wizz on their 'fire'. :gig:
  12. Peter V

    Okay, new discussion: welding

    Little trick with aluminum: run your torch over it with the oxygen off to make it sooty. By some freak of coincidence, soot burns off at exactly the right pre-heat temperature for Aluminum, so you'll know when to stop heating and not burn holes in it. :)
  13. Peter V

    Okay, new discussion: welding

    It's all about that flux. Aluminium needs to be oxide-free to weld, but it oxidises in under 5 seconds. The flux acts as a cleaning agent. Not sure it would be much of an O2 barrier as in stick welding. But it must be doing something, because the gas from your torch is not inert enough on it's...
  14. Peter V

    Anyone interested in making aviation history?

    Those annoying laws of physics are the main restriction on speed of light travel. There are only two things faster than light; shadows and patterns, and neither take passengers.
  15. Peter V

    Header tanks scare me...

    Actually there little harm in gas hitting exhaust manifolds. It evaporates quicker than it can heat to a combustible temp. This happens to me a bit too often when I'm half asleap fueling my motorcycle. It's air cooled, so gets mighty hot. Fuel running over the engine gets instantly vapourized...
  16. Peter V

    Bizarre Homebuilt

    There would be a few factors. Firstly mounting your wings on a single pivot would involve prohibative stresses for any sizable aircraft. Also, it would be a bore to fly recreationally. No aerobatic ability at all. Another problem is getting the engineering right. But the benefits are...
  17. Peter V

    Bizarre Homebuilt

    Oh, and the website: http://spratt.103.free.fr/spratt103_english/welcome.htm
  18. Peter V

    Bizarre Homebuilt

    It's still under development. The photo is misleading. Here's the land based version: I believe that the seaplane version will require more power than it was tested with (25hp) I definately want to build one, based on its looks, cost and the fact that a control wing makes a lot more sense...
  19. Peter V

    Bizarre Homebuilt

    Here's the most ultralight thing on water. It's a control wing, so the fusalage is always level and it sits on a pair of surfboards. Like a mosquito on water. It doesn't displace.
  20. Peter V

    exhaust pipe drag

    The Lycomings are commonly turbo charged - the engine is so basic and mild, that all manner of improvements can been done to them. The turbo will add at least 20hp at sea level. Take-off and climb rates will benefit, but there'll be little advantage at cruise. But, I don't think the Grumman has...
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