Beech GB-2 on display http://aeroweb.brooklyn.cuny.edu/specs/beech/gb-2.htm Mark, I like planes too!
Want to keep your WHOLE PAYCHECK? PLEASE VISIT http://www.fairtax.org ----- Original Message ----- From: "David Shugarts" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Wednesday, March 19, 2008 9:17 PM Subject: Re: catalina27-talk: Keel Fairing > > > > > If you absolutely must have a GB-2, it will be very hard to find, but if you > look for essentially the same aircraft with a different engine and call it a > Staggerwing Beech, you will have reasonably good luck. Walter Beech called > it a Traveler when he brought it out in 1933 and it was in production > through the war, when the Navy called the D17 a GB-1 or GB-2 and gave it > slightly different R-985 engines. In other military branches, it was the > UC-43. > > Here is a D17S for sale in California: > > http://www.eaa1279.org/Member%20Photos/MPhGrangerHaugh/MPGrangerNC582ForSale > /NC582ForSale.htm > > This D17S is for sale in Australia: > > http://www.staggerwingforsale.com/ > > And you are sure to find more. > > For reasons that might have had to do with military service, I have never > seen a Staggerwing that wasn't either bright yellow, or bright orange-red, > like a Ferrari. > > Regards, > > Dave Shugarts > > > > > On 3/19/08 9:11 PM, "nliner" <[EMAIL PROTECTED]> wrote: > > > Since we are over to airplanes, does anyone know where a Beech GB-2 may > > be found. > > My father-in-law owned one the the past and is wondering where it might > > have gotten off to. > > Did not if Dave S. was familiar with this model. > > > > David Shugarts wrote: > >> Hi, Dave-- > >> > >> Now it's getting interesting. I just wish we had a boat designer to chime in > >> here, as we are way over on the aviation side of this thing, I think. > >> > >> As an aviation editor for about 15 years, I got to hop into a lot of > >> aircraft, including the 177RG, which I liked a lot. Our company plane was an > >> M20J and I also did aerobatic training in an 8KCAB, which has the > >> "semi-symmetric" wing airfoil because they figured you'd want to be inverted > >> a lot. (There's one of those still missing, with Steve Fossett in it.) > >> > >> Regards, > >> > >> Dave S. (II) > >> > >> > >> On 3/17/08 2:32 PM, "David Shaddock" <[EMAIL PROTECTED]> wrote: > >> > >> > >>> Hi, other Dave S.-- > >>> Your hunch is correct; laminar flow in water disappears at a pretty low for > >>> the waterline lengths and foil lengths we're discussing. After I wrote my > >>> comments earlier, I went back through the thread and found the link to Bryon > >>> Anderson's excellent article, which explained everything I was trying to > >>> cover in a better fashion, with diagrams too. He mentions 5 knots as the > >>> approximate speed at which we lose laminar flow. That's oversimplifying, > >>> but it gives you an idea. But laminar flow has a lot to do with the NACA > >>> profile--some profiles intentionally move the maximum depth aft in order to > >>> maximize laminar flow; the idea is to keep the lift working for you as long > >>> as possible. My last plane was a Cessna 177RG, which had a laminar flow > >>> wing designed to keep the flow 'attached' for 70% of its surface or better > >>> at speeds of about 170 mph. It took a long time getting off the ground, but > >>> was incredibly efficient in the air. It was very different from my friend's > >>> 175 (we traded for a while so he could get his commercial license), which > >>> had a fat high-lift wing that got you off the runway in a third of the > >>> distance but only provided 2/3 the top speed for the same power and fuel > >>> burn. > >>> > >>> Just because a flow goes turbulent, we're still interested in it and it can > >>> still perform some useful work. Besides, it's kind of a necessary evil; you > >>> can't just provide the part of the foil that gives you laminar flow and then > >>> remove the rest <grin>. The whole profile works together. > >>> > >>> Now, you mentioned vortex generators... They sell dimpled surface material > >>> for airplanes to put on the surfaces where the flow starts to detach, under > >>> the theory that the dimples (like the ones on golf balls, except standing > >>> proud of the surface) generate mini-vortices that help keep the flow (albeit > >>> turbulent) attached. Makes me wonder what this would do on the aft faces of > >>> a keel. I notice my BMW has raised bumps all over the edges and strut for > >>> the side-view mirrors, to cut wind noise by keeping the flow attached so it > >>> can't escape and whistle. > >>> > >>> But let's talk for a minute about porpoises. Capable of 25 knots > >>> underwater, and without a turbulent boundary layer... I guess they don't > >>> understand Reynolds numbers. Apparently they have a paper-thin outer skin > >>> with a thin spongy layer below that covering their real skin. One theory > >>> says they can detect turbulence and adjust their body shape to reduce it by > >>> controlling this soft layer. Dr. Kenneth Davidson studied them heavily and > >>> figured their speed was more due to their streamlined shape and the smooth, > >>> oily skin, but later research does suggest that the softness is apparently > >>> as important as the skin. But I wonder why my inflatable isn't quicker... > >>> Anyway, since I don't see a mechanism for the porpoises to control this fat > >>> layer, maybe it's a passive thing. I don't think I'm ready to plaster my > >>> keel with neoprene to try it out, but it makes me wonder if the flexible > >>> layer couldn't react to impending turbulence and change shape just enough to > >>> keep the flow attached. > >>> > >>> Dave Shaddock > >>> > >>> -----Original Message----- > >>> From: [email protected] > >>> [mailto:[EMAIL PROTECTED] On Behalf Of David Shugarts > >>> Sent: Monday, March 17, 2008 12:14 PM > >>> To: [email protected] > >>> Subject: Re: catalina27-talk: Keel Fairing > >>> > >>> > >>> > >>> > >>> > >>> Hi, Dave-- > >>> > >>> That's all true, more or less, but what I have a strong hunch you will find > >>> is that these foils do not give us laminar flow at our speeds and angles of > >>> attack. > >>> > >>> In other words, going to windward, I believe you would find that we are > >>> nearly always in some form of turbulent flow, at some point in the keel > >>> section, unlike aircraft, where we do get laminar flow most of the time, > >>> over most of the wing. > >>> > >>> (BTW, the ratio of Reynolds numbers is 13:1, water versus air. Don't hold me > >>> to it, but I believe this is the practical consideration when modeling > >>> foils.) > >>> > >>> These days, there are inexpensive underwater cameras that could perhaps show > >>> us what our keels are doing. It isn't a fair comparison, but I get a good > >>> look at my rudder and it always looks like it's in some degree of turbulent > >>> flow going to windward. (I have the old rudder, which is an anachronism.) > >>> > >>> Regards, > >>> > >>> Dave S. > >>> > >>> PS-I am very familiar with the root versus tip design concept for beneficial > >>> stall behavior in aircraft, and we could throw in wing twist if we wanted to > >>> complete the picture. And let's not even get started with Whitcomb winglets, > >>> stall fences and stall strips, not to mention vortex generators. > >>> > >>> > >>> On 3/17/08 12:31 PM, "David Shaddock" <[EMAIL PROTECTED]> wrote: > >>> > >>> > >>>> The Cessnas and other aircraft sometimes use different foil shapes at the > >>>> root and tip in order to make sure the inner part of the wing (closer to > >>>> > >>> the > >>> > >>>> fuselage) stalls first, making the aircraft dive and regain speed while > >>>> still providing some control out at the wingtips to avoid a spin. This > >>>> isn't an issue with sailboats. > >>>> > >>>> But our keels can still stall--the keel provides windward lift if it > >>>> > >>> doesn't > >>> > >>>> stall, at the expense of some leeward slip. If the keel stalls, you lose > >>>> the lift and you see a lot more leeward slip/skidding. > >>>> > >>>> There are so many NACA profiles that it's hard to imagine anyone using > >>>> something that's NOT a NACA profile--they have tested and published > >>>> > >>> results > >>> > >>>> for hundreds of them, with some having only a tiny variation from others. > >>>> But those tiny variations can make measurable differences, especially > >>>> > >>> since > >>> > >>>> we're operating our profile in a medium 800 times denser than air. I have > >>>> > >>> a > >>> > >>>> book I used for aircraft design purposes that's got everything they had > >>>> published through about 1990. At any rate, selection of the ideal profile > >>>> for a sailboat involves knowing the aspect ratio as well as the target > >>>> speeds. For example, there is a concept called the lift/drag bucket--a > >>>> high-lift keel profile provides a lot of drag, but might be a worthwhile > >>>> price to pay if you're trying to achieve the best VMG in light air, > >>>> > >>> because > >>> > >>>> at low speeds the drag doesn't hurt as much and adding lift while > >>>> > >>> minimizing > >>> > >>>> leeward slippage pays off. For higher speeds, a lower-lift profile works > >>>> better because when the boat is moving faster through the water, you'll > >>>> > >>> get > >>> > >>>> a resultant increase in the actual lift windward and have less drag to > >>>> > >>> worry > >>> > >>>> about--but overall you'll see more leeward slippage. > >>>> > >>>> A bulb at the bottom of the keel offers two things--for one thing, it > >>>> minimizes the tip vortex (which adds a great deal to drag), but mainly it > >>>> helps provide a lot of mass at the extreme draft, which provides more > >>>> righting moment. If the rules allow, you can carry more sail because of > >>>> > >>> the > >>> > >>>> extra righting, and you'll heel less which means more sail upright and > >>>> working for you (although heeling may increase your waterline length on > >>>> > >>> some > >>> > >>>> hulls and raise your speed). If the rules don't allow added sail, you can > >>>> take advantage of the increased righting moment by cutting weight out in > >>>> other areas and you'll accelerate faster. > >>>> > >>>> The profile Tim has picked out for his sportboat is a good one; at the > >>>> speeds he might be getting on a planning boat, he could probably have done > >>>> well with a narrower profile, too, but this way he's covered for a wide > >>>> range of conditions. > >>>> > >>>> A lot of this information is in Steve Killing's book on Yacht Design and > >>>> also in Skene's Elements of Yacht Design--but the later publications of > >>>> > >>> that > >>> > >>>> are much more informed than the early ones). > >>>> > >>>> Dave Shaddock > >>>> > >>>> -----Original Message----- > >>>> From: [email protected] > >>>> [mailto:[EMAIL PROTECTED] On Behalf Of David Shugarts > >>>> Sent: Monday, March 17, 2008 10:52 AM > >>>> To: [email protected] > >>>> Subject: Re: catalina27-talk: Keel Fairing > >>>> > >>>> > >>>> > >>>> > >>>> Hi, Tim-- > >>>> > >>>> I think your summation of it as "like a Chevy" is a pretty good analogy. > >>>> > >>> To > >>> > >>>> go back to the source, I have now heard Frank Butler answer a number of > >>>> sophisticated questions with what sure sounded like naivete to me, so I > >>>> > >>> have > >>> > >>>> a hunch that our factory keel section was a "oh, whatever" decision at the > >>>> time. Then these better keel sections would naturally be an improvement, > >>>> > >>> but > >>> > >>>> only because the bar was set so low. > >>>> > >>>> It would be interesting to hear from an expert here, because I just feel > >>>> > >>> as > >>> > >>>> though the designers of the cool toys are way beyond NACA foils. Or > >>>> > >>> perhaps > >>> > >>>> they really are more about the bulb than the keel section itself. For > >>>> instance, if we could hang a heavy lead bulb on a carbon fiber keel, we > >>>> would probably do it, and we might find that ANY keel foil would be fine > >>>> > >>> for > >>> > >>>> the purpose. > >>>> > >>>> BTW, this link: http://www.hanleyinnovations.com/glossary.html, shows a > >>>> > >>> few > >>> > >>>> cases where the NACA 0012 was used in aircraft, but it also shows that > >>>> > >>> some > >>> > >>>> venerable aircraft (e.g., the Cessna 150/152) had one foil at the wing > >>>> > >>> root > >>> > >>>> and another at the tip (in other words, more sophisticated). Notably, the > >>>> B-17 Flying Fortress had it as the root foil (love that airplane!). > >>>> > >>>> Regards, > >>>> > >>>> Dave S. > >>>> > >>>> > >>>> > >>>> > >>>> On 3/17/08 12:03 AM, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > >>>> > >>>> > >>>>> I don't profess to have any knowledge whatsoever when it comes to fluid > >>>>> dynamics, I have just been going on threads on SA and bits and pieces of > >>>>> knowledge that I've read from different designers. > >>>>> > >>>>> I think that as far as high performance (e.g., sport boats, hulls that > >>>>> will plane > >>>>> off the wind) sailboats are concerned, a bulb on a keel foil is pretty > >>>>> much the > >>>>> name of the game. Certainly heavy displacement and cruising boats will > >>>>> look toward other keel configurations. But the NACA foils offsets have > >>>>> > >>>> pretty > >>>> > >>>>> much been determined to be the go-to configurations for fast keel struts > >>>>> in the sportboat world. There are a few arguments over whether a 0011 > >>>>> > >>>> section > >>>> > >>>>> might be faster than a 0012 seciton (with a resulting decrease in > >>>>> strength/robustness > >>>>> to loads, etc) for example, but the 0012 shape seems to be the chevy > >>>>> pickup when > >>>>> it comes to most foil sections below the waterline. > >>>>> > >>>>> These are fairly simple shapes. Pretty easy for an amateur to cut with a > >>>>> hot wire, > >>>>> or for a CNC machine to do it. > >>>>> > >>>> (http://www.youtube.com/watch?v=q7uvq4RlhHM) > >>>> > >>>>> I can certainly imagine that areonautical designers would have the need > >>>>> > >>> to > >>> > >>>>> come up > >>>>> with more complex shapes for specialized, shape-specific demands, > >>>>> > >>> executed > >>> > >>>>> at high speed with enormous G-force loads in the atmosphere, and new > >>>>> materials and production techniques would allow for a huge amount of > >>>>> variability when it comes to foil offsets these days. > >>>>> > >>>>> But these are just simple symmetrical foils shapes that you can order up > >>>>> and get made pretty cheaply on-line...I just ordered a 54" piece of > >>>>> spyderfoam cut to NACA0012 sections, > >>>>> for about a hundred bux incl. delivery. It's a dream-world out there now > >>>>> for home boat (or aircraft) builders! > >>>>> > >>>>> tf > >>>>> > >>>>> > >>>>> > >>>>> > >>>>> > >>>>>> My ears perk up here. First, I confess ignorance. Are boat keels based > >>>>>> > >>> on > >>> > >>>>>> NACA foils, and do they apply to water, as opposed to air? Perhaps there > >>>>>> was > >>>>>> a series of NACA foils intended for water? I just never paid attention > >>>>>> > >>> to > >>> > >>>>>> that part of things, although I studied NACA airfoils for my own > >>>>>> > >>> purposes > >>> > >>>>>> many years ago. I vaguely recall a factor called Reynolds Number that > >>>>>> would > >>>>>> govern foils in various media, such as air and water. Can you elaborate? > >>>>>> > >>>>>> Regards, > >>>>>> > >>>>>> Dave S. > >>>>>> > >>>>>> PS--I was just a layman studying the foils at the time, but I went > >>>>>> > >>>> through > >>>> > >>>>>> them all pretty carefully. It seemed to me that they were kind of > >>>>>> > >>>> empircal > >>>> > >>>>>> in nature. I got the impression that the great virtue of a NACA foil, > >>>>>> > >>> for > >>> > >>>>>> an > >>>>>> aircraft designer of the 1930s or 1940s, was that it was thoroughly > >>>>>> > >>>> tested > >>>> > >>>>>> and predictable. However, it seemed as though a lot of developments of > >>>>>> later > >>>>>> decades, such as the Clark-Y, not to mention variable sweeps and tapers, > >>>>>> variable chords and foils in a given wing, etc., began to favor > >>>>>> > >>>> departures > >>>> > >>>>>> from the NACA foils (except when mere predictability was the goal, as in > >>>>>> vertical stabilizer foils). So, although I later got into aviation > >>>>>> > >>>> writing > >>>> > >>>>>> and was constantly looking for NACA foils, I didn't find many in the > >>>>>> > >>>> wings > >>>> > >>>>>> of light aircraft. In my time, we saw NASA come out with the GAW-1, and > >>>>>> > >>> I > >>> > >>>>>> have always assumed that later, composite aircraft designers were free > >>>>>> > >>> to > >>> > >>>>>> work with an infinitely variable foil in mind. > >>>>>> > >>>>>> > >>>>>> > >>>>>> > >>>>>> On 3/16/08 8:40 PM, "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote: > >>>>>> > >>>>>> > >>>>>>>>>> but they also value every advantage they can get. > >>>>>>>>>> > >>>>>>> key words^, huh? > >>>>>>> > >>>>>>> nice explanation, Chris. > >>>>>>> > >>>>>>> So I guess Compu-Keel is still around? > >>>>>>> > >>>>>>> http://www.compukeel.com/ > >>>>>>> > >>>>>>> odd because you get NACA foil specs on-line for free...but I guess all > >>>>>>> class > >>>>>>> legal keels cant be derived from NACA sections. > >>>>>>> > >>>>>>> tf > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>> > >>>>>> > >>>>>> > >>>>> > >>>>> > >> > >> > >> > >> > >> > >> > > > > > -- > Internal Virus Database is out-of-date. > Checked by AVG Free Edition. > Version: 7.5.516 / Virus Database: 269.21.4/1310 - Release Date: 3/4/2008 8:35 AM > >
