Today's Message Index:
----------------------
1. 08:34 AM - Brodhead (Lagowski Morrow)
2. 09:48 AM - Re: GN-1 airfoil information needed (jimd)
3. 12:56 PM - Re: GN-1 airfoil information (Thomas Bernie)
4. 01:07 PM - Re: GN-1 airfoil information (Thomas Bernie)
5. 03:01 PM - Re: GN-1 airfoil information (jimd)
6. 07:06 PM - GN-1 airfoil information (Oscar Zuniga)
Message 1
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I am trying hard to finish my plane in time for Brodhead. I'll be there
by plane or car no matter what.
Will start assembling all the tail pieces and wings/ailerons to the
fuselage in the next two weeks. All the finish painting is done and the
engine (65 Cont.) is back on. Need to make engine cowling. install
windshields, paint all cowlings and attend to a "few" more details. Then
it's final inspection, air worthiness certificate and 25 hours before
leaving the neighborhood here in N.W. Michigan.
Jim Lagowski -- NX221PT
Do not archive
Message 2
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| Subject: | Re: GN-1 airfoil information needed |
Ok,
How about the MAC for the pietenpol wing? If I can get that value I can get a ballpark
idea of the biplane MAC values, and use it to have a better idea of where
the landing gear should be placed.
Jim
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=182500#182500
Message 3
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| Subject: | Re: GN-1 airfoil information |
Hi Jim,
My GN-1 was built according to the CAD plans -- the plans are loaded
with errors and the weight and balance example is bogus. That being
said, the aerodynamic is supposed to be 14 inches, but the example
aircraft uses J-3 wings. I'm in the process of determining the real
crew and fuel moments, since the plans can't be trusted.
Regards,
Tom Bernie
Gloucester, Mass
On May 10, 2008, at 5:47 PM, jimd wrote:
>
> Hi,
>
> Just had an A&I leave my house after looking over my biplane GN-1
> project. He had a concern about the landing gear placement of my
> plane, based on the weight/placement of the engine.
>
> To correctly determine where the gear should be he said I needed to
> find out where the CG of the plane is, but with it being a biplane
> configuration, he said that I needed to have the mean center of lift
> information for both the upper and lower wings, as well as a number
> of measurements from the assembled plane, like information about the
> spacing horizontally between the wings. Then once the weights, and
> measurements are known, the acceptable range of locations for the
> axle of the landing gear can be determined from some engineering
> formulas.
>
> Did some searching, found two engineering articles on finding the CG/
> center of lift on biplanes, and they require information about the
> airfoil.
>
> I was able to find information on the Pietenpol FC-10 airfoil, which
> I believe is what my lower wing has, as the Aerial biplane
> conversion plans say the airfoil is the same.
>
> http://www.airminded.net/piet/piet.html has piet airfoil info with
> Cl,Cm,Cd, type info.
>
> However presuming my plane has the Gregga airfoil, which the plans
> say have a rounder leading edge.. and which appear to be thicker.. I
> would think it is a different airfoil, with different values. Have
> not seen it listed in the common airfoils databases.
>
> Anyone have information on the GN-1 airfoil? I have the plans, have
> a jig, and wings, but only can guestimate it as being like the piet.
>
> We are thinking I may have to rework the landing gear to get it
> right, but no one knows how much if any it must be changed.
>
> So any GN-1 ordinates, or the Cl,Cm,Cd type info, or naca airfoil
> numbers... anything like that would be helpful.
>
> You can see my gear/plane on the westcoastpiet site, its under Jim D.
>
> Thanks,
>
> Jim
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=182401#182401
>
>
Thomas Bernie
tsbe
Message 4
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| Subject: | Re: GN-1 airfoil information |
"aerodynamic" should read "aerodynamic center of the wing"
tb
On May 11, 2008, at 3:53 PM, Thomas Bernie wrote:
> >
>
> Hi Jim,
>
> My GN-1 was built according to the CAD plans -- the plans are
> loaded with errors and the weight and balance example is bogus.
> That being said, the aerodynamic is supposed to be 14 inches, but
> the example aircraft uses J-3 wings. I'm in the process of
> determining the real crew and fuel moments, since the plans can't be
> trusted.
>
> Regards,
> Tom Bernie
> Gloucester, Mass
>
>
> On May 10, 2008, at 5:47 PM, jimd wrote:
>
>>
>> Hi,
>>
>> Just had an A&I leave my house after looking over my biplane GN-1
>> project. He had a concern about the landing gear placement of my
>> plane, based on the weight/placement of the engine.
>>
>> To correctly determine where the gear should be he said I needed to
>> find out where the CG of the plane is, but with it being a biplane
>> configuration, he said that I needed to have the mean center of
>> lift information for both the upper and lower wings, as well as a
>> number of measurements from the assembled plane, like information
>> about the spacing horizontally between the wings. Then once the
>> weights, and measurements are known, the acceptable range of
>> locations for the axle of the landing gear can be determined from
>> some engineering formulas.
>>
>> Did some searching, found two engineering articles on finding the
>> CG/center of lift on biplanes, and they require information about
>> the airfoil.
>>
>> I was able to find information on the Pietenpol FC-10 airfoil,
>> which I believe is what my lower wing has, as the Aerial biplane
>> conversion plans say the airfoil is the same.
>>
>> http://www.airminded.net/piet/piet.html has piet airfoil info with
>> Cl,Cm,Cd, type info.
>>
>> However presuming my plane has the Gregga airfoil, which the plans
>> say have a rounder leading edge.. and which appear to be thicker..
>> I would think it is a different airfoil, with different values.
>> Have not seen it listed in the common airfoils databases.
>>
>> Anyone have information on the GN-1 airfoil? I have the plans, have
>> a jig, and wings, but only can guestimate it as being like the piet.
>>
>> We are thinking I may have to rework the landing gear to get it
>> right, but no one knows how much if any it must be changed.
>>
>> So any GN-1 ordinates, or the Cl,Cm,Cd type info, or naca airfoil
>> numbers... anything like that would be helpful.
>>
>> You can see my gear/plane on the westcoastpiet site, its under Jim D.
>>
>> Thanks,
>>
>> Jim
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=182401#182401
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
> Thomas Bernie
> tsbe
>
>
Thomas Bernie
tsbe
Message 5
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| Subject: | Re: GN-1 airfoil information |
Sounds like you could use same kind of info. Saw Xfoil could figure some of the
info if I figure out the coordinates, but it didn't look like it would give the
MAC value. There is pricey software that will give it, but I don't plan on
using this kind of thing much. There is an EAA spreadsheet to calculate the equivelent
biplane MAC, once I get the rest the values, then I can find out what
the acceptable range is for locating the landing gear axle.. which is really
important.
Have little doubt someone has these numbers and did this same exercise.
Jim
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=182559#182559
Message 6
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| Subject: | GN-1 airfoil information |
Jim wrote;
> Just had an A&I leave my house after looking over my biplane GN-1 project.
Jim, that's always a good thing but remember that these are experimental aircraft
and most A&Ps/A&Is are from the certified world and are usually on unfamiliar
ground. Not only that, they tend to forget that we aren't shooting for certification
and are essentially test pilots, so if we don't get things bang-on
when we begin testing the aircraft, we can make adjustments and it doesn't affect
all of the engineering paperwork that we (didn't) send in to Oklahoma City
when we registered the aircraft. That said, my next statement is that I'm NOT
an aeronautical engineer and I'm shooting from the hip with what follows, but
here goes.
> To correctly determine where the gear should be he said I needed to find out
where
> the CG of the plane is
Correct, but some of that info should have come with the St. Croix "Aerial" biplane
plans that you got from Chad Wille. If not, I guess then you are truly on
your own here.
>but with it being a biplane configuration, he said
> that I needed to have the mean center of lift information for both the upper
> and lower wings
Probably correct if the wings are staggered, which I don't know since I've never
seen the plans for the Aerial, but if there is no stagger then it's just a geometry
problem. If there is no stagger, then in the level configuration (where
W&B is done) the CG range will be the same as for most airplanes in our size
and class... 22 to 34% of the wing chord, or 13.2 to 20.4" aft of the wing leading
edge.
> as well as a number of measurements from the assembled plane,
> like information about the spacing horizontally between the wings. Then once
> the weights, and measurements are known, the acceptable range of locations for
> the axle of the landing gear can be determined from some engineering formulas.
There are good, useful rules of thumb for these things and you're on the right
track with your thinking. Many of the early airplanes, homebuilt and otherwise,
were biplanes so a lot of thought has gone into their design and setup. I
will look through what I have in the way of "armchair engineering" books on the
subject, such as Evans' "Lightplane Designer" and see what I can find.
> However presuming my plane has the Grega airfoil, which the plans say have a
rounder
> leading edge.. and which appear to be thicker.. I would think it is a different
> airfoil, with different values. Have not seen it listed in the common
> airfoils databases.
I don't think much changed between the Pietenpol and the Grega until it comes to
the sharpness of the stall (thus the rounder leading edge), and I would think
that for purposes of setting up your landing gear it wouldn't matter too much
(even though you're essentially in the stall configuration in a 3-point landing).
You have to start somewhere unless you are determined to make it an engineering
and aerodynamic analysis, in which case I can't help.
As to the earlier mention of the mean aerodynamic chord (MAC), that is for tapered
and swept wings, and your wings should both be constant-chord with no sweep
so the MAC is simply the chord, which should be 60" for both wings.
Oscar Zuniga
Air Camper NX41CC
San Antonio, TX
mailto: taildrags@hotmail.com
website at http://www.flysquirrel.net
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