Brodhead Pietenpol Association

Original Posted By: "Pieti Lowell"
Donato,You have both sets of plans, so you should be able to see the differences betweenthe two designs. While I don't have a set of GN-1 plans, the "improvements"that I have been able to discern don't seem to fall within the definition ofthat word. The most noticable changes are:1. Plywood fuselage side skins run all the way back to the tailpost, rather thanstopping at the rear cockpit. This feature adds strength and weight where itis not needed - why bother?.2. The use of Piper Cub landing gear. Surplus Cub landing gear is no longer readilyavailable, so IF you can find a set, they will not be cheap. But more importantly,the landing gear attach points do not line up with the rear lift strutattach points. Structurally, this does not make sense, and aesthetically itisn't right either. So, if you will need to build your own gear, why not makea set of gear that was designed for the plane that you're building, as opposedto building a replica of landing gear that was designed for a different plane.3. Different cabane strut mounting brackets. For some reason, Grega redesignedthe mounting brackets for the cabane attachments, and in doing so, eliminatedthe possibility of tilting the cabanes fore or aft, for W&B adjustment. As a result,the GN-1 does not offer much ability to compensate for CG that varies fromthe norm, other than adding ballast, or building a new motor mount. One ofthe beauties of the Pietenpol design is the ability to tilt the cabanes, andeffectively move the wing back (actually, it moves the entire fuselage forward)to account for tail heaviness. This is a far superior method than adding ballastin the nose or tail.So, from a design perspective, I personally cannot see any benefit of these three"improvements". And, since the feedback from pilots that have flown both seemsto indicate no noticeable difference in flight characteristics, one wouldhave to wonder why one would choose the GN-1 over the Pietenpol plans.I think that the reason why many builders chose the GN-1 over the Pietenpol wasthat for many years, the GN-1 plans were only $25, whereas the Pietenpol planswere two or three times that price. However, a savings of $25 or $50 on theoverall cost of an aircraft is extremely insignificant, and really should nothave been a deciding factor. But people can be funny sometimes.Bill C.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Wash Out

Original Posted By: steve(at)wotelectronics.com
It is important that a little wash-out is necessary in order to make nice gentlestalls and good landings.Some of the wings that I saw at Brodhead had no washout, gap-seals are necessarybut do not take the place of washout.I suggest 1/2" to1.0" if there is no dihedral, it makes a great difference duringthe stall. As the stall moves outward the stability increases when controldecreases.If wash-out is applied to the wing, is the angle of incident required to be alsochanged ?Has anyone read the article about the adjustable angle of incident airplane thatwas featured in the 30's ? I read it many years ago and don't remember all thefacts. That is the price one pays for getting in their 80's. You all will haveto deal with it one day , so take notes.Pieti LowellRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Tue, 02 Aug 2011 09:47:54 -0400

Original Posted By: Michael Perez
Bob,That is very impressive progress for one year. Wow.Just to be clear, when you say you were told to make the cabanes the same length,do you mean the same length as the Pietenpol plans show, or the same lengthfront and back?I was mentioned in a couple of replies to your question, so I thought I shouldchime in. First, a disclaimer; I have built standard Pietenpol airfoil ribs formy plane, not Riblett airfoil ribs. The calculations that I did were in responseto some questions that came up here on the List, and are theoretical - notproven. However, they seem to make sense, and appear to be in concurrence withLowell's real-world experience. As far as we know, Lowell has the only flyingexample of an Air camper with the Riblett wing.Here's a link to the calculations:http://forums.matronics.com/viewtopic.p ... 336915Bill C.Read this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Tue, 2 Aug 2011 08:06:41 -0700 (PDT)

Original Posted By: Dan Yocum
Does a Pietenpol really need any wash-out for purposes of taming the stalling characteristics?Hershey bar wings that have no wash-out have a stall that startsat the root and progresses toward the tips anyway. I've been trying variousthought experiments involving dihedral vs. no dihedral and don't see how thebasic stall behavior of a wing with no wash-out would be affected either way.(Unless perhaps there is large angle of cross flow, but didn't our flight instructorsconstantly harangue us about the desirability, even the absolute necessity,of keeping the ball centered?)Well, a little bit of wash-out will make an already manageable stall behavior evenmore pleasant. With wash-out beginning at the inboard end of the aileron,you wouldn't need more than 1 deg or so at the tip (trailing edge up 1" at tip),which would conveniently reduce the induced drag a little at climbing angleof attack.Yes, reducing the angle of attack toward the tips to implement the wash-out willreduce the total wing lift slightly at the same angle of attack at the wingroot. However, the average reduction in angle of attack from the inboard end ofthe aileron to the tip will be 1/2 deg and, since the aileron takes up a littleless than half the semispan, the net effect would be to require increasingthe wing incidence at the root by a little less than 1/4 deg. This is somethinga builder starting from scratch may want to consider, but it's not too criticalbecause compensation can be made by adjusting the angle of the horizontalstabilizer or changing the angle of the elevator (nice to have a trim tab inthe latter case).There have been a number of airplanes with wing incidence adjustable in flight.The ultimate was George Spratt's Control Wing, which has an airfoil with a positivepitching moment, which allows the wing to pivot freely around a spanwisehinge axis to accommodate changes in the relative wind. If you fly into a sharp-edgedupdraft, the wing simply noses down on its own to maintain a constantangle of attack. Since the wing has a lot less rotational inertia than the entireairframe (fuselage, tail, and rigidly attached wing) and doesn't have towait for the horizontal tail to enter the gust, the g loads in turbulence arereduced by about 75%.http://speleotrove.com/wings/controlwing_plans.htmlHmmm..... That site's link to http://www.georgespratt.org/ kept timing out on me. Hopefully some or all of the links at this archive site will produce results:http://web.archive.org/web/200905241808 ... ------Bill FrankRead this topic online here:http://forums.matronics.com/viewtopic.p ... ______Date: Wed, 10 Aug 2011 13:50:59 -0500

Original Posted By: "Bill Church"
>> Subject: Pietenpol-List: Piet vs. GN-1>>>> >>>> I have all of the Pietenpol plans and just purchased the GN-1 plans. >> I> have read some great posts on the pros and cons of each, but I need > more> details. I am not 100% sure at this time which airplane I should > build.>>>> Can anyone please tell me why you chose to build and fly the GN-1 >> over> the original Pietenpol? Do they fly the same? Any major cost > differences> or building skills needed?>>>> Thanks a bunch, please send me all of your thoughts pros and cons.>>>> Blue skies,>> Donato>>>>>>>>>> Read this topic online here:>>>> http://forums.matronics.com/viewtopic.p ... ___Subject: Pietenpol-List: Re: cabanes