Pietenpol for Thailand, Pt. #2


Here is the second letter from Cy Mao in Thailand, about his proposed lightweight Pietenpol.



Thank you for kind words of King Rama IX and Thailand. Both are deserving of your kind praise.

I think I will try to build this and if over 550 Lbs I will only have to license as airplane, not ultralight but in the process I will discover the lightest Pietenpol practical to build. Or perhaps as you mention use Rotax but I like reliable 4 cycle and sounds nice too so could look at this UL-260. Also perhaps Volkswagen but I think not best RPM for Pietenpol like this and I think not so much lighter than A65.

I will follow your suggestions and am curious just which fittings and such you believe are overbuilt and can be aluminum not steel. But this is not yet critical to know. I will first build ribs.

Of course I’m also interested in your light landing gear you mentioned and the two piece wing you talked about.

I meant to ask if you think 1″ routed spar is lighter or the 3/4″ solid spar I read about. You mentioned a 3/4″ spar and still router it too. So I would think this for sure the lightest. How much to router I will ask later.

First I will build ribs 1/4 x 1/4 so I need to plan spar thickness to build ribs to fit this spar. I believe you suggest lightest possible is 3/4″ and then router too. Is this correct?

Also if I plan to build two piece wing as you mention what is the rib count for this version. I have only seen one and three piece wing views. Not sure how many ribs I will need if two piece wing.

Of course I will report my discoveries such as how much weight is saved by 1/4 x 1/4 capstrips and other things to change and finally of course if something breaks we will all know it is not enough.

You ask my address sir:

KGC – Unit 708 -Emerald Development Group
94/81 MOO 7, Vichitsongkarm Rd
Kathu, Kathu, Phuket, 83120

Note Delivery in Thailand sometimes slow or never shows up. Best if can track and return to yourself if necessary. Also I am happy to pay for book as well. When I see your video I already know I need one.

Thank you Kuhn William

Image result for Roger white pietenpol

Above, Roger White’s Pietenpol. It has a steel tube fuselage and an A-75. It is still flying in the hands of a new owner, I’m pretty sure it is more than 25 years old. I saw it in person at Brodhead many years ago. Notice it has Vee cabane struts, yielding a two piece wing and no center section.  I believe this is far lighter than a center section, and it is also stronger. I do not know the finished weight of the plane, but it was visually a very good performer. Roger’s EAA # is 42, he built a number of planes.



 Roger White stops by my tent at Oshkosh 2010. Note he is wearing a CIB from Korea.  He is a first class American.


Response to the letter: 


I believe you are correct, the VW isn’t radically lighter than a 65, but a UL-260 is a four stroke, light, and it makes very good thrust.


I would plan on 3/4″ spar slots in the ribs, I will see if I can get you some examples of classic planes with 3/4″ spars. I would still route them.


Manual is on the way tomorrow. I will see if I can find a picture of the 590 pound plane we weighed.


Thanks, William

3 Replies to “Pietenpol for Thailand, Pt. #2”

  1. Following this with great interest! William, when you say routed spar, are you referring to a solid wood spar with lightening holes routed out in a truss-like pattern?

  2. On this two piece wing is there still one fuel tank off center? To put one tank on each side of the middle I think will add back some weight. Maybe want to fly heavy on one side though with only tank on one side, but not far from center so maybe does not matter. Or can use fuselage tank but I like gravity for fuel pressure. Cannot fail. So for this good to have fuel up high in wings.

    Not look as nice as other PIet with cabane struts not straight up, but if simple and light better to have under 550 pounds and not look the same as some other Pietenpol.

  3. One additional thought on this pictured airplane. It is said it has steel fuselage. This probably makes it easy to weld the cabanes to the steel longerons at any desired angle. Has this two piece wing been built on a wooden fuselage? I wonder if the attach of the cabanes to the wooden longerons would be more tricky in the brackets to attach. Fairly simple in the original attach of the cabanes straight vertical, but perhaps not the same at this angle?

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