Today's Message Index:
----------------------
1. 08:51 AM - Help with Spar Decision (Ozzietx)
2. 09:37 AM - Re: Help with Spar Decision (Jack Textor)
3. 01:35 PM - Re: Help with Spar Decision (braywood)
4. 02:11 PM - Re: Help with Spar Decision (Greg Cardinal)
5. 03:13 PM - Re: Cont. 0200 prop pitch (pjb)
6. 08:48 PM - Re: Sky Scout Plans (taildrags)
7. 09:52 PM - Re: Help with Spar Decision (John Woods)
Message 1
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| Subject: | Help with Spar Decision |
I am in the process of building my rib jig, and need to make a decision
on what size spar slot to incorporate.
My priorities are Safety, Weight and cost in that order.
I weigh a little over 200 lbs, and will likely have passengers in that range.
I am attempting to keep my weight down as low as possible. Yes, I know if I were
to lose some weight, that would also help me.
I had initially decided on a 1" routed spar.
My concerns with that are weight, and my ability to rout an expensive blank
without screwing it up. I also hate to waste the wood that will be routed out.
Ultimately, I'm sure I can eventually determine how to rout it out.
I have seen mention, and some drawings of the "UK box spar"
I have spent hours using the search function, but have not seen a solid
opinion, and explanation of this design.
>From what I understand, this is a required method in the UK for Piet builders.
Apparently it is quite light, and strong. From my model airplane
experience, it seems like a great option, that includes a strong D box.
>From what I have read, this is a modification that has actually been properly
stress analyzed.
I have read many times, just build it as Bernard designed it. I get that, and may
very well do exactly that.
I am seeking qualified opinions on the UK box spar idea. In my mind (sometimes
a dangerous place) this seems stronger, lighter, and less expensive option.
I do have a complete woodworking shop to fabricate any type of spar.
I would appreciate any input form people that truly understand the box spar design.
Here are a couple of links in which it was discussed:
http://forums.matronics.com/viewtopic.php?t=65138&postdays=0&postorder=asc&start=0&sid=c79b4120a295a0875655e3c1870c5f8a
http://pietenpol.cpc-world.com/?page_id=4376
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472946#472946
Message 2
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| Subject: | Re: Help with Spar Decision |
This what I did, not flying. Design was checked by engineer.
http://textors.com/SparSketch2.jpg
Other pictures here http://textors.com/PietProject.html
Jack Textor
Sent from my iPad
> On Sep 17, 2017, at 10:51 AM, Ozzietx <ozzietx@gmail.com> wrote:
>
>
> I am in the process of building my rib jig, and need to make a decision
> on what size spar slot to incorporate.
> My priorities are Safety, Weight and cost in that order.
> I weigh a little over 200 lbs, and will likely have passengers in that ran
ge.
> I am attempting to keep my weight down as low as possible. Yes, I know if I
were to lose some weight, that would also help me.
> I had initially decided on a 1" routed spar.
> My concerns with that are weight, and my ability to rout an expensive blan
k
> without screwing it up. I also hate to waste the wood that will be routed o
ut.
> Ultimately, I'm sure I can eventually determine how to rout it out.
> I have seen mention, and some drawings of the "UK box spar"
> I have spent hours using the search function, but have not seen a solid
> opinion, and explanation of this design.
>> =46rom what I understand, this is a required method in the UK for Piet bu
ilders. Apparently it is quite light, and strong. =46rom my model airplane
> experience, it seems like a great option, that includes a strong D box.
>> =46rom what I have read, this is a modification that has actually been pr
operly stress analyzed.
> I have read many times, just build it as Bernard designed it. I get that, a
nd may very well do exactly that.
> I am seeking qualified opinions on the UK box spar idea. In my mind (somet
imes a dangerous place) this seems stronger, lighter, and less expensive opt
ion.
> I do have a complete woodworking shop to fabricate any type of spar.
> I would appreciate any input form people that truly understand the box spa
r design.
> Here are a couple of links in which it was discussed:
>
> http://forums.matronics.com/viewtopic.php?t=65138&postdays=0&postorder
=asc&start=0&sid=c79b4120a295a0875655e3c1870c5f8a
>
> http://pietenpol.cpc-world.com/?page_id=4376
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=472946#472946
>
>
>
>
>
>
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>
>
>
Message 3
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| Subject: | Re: Help with Spar Decision |
Here is a part of the UK spar drawing - gives you an idea of how it is built -
similar to Jack's, but the web is on the front side of the spar. Several areas
are blocked in with additional spruce between the caps and some sections of 1/8"
ply on the backside as well.
I have not built mine yet, but will use this design, as it requires much smaller
pieces of wood! I am told it has been analysed, but have not been able to get
any of that info. It is supposed to be good to 1200lb.
Mark
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472954#472954
Attachments:
http://forums.matronics.com//files/front_spar_section_detail_431.jpg
Message 4
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| Subject: | Help with Spar Decision |
Not UK box spar but worth investigating...
http://www.westcoastpiet.com/images/Construction/I%20Beam%20Analysis.pdf
Greg Cardinal
Minneapolis
-----Original Message-----
From: owner-pietenpol-list-server@matronics.com
[mailto:owner-pietenpol-list-server@matronics.com] On Behalf Of Ozzietx
Sent: Sunday, September 17, 2017 10:52 AM
Subject: Pietenpol-List: Help with Spar Decision
I am in the process of building my rib jig, and need to make a decision on
what size spar slot to incorporate.
My priorities are Safety, Weight and cost in that order.
I weigh a little over 200 lbs, and will likely have passengers in that
range.
I am attempting to keep my weight down as low as possible. Yes, I know if I
were to lose some weight, that would also help me.
I had initially decided on a 1" routed spar.
My concerns with that are weight, and my ability to rout an expensive blank
without screwing it up. I also hate to waste the wood that will be routed
out.
Ultimately, I'm sure I can eventually determine how to rout it out.
I have seen mention, and some drawings of the "UK box spar"
I have spent hours using the search function, but have not seen a solid
opinion, and explanation of this design.
>From what I understand, this is a required method in the UK for Piet
>builders. Apparently it is quite light, and strong. From my model
>airplane
experience, it seems like a great option, that includes a strong D box.
>From what I have read, this is a modification that has actually been
properly stress analyzed.
I have read many times, just build it as Bernard designed it. I get that,
and may very well do exactly that.
I am seeking qualified opinions on the UK box spar idea. In my mind
(sometimes a dangerous place) this seems stronger, lighter, and less
expensive option.
I do have a complete woodworking shop to fabricate any type of spar.
I would appreciate any input form people that truly understand the box spar
design.
Here are a couple of links in which it was discussed:
http://forums.matronics.com/viewtopic.php?t=65138&postdays=0&postorder=asc&s
tart=0&sid=c79b4120a295a0875655e3c1870c5f8a
http://pietenpol.cpc-world.com/?page_id=4376
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472946#472946
Message 5
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| Subject: | Re: Cont. 0200 prop pitch |
Heavy Iron wrote:
> Hi Patricia,
>
> I have a McCauley 71-46 that turns about 2275 static on a C85 if you want to
try it. I am based at CGV2 which I think is near you.
>
> Cheers,
> Ron
Hi Ron,
That's very nice of you to let me try your 71-46 but I think it
would be a little too coarse a pitch.
So far I've tried:
The original wood 74-38 which was way too fine. Overspeeded on take-off
and in level flight.
A wood 72-40 which produced full throttle static rpm of 2625
[ we also flight tested this one and it overspeeded in level flight but not on
take-off.
A metal 73-45 which produced full throttle static rpm of 2375
[ we didn't flight test this one]
Yes, CGV2 is near me.
Cheers,
Patricia
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472957#472957
Message 6
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| Subject: | Re: Sky Scout Plans |
Back on Sept. 7, Doug wrote-
>By my estimate your pilot CG at 49.64" from the leading edge leaned back 4"
>would be about 11" forward of the seat back and bottom intersection if your
>plane is built according to the long fuselage plans. Or about 7.5" if the seat
>back is at a 15 degree angle as Ray built his Sky Scout. I imagine it is
>somewhere between those two values.
OK, today I spent some time taking measurements of my airplane with the fuselage
leveled and plumb bobs dropped off the leading and trailing edges of the wing.
Some very interesting findings, some that surprised even myself.
1. The wing chord on NX41CC is actually 60.5", apparently due to the metal trailing
edge piece extending an extra 1/2" past the tails of the ribs as compared
to plans. All this time I've been using 60" and never checked it. Lesson No.
1.
2. The cabanes are 23-1/4" (front) and 22-1/2" (rear) between pivot points, which
makes them 2" taller (front) and 2-1/4" taller (rear) than plans. This raises
the wing a little and subtracts 1 degree from the angle of incidence. Again,
I never knew this about my airplane, so Lesson No. 2. I do know that it is
very difficult to ever get a sharp or crisp stall, especially power-off, so
perhaps slightly less wing incidence is the cause.
3. The cabanes are actually tilted back 3-1/2" from the vertical, and I've always
thought that they were tilted back 4". Lesson No. 3. Boy, why did I ever
think I knew this airplane? ;o) This gives me just a bit of encouragement that
I can still incline the cabanes back a tad if I ever need to adjust the CG
to get it forward a bit more.
4. The rear seat back on NX41CC is not perfectly square in both directions so all
I can say is that it's somewhere between 83.7 and 84 degrees from the vertical
(inclined back about 6 degrees), which places it just about exactly where
the geometry works out from the plans. I fly very little of the time sitting
in the complete upright position, so I have never felt like the seat back is too
straight for me. My seat back has a little bit of naugahyde-covered foam padding
and that seems to be fine.
5. The corner where the pilot's seat back meets the pilot's seat bottom is 1.5"
forward of the wing trailing edge. With the pilot's CG at a measured/computed
49.64" aft of the wing leading edge, that places the pilot's CG 9.36" forward
of the bottom corner of the seat bottom. Doug said it would be somewhere between
7.5" and 11" forward of the corner. Halfway between those two values would
be 9.25", so his math was wayyyy off... a good 7/64" off ;o) Doug, you're
*good* with numbers-!!
--------
Oscar Zuniga
Medford, OR
Air Camper NX41CC "Scout"
A75 power, 72x36 Culver prop
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=472969#472969
Message 7
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| Subject: | Re: Help with Spar Decision |
Just a word of caution. If you decide to build the Jim Will's "UK Box Spar"
then be aware that the wing design has changed from the original.
The Jim Will's design has a different strut attachment point on the wing
and four bay's per wing panel rather than three.
I'm sure the strut attachment location is significant in the Will's spar
design.
Whether the four bay has any significance to the final design strength, I'm
not sure.
I am building my wing using Jim will's design as I can't afford to purchase
solid spruce spars here in Australia.
JohnW
On 17 September 2017 at 23:51, Ozzietx <ozzietx@gmail.com> wrote:
>
> I am in the process of building my rib jig, and need to make a decision
> on what size spar slot to incorporate.
> My priorities are Safety, Weight and cost in that order.
> I weigh a little over 200 lbs, and will likely have passengers in that
> range.
> I am attempting to keep my weight down as low as possible. Yes, I know if
> I were to lose some weight, that would also help me.
> I had initially decided on a 1" routed spar.
> My concerns with that are weight, and my ability to rout an expensive blank
> without screwing it up. I also hate to waste the wood that will be routed
> out.
> Ultimately, I'm sure I can eventually determine how to rout it out.
> I have seen mention, and some drawings of the "UK box spar"
> I have spent hours using the search function, but have not seen a solid
> opinion, and explanation of this design.
> >From what I understand, this is a required method in the UK for Piet
> builders. Apparently it is quite light, and strong. From my model airplane
> experience, it seems like a great option, that includes a strong D box.
> >From what I have read, this is a modification that has actually been
> properly stress analyzed.
> I have read many times, just build it as Bernard designed it. I get that,
> and may very well do exactly that.
> I am seeking qualified opinions on the UK box spar idea. In my mind
> (sometimes a dangerous place) this seems stronger, lighter, and less
> expensive option.
> I do have a complete woodworking shop to fabricate any type of spar.
> I would appreciate any input form people that truly understand the box
> spar design.
> Here are a couple of links in which it was discussed:
>
> http://forums.matronics.com/viewtopic.php?t=65138&
> postdays=0&postorder=asc&start=0&sid=c79b4120a295a0875655e3c1870c5f8a
>
> http://pietenpol.cpc-world.com/?page_id=4376
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=472946#472946
>
>
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