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Voidhawk9

Open-Ez wing spar-cap thickness (thicker than a Long?)

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I've been studying spar caps in various canards (for my own education), and I expected to find that the Open-Ez wing spar caps would be the same as in the Long-Ez plans - but they are not, they are substantially thicker. Almost the same as a Cozy wing, in fact (Nat claimed in the Cozy newsletters that the spar caps and shear webs were made 25% thicker than <something not specified - Long? Cozy III? [isn't that the same as a Long?]> but that does not seem to be entirely accurate either.)

I'm looking at the Long plans from the TERF CD - did the spar caps get 'upgraded' in the CPs, or is the Open-Ez designed for higher G-loads?

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The Open-EZ does not introduce any new design changes.  The Open-EZ specifications are meant to be identical to those of the Long-EZ.

The TERF CD contains the Long-EZ plans, which require all applicable Canard Pusher updates to be accurate.  

Are comparing the TERF CD's Long-EZ plans with something else you have on hand?

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I measured the spar-cap troughs in the templates. This doesn't take into account the shear webs, but that is the same case for the Cozy anyway. For the Long, the spar caps are defined in the plans as the number of plies, for the 'old' .038" thick tape.

 

I will attach my data & some visualization graphs here. I'd be happy for anyone to review my numbers and see if I've gone wrong somewhere!

spar_cap_comparison.pdf

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I don't understand why you are comparing the spar cap lay-up to other aircraft? There could be scaling issues with your drawings. Just follow the spar cap schedule.

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Open-Ez and Long-Ez are supposed to be the exact same design.

I'm not building one (I have an Aerocanard project).

Edited by Voidhawk9

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On 9/8/2018 at 10:29 PM, Voidhawk9 said:

I've been studying spar caps in various canards (for my own education), and I expected to find that the Open-Ez wing spar caps would be the same as in the Long-Ez plans - but they are not, they are substantially thicker.

I suspect the source of your data is off (as Keith also suggests with scaling issues on your drawings).  Putting the Cozy drawings aside for now, I assume you must be comparing the following:

  1. Long-EZ drawings that you have acquired from somewhere.
  2. Open-EZ drawings that you have carefully printed and measured, or measured on the computer using a digital tool.

As Keith points out it's most important to follow the layup schedule, but I am still concerned over the above and the source of your data.  

Please share more about how you came to #1 and #2 above.  Are the Long-EZ drawings copies you received from somewhere?  I know I once received drawings from someone in Australia and ended up throwing them out suspecting they were copies of copies.  The Open-EZ drawings were taken from actual Long-EZ drawings and verified against other actual Long-EZ drawings, so I trust what's in the Open-EZ drawings but can't verify what you may be comparing to.

At the end of the day the Long-EZ and Open-EZ drawings should have identical measurements.

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1. Long-Ez plans from the TERF CD, referencing the layup schedule and tape thickness.

2. Open-EZ drawings (Rev5 I believe), measured DIGITALLY.

3. Cozy digital M-drawings from here: http://www.cozybuilders.org/cad_files/Cozy_MKIV_M-Sup_1.2_Draft.pdf Again, measured DIGITALLY, so no printer distortion.

 

But don't take my word for it! Check for yourselves and I'll be happy if you can show me where I'm wrong. :)

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Ah, I think I see the issue:  comparing drawings to a layup schedule was never meant to be.  😉

In other words, and still putting the Cozy aside, given (a) and (b) below, the conclusion is true:

a) The layup schedule and tape thickness noted in the Long-EZ plans on the TERF CD matches the printed Long-EZ plans last published by the Rutan Aircraft Factory. 

b) The Open-EZ drawings Rev. 5 matches the printed drawings last published by the Rutan Aircraft Factory.

Conclusion:  You could compare your #1 and #2 using the original Rutan Aircraft Factory counterparts and produce your same results.

Now what?

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Now you're telling me that a Cozy spar caps are about the same as a Long. :)

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Still putting the Cozy aside, no. 😉

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Well if we put aside the wings entirely, the project gets much easier to build too. :huh:

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Seriously, where are we at with this?  Are we good, or am I still confused?

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This conversation is very hard to follow.... what language is this?

  • Haha 1

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9 hours ago, Jon Matcho said:

Seriously, where are we at with this?  Are we good, or am I still confused?

I don't see any evidence that I'm wrong so far. Disregarding a significant portion of the data I presented and telling me I'm wrong is not very convincing. ;)

If someone could verify my measurements (or show me where I went wrong with them), then we might be getting somewhere. Even better, if someone could measure some original Long spar cap troughs from the templates (which I don't have) then we'd have full apples-to-apples comparison.

Edited by Voidhawk9

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On 9/10/2018 at 3:35 AM, Jon Matcho said:

1) As Keith points out it's most important to follow the layup schedule...

2) At the end of the day the Long-EZ and Open-EZ drawings should have identical measurements.

Your point 1) above is exactly incorrect. It's MOST important to cut the cap troughs to the right dimensions and then fill them to the top with fiberglass, however many plies it takes. Since the tape thickness has varied substantially over the years, the overall thickness of the cap is what matters, not how many plies one put down to get there.

The ONLY thing that matters is correct trough depth.

Point 2) is correct, but apparently Cameron believes that they are not identical. I don't have either OE or LE "M" drawings/templates, so I can't settle this debate.

  • Thanks 1

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On 9/10/2018 at 6:35 AM, Jon Matcho said:

As Keith points out it's most important to follow the layup schedule, but I am still concerned over the above and the source of your data.

I'll go out on a limb and say that Keith and I both meant "just follow the plans."  Where else would one "follow the layup schedule"?

On 9/11/2018 at 10:54 PM, Marc Zeitlin said:

Your point 1) above is exactly incorrect. It's MOST important to cut the cap troughs to the right dimensions and then fill them to the top with fiberglass, however many plies it takes. Since the tape thickness has varied substantially over the years, the overall thickness of the cap is what matters, not how many plies one put down to get there.

My point is not "exactly incorrect" and is not even "just" incorrect.  If anyone were to follow the plans exactly ("follow the layup schedule") their planes would build and fly as intended by the designers.

In the Cozy IV plans (not sure why we're discussing the Cozy in the Open-EZ topic, but OK) Section 14 Step 6 states (bolding and underlining is mine):

  • Some deviation from theoretical is acceptable, if due to the tape being thinner or thicker than .025 after removing cross threads.
  • It is acceptable to use one or two layers more, or one or two layers less, to fill up the trough.

For the Long-EZ Section 14 Step 7 is also clear on how to do this:

  • Measure the depth of the spar -- if the layup is over-size, sand (maximum of .04) to size.

I have not checked the Canard Pushers, but in either case following the plans and incorporating all changes (Canard Pusher newsletters, or Cozy newsletters if we're talking about an Open-EZ 4!) will produce a good result.  Perhaps there are developments in the Cozy community post-Nat Puffer, and I would certainly research these tips and recommendations (notably from Marc -- the human center of the Cozy universe -- and several others such as @Kent Ashton).  

On 9/11/2018 at 10:54 PM, Marc Zeitlin said:

...Cameron believes that they are not identical. I don't have either OE or LE "M" drawings/templates, so I can't settle this debate.

I suspect Cameron does not have Long-EZ drawings so a methodology to link the Long-EZ plans in the plans-only TERF CD to the Open-EZ drawings (same measurements as Long-EZ drawings) is flawed from the onset.  My point is that the same confusion would have been produced in 1984 by doing the same thing with Long-EZ Plans and Long-EZ drawings.  Presently there are no Open-EZ plans per se; one needs to use Long-EZ plans.  

On 9/8/2018 at 10:29 PM, Voidhawk9 said:

I've been studying spar caps in various canards (for my own education), and I expected to find that the Open-Ez wing spar caps would be the same as in the Long-Ez plans - but they are not, they are substantially thicker.

Cameron, how specifically did you get your Open-EZ measurements?  If you are interpolating top/bottom trough sizes from the Open-EZ drawings, please do the same with actual Long-EZ drawings and I assure you that you will end up at the same place.

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The cap or the trough sounds like the chicken or the egg 😏 Isn't Everyone is correct? Mark says its the depth of the trough and John says its the cap thickness but I would think your plans SHOULD make it obvious that they are the same. Why don't you call Steve James at Eureka 702-416-8729 and ask him what depth he cuts the spar trough. (obviously its tapered)

 

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Void,

Could it be that you are using dimensions for the added spar cap layers, for example: .450" for the top CS root from the Long EZ plans? Then comparing this to the measurement from page A11 spar cap template? These templates are meant to define total material to be removed from the foam prior to glassing outside of CS spar. I measured (digitally) the open ez top CS spar root at .49" depth. The original shear web was 3 plies of BID which adds about .010" per ply (add .030") In the end, .030" shear web + 0.450 spar cap nets 0.48" total depth. I for one am not going to loose sleep over ten thousandths thickness, even if it is in my spar cap.

If I'm way off on this folks, let me know.

Jay

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