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Permalink Reply by Harvey Richards on February 21, 2009 at 9:20am

Thats an excellent idea Robert. That was my first thought when I saw the skeleton of the 750 Stabilizer.For little weight gain it will hold the end ribs out and stop the skin from rounding up in the middle where it makes the sharp radius at the top and is not riveted down.

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Permalink Reply by Jonathan Porter on February 21, 2009 at 1:27pm

Hmmm. the 701 does not need the extra - but looking at this we wondered about simply adding a top and bottom L angle with rivets = less weight + support to ends + added twist resitance (although it may 'round up' a small amount still)! I am intrigued at the angle keepers on the top version of STABS2.jpg!

Thanks for sharing this - it is a great insight.

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Permalink Reply by Robert Pelland on February 21, 2009 at 3:20pm

Elizabeth, I believe you are referring to the STAB.JPG pic. It's just to keep the ends aligned up properly when skinning the stab. Once the skin is fitted,correctly, we could remove them completely since they are no longer needed.

I like your setup

regards
Robert

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Permalink Reply by Ron D Leclerc on March 7, 2009 at 9:27am

Robert... Great looking photos of your stabilizer... as you know I am doing the same thing, but with a full width of 8.0'. I have a question in building the elevator, which also be extended and... specifically with the trim tab:

The trim tab on the 701 (575mm(22.64")) is mounted on the "pilot side" of the elevator... can the trim tab be mounted on the passenger side?

I will eliminate the 18mm bent flange at the trailing edge and skinning it like the 750 and plan to increase the size of the trim tab to... about 914mm(36") with the same design as the 750... is 36" overkill, I see the 750 has a full width trim tab?

I don't have any drawings for the 750 elevator to work from... so I'm sort of winging it!!

Again great looking stabilizer... Ron

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Permalink Reply by Jonathan Porter on March 7, 2009 at 12:45pm

Hmmm. I think that, but do not know for sure, but having the trim on the 'prop-wash' side may be more efficient. Clearly it will work on either side to more or less the same extent in the cruise - but there must be a reason that all of my planes have the trim on the pilot side - unless it is also so that you can stick your head out of the window and check operations during your pre-flight/vitalc-checks - which you could not do if it was on the other side. Hope that tickles some more technical responses.

Be careful making the trim too big - I have one plane which is so sensitive in trim it is possible to make it more than hard work to fly!

Enjoy!

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Permalink Reply by Robert Pelland on March 7, 2009 at 4:10pm

Ron,

Thank you for your kind words. The stabilizer is more then pleasent to work on, sadely the same cannot be said for the elevator. I have been working on mine for the past day or two, and I have gotten nowhere. Like yourself, I had originally planned on skinning it in the same fashion as the 750, but I'm afraid I won't be able to do so.

The problem lies in the thickness ( .025 ) of the material that is used for the spar. It won't keep it's shape once bent, ( look's more like a Banana ) and since I did not have the .51 dies at the time, I cut the holes to the next larger size .61. This coupled with the thickness of the material, does not leave much metal left to keep the spar straight. Another problem is trying to get the frame attached to the table and proper aligned so that the skin can be attached. When you finally are able to attach it securely to the table, it becomes impossible to cover it using the bent skin technique that is uised on the 750 since you no longer have access to the under side of the frame since it's firmly fastened to the table top. I am still having issues with it,, and have not decided the exact way it will be done.

As for the trim tab, I whole heartedly agree with Elizabeth concerning it's large size. The dimension of the tab is 116 x 1129, which works out to 25% of the total flying surface, of the left side of the elevator. Long ago I was taught that the tab was to control the flying surface, not to fly the plane, so I don't understand the large size.

Good luck with your choices

Attachments:

• elevator.JPG, 104 KB

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Permalink Reply by Ron D Leclerc on March 9, 2009 at 9:28pm

G'Day Robert...

Had a rough weekend making flaperon nose ribs(10) and rear ribs(22), very very time consuming and frustrating... but I got them done after much "@%#&*&", you know what I mean!

You know that when I looked at the elevator and the size of the holes 65mm, that they said can be cut if you do not have the 50mm dies... kind of got my attention when I checked my 65mm dies and the width of the spar, not much will be left there. So I made some 50mm dies specicailly for the elevator spar, we will see if that helps. Also I was told to make the spar flanges 2" - 3" initially to get the spar to hold its shape until you can get to the skinning part done, then trim to size, don't know if that will work but I'm told that it does!

In regards to the trim tab, I've reviewed a lot of the posts on the 701/801 forum and from some of the remaks there, there is general comments are that the trim tab is to small and should be larger, almost 6" longer. A general view also that seems to be missed by everyone is that the 18mm flange on the trailing edge should be straightened out, instesd of bent up, apparently approved by Zenair for anyone who has called about it. From what I gather it was put there when the unit was built to the 980lb range with the 2 stroke 583 engines, but is not needed now with the heavier used and increased gross weight... 1100lb.

I've reviewed the elevator and trim tab on the 601 which is of the same design as the 750 and it is 67mm x 895mm. It would be less then the 895mm, somewhere in the 750 range, there is about 900mm of room with the modified elevator width, but will try and keep it at the 750 range.

The reason I asked about about whether the trim tab is installed on the pilots side... it seems to me it depends on the rotation of the prop CW or CCW??? With the Rotax the prop turns CW, with the Belted VW its CCW! This is a thought that I had before I started on the elevator.

Have fun with the elevator and don't let it get you done... there is a way
Ron

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