I'm still travelling and haven't finished mine, but here are some build log photos.


Also, the good EPO one is on sale for $99 right now here.

Views: 14135

Comment by Ron Jacobs on May 27, 2010 at 6:21pm
Checked out the site where it is on sale for 99.00. Seems sketchy. Can't get a shipping estimate and the site appears to be somewhat a work in progress.

Developer
Comment by Pete Hollands on May 28, 2010 at 12:43am
Looking forward to seeing it pull some loops without the wings breaking off at each end.
Comment by tshado on May 28, 2010 at 12:59am
Hello Pete,
I have also been following this thread on RCGroup.
This happened on the EPS version which was first released.
The new EPO version is much stonger and people reported good first flights.

Best regards, Jean-Claude

Moderator
Comment by Morli on May 28, 2010 at 3:11am
@ Pete , Tshado is right. The model in that crash pic is EPS and he was offered a EPO model free as replacement. Some reported a failure Even on newer model but I doubt it unless i see it. Haven't built mine yet ,Will find out soon and let you know.;)
@ Ron, if I remember correctly that site says( some where) that it is 139$ with free shipping ( 99$ + 40$ for shipping ). I am not sure if it is really EPO or not but it could be.
Comment by Riccardo Kuebler on May 28, 2010 at 3:38am
Hi,

has anyone tried to put carbon plates to stiffen the wings. I mean 1x3x1000mm or 1x5 or 0.5x5 vertically, one at about 30% one at about 70% of the wing chord all the wing along, both on top and bottom side.
Simply do a cut with a balsa knife, insert medium CA glue (not the foam/styro one, the normal instead) all along, insert the carbon plate, spray with activator, done.
You will have some sort of "box" or "spare".
This is a very effective way to improve rigidity of those wings. I did it several times, on my Arcus f.e.

Best regards,

Ric

Moderator
Comment by Morli on May 28, 2010 at 4:21am
Hi Ric ,
I had planned to do one of this if required. Do you think one of this mod will work? the extension is carbon square rod (2mm x 2mm). One rod is long enough to be cut in half and used for both. It will extend the carbon support to almost 80% and is light enough. The wing is suppose to be two pc for ease of transportation, so will be bit of additional challenge to add this extension fixed to existing CF tube. but doable I think. Alternate is to cut the existing Rod in half and glue it permanently into the wing halves.Use slightly bigger tube to join them together at field. Using a fixed one length CF tubes to join the two wing halves is also part of problem i current design I think since this portion is stiff , if a bit of flexibility is built in center where wings are joined may distribute the stress which occurs at end of CF tube currently. What do you think?


Developer
Comment by Pete Hollands on May 28, 2010 at 5:52am
I agree with Ric and Morli. I think that most people find that they need to strengthen these wings. If you look in the picture above, you will see that the main carbon tubes finish in such a way as to considerably weaken the wings. The cross section of the wing at this point is considerably reduced by the in-board aileron slit. The channels for the carbon tubes also make cuts in line with the aileron slits. So there is only a little foam left to resist torque forces the remaining wing just outboard of the main carbon tubes.. The mode of failure shown in theRC groups photos shows the wing failing at exactly this point. So my belief (as a mechanical engineer) is that this is a failure of structural design, and not a failure of materials science. You can upgrade to Elapor, but there is still a significant focussing of stress lines by the end of the carbon tube at exactly the weakest point of the wing.

It seems to me that you will want to insert carbon fibre rods from the in-board edge of the wing, running past the origin carbon fibre rods as in the picture above. You may not need to run them to the very outboard end of the wing.

It is for those reasons that I doubt the structural integrity of the newer planes made with the stronger foam, when they pull loops with 1.5Kg of all up weight. But my chat is theory. I look forward to seeing the practical results.

There is no doubt that these planes have a lovely specification for aerial survey work with a UAV. They just need some "tweaking".

Moderator
Comment by Robert Krogh (hooks) on May 28, 2010 at 8:12am
Also 99 $ on FPV flying
Comment by Riccardo Kuebler on May 28, 2010 at 9:43am
Morli,
I would not use 2x2mm rods. Square tubes should do the work better, but you have to cut a lot. What I meant is to do a single long cut and insert vertically a flat 1x5mm.
The problem with the Arcus was flutter at high speed and lift force when doing aerobatics on pitch axis (loopings). I broke two times the carbon rod (one was a little too small in his section and the other was stressed too much in a crash, the last one :( ), but as you can see I never broke the wings. Only the extreme tip broke because of the last crash at the carbon fiber flat rod end.
If you want to really stiffen the wings you have to use them vertically and on both sides. This way foam becomes as a filling material between CF plates and you will have a real spare extension.
It has to superimpose the CF joining rod, if not you get a very weak point. It will absorb all the stress in this point.

Comment by Rana on May 28, 2010 at 10:03am
Excellent blog @RC Groups "Skywalker 168cm FPV plane"

All downloaded photos from the above Blog in one zip file.
Skywalker 168cm FPV plane _All_Photos.zip

Mine Skywalker has arrived, I have paid around 210US$ delivered to my doorstep.

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