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Author Topic: Show us your P-30's  (Read 61478 times)
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Tmat
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« Reply #325 on: April 11, 2011, 09:02:27 AM »

Dan beat me to it. With fixed surface models this works surprisingly well (left of wind launch).

That said I'm all over the VIT deal. Grin

Tmat
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« Reply #326 on: April 11, 2011, 09:11:05 AM »

Nice mod of the line winch! I just cruised the Ikara site, but they don't seem to offer that any more (it's MUCH nicer than the one offered by GRAUPNER).
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Tapio Linkosalo
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« Reply #327 on: April 11, 2011, 09:19:46 AM »

Oh, sorry. It's not Ikara but Ivan Horejsi. I bought mine from Mike Woodhouse.

Also, did not want to wait to get new drums while making new towlines, so I made my own. Two 3mm lite-ply disks and one 10mm fron ordinary ply, sawn with a circular saw/drill (for circular holes), glued together and doped.

Launching to the left? Did not came to thing of that. But anyway, holding the model in any other direction than pointing towards the wind felt quite awkward, so I think I rather built the VIT and launch dead into the wind... The new model with Eggleston airfoil will for sure have a VIT and AR.
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Pit
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« Reply #328 on: April 11, 2011, 09:22:07 AM »

Thanks Tapio. I think Mike still carries them.
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CometsGallor
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« Reply #329 on: April 18, 2011, 02:10:58 AM »

This is a new P-30 I built and test flew a couple weeks ago. The wind got a bit strong before I could get it working well, but I did learn a few things about my design that needed to be improved. Now I am building a new fuselage and stab for version 2. I will try and refine the original as well and working on the new parts.
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applehoney
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« Reply #330 on: April 18, 2011, 01:26:18 PM »

Very neat and practical.
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FF Bruce
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« Reply #331 on: April 18, 2011, 05:05:13 PM »

I like it, what changes will you be making? I do have one question, and a lot of people do it, why the round rudder when all the other parts are square?
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CometsGallor
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« Reply #332 on: April 19, 2011, 02:28:23 AM »

FF Bruce,

Thanks, one of the changes will be a new elliptical stab that will complement the rudder. I was trying several things I had never tried on the stab, and it is a bit heavy but I was amazed at the torsional stiffness. The outer frame is all laminated and that was a first for me, and the geodetic (sp?) construction was also a first. Both are worth further developing my skills on. I am also building a new fuselage using warren truss construction since an article in an older NFFS symposium publication suggested I might be able to build one lighter and stronger than a rolled tube. I had a fun time developing a tool to help cut all the truss pieces consistently. I will add a picture of it when the bones are done. I also needed to improve my DT wing release since it showed the potential to not fully release, and that could be a bad thing. I am not sure there is all that much science in my changes, I just really like building and trying new things.
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Tapio Linkosalo
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« Reply #333 on: April 29, 2011, 03:50:56 AM »

Flying, on the other hand, was another thing with a "fixed" model (no VIT, no AR). Launching into a 6 to 8 m/s wind means that the initial speed is much faster than the model is ever trimmed for. My first launch into the wind and 40 degrees up looked OK to start with, but then the model stalled (it was not even on the back), and dived into the ground. The following 2 launches were safer, but this time I launched the right of the wind, and the models made half a turn and spend some 5 seconds of flight time flying level, before catching up with the wind and starting to climb. I think for such high winds a VIT would have helped a lot, so that the model could have tolerated such high initial speed better.

Last night did some test flights with the same model, but in calm. Again, the model banked seriously during the burst. First I thought that it is only as I wind now properly (with the new torque meter), but looking more closely I noticed that my wing had warped, with wash-out on the inboard section. Bad! Luckily with a 2-piece wing I could add some packing to get it overall rather flat, and the next test flight was much better. It is funny how much more altitude you can gain when the model is climbing upwards all the climb phase! :-) A VIT might be of some help, but the trim was pretty good even with tail feathers fixed.

The towline-winch winder was working OK.
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CometsGallor
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« Reply #334 on: April 30, 2011, 07:34:53 PM »

I finished a new version of the P-30 I started last month. I decided to make everything new but the wing and I tried lots of techniques new to me. Because one of our club members had given a great presentation on building geodetic structures, I made a new stab using that technique. I also wanted an elliptical shape so I tried laminating the outer frame. On the fuselage I wanted to try a warren truss, based on a great article in an old NFFS symposium publication. I had to make some changes to the DT release which resulted in trying to do some building with carbon fiber. Because the truss was so rigid, I covered  it with tissue not polyspan. I am hoping to start some glide testing when the wind stops, with first power flights later this month. The plane is still 12 grams heavy, so next I will work more on weight reduction, hopefully without sacrificing strength.
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crashcaley
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« Reply #335 on: April 30, 2011, 07:58:10 PM »

CG, that sure is some nice work. Were you able to use lighter wood in the fuselage with that kind of structure. Sure looks like a lot of wood, and looks very strong.

Caley
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DerekMc
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« Reply #336 on: April 30, 2011, 08:02:39 PM »

On the fuselage I wanted to try a warren truss, based on a great article in an old NFFS symposium publication.

Which sympo was the article in? Would love to take a look at it.

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Derek
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« Reply #337 on: May 01, 2011, 09:33:31 PM »

Thanks Caley, I used 7 pound wood in this model, and since it was so strong I will try another with smaller wood. I only have one piece of 6 pound wood so I will try smaller first.  The article was in the 2001 NFFS report, "Finite Element Torsional Stiffness and Buckling Analysis of Large Dawn Unlimited Rubber Model Fuselages" by Jeffery R. Annis.
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« Reply #338 on: May 02, 2011, 06:30:58 AM »

It looks even better than the original. I also agree that the fus looks solid. Perhaps the truss members could be lighter in one dimension or as you suggest of softer balsa leaving the longerons the same size and hardness.
That pretty eliptical tail seems to be asking for an eliptical wing of simailar AR to the present wing. It would be a pain to build though.
John
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applehoney
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« Reply #339 on: May 02, 2011, 10:00:44 AM »

Quote
It would be a pain to build though

Not in the slightest. I've built a lot of them - changed to thin laminated edges .... or even a strip of wetted 3/32 sq for a TE on a 30" wing ... and they're very practical and very warp resistant even with straight ribs. With geodetics they'd be totally warp proof but it could be a pain to lay out the ever-changing rib angles in such a shape.

So saying, my early P30 version of the 'Ellipsis' was the least successful of the series even though it flew well and was eventually lost to a forest. Maybe try another sometime to see if it can be improved.
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« Reply #340 on: May 02, 2011, 09:32:43 PM »

That does look nice and its a tempting thought.
John
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CometsGallor
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« Reply #341 on: May 02, 2011, 11:14:50 PM »

I just tried a few test glides in the back yard with more tests to follow when I move to a more open space, bu the first few tests look like the plane may do ok. It at least gave me enough hope on the design to build another and try to get the weight down to the 40 gram target. I tried putting a very few turns on the motor and even with only twenty or so turns the plane wanted to hold altitude very nicely.

Applehoney: I did use 4 lamination layers of 1/32 to build the stab frame and like you said it was very rigid. The wood I used was heavier than it should have been, so I will build another with lighter wood. When you made your lamination, what type of adhesive did you use?  I think I will try one without  the geodetic, or maybe partial geodetic. I think I would like to target for a stab no more than 3.5 grams. The current one is 5.3 grams. I will also work on some elliptical outer wing panels to balance the aesthetics.  I am a bit concerned about giving up too much lifting surface and or sacrificing the aspect ratio just for the sake of looks. There seems to be a great deal of work done by many outstanding fliers that supports the higher aspect ratio configurations. Then again perhaps a new combination of airfoil / aspect ratio / plan form is capable of raising the bar. I love the sense of opportunity with this hobby.
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Tapio Linkosalo
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« Reply #342 on: May 03, 2011, 12:03:06 AM »

I have been working on this P-30 timer for the new model, but decided that I'll use my old model as a testbed. The idea started from clying CLG's last summer and consistently losing them in the grass, why not rig the timer with a beeper instead of a LED to show the settings and status, and then double the beeper as a locator after the flight. Also the new small linear servos from China seemed useful for the purpose. The finished prototype is a bit too heavy to use in CLG I think (or then again, maybe not, have to try!): the timer and servo weight 3.8 grams, and the 50mAh battery in the pic is 1.8 to 1.9 grams, so it is 5.7 AUW. A smaller battery could reduce the weight a little, but then I'm afraid that if the model is "lost" for a longer period, the battery would be drained below safe lower limit and damaged. There is no room to make fancy battery monitoring features to such minimal timer. This timer uses the same Palm software as my F1A and F1B timers to set the settings, there is a maximum of 7 servo positions for the flight (plus DT). In addition to a single servo, also external RDT can be connected (but I'm not sure if I want to risk a RDT RX on a P-30!).
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applehoney
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« Reply #343 on: May 03, 2011, 12:54:43 AM »

Comets - laminations made with Ambroid. Have since found that one strip of wetted 3/32sq or 1/8sq is more than sufficient for TE's on recent Mulvihill wings, dependent upon span/size..

Aspect ratio - not too much you can do on a P30 as you are limited to span and wing area is important. I find that low aspects do fly very well - check out my 'Ellipsis' in the rubber model section
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« Reply #344 on: May 03, 2011, 01:12:33 AM »

Applehoney: Thanks for the Ambroid tip. I will try that on my next lamination. I saw your 'Ellipsis' picture posted earlier and I really like the design alot. Some information I read in NFFS annual reports suggested that the larger root chord limited the altitude due to more drag, so I was concerned. I had started to build a larger chord wing  but decided to stick a bit closer to the models that I understood to be currently competitive. I do not have enough experience under my belt to get too radical yet. But it sounds like I would not be too likely to create a nonflying disaster. I will be and sure and post my next wing effort.
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« Reply #345 on: May 10, 2011, 06:52:51 AM »

my last P30
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Pit
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« Reply #346 on: May 10, 2011, 07:38:32 AM »

Nice looking drawings!  Have they flown?  The values shown for the wing panels, are they for wing twist?
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« Reply #347 on: May 10, 2011, 08:20:39 AM »

this is rear view. Tail is leaning for left glide circle.
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albisko
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« Reply #348 on: May 10, 2011, 08:56:41 AM »

some photos
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dosco
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« Reply #349 on: May 10, 2011, 09:23:53 AM »

some photos

I like your airfield!!

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