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Colin Leighfield24/10/2013 19:18:51
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5919 forum posts
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Calm down Graham, think of your blood pressure!

Richard Harris24/10/2013 22:51:44
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2051 forum posts
1890 photos

Carl,

I am liking the built up wing, is it a symmetrical section you are using?

Trying to resist starting mine, can't help but feel the fuselage is a bit flat on the bottom? a bit of curvature may well be in order me thinks, I do like a curvy model!

Anyone thought about adding flaps?

Rich

Bob Cotsford25/10/2013 10:57:22
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7923 forum posts
436 photos
Posted by GrahamC on 24/10/2013 18:52:11:

Well I'm still waiting for the plan....hopefully tomorrow! But when it comes, I am going to go for it! I have all the wood and hardware... so I'm not planning to hang around!.... watch this space...!

me too, postman has been and gone and nothingsad

Never mind, i hope to buy 'enough' suitable sized wood at Gaydon on Sunday, I guess it's all 1/4, 3/16 and 1/8" sheet?

IanR25/10/2013 11:24:36
775 forum posts
4 photos

Na Na Na Na Naa. The postman has just brought mine. I expected the plans to be rolled but they're folded. At least the creases have not been pressed down and I expect the plans will straighten out when pinned down. Now, to try and get myself a flat building board.

In the meantime, I'm hoping Graham will put his wood list on here wink 2

GrahamC25/10/2013 12:56:59
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1229 forum posts
196 photos

Still no plan... sad

Maybe tomorrow! If so I'll make a start!

Colin's advice re blood pressure was very apposite as the Doc told me on Thursday that "if its still that high next week" its pills for me... but I promise that the lack of a plan is not the cause... it has more to do with a very dodgy knee curtailing nearly all exercise for a month or so. The joys of middle age!

Colin Leighfield25/10/2013 13:36:12
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5919 forum posts
2481 photos

Hmmmm- - -. I was middle aged once, can't quite remember when it was. Never mind Graham, it only gets worse!

Good luck with the knee.

Erfolg25/10/2013 15:04:01
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11313 forum posts
1121 photos

Richard

It is a symmetrical wing, using NACA 0010. This decision will require some changes to the airframe, as we all know that symmetrical systems generate no lift at 0 degrees AoA. I have no appreciation of the nominal zero lift AoA of a so called plank wing, although I guess a lot will depend on the radius sanded on the LE, determining the effective camber.

So in my case I am thinking that I will set the wing at an angle to provide a AoA of +3 degrees. So that the model does not fly nose high, when in level flight. This leads to the need to alter the booms to ensure that tail plane does not need permanent down again in level flight.

I am not sure that I have selected the best airfoil for my wants. It is worth reminding myself what I wanted, which was a broader flight envelope, where the emphasis is at the lower end of the speed spectrum, willing to sacrifice top end speed.

From that perspective, I have found that NACA 0015 provides very good characteristics at the stall, being low speed and benign. The down side as speed increases, the induced drag also rises rapidly, hence the selection of a thinner section.

My background has been essentially gliders, where i have flown and built a lot models using various wing sections. I have found that highly cambered sections, often found with undercambered sections, are a waste of time in all but still air and you want to travel, then the drag increases dramatically. Although working well in lift, it is just that it costs a lot to travel to it. I have found that Eppler 205 allows good speed, with acceptable sink, although, slowing the model up, it is not the best and the stall when it comes, can take some height to recover. Retrospectively, I think I should have gone for MH 31 or 32, both have a low camber, and do allow a good turn of speed, whilst they are not particularly well suited to loitering, without flapping, the one model I have built using it, on reflection is not bad, without flaps.

So on reflection, I think I should have gone for M31/32, as the minimal changes would have been required, and I probably would have obtained my low speed handling characteristics. Or if determined to use a symmetrical section, HM 23 would have possibly cut the mustard, being 2 percent thinner, with a good rounded leading edge (no quite to section coordinates), probably providing the good stall characteristics.

As the saying goes "cut wood in haste, relent at leisure".

 

Edited By Erfolg on 25/10/2013 15:12:28

Edited By Erfolg on 25/10/2013 15:13:01

Edited By Erfolg on 25/10/2013 15:15:32

IanR25/10/2013 16:31:08
775 forum posts
4 photos

Erfolg, I suppose I'm being a bit too simplistic but could you not simply "flatten" a section of the bottom of your NACA 0010 profile to provide a less than fully symmetrical wing which would then mount at zero degs incidence?

Erfolg25/10/2013 16:47:44
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11313 forum posts
1121 photos

Ian, most of the wing sections mentioned are near to flat bottomed HM31, 32 E205.

I am no longer certain why NACA 00,, series was chosen other than their performance is pretty (should be identical) much the same inverted or upright. I guess I would have gone for a so called flat bottomed section, if I had realised earlier that other changes are required, to make it work. I think I would also have gone for a 8% thickness, to be nearer a sheet wing, looking for almost peripheral benefits, rather than substantial improvements.

Anyway, what is done, is done and time will tell if any benefit and debits arise from these changes, when we all meet at Greenacres.

Colin Leighfield25/10/2013 16:53:43
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5919 forum posts
2481 photos

This is interesting. I'm not sure that you're going to get what you're looking for here Erfolg. For some odd reason at these model sizes it's starting to look as if flat plate sections perform remarkably well at very low speeds and don't have any vices. The experience with the Tucano has surprised me very much and although the Pushy Cat wing is moderately swept, the write-up on it says that it's extremely forgiving, by the sound of it.

However, what you're doing gives us the chance to find out what the differences are.

Vecchio Austriaco25/10/2013 17:02:28
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1498 forum posts
707 photos

Have a look into the competitors blog - and I have to say you are very busy here!

I like Carl's approach of making his own wings - I was using E205 some 30 years ago on my small (2050mm) aerobatic glider Roitelette Acro. Why? Well I broke the original wings and had to make a new set...angry 2

Worked very well, stall was better than the original (for me unknown) profile. I really look forward to your first flying experiences, no matter what profile you are choosing.

So - I wish you a lot of "Erfolg" (=success) in your project...

VA, nosy to see what the others are doing....

Edited By Vecchio Austriaco on 25/10/2013 17:03:01

Erfolg25/10/2013 18:17:37
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11313 forum posts
1121 photos

Colin

Although it was not my intention to investigate flat plate, although not flat plate wings relative to built up, it does interest me. It may not be quite the true comparison that it could be, as my tips have been increased by 25mm. I had considered going to 2/3 rds.

I did have another plan, which was Depron wings. One using the EK section and the other, doing a lot of filing, both covered with glass cloth and Water Based Varnish. It was having to travel that decided me, that this was not the way to go.

Gerhart?

I quite like E205, and I to first used it over 30 years back. Although some claim that Clark y behaves identically, I am certain that they have never flown model gliders. Although similar, I think it is the max thickness being slightly further back, the higher entry and consequently slightly lower camber that makes a difference. I have used the same section more recently on my Ta 152, which not only has tremendous speed, but a really good glide. A real fan.

I have tried other sections, I generally have concluded that it is a good rounded LE without sharp edges and a moderate camber that produces a good all round section.

Now recent progress, I have inserted all the shear webs (graduated width) and attached the top spar. I am ready to sheet the wing, which will take me some time. I am not feeling well, all say awww at this point. Plus I am decorating my girls house, which diverts some time. Now you are supposed to say what a martyr.

Edited By Erfolg on 25/10/2013 18:18:05

John Privett25/10/2013 18:45:40
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5944 forum posts
236 photos
Posted by IanR on 25/10/2013 11:24:36:

I expected the plans to be rolled but they're folded. At least the creases have not been pressed down and I expect the plans will straighten out when pinned down. Now, to try and get myself a flat building board.

Ah, now I think I see... As I said earlier, when I looked into buying the plan a couple or so years ago I was put off by the cost of the postage. I recall the postage was actually about the same price as the plan, or possibly even higher.

Now that was probably because they use to send plans rolled-up in a tube. But the Post Office "adjusted" postage prices 2 or 3 years ago and I suspect the cost of of posting a lightweight, but slightly bulky tube went up enormously. So it seems Traplet (and probably others) can now only offer a sensible price for postage by sending plans folded. In any case, the plan I got (the free one included with the mag) was folded too!

ken anderson.25/10/2013 18:47:22
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8424 forum posts
772 photos

erfolg-what a martyr.....I take my hat of to you for your knowledge of the various wing sections......all the PC's that I have built and flown have had the wings made from the 6mm sheet and planed/shaped as per the plan.....I had my doubts about the sheet wing etc........but it works a treat.....and all my respect to the lad who designed it(Ron laden) ...

ken Anderson....ne....1...ron laden dept.

Colin Leighfield25/10/2013 19:28:40
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5919 forum posts
2481 photos

Good on you Erfolg and I hope you feel better soon.

IanR25/10/2013 19:37:17
775 forum posts
4 photos

Awww, what a martyr.

Ian ( the things you have to do to keep in with people Dept)

GrahamC26/10/2013 18:10:06
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1229 forum posts
196 photos

When I arrived back from Tesco this morning guess what.... The plan had arrived... And the ladies of the house went to the theatre this afternoon... so look what I did....

p1010964.jpg

And...

p1010965.jpg

I've got a video to edit... and then I'll start a build log. I'm hoping to put in enough information to encourage some new builders to have a go!

Richard Harris26/10/2013 18:14:33
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2051 forum posts
1890 photos

Nice work Graham thumbs up

John Privett26/10/2013 18:46:31
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5944 forum posts
236 photos

That's quick work, Graham! Looking good too.

WolstonFlyer26/10/2013 18:48:44
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2104 forum posts
189 photos
Very nice!

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