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Author Topic: Swing Control  (Read 14641 times)
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sx976
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« Reply #225 on: June 24, 2020, 09:30:08 AM »

I have had no success trying to glue Depron with PVA. PVA needs to soak into the grain, and Depron doesn't have a grain. I have also ordered highly expensive glues from Amazon like Titebond II and Gorilla glue for other projects. Sometimes you just have to bite the bullet!! I order Uhu Por on Ebay from England. 4 packs for around €15. Don't know if they ship to India. I live in Germany and it's a German product and it's still cheaper from England!  

Chris P
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« Reply #226 on: June 24, 2020, 09:49:23 AM »

I flew the new Guillow’s Sky Raider in our sports hall this morning. I was expecting to have to adjust the trim by cutting in elevators, but it flew perfectly. I had applied the same criteria as I used for the Felix IQ 60 and wanted to see if a swept wing model reacted differently. There was no difference. The new Sky Raider with a CG balance weight up front is at 51g under half the weight of the old one (ballasted) and flies slowly and majestically in our hall. It would definitely need ballasting for outdoors flying, but I intend to fly it only in the sports hall.

The model comes out of the bag with the tailplane set at a healthy negative angle. This proved exactly right for Whip Control!

This is the setup I used :

Fuselage tether 43mm behind the LE at the root.
CG 62mm behind the LE at the root. Corresponds to 15% at MAC.
Outer guide 97mm in from the tip. Front edge of the wire loop 39mm in front of the LE which gives a forward line sweep of 3 degrees. Loop bent upwards ca 22mm to line up horizontally with the fuselage tether.

I have now been trying out 0.3mm Spider Wire for a couple of weeks and I like it. I changed from monofilament to thread, which was an improvement, but Spider Wire is definitely better.

Chris P
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sx976
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« Reply #227 on: June 24, 2020, 10:05:56 AM »

Here's an F-15 for Depron :
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« Reply #228 on: June 24, 2020, 07:46:03 PM »

It's good to see the setup working well on the Skyraider, Chris.

It sounds as though the CG position would work well as a CL model with that CG and 2 line control to a tail/elevator set at zero degrees.

I agree re your comments on UHU Por for Depron - it is the best glue to use. Also Depron is becoming hard to obtain in some sizes and there are alternatives such as Graupner Veroboard or aerofoam.

John.
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« Reply #229 on: July 01, 2020, 06:42:26 AM »

Flew in our hall this morning. I wanted to try out the third test model, a 600mm EPP SBach. I had cut in a little more negative incidence for the tailplane and used exactly the same setup as the first two test models. The model flew perfectly without the need of any adjustment at all. I think I have finally cracked the setup for Whip Control !

I wanted to keep the Guillow's Sky Raider light, so I just glued on some Cold War style RAF roundels (Valiant, Victor, Vulcan) and a bit of black paint to represent a cockpit. It'll do. I'll do a black cockpit on the SBach too now that I know it flies.

Chris P
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« Reply #230 on: July 02, 2020, 01:32:05 AM »

Neat Chris. I checked out the angle between the tether point and the CG at the wing root on CAD and came up with 8 deg which was where I was expecting it to be.

Have fun.

John
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« Reply #231 on: July 02, 2020, 08:07:31 AM »

Hi John

I always file my data sheets, so it was easy to check. I had set it up as 3 degrees forward sweep from the front of the outer guide loop to the centre of the fuselage tether loop.  I had not calculated  the angle from the front of the outer guide loop to the CG at the wing root as you show. You were very close, it is 8.6 degrees! If you took it to the CG at the fuselage centre line, it would be 7 degrees.

Chris P

PS - I have discovered the down side of Whip Control - Tennis Elbow!!!
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« Reply #232 on: July 02, 2020, 07:28:25 PM »

Quote
PS - I have discovered the down side of Whip Control - Tennis Elbow!!!
  That's annoying and I don't think it will ever be a paying proposition like professional tennis Smiley

Actually i think that the heavier models may give you a easier time- after getting them up to speed their momentum will carry them for a couple of laps perhaps.

happy whipping.

John
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« Reply #233 on: July 03, 2020, 05:33:01 AM »

I was originally using our fabulous Sports Hall just for testing, but I'm finding flying light, slow models there very enjoyable. I think whatever the next project is, will be optimised for indoor flying.

Chris P

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« Reply #234 on: July 07, 2020, 12:34:32 PM »

Re : Reply #213 Whippersnapper

I managed to get up to the flying field today to do some RC flying. I took along the Whippersnapper I had made. It was a bit too windy for my liking, but I flew it anyway. In a few words :

Yes, it will fly loops !!

Yes, it will fly inverted !!

Yes, it will fly bunts !!

Yes, it will fly eights !!

Who would have thought that !! All a bit untidy, but for something that crude I'm totally impressed!!

Chris P
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« Reply #235 on: July 09, 2020, 02:30:00 AM »

One of my club colleagues wants to have a go at Whip Control, so I decided to knock up a model for him to get started. I bought five 48cm foam gliders from AliExpress for under €10. This would also be a great way for someone to build a very inexpensive model just to try it out.

I added 20g under the cockpit so that the model balances 15mm from the leading edge at the root. The fuselage tether point is exactly at the leading edge. The tether has a 90 degree bend and is fitted into a horizontal cut in the fuselage. The wing guide is 130mm out from the root and the front edge of the loop is 15 mm from the leading edge to give 3 degrees forward line sweep.

The tailplane is fitted into the top slot. A little down elevator was found to be necessary during flight trials and was cut in with an Xacto knife and fixed with CA glue. The huge amount of longitudinal dihedral to allow the forward CG means that it is a very stable flyer.

The model weighs 70g, so can be flown indoors and outdoors in not too windy weather.

Chris P
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« Reply #236 on: July 09, 2020, 08:19:00 PM »

Loops and bunts - that is pretty good going Chris. I guess that was on around 30' of line?

Re the foam model - original design by Multiplex. They are pretty good FF gliders as well but also make very interesting small RC models. I had one with 3 channel control and a folding prop. Ailerons,elevator and motor with a folding prop.

I hope your friend enjoys the whip version!

John
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« Reply #237 on: July 10, 2020, 01:18:42 AM »

Loops and bunts - that is pretty good going Chris. I guess that was on around 30' of line?

Re the foam model - original design by Multiplex. They are pretty good FF gliders as well but also make very interesting small RC models. I had one with 3 channel control and a folding prop. Ailerons,elevator and motor with a folding prop.

I hope your friend enjoys the whip version!

John

I only had my small indoor pole with me, so the Whippersnapper was flying on a pole + line length of 23 feet. I hope to get some RC flying in this weekend, if the weather behaves, and will try the model on longer lines.

I also spent an hour converting the Brewster Bermuda back to 2 lines with elevator. Will try that out too.

Chris P
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« Reply #238 on: July 13, 2020, 12:35:55 PM »

I was able to try the Brewster Bermuda with two lines. Rubbish!! Even though it flew acceptably well on one line, it was back to the old problem of the outboard wing low and the model yawed outboard.

I just can't add any more weight to move the CG forward, so I will have to build something new. Very frustrating.

I'm adding the photo again which is still haunting me !!

Chris P
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« Reply #239 on: July 14, 2020, 01:51:46 AM »

This is the only plan for a 2-line model that I have ever found showing the CG, bellcrank and line positions. According to the article it will do wingovers and loops. That's a good starting place!

The choice of an F-15 gives a very long nose moment arm so that huge amounts of lead are not needed. The wing & tail are set at zero/zero, so I assume it flies in level flight with a healthy amount of up elevator. In fact there is a very large degree of elevator movement shown.

I get the CG at 3.7% MAC and the pivot at 18.2%. It's interesting that the bellcrank pivot is behind the CG like on a normal control line model. On the Bermuda I had it the other way around (CG aft of pivot) as on a single line whip control model. Maybe that was the fatal flaw. 

If possible I may use one of my 48cm foam gliders to try a setup something like this before embarking on a new scratch build.

Chris P
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« Reply #240 on: July 15, 2020, 08:47:12 AM »

I spent a few hours yesterday converting one of the 48cm foam gliders to 2-line control using the setup criteria from the F-15. No trouble was taken to make it look pretty.

Well, it flies! It responds to elevator control OK. It's quite sluggish on up elevator and more lively on down. This was in our hall and I now need to fly it outdoors.

Quite a breakthrough and a step in the right direction.

Chris P
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« Reply #241 on: July 15, 2020, 09:05:16 PM »

That's good progress Chris.

One question answered another raises it's hand  Smiley - that of the sluggish response to up elevator.

Hope it works ok outside.

John
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« Reply #242 on: July 18, 2020, 01:23:34 AM »

We're supposed to have good weather tomorrow, so we'll be taking a picnic up to the flying field. I want to investigate the 'single line aerobatic concept' a bit further. Last night I built a second Whippersnapper, this one enlarged by a third. The original plan is based on 3'' wide balsa, so scaling it up by a third meant it was a no brainer to build from German 100mm (4'') wide material. I cut the pieces out on my Proxxon circular saw in a few minutes and had the thing done in just over an hour including glue drying time.

Flying my two line model has definitely contributed to what I think is tennis elbow. I have been using  relatively heavy fibreglass rod and having to hold it in one hand with the control line handle in the other has strained my ancient joints. If I get the two line model flying halfway decent, I will splash out on a lighter carbon pole.

Chris P
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« Reply #243 on: July 19, 2020, 01:27:12 PM »

The Whippersnapper is HUGE fun to fly. The enlarged version even more so. If there are enough bits in my scrap box, I'll build a twice sized one. Loops, eights, inverted flight are all possible at breathtaking speed. The twin boom design is great, as wrapped around solder can be easily moved to trim the model. And it bounces away from crashes without damage.

I tried looping one of my 48cm foam gliders ballasted for outdoor flight. That worked as well!

I also flew the 48cm foam glider converted to two lines. It also loops, but it's all a bit clumsy as the pole is heavy and you have a pole in one hand and a control line handle in the other. Needs a lot more practice, and maybe a lighter pole.

Chris P
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« Reply #244 on: July 20, 2020, 02:52:28 AM »

Chris, I just came across this video. Thought you might be interested.

https://www.facebook.com/ljubetic/videos/10158805749102112

Cheers,
John.
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« Reply #245 on: July 21, 2020, 01:21:24 AM »

Amazing! Lots of skill there.

What do you think is the secret to the aerobatic qualities of your Whippersnapper Chris?

John
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« Reply #246 on: July 22, 2020, 07:11:05 AM »

Amazing! Lots of skill there.

What do you think is the secret to the aerobatic qualities of your Whippersnapper Chris?

John
Fabulous video!!  He's a real showman.

I really don't know what the secret of the Whippersnapper is. Maybe it's a brick on a string, or flying like a streamer on the end of a pole ?? One of the nice things about the design is being able to easily slide the solder nose weight back and forth to get the right balance. When flying loops, I find it better the lead the model by half a circle, rather than being in synchronization with it.

I built the third one. Flies nicely in the hall, but I need to get it outside. The three sizes are #1 Original span 9'', #2 Enlarged to span 12'', #3 Enlarged to span 18''

Chris P
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« Reply #247 on: July 23, 2020, 01:26:16 AM »

I found some details of the Jim Walker P39. Particularly interesting was the model span - 19'' and its weight - 2 1/2 ozs = 71g. My largest Whippersnapper is 18'' span, weighs 57g and is aerobatic on one line. So it would be an excellent starting point for a two line model. With the modifications for two line control it would probably be dead nuts on the 71g.

I was also interested by Jim Walker's bellcrank design which has a degree of self-neutralising with the pivot point not inline with the leadouts. I would copy that.

I have ordered a light carbon pole. It only cost a tad over €10 from AliExpress. I now think that the Jim Walker models were flown on fairly short lines. My current two line fibreglass pole weighs 333g, the new carbon pole only 118g.

I probably have just enough wood in the scrap box to build a new model.

Chris P
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« Reply #248 on: July 24, 2020, 07:45:03 PM »

That was an interesting discovery Chris. That bell crank design could help considerably but on the couple of plans I have seen - only conventional bell cranks have been shown. Jim Walker was certainly innovative - also a salesman. The P39 is supposedly a trainer and yet on the box he reckons it will do 90mph Smiley

John

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« Reply #249 on: July 28, 2020, 07:19:00 AM »

I have had a few other things to do, so I have only just got around to starting the Whippersnapper two line conversion I did the elevator this morning using wire in tube, piano hinge style. I haven't yet 100% decided how to do the bellcrank and tip guide. The design of the Whippersnapper is perfect in case I have to move the bellcrank!

I'm coverting the larger of the 3 models rather than building a new one.

Chris P
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