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Peter

Whatever happened to Macfloatyface?

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Peter

Those with long memories may recall that last February I posted and article about an alternative approach to the current crop of super light F5J models with moulded skins and very thin wing sections. This involved making a built up wing with a good old SD7032 10% thick wing section using the theory that the high lift generated at slow speed would float around on those rare occasions in the UK when there was no thermal activity and no wind - ooh, and save loads of money!  It earned the nickname of Macfloatyface.

It ended up looking something like this:

DSC01475.thumb.JPG.c11eae682d7b58e52e8780d3543ca177.JPG

Did it work? Well sort of....

It certainly floated about in straight lines but turning was a nightmare. Ailerons just do not work at such low speeds and nothing happened after a control input until it just lurched into an uncontrolled turn. Now I remember why the thermal soarers of the 80s and 90s used rudder/elevator controls only and loads of dihedral.  The second problem was that the built up structure on the flaps and ailerons tended in storage to warp so it flew differently on every outing. The  result was that it was virtually impossible to use in a competition.

What to do? The only answer seemed to be a rebuild.

The problem of the twisty flaps/ailerons was solved by recycling moulded parts from old damaged F3J Tragi panels. The wing was then rebuilt using the same spar made from 10 X 0.5mm carbon strip and bound in kevlar thread and  thinned to the same depth as the Tragi wing at around 7%. The basic construction remained the same conventional balsa D box L and capped ribs behind the spar. Covering is film over lightweight doped tissue to add some torsional strength.

My other F5J models fly very well using a Tragi wing on an Optimus fuselage but I did not have a spare fuselage so set about finding a cheap alternative and came up with a pod and boom from CLM Pro in Bulgaria on ebay. Its a bit basic but it was cheap and you get what you pay for!

So now it looks like this:

                                                           IMG_0428.thumb.JPG.bf16ab8319e1920820589269094173d6.JPG

Looks a bit like an Optimus, doesn't it? Well, there's not much wrong with that because the Optimus is a superb model but it's not an Optimus so its called an Noptimus (sorry Neil).

How does it fly? Well its nearly Christmas so the number of calm days for test flying is a bit limited but so far the handling in turns is a great improvement and it doesn't need de-warping every time I take it out.  We shall see.

 

 

 

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thermaldoctor

I like it Peter no need to apologise. Noptimus looks good. Nice work getting a CLM pro fuse linked up to an all moving tail fin arrangement. Like Optimus wings, the Tragi airfoil is one of the best so I'm sure it will work well if you can get it to turn effectively.

I look forward to seeing it in action if it proves successful. 

Best of luck with it it

Neil

Of course if it doesn't work out you will be forever known as the N umpty

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SilentPilot
42 minutes ago, Peter said:

It certainly floated about in straight lines but turning was a nightmare. Ailerons just do not work at such low speeds and nothing happened after a control input until it just lurched into an uncontrolled turn.

 

That’s quite reminiscent of big full size gliders! I remember the first time I flew a Duo Discus I thought it was an absolute pig to fly, so hard to coordinate the turn properly, until I was told to forget my training and lead with the rudder. Once you did that it was like a pussycat!

Not sure if a similar thing would work on models but checkout the rudder arrangement on a Numbus 4. When you give rudder it also applies proportional spoiler actuation to the extreme outboard ailerons to get it to yaw :D 

 

Tony

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pete beadle

Hi Tony

Many years ago I bought, built, and flew a Graupner Cirrus. I didn't know it at the time but the Cirrus was a semi-scale Cirrus/ASW15 (so I was told anyway)

After flying it on rudder/elevator and usually in low wind speeds I got used to the light weight, low penetration and steep straight dihedral and had many, many smooth, scale--like flights but, one day, I got it into my head that, if I bought a pair of wings with ailerons, it would be even more scale-like, and more precise so, I bought them, built them and flew the Cirrus, with less dihedral and ailerons and prepared to be delighted with the new, more precise, aileron-fitted Cirrus

IT WAS A DOG! I'd never experienced the combination of Dutch rolling and adverse yaw it now featured, and barely got it down to the side of the hill without smashing it to pieces, after a really incident-filled maiden aileron-equipped flight, barely under control from launch to landing

Luckily though, a fellow Cirrus owner/flyer was there and he walked over and gave me some sage advice......go back to rudder/elevator with rudder as the primary turn control, replace the lesser dihedral wing joiners with the older and greater dihedral ones , mix the rudder with the ailerons about 20% so you could see them working in a scale-like manner.......and go again

The next flight was a total delight, a real transformation!  Effectively I got back my R/E control and my more scale-like, aileron appearance, and I flew it that way for years on flat-field and slope. So, my advice is ....for slow speed control use rudder, for scale appearance mix the ailerons to the rudder and practice smiling....a lot!  

Good luck

Pete

BARCS1702

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Peter

The fin and rudder came from on old Optimus which had been repaired after a mid air in Bulgaria. They had gained a little weight but we all do as we get older. Attaching them to the boom and connecting the elevator drive bellcrank was not a problem but mating the Tragi tailplane was a lot more difficult. The pivot/drive pin spacing is the same on both, hardly surprising as Alesandre used a Tragi wing and tailplane on his original Optimus prototype fuselage. The problem was that the proper Optimus tailplane wraps round the fin and has recesses for the pivot bearings which are located in the fin so it was a fiddly job to modify the Tragi parts to fit without adding weight in the wrong place.

Anyhow it has been and interesting and satisfying experience and brings back memories of the good old days when we used to design and build models.

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