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Algebra short kit build thread

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AndyWarlow
Posts: 21
Joined: 19 Aug 2018, 11:08
Location: Reading

Re: Algebra short kit build thread

Post by AndyWarlow » 19 Nov 2018, 16:47

With the wing joining rods in position, the AMT and its control rod could now be added.

Looking at the size of the tail-plane, I positioned the bell-crank 65mm up from the bottom of the fin, where the tail-plane seemed a good fit, and drilled holes on each side to take the tube on which the bell-crank pivots. The bell-crank is supplied with the kit but I found the shoulder to be too wide to fit inside the fin so sanded it back and also drilled it out to take the pivot tube. As soon as the pivot tube was fitted through the holes and lined-up with the wing it was apparent that it was not level so I widened the hole on one side to allow adjustment and then added a couple of nylon washers on either side of the pivot tube on the inside of the fin. I could then adjust until parallel with the main wing and epoxy the washers to hold the tube in its correct position. Easy to do but a bit fiddly. When the glue had dried, I had been so careful with the glue making sure the bell-crank was free to pivot that the tube was still able to slide sideways. I subsequently glued a couple of small washers over the tube on the outside of the fin to correct this before cutting off the excess tube.

With the AMT bell-crank now in position I followed Peter’s build and used a 75cm long 5mm carbon tube for the control rod. This is a bit shorter than required so at the front I used a short 3mm diameter carbon rod that fitted snugly inside the carbon tube and then glued this to a threaded extender and clevis. At the back I glued a short length of 3mm carbon tube into the larger tube, into which I then glued a 2mm threaded control rod and clevis. I had hoped to get a straight run from servo to AMT bell-crank but I found that my servo was too high so I had to put a kink in the rod at the back to give free movement to the AMT. The last step is to glue the fin post into the tail fin but before doing this, check that the bell-crank has sufficient movement. I decided to carve some balsa out of the inside of the fin post to allow more ‘up’ elevator movement although what I now have is probably too much.
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Peter Balcombe
Posts: 926
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: Algebra short kit build thread

Post by Peter Balcombe » 19 Nov 2018, 17:32

Well done Andy, soon have it flying at this rate :D :D
I started off with a 1m long tube for the pushrod & reduced the length as necessary once I had measured the total length required, taking account of clevises etc.
I epoxied short 2mm threaded rods into each end & always use metal clevises.
I’m pretty sure that I ended up cranking my pushrod run a little bit as well - the rear fuselage is quite narrow.

It’s always better to have bit more AMT movement than too little as you never quite know how it’s going to go with the first launch of an AMT equipped model.

I’m sure you I’ll love it when you get it in the air.
Peter

AndyWarlow
Posts: 21
Joined: 19 Aug 2018, 11:08
Location: Reading

Re: Algebra short kit build thread

Post by AndyWarlow » 20 Nov 2018, 18:21

Thanks for the encouragement Peter.

Finally the rudder control can be installed. Peter used a wire operated closed-loop in his build and I have used the same method on several of my gliders but I don’t particularly like this method as the wires tend to clutter-up the space inside the fuselage. Luckily, as I was looking for carbon tubes on the Hyperflight site, I came across their pushrod sets comprising a thin carbon rod running in a low friction plastic tube. This looked both flexible and strong so I bought the 1.5mm rod in a 3mm outside tube, which turned-out to be a good size.

First step was to temporarily hinge the rudder to help decide where the control horn should go. I then inset and glued into the rudder a small square of 3mm ply sheet so that I could screw the control horn on to the rudder ( I will also do this for ailerons and flaps). Lining-up the control rod along the outside of the fuselage from rudder to rudder servo let me work out where the control rod outer should exit the rear fuselage. A quick drill hole was then filed to a slot and with the fuselage held upside down the outer tube was pushed through allowing it to snake its way down the fuselage, over the wing rods, and exit at the canopy hatch next to the servo tray. Holding the fuselage upside down as you do this ensures the rod passes over the top of the wing rods.Epoxy putty was used to hold the control rod tube in place at both ends and threaded couplers epoxied onto each end of the rod. The end result is a very light, smooth operation and I will probably bear this method in mind for other builds. Threaded couplers are easily epoxied onto each end.

As yet I am unsure where to position the receiver in the fuselage. Initially I put a receiver tray low down behind the servo tray but then found that when the aileron and flap servo leads are in the fuselage, space gets a bit tight. Now, I think I will pop the receiver behind the battery at the front after adding lead to get the required CoG.

With no more bits left lying around the build appears complete so Oracover has now been ordered to cover the tail-plane and wings.
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AndyWarlow
Posts: 21
Joined: 19 Aug 2018, 11:08
Location: Reading

Re: Algebra short kit build thread

Post by AndyWarlow » 14 Dec 2018, 17:47

Prior to covering the wings I first strengthened the wing roots with epoxy and fibreglass cloth as per plan. I used 78g/sq m cloth for this but found the finish to be uneven so after a bit of sanding back I added a further covering of 24g/sq m cloth and Poly-C over the top to provide a much smoother finish. While doing this I also applied this lightweight cloth/Poly-C to a few inches of each wing at the wing tip to strengthen against inevitable knocks. Finally, I covered both tailplane halves with the same 24g/sq m cloth and Poly-C.

With that out of the way, the wings, tailplane halves and rudder were covered in Oracover. Peter tells me that he fibre-glassed his wings and then spray painted them. I tend to add too much weight when I spray so I am much happier to go with the iron-on covering which, incidentally, went on very smoothly. Given how light the covered wings feel I probably could have covered the whole wing in 24g/sq m cloth and Poly-C before the Oracover covering to help against knocks and hanger rash, and the wings would still be light. However, Poly-C is a water-based varnish and can warp thin balsa so maybe this is not such a good idea unless you first seal the balsa, which obviously adds more weight! I am hopeful that my grassy landing zones will not result in damage to the wings, although only time will tell.

With the wings covered, the aileron and flap servo hatches could then be cut out, the servos held in place, and the aileron and flaps marked where the control horns should go. Then I cut small pieces of 3mm plywood sheet and glued these into each aileron and flap so the control horns could be screwed into position after covering. With that, the ailerons and flaps were covered in Oracover.

Both ailerons and flaps were hinged to the wing trailing edge using tape and a strip of Oracover. The flaps are bottom hinged so tape on the top of the hinge line and oracover on the bottom. The ailerons are top hinged so tape on the bottom and Oracover on the top. I find that this combination of tape and Oracover gives strong, flexible hinges with a neat finish.

The servos were then screwed into the servo holders and soldered on to the servo leads installed in the wing earlier. The servos are connected to the control horns using a couple of clevices and a short length of threaded studding. I use metal clevices on the ailerons but have one nylon clevice on each flap as a weak link. Experience shows that when landing using full flap I forget to raise the flaps just before touching the ground and in a poor landing there is a high the risk of damage, hence the weak link.

So the end is now in sight with just a few things to complete. I need to sort out/programme all the control movements, which I have already started, and look for servo covers for aileron and flap before finishing the bottom covering with some coloured trim. Finally I need to add the Multiplex wing retaining system to both wings and then sort out the nose weight to get the correct CoG, starting at approx. 75mm behind the wing LE at the root, as per Peter’s suggestion.
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: Algebra short kit build thread

Post by Peter Balcombe » 14 Dec 2018, 18:43

Well done Andy, she looks very nice indeed.
I’m sure you will love flying her.

AndyWarlow
Posts: 21
Joined: 19 Aug 2018, 11:08
Location: Reading

Re: Algebra short kit build thread

Post by AndyWarlow » 29 Dec 2018, 13:57

Fitting the Multiplex wing retaining system to both wings was very easy and the wings now lock into place with a satisfying ‘click’. Getting them off again is a different matter as the two wing retaining rods do now allow much wing movement, so if you forget the little wedge which Multiplex supply to remove the wings you might find getting the Algebra home a bit of a problem.

With such a long nose, relatively little lead is required to arrive at the CoG. I used liquid lead shot mixed with epoxy glue and pushed this right to the front but in doing so I added a bit too much so now have to move the battery back slightly to get the correct CoG at 75 cm from the wing leading edge, which Peter suggests as a good starting point. This will be tuned via dive tests to determine the best position. I am also moving the receiver back to behind the servos as this is a better place for it.

The all-up weight comes out at just over 1.5Kg and to me this feels a light glider for its size. I now need to find some brass rod to fit inside the ballast tubes as I suspect a bit of ballast will come in useful.

I am still looking for servo covers to fit over the servo horns as all the ones I have found are not deep enough.
Programming of the control surfaces is also complete with crow, coupled aileron/rudder and speed, normal and thermal flight modes all set up. Speed raises the flaps by a couple of mm and thermal drops them by the same amount. I suspect most of my flying will be using normal where the flaps are lined-up to the ailerons.

A flying colleague was so impressed with the look of the Algebra that he, too, has order the short kit. I am pleased to say that the kit now comes with both wings shown on the plan and the rib positions on the plan do now line up exactly with the web spar and false LE/TE. This will make building much easier/accurate and it is great to see a supplier taking note of comments and making changes.

Now the wait is on for the right weather conditions and the right slope and looking at the weather forecast, that might some time away.
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AndyWarlow
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Joined: 19 Aug 2018, 11:08
Location: Reading

Re: Algebra short kit build thread

Post by AndyWarlow » 08 Jan 2019, 19:43

Over the past few days the forecast for today had been looking promising for the Algebra maiden flight and today turned-out exactly as forecast - sunny with a good 13mph wind coming from the NW/NNW - so off we went to Uffington White Horse in Oxfordshire, my nearest slope for this wind direction.

First flights with my smaller 1.5m mouldie showed loads of lift, albeit conditions were not as smooth as might be hoped. Encouraged by my flying friends, who assured me that conditions were fine, and with an extra 15grm stuck on the outside of the nose of the Algebra just to be sure it was nose heavy, it was time to give it a go.

Since this is the biggest wingspan glider I have built and flown I was nervously on the sticks expecting the unexpected as my friend launched the Algebra, but from the word go it was a total non-event and things went very smoothly indeed. From launch the Algebra happily climbed away with no trimming required. Coupled aileron/rudder as suggested by Peter are another first for me and I was expecting turns to be slow, but far from it. Initial hesitation in turns just meant I had to use a bit more aileron than I was familiar with and as the flight continued I became more and more confident flying this agile, elegant glider. A couple of loops were executed, but it was too early for me to try rolls, and in the slightly turbulent conditions I had to pay attention in the turns as the wings were sometimes kicked into a tighter turn than planned, but a bit more air time to build experience and confidence and I am sure this will become a firm favorite.

It was very easy to gain height in preparation for the dive test and I was glad I had added a bit of extra weight to the nose as once in the 45 degree dive the Algebra stayed put, which shows my CoG to be spot on!

A test of the crow braking while flying showed no change in attitude as the crow braking was introduced, which was reassuring, so now was time for the dreaded landing. I am pleased to say that the landing went well and following a nice, smooth turn on to the landing approach and the wings nicely level, I gently applied crow braking. The Algebra slowed up nicely so I began to push the nose down but the landing place was less than ideal as the ground sloped away so more down was required which lead to a faster than planned landing. However no damage was done and I was both relieved and delighted with how successful this first flight had been.

I now need to see if I can get a bit more flap and aileron movement to improve crow braking without spoiling the set-up, but other than that my plan to use the Algebra as an advanced trainer has been entirely successful so thank you to Peter and Cliff for producing this lovely kit.

I think that a few more flights will give me a chance to finalise the trim of the Algebra after which I will post all the various control surface movements and CoG so anyone contemplating building an Algebra will have my settings and those that Peter has posted for comparison. I will also look at some brass rod for ballast slugs to see how the Algebra flies with a bit more weight and let you know.

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Cliff Evans
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Re: Algebra short kit build thread

Post by Cliff Evans » 08 Jan 2019, 23:07

Glad it went well for you Andy. It is a lovely glider. Very glad you are happy with it.

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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: Algebra short kit build thread

Post by Peter Balcombe » 09 Jan 2019, 07:24

Well done Andy.
Hope all goes just as well in all future flights & will be interested to hear of ballasted operation.

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