Algebra short kit build thread

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

Algebra short kit build thread

Post by AndyWarlow » 24 Sep 2018, 18:08

It was Peter Balcombe's build thread that introduced me to the Algebra while looking for a glider as a follow-on to the the Phase 6 I fly and which would continue to hone my 'crash-landing' skills. The built-up wing should also be repairable in the event of an accident (when, not if) or worse case I might need to sweet-talk Cliff into producing just a replacement wing kit. As a further plus, it seems a good price. So for all the above reasons, I now have a Algebra short kit and it seemed a good idea to do a build thread as a follow-on to Peters prototype builds.

So what do you get in the kit? Well the short answer is 'quite a lot'.

For each wing there is a full set of laser cut wing ribs (24 in total) plus full depth plywood spar webbing, false leading edge and trailing edge, 2 wing servo frames and a wing tip. There is also a set of 4 jigging wing beds to help maintain washout when sheeting. In addition Cliff also supplies laser cut tail-plane halves, rudder post, rudder, AMT bell-crank and fuselage servo plate. Along with all this lovely wood comes a fiberglass fuselage, wing plan and finally, to finish it all off, some decals. The laser cut ribs not only slot into the main spar webbing but they also push into both leading and trailing edges so the resulting wing structure should be fast to build and accurate.

Having worked out what balsa I need to complete the build I am now waiting on my order from Balsa Cabin plus a few other bits and pieces to arrive before I begin my build.

This build should be a test of how well the kit and plan work for an average builder and having looked at the plan in more detail over the past few days I have had several queries which I must thank Peter for helping resolve via his build thread. Hopefully there will not be that many more queries as the build progresses.

Given that this is a larger wingspan than other kits I have built, I now think that my building board may be a bit short so before building commences I now need to go and check if a bit of re-jigging is required!
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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 » 02 Oct 2018, 17:39

With the wood, wire, tubes and glue finally all arriving, building has commenced and very quickly one wing frame is now ready for sheeting the upper surface. The laser cut parts fit together well, creating an accurate, square structure. The slowest part was fitting the balsa TE strengthening bits between each rib at the TE and then carefully sanding both the false LE and the TE to match the rib contours. The rib 'legs' ensure the correct washout is built in to the wing but they are easy to break off, as I found out when putting pressure on them sanding back the TE. Putting a length of balsa under the TE keeping the legs off the ground resolved the problem.

I built over the plan just to make sure the ribs were correctly aligned when gluing to the webbing. It soon became apparent that the wing is slightly longer than the plan but the second wing should be exactly the same size as the first so no problem.

8 servo frames are supplied, 4 for Corona servos and 4 for what I think are Hobby King. These two sets proved to be exactly the same size and shape so I glued them in pairs to provide a thicker frame into which I plan to screw my smaller KST servos.

Next step is to sheet the top and bottom surfaces and complete the first wing.
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Peter Balcombe
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Re: Algebra short kit build thread

Post by Peter Balcombe » 02 Oct 2018, 18:22

Andy,
Yes, I think the reason for the plan being slightly shorter than the parts is probably down to me rather than the printer!
I think that the DevWing output I used must be the one which takes the dihedral angle into account, so gives a “projected” panel length rather than the “real” length.
However, as you will have found, the interlocking parts means that everything goes together exactly the same on each wing.
I will double check & correct if necessary.

P.S. Don’t forget to add your servo wires & any servo hatch surrounds before fitting the lower skins!
Peter

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

Re: Algebra short kit build thread

Post by AndyWarlow » 11 Oct 2018, 21:50

Sheeting the top of the wing was quite simple as I used 4” x 48” sheets from Balsa Cabin to avoid a join to get the length required. I also used 48” balsa stick and spruce spars for the same reason.

Once the top was sheeted, as Peter has mentioned there are a few things that need to be done before sheeting the bottom, some of which are easily forgotten – fit the aileron servo frame, stick balsa across front and back of servo frames to support the wing sheet when the holes are cut for the servos, servo extension leads for flap and aileron servos, corner gussets if not already in place and the ply end caps for wing joiner and ballast tubes. With all of these bits done, it is simply a case of breaking off the rib legs and then sanding down both the false LE and the TE to match the ribs.
Finally, I could sit the wing in the 4 wing beds ready for fitting the bottom balsa skin.

And this is where is all started to go a bit wrong! On laying the wing in the wing beds it became apparent that the wing was warped. These are longer, slimmer wings than I am used to sheeting and I think my wing skinning technique must be a bit lacking. Anyway, I dampened the top skin, protected the balsa wing beds from the damp wood, laid the wing in the beds and put weights on the spar. Left to dry overnight, the wing was now straight so I carefully sheeted the bottom of the wing, put some weights on top of it and left it to dry. When I removed the weights, it too was warped, so this time I dampened both sides, weighed it down on the wing beds and again left it to dry. This resolved the problem so I could then add the balsa leading edge and shape it followed by the spruce leading edge and then shape it.

The laser cut wing tips are 3/8th balsa so need to be glued to ¼” sheet to give the required thickness before being glued in place and shaped.
That just leaves the wing root end plate to be shaped from PCB material, or in my case from ply sheet. I will make these for both wings while building the second wing.

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

Re: Algebra short kit build thread

Post by AndyWarlow » 02 Nov 2018, 20:37

I have been a bit slow building these past few weeks but now both wings are practically complete and they do look very slim and elegant. Although they were relatively straight to build, shaping the leading edges, trailing edges and wing tips did take more time than I expected, especially shaping the spruce leading edge which I am sure has blunted my sanding block!

If, like me, you are not familiar with building from a plan which shows just one wing then Cliff does sell plans showing both wings and this will be of help. I didn’t realise this alternate plan was an option when I bought the kit so used the plan I had showing the one wing. Why I say this is because the first three root ribs need to be very carefully and correctly positioned relative to the spar web as they are key to the shape of the wing. If you do not get these correct, then one wing will be more swept back than the other. I thought my second wing was fine and it was only by luck that I checked the second wing against the first before the glue was set that I could see they were different and was able to correct my error which resulted from working with an upside down plan.

With that out of the way, even though I took more care with the sheeting on this second wing, just like the first wing it ended-up warped and had to be dampened, laid in the wing beds, weighed down and left to dry to get the correct washout.

Finally I had to shape the ailerons/flaps from trailing edge stock plus balsa strip to get the correct depth and then cut to size and cut and fit thin ply end caps to aileron and flap. Then ply root caps could be shaped and fitted but as you can see there is a gap between the root caps and the flaps. I decided to reduce the width of the flaps slightly and will glue this bit of trailing edge to the wing to better support the end of the root cap which otherwise is likely to get knocked and damaged.

Now they need to be fibre-glassed around the wing roots as per plan and then covered. I will do this alongside work on the fuselage.
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AndyWarlow
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Re: Algebra short kit build thread

Post by AndyWarlow » 18 Nov 2018, 17:58

Like the wings, the fuselage build is relatively easy but still takes time.

First thing I did was to add some piano wire canopy fixings as per the photo before moving on to the tail-plane.

For the tail-plane, as per Peter’s suggestion, I glued the joiner tubes into the tail-plane halves before shaping them as it is easier to align them with flat surfaces on the tail-plane halves. Having made the two holes in each tail-plane half, I joined them with one piece of tube for the front and one for the back to enable me to make sure the tubes were correctly aligned left/right and up/down as shown in the photo. Once the epoxy had set I then cut the two halves free and shaped then to a symmetrical section. I used aluminium tube which was a good fit over the 14swg wire. Before gluing into the balsa, I nipped together the ends of the tubes to keep glue out.
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Peter Balcombe
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Re: Algebra short kit build thread

Post by Peter Balcombe » 18 Nov 2018, 18:04

Looking good Andy :)

AndyWarlow
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Re: Algebra short kit build thread

Post by AndyWarlow » 18 Nov 2018, 20:49

Next comes the wing joiner rods.

These were made from 6 swg piano wire, each rod 240mm long. Both rods were bent so that when laid flat, the bottom of the bent end was 10mm above the surface. According to Peter, this should give the correct dihedral.

There are dimples in the fuselage where the wing joiner rods appear to go but these should be ignored. Instead, the front joiner hole centre should be 415mm from the nose and 24mm up from the bottom of the fuselage. The rear joiner hole is another 96mm back, centred 21mm up from the bottom. Having measured, measured again and then carefully drilled the holes, when test fitted both rods were well out of where they should have been! Just a few millimetres out with the holes and the effect on the rods is significant.

It took a bit of pondering but eventually I enlarged some of the holes to allow the rods more movement and then made plywood plates drilled to fit tightly over the rods. To get the rods in the correct position I put the wings on and then, with the aid of a book under each wing for support, I adjusted both wings to be equidistant from the tail fin i.e. equally swept back, and the same height off the work surface with the tail-fin at 90 degrees i.e. equal dihedral. The plywood plates were then epoxied to the inside of the fuselage to hold the rods in the correct position. The front plates were epoxied into place first and once the glue had set the clamps were removed to allow access to the back plates which are much more fiddly due to lack of access space. I made the front ply plates longer so they would also provide strength for the Multiplex wing locks when added.

Finally I added some epoxy putty around the rods to keep them from twisting. Probably not necessary and a bit 'belt and braces'.
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Peter Balcombe
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Re: Algebra short kit build thread

Post by Peter Balcombe » 18 Nov 2018, 21:13

Andy, I agree with adding something to try to stop the rods twisting, especially the front one which is easiest to get at.
I had simple ply plates epoxied to each side of my front one, forming a simple box.
This worked well for a while, but then the epoxy failed & it needs replacing as the rods now move & make rigging more awkward as you have to get the rods centralised & parallel for the wings to slide on!

AndyWarlow
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Location: Reading

Re: Algebra short kit build thread

Post by AndyWarlow » 19 Nov 2018, 13:05

Peter, given what you say, and with the AMT control rod in place, I have now been able to extend the epoxy putty so that it covers all of the front rod. Given my less than controlled arrivals, I am not sure this will do the trick but only time will tell.

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