Algebra build thread

All non-scale topis should go in here for discussion.
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Peter Balcombe
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Location: Clevedon, North Somerset, U.K.

Re: Algebra build thread

Post by Peter Balcombe » 23 Sep 2018, 17:35

Ok Andy.
The wings should go together quickly & tailplane is just a matter of shaping balsa once you have the joiner tubes in place.
(I set tailplane joiner tubes in place in both halves at the same time before shaping, using the flat surfaces on tailplane blanks to get both halves parallel & used the joiner wires to align the tubes) Draw centrelines around tailplane blanks to help get each half the same when carving the section profile & remember to get left & right halves if using the non symmetrical section!

Fuselage work is pretty minimal (wing joiner tubes/servo lead access + servo tray at front end) with most work at the back end, installing the AMT crank/pushrod & then the rudder + pull/pull wire leadouts in the appropriate place.
Note that the fuselage wing root dimples are for the original design and should be ignored for this version.
Note that servo tray needs to be installed so that the AMT pushrod/pull-pull wires pass underneath the fuselage wing joiner tubes, rather than try to go through them!

I installed my canopy with a bit of ply spaced off under the front to enable the canopy to slide on, then fitted a commercial sliding pin type latch at the rear. The crow braking option now provided avoids any need for installing canopy braking!!

Good luck with the build. Let me know of any issues & I will assist/amend the drawing to suit.
Note that my drawing mainly covers the wing & tailplane build, assuming the builder is experienced enough to fill in any general assembly gaps/build to his taste. There is an original Sean Bannister plan about, but that is for a RES model, so not everything is relevant.
Peter

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

Re: Algebra build thread

Post by AndyWarlow » 24 Sep 2018, 16:33

Hi Peter,

I would like to think that I will be a good test in terms of my build experience and tackling the Algebra but some elements of the Algebra build are a bit confusing. Anyway, we shall see!

In your build thread you say 'I had noted the 60/40% tail-plane camber note on the original plan & will need to try to incorporate this when I profile the balsa blocks to section.' I have never come across a tail-plane with this type of camber before. Did you incorporate this in your builds and how important is it?

I also now notice that each wing root has an end plate of PCB material. I assume this is to protect the wing root from damage and so it must cover the leading edge and wing skins. Could this be made from plywood?

You mention that the dimples in the fuselage are not to be used as drill guide-holes as they are for the original design. Since the fuselage does not have wing shoulders as a guide to where the wing sits, what is the position of the wing on the fuselage?

Sorry for all these questions but hopefully, via this forum, your answers will be available to other builders who choose this kit.

Andy

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Peter Balcombe
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Re: Algebra build thread

Post by Peter Balcombe » 24 Sep 2018, 18:08

Andy,
I tried to mount the wings in the same position on the fuselage as on the original Algebra, but because my wing joiner/attachment arrangement is different then the various holes need to be in slightly different places.
Having just measured my model, the front joiner hole centre is 415mm from the nose and 24mm up from the bottom of the fuselage. The rear joiner hole is centred 21mm up from the bottom.

Although I have shown the 60/40 tailplane camber as used on the original Algebra, I don’t think it really matters if you build as a symmetrical section. My understanding is that the reason for the non symmetrical section was to cause the model to tend to automatically pull out of a dive - originally designed as a thermal soarer.

Yes, you could use a ply wing root cap if you like. This is mainly to beef up the fuselage interface area.
Peter

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

Re: Algebra build thread

Post by AndyWarlow » 24 Sep 2018, 18:17

Peter,
Thanks for all your advice and information to date which I will incorporate into the build thread that I have just started. Hopefully by the end of my build you will have a better idea of what information is lacking from the plan that could be added as notes to support builders.
Regards
Andy

Martin G
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Location: North Wiltshire

Re: Algebra build thread

Post by Martin G » 24 Sep 2018, 21:04

If I remember correctly, didn't the Algebra tailplane fit upside down?
This made it "lift" downwards the faster it flew which is what caused the nose to lift. A symmetrical section, properly trimmed for incidence, would "hold" the pitch angle far better. The cg would then govern how quickly the model pulled out of a dive.

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Peter Balcombe
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Re: Algebra build thread

Post by Peter Balcombe » 24 Sep 2018, 21:26

Martin,
That’s correct. It was designed to have the opposite of a “lifting tail”, thus the faster it flew (I.e. if it started diving) the greater the equivalent “up elevator” force generated to help return it to level flight?
(Remember that the original Algebra was Rudder/Elevator + Spoiler for thermal soaring).

I built mine as such & it flies very nicely indeed, but would probably prefer a symmetric tailplane section for general flying.
I might even build an alternative tailplane set for the current model & see what difference it makes.

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Peter Balcombe
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Re: Algebra build thread

Post by Peter Balcombe » 05 Oct 2018, 14:42

Just checked the CoG location on my Algebra & it is currently approx. 75mm behind the wing LE at the root.
This is fine for general flying, but you may wish to start a little bit forward of that & work back to suit your flying style.

In light lift, a little bit of flap deflection helps a lot.
Rolls & loops are on the aerobatic menu, but the small rudder makes stall turns a challenge.

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

Re: Algebra build thread

Post by AndyWarlow » 02 Nov 2018, 20:45

Peter,
Sorry, more questions.
I presume by your comments 'awaiting their warpaint when the weather warms up a bit' in your build build narrative that you painted your Algebras, presumably having first fibre-glassed the wings. Would Oracover/Profilm be an acceptable alternative and provide enough strength. If not, what weight cloth did you use?
Andy

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Peter Balcombe
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Re: Algebra build thread

Post by Peter Balcombe » 02 Nov 2018, 21:35

Andy,
I use a lightweight glass cloth (25gsm?) on all of my fully sheeted builds & then spray using rattle cans.
One reason for this is the abundance of gorse etc. at Crook Peak.
I also glassed the tailplanes but put a white film covering on the rudder.
I would have thought that Oracover/ Profilm would make a good alternative as long as you remember that the wing skins will take less ‘finger pressure’ during handling.
Peter

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

Re: Algebra build thread

Post by AndyWarlow » 30 Nov 2018, 21:25

Peter,

One final bit of information please on your Algebra. I know that control throws are are a matter of personal taste but can you advise the ones you have on the Algebra so I have something to start from, including the most important aileron, flap and elevator for crow braking.

Thanks. Andy.

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