Scale Soaring UK

The original Algebra glider was designed by Sean Bannister many moons ago and Algebra variant kitted by Dick Edmonds under the EMP banner.
Although the original Sean Bannister model had a ply fuselage, later versions used polyester/glass mouldings made by John Hall, who also made fuselages for the Pat Teakle Sailplanes range.

Although these kits went out of production long ago, John Hall has offered to make the fuselages available again, so Cliff Evans is keen to offer an updated 'Algebra' range of short kits based on the original fuselage.
The most successful model in the range was the 100" or 2.5m Algebra, so I have taken on the task of designing a new built-up construction type wing with ailerons & flaps to enable camber control and crow braking instead of the previous inboard flap arrangement.

The new wing is attached using 6SWG rods as before and also contains an aluminium ballast tube to take 7/16" diameter ballast slugs.
Aileron and flap are operated by slim wing servos. The cruciform tailplane is mounted fairly high on the fin to avoid ground damage and is of the AMT type.

Although not a full build thread, the following should give an idea of progress so far as we catch up with what has been done in the last few weeks.

I started on the wing assembly to check out assembly of the new design after Cliff had laser cut the parts.
The basic structure goes together quickly as the ribs are slotted onto the full depth ply spar webbing, with the front ends tied together by a false LE and the rear ends slotting into the balsa TE spar.
A flap servo tray is also inserted at this point. (similar aileron servo mount is laid onto the underside of the top skin later)
Once the main spar have been glued in plus the joiner & ballast tubes, the false LE & TE spars are sanded flush with the ribs tops and the upper sheeting added.

Looks nice Great model all back to the 1980s

Remember to use the upside down camber on the tailplane Peter. Most Important !
Brian

Thanks for the reminder Brian.
I had noted the 60/40% tailplane camber note on the original plan & will need to try to incorporate this when I profile the balsa blocks to section.

You guys may be interested to know that Sean Banister has come back into modeling and is a member of my local club. I am sure he will be keen to know of the regeneration and interest in one of his designs.

AEB

I'm following this thread with interest. I have an original fibreglass fuselage in the attic.
I bought a 3m aileron Algebra second hand in 1995. The wings didn't last long and I built a 100S set of wings for use in competitions. I think the model got through four sets of wings before retiring to the attic.
Hopefully a wing only short kit will be forthcoming.
Martin.

Thanks guys.
Please note that the current wing design is for the less swept back version similar to the EMP kits, but probably easy enough to realign joiners & root rib to increase the wing sweep.

Meanwhile, once the top wing skin is in place the building tabs can be removed from each rib and servo boxes/cabling etc. done prior to preparing the wing underside for the bottom skin. I also fitted a hardwood block inside the root rib between the main spar and forward joiner tube to accept a MPX Unilock wing fastener later. The aileron servo mount is a laser cut ply shape which is simply glued to the upper wing skin. Servo is clipped into this and may be secured with a few dabs of hot glue.
A further addition was 1/8" balsa strips between each rib at the trailing edge spar. This increases the spar thickness to 1/4" to carry the control surfaces/hinging.
In order to preserve the correct wing washout when applying the lower skin, I laid the wing in a simple cradle made from four 1/4" upper surface templates as shown in the photos below.

Once the sheeting done, sand back sheeting at LE to the false LE before fitting the LE. As I had designed for a 3/8" total thickness, I fitted an 1/8" balsa strip plus a 1/4" hardwood strip to reduce weight, but any combinations of balsa/hardwood can be used to suit your taste/landing areas.

The balsa wing tip blocks are then added and sanded to the wing profile. The tip TE and control surfaces are made from 1.5" x 3/8" tapered stock balsa.

Note that although this build is for a 2.5m span wing, the intention is to be able to use alternative wings (certainly 3.2m) on the same fuselage joiners in due course.

john greenfield wrote: ↑12 Nov 2017, 09:18 You guys may be interested to know that Sean Banister has come back into modeling and is a member of my local club. I am sure he will be keen to know of the regeneration and interest in one of his designs.

AEB

that is interesting sean Banister has also joined my club also. ( ivinghoe soaring a )

Cliff Evans wrote: ↑12 Nov 2017, 12:17 Would be great to get Sean's views.

john greenfield wrote: ↑12 Nov 2017, 09:18 You guys may be interested to know that Sean Banister has come back into modeling and is a member of my local club. I am sure he will be keen to know of the regeneration and interest in one of his designs.

AEB

I will ask him next time I see him.

AEB

Meanwhile, the two 6SWG wire wing joiners have been bent to give 2.5 degree dihedral angle & bonded into the fuselage with polyester resin plus a ply faced resin box around the forward joiner. (it is a bit more difficult to get to the rear joiner, so this just has a fillet of resin on the inside).

A servo tray for the rudder & elevator servos plus switch has been mounted on bearers glued to the sides with resin.
The AMT pivot has also been fitted as per Sean's design so that the cruciform mounted tailplane is fairly high up the tail for ground clearance.
The AMT uses 14SWG wires with the pivot in a brass tube which is secured to the fin using externally fitted M3 steel washers due to lack of internal fin width. M3 washers also fitted between the AMT crank and each fin side to avoid resin getting into the crank bearing surface.

10mm thick tailpane halves also cut from light balsa and fitted with AMT wire tubes. A line has been drawn around the tailplanes 6mm up to identify the 60/40% thickness point to get the inverted camber when profiled later.

Elevator pushrod made from 5mm Carbon tube with clevis fittings epoxied into each end. The rear fitting also contains a crank to lift the AMT pivot attachment clevis to the correct height. The pushrod passes above the wing joiners at forward end, so everything has full and free movement.

The rudder C/L wires will pass from the servo arms via a tube on the right hand of the fuselage through exit tubes bonded into the lower part of the fin to reach the rudder horns.

Finally, a photo showing the main components put together. Starting to look the part now.

In my 'in-house model shop' , i.e. the attic. I have a ready-to-fly 2.5 metre Algebra (ply fuz) complete with Fleet servos , a part built 2.5 metre version plus two rare unbuilt 2 metre kits. I remember seeing Sean flying the original at the Silent Flight Nats back in the 80s, it certainly used to shoot up the line!

I have an algebra, told it maybe a mick reeves version! The airframe is over 40 years old now, so im reluctant to fly it. If anyone has a kit of this version or can shed any more light please pm me!

Good luck with the build, looks great!

Well being a new member and corresponding with Peter on his Algebra I've decided to design a new wing for my untouched kit from many moons ago. The original unbuilt wings have de laminated but I always loved the lines of the Algebra. The wing is an Aegea/Supra hybrid at 120" Using AG35 - AG37, I may change the section but this is a first draft and it would be quite easy and quick to build, EDA is 6 degrees. Please feel free to comment or suggest any improvements. This is my first real go with Wing Helper, I have Profili Pro and Compufoil, if version 4 comes out as promised by the end of the year I think it will be a great tool.

Could anyone point me please to who does laser cut ribs and webbing.

Tony

Obviously I've done someting wrong with trying to upload a scree shot! Apologies all

Cliff Evans wrote: ↑26 Nov 2017, 16:11 I do laser cutting!

And very good it is too, if I may say so....



BC

Hi Cliff

I'm not quite finished with the draft yet. I need to order some carbon and select some more wood to get the exact measurements then I can finish off the wing plus do the tail feathers. Can you cut the webs as well as the ribs and is dxf ok? If you don't mind sending me your e mail address in a pm I'll send you the files when I'm done which will include a full wing planform, plus some notes which should be sometime this week. I'm in no massive rush to get them cut as I wouldn't start building until the New Year with Christmas coming up and I'm sure you're probably busy.

All the best, Tony

A 2nd Algebra started and the opportunity taken to get a photo of the inside of the wings just prior to adding the lower sheeting.

Looking good Peter , keep at it .

I'm glad to see there are other fans of the Algebra out there. I love flying mine, I've even fitted it with a tow release! I'm keen to get a replacement fibreglass fuselage as mine is a bit of a mess, are they being sold by anyone yet?

Rob

Two new Algebra now awaiting their warpaint when the weather warms up a bit.

Nice Decals.....



BC

Got a clubmate to take some flying shots during the maiden flight yesterday (thanks Andy).
Poor sky background conditions, so not the best for photography.

However, a successful maiden flight, plus another once a small amount of lead had been added to the nose.
She flies very nicely, has a good speed range, is very agile yet soars with the best of them and the crow braking is handy for landings.
Hope to get some better flight shots on another occasion.

Congratulations. A fitting conclusion to the project.

A couple more photos in better conditions, courtesy of Andy Davey.

Hi Peter,
I have just purchased an Algebra kit from Cliff and am trying to work out the various additional bits I now need before commencing the build. One area that I am struggling with are the brass wing joiner tubes and ballast tube as the holes in the wing ribs are obviously cut to a specific outside diameter. Can you help me by telling me where you obtained the tubes for your build. Thanks. Andy

Andy,
The joiners are 6swg piano wire/6swg I.D. brass tubes & the ballast tube is 1/2” O.D. aluminium tube.
This info. is labelled on the plan between the root end of the wing & the R1 cross section.
Note that the tubes are parallel to the wing surface as the two joiner rods are bent to give the required dihedral angle of just over 2 degrees each side.
Although not shown on the wing plan, my joiner rods were both identical, each being 240mm long and bent in the centre until the lower edge of one end was 10mm above the lower edge of the other section.
Note that this is less than for the original Sean Bannister design due to the aileron wing.

The tailplane is attached as per the Sean Bannister design using an AMT crank with 14swg piano wire & brass tubes.

You should be able to find the materials at any good model shop, else try an online shop such as Sussex Model Centre.

Note that if you use the ballast tube then you would need to make up suitable lead slugs/spacers or or similar to suit the I.D. of the ballast tubes. I have not yet done this. The ballast tube size is as per the Sean Bannister design.
Hope this helps.
Peter

Hi Peter,

Thank you for the info. I had worked out the tubes/joiners etc from the plan but wasn't sure if I could buy my 6swg tubes from any supplier and they would still fit the holes cut in the wing ribs or whether tubes from one supplier worked better. As I need to order materials from the Balsa Cabin I will also get the rods and tubes from them and see how I get on.

When you say that 'the lower edge of one end was 10mm above the lower edge of the other section' I take this to mean that when laid flat, with the bend in the middle, one end is now 10mm above the flat surface. Have I understood you correctly?

Regards
Andy

Andy,
Yes the joiner tubes are bog standard 6swg brass tube & the rib holes are sized to suit.
I was able to slide the tubes straight into the assembled rib structure without any trouble.
Yes, having one end of the wire angle flat on the bench & looking for the lower surface of the other end being 10mm above the bench would work equally well.
I bent one joiner to correct angle & then made the 2nd to be exactly the same when placed together flat on the bench.
As long as both wires are bent to the same angle, the exact angle is not so critical.

Andy,
The 1/2” Aluminium tube is K&S part No. 83035.
I cannot recall where I got mine from, but see it listed both on eBay and on the Elite Models website at about £4.50 per 12” length.
Even if you don’t intend to use ballast, it might be worth installing the tubes as they will add strength to the wing root area.
Peter

My original 100S Algebra had 18" ballast tubes if I remember correctly.
I was lucky enough to get hold of some offcuts of titanium tube from the scrap bin at work. Those wings were strong!

Peter,
I have now ordered balsa, piano wire and joiner tubes from Balsa Cabin. The aluminium tube is coming from an engineering company and servos have already arrived so once the balsa makes an appearance I am ready to build and will start a new build thread. Thanks for your help to date. Andy

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

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

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

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

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.

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.

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.

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

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

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.

Andy,
Just measured my current setup which gives the following control surface movements:

Rudder: approx. 28mm each way measured at base of rudder
Elevator: front joiner 8mm up (pitch down) & 6mm down (pitch up)
Aileron: 23mm up, 10mm down (tip end)
Flap: 0 up, 30mm down measured at root end (approx. 50 degrees)

Full Crow uses full flap, 15mm up aileron & 2mm elevator pitch down. (Not yet fully sorted)

I use coupled aileron/rudder set to 50%.

As I can set flight modes, I have launch, cruise & land modes, with crow only available in landing mode.
Hope this helps.
Peter

Peter,

Thanks for the info. I can now make sure I have allowed for this much movement before covering the ailerons and flaps.

Andy.