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Algebra build thread

All non-scale topis should go in here for discussion.
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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Algebra build thread

Post by Peter Balcombe »

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.
Attachments
First wing structure
First wing structure
Root structure
Root structure
Sheeted wing
Sheeted wing
steve dowell
Posts: 21
Joined: 18 Mar 2015, 09:00
Location: pentewan cornwall

Re: Algebra build thread

Post by steve dowell »

Looks nice Great model all back to the 1980s
B Sharp

Re: Algebra build thread

Post by B Sharp »

Remember to use the upside down camber on the tailplane Peter. Most Important !
Brian :)
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: Algebra build thread

Post by Peter Balcombe »

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.
john greenfield
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Joined: 18 Mar 2015, 07:52
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Re: Algebra build thread

Post by john greenfield »

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
AEB = Aeronautical Energiser Bunny (with thanks to CW)
Martin G
Posts: 82
Joined: 18 Mar 2015, 13:27
Location: North Wiltshire

Re: Algebra build thread

Post by Martin G »

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

Re: Algebra build thread

Post by Peter Balcombe »

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.
Attachments
Wing beds
Wing beds
Sheeted wing underside plus tips & LE
Sheeted wing underside plus tips & LE
Aileron servo box
Aileron servo box
Aileron servo
Aileron servo
Flap servo box
Flap servo box
Flap servo
Flap servo
roo Hawkins
Posts: 557
Joined: 18 Mar 2015, 20:12
Location: Northamptonshire

Re: Algebra build thread

Post by roo Hawkins »

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 )
john greenfield
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Re: Algebra build thread

Post by john greenfield »

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
AEB = Aeronautical Energiser Bunny (with thanks to CW)
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Peter Balcombe
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Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: Algebra build thread

Post by Peter Balcombe »

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.
Attachments
AMT crank installation
AMT crank installation
Fin AMT mounting
Fin AMT mounting
Fuselage servos & joiner installation
Fuselage servos & joiner installation
Overall fuselage
Overall fuselage
Initial assembly
Initial assembly
Tailplane halves
Tailplane halves
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