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E-Diamond

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.

E-Diamond

Post by Peter Balcombe »

Many years ago (when Pat Teakle was selling his short kits), John Hall (who made Pat's fuselages) had his own range of models which included the 100" Diamond plus others such as the Prelude, Albion etc.
John still has his fuselage moulds and is interested in making some of his old models available again via Laser Cut Sailplanes (LCS).

As a result, I have recently designed new built-up flying surfaces to go onto John's Diamond fuselage to upgrade it to a 3 metre electric soarer, albeit using the same root wing profile, but transitioning to S3021 along the inner panel.
The wing is designed as a 4 piece affair, with zero dihedral on the centre sections to make it easy to use a single carbon joiner tube. The outer panels have 4 degrees dihedral & are plugged on using 3mm carbon rod joiners, with the end sections of these cranked up by a further 4 degrees.
The wing panels can be left joined to ease rigging.
No spoilers are fitted as separate flaps & ailerons give pretty much full span control.
The wings have a sheeted D box and rear open structure, whilst the AMT has been enlarged for the increased span and is fully built-up, as is the rudder.

John told me that when he retooled the Diamond a few years ago, he made the fuselage nose section circular, so blending in the motor mount and spinner should be easier ;)

Anyway, I made a start on the tail feathers last week, making these up as simple structures from 1/4" Sq. balsa & 1/8" balsa strip ribs, LE & TE, plus brass tubes to suit an available AMT crank. The rudder has also been enlarged a little.
I received a set of laser cut ribs from Cliff Evans at lunchtime today, so by teatime had the basic RH wing structure largely glued up using Aliphatic glue as shown in the pics. Once this has fully set, I will add the joiner tubes & then the top spar pieces.
Attachments
Diamond fuselage
Diamond fuselage
AMT tailplane
AMT tailplane
Rudder
Rudder
Wing structure
Wing structure
3D view
3D view
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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: E-Diamond

Post by Peter Balcombe »

With main & panel joiners in place, we now have a complete RH wing structure less the rounded tip shaping.
Attachments
RH wing structure
RH wing structure
B Sharp

Re: E-Diamond

Post by B Sharp »

Interesting Peter! I remember these models from back in the day. I will watch this build with interest. My only thought at the moment is with regard to the fuselage installation. Looking at the fuselage picture, fitting a motor,esc,lipo,2 servos and an rx in front of the wing will be a tight squeeze. Will it bring the CG too far forward?
What is the profile on the wing root? Will it be a problem to blend it to S3021 on the inner sections?
Brian. :)
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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: E-Diamond

Post by Peter Balcombe »

Hi Brian,
The fuselage moulded wing root section is E193 which thus defines the wing root section.
However, it’s easy these days to progressively transition the section to S3021 using a CAD program such as DevWing
This is what I have done over the length if the inner panel & the proof of the pudding will be in the wing build currently well on the way.
(I have now got the 2nd wing basic structure nearly assembled & even managed put the inner panel upper D box balsa skin on the RH wing this afternoon)
Note that another reason to split the wing at the flap/aileron break is that apart from wanting to define an airfoil section at this point, it also allows me to easily modify the rest of the wing planform/section without affecting the inner section/joiner part.

Tomorrow, I plan to sort out the fuselage joiner tube installation as this will then allow me to check the wing fit & get a feel for the overall model weight/motor sizing.
I can’t remember what the original 100” Diamond weighed in at, but I’m hoping for an overall weight between 4 & 5lbs to allow something like a 3548 motor running on a 3S Lipo for relaxed climb & soaring.
The plan is for ESC & battery forward/in the front part of the hatch area, with Rx & 2 small servos in front of the wing joiner.
Time will tell if this can be achieved.
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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: E-Diamond

Post by Peter Balcombe »

Fuselage wing roots drilled for joiners and Uniloc placement, so dry fit of the various bits tried.
Apologies for the rather cramped pics, but it was bit wet outside :o
Pics of the Habicht version (inner wing panels only, plus one with outer panels also. (Tips will be fitted after outer panel D box has been skinned.)

An initial weight check looks good for <5lb AUW.
Attachments
Inner panels
Inner panels
With outer panels
With outer panels
B Sharp

Re: E-Diamond

Post by B Sharp »

That is looking very presentable Peter and the proportions look about right. Can you tell me what is the tail volume ratio to the wing?
Why all the questions? I was thinking of designing a 3 metre electric soarer to replace my ageing Graphite and this may be a possible alternative.
Brian. :)
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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: E-Diamond

Post by Peter Balcombe »

Brian,
The tail volume comes out at 9.7% which is pretty close to the 10% I was aiming at.
The total wing area is 6.44 sq ft according to my calcs, so with an AUW weight of <5lbs, the wing loading should be <12.5oz/sq ft.
It looks as if it should soar well :)
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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: E-Diamond

Post by Peter Balcombe »

Moving on to the tailplane installation, I have thickened up the fin sides by fitting 1.5mm ply root plates each side - thus increasing the AMT crank pivot tube fixing area.

Meanwhile at the forward end of the fuselage, a removeable ply tray has been fitted at the rear of the hatch area to carry the AMT & rudder servos. The forward hatch area is for the power train battery, where a 3S Lipo fits with ease.
There is still 6” forward of the battery to accommodate spinner, motor & ESC, plus ballast if needed.
The Rx can probably go just behind the servos, but if a FrSky G8 series or similar it can go almost anywhere.

The rudder pull-pull wire exits are currently being fitted prior to making up the AMT pushrod & then fitting the AMT crank.
Attachments
2D474739-F176-47C0-9252-67C70FE89A81.jpeg
E4B6FB7C-FA24-469F-A902-2F468AD3C9B6.jpeg
03A609C4-0E45-4647-8C01-A9D9036365DA.jpeg
User avatar
Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: E-Diamond

Post by Peter Balcombe »

Most of the skinning compete now, plus flappy bits made and the tips attached.
Soooo... time for a quick assembly to give a better idea of what the finished shape will be - even if not covered.

Although I have designed the outer wing sections to be detachable from the flat inner wing panel, I think that in retrospect it will be prudent to glue the joint to give a 2 piece wing for flight. (The 3mm carbon rod joiners do not give a 'solid' enough attachment for my liking, although no doubt this could be improved with larger/tighter fitting joiner items).

I will start on the motor installation once the airframe is otherwise complete.
Attachments
All assembled_no canopoy.jpg
All_assembled canopy.jpg
All_assembled front.jpg
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Peter Balcombe
Posts: 1399
Joined: 18 Mar 2015, 10:13
Location: Clevedon, North Somerset, U.K.

Re: E-Diamond

Post by Peter Balcombe »

Looking at the power train at present before I cut the nose off to fit an epoxy motor mount ;)
With overall weight coming in at around 4.5lbs, I am looking at having say 350w available from a 2200mAH 3S Lipo.
So am currently looking at an Overlander Thumper 3548/05 motor driving a 13x5 ish Aeronaut folding prop.

Stan Yeo does epoxy motor mounts for 35 size motors at 37.8mm & 41.8mm diameters & my fuselage moulding thickness is approx. 1.5mm, so am looking at using the 41.8mm ring together with a 45mm cool nose spinner & appropriate yoke/folding blades. A 60A ESC is recommended for this motor.
Cutting the nose back to 45mm diameter will remove approx. 50mm in nose length, which I would imagine is fairly close to the spinner length.

I know that a 3548 motor is probably a bit of overkill, but would rather have some scope for extra power if I need it - at least on this beta build.
A 28 size motor doesn’t appear to be powerful enough, so it may be possible to reduce the 35 series motor length.
With the simple (free) electric flight calculator readily available to me, it looks as if the above power train arrangement should do the job (I cannot input exact components), but wondered if anyone out there had any better info/thoughts?
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