Scale Soaring UK

Another design from Jilles Smits, this time at 1:2.5 scale (5.26m span).
Estimated flying weight is 11Kg.

Due the pod & boom nature of the fuselage, the building board for the pod construction is much smaller than usual - a 4ft building plank is more than adequate.
Initial construction has just started with the main formers screwed to the board along a centreline & then the initial laser cut longeron & keel/spine pieces glued in.
At present, I have only glued Formers 1, 2, 3 & 5 to the front keel & top spine, plus what must be a ballast tray between F1 & F2. The rest is dry fitted.
The battery tray can be seen between F1 & F3
The design assumes a 34mm wide wheel, but I am fitting a more solid 40mm wide FEMA wheel. Hence the wheel attachment plates & associated rear keel pair spacing has to be widened to suit.
Cliff is currently cutting some replacement mid section formers, so the build will continue when these are available.

With the formers affected by the wheel size now tweaked, the rest of the laser cut structure can be completed.
The lower keel pieces are nicely notched to ensure that everything is self registering.
A couple of missing slots found on one piece, but the cutting files can now be amended to fix that for future builds
Just a handful of internal wing root spacers to add now to complete the initial laser cut parts assembly before starting to add strip wood stringers, joiner tubes, tow release assembly etc. followed by balsa planking.
There are also 3D printed nose & tail cones to fit.

Great! The Bowlus Albatross is a really beautifull plane!
I follow!

The fuselage pod build is progressing, with the upper longerons now in place.
It’s worth noting that it’s a good idea to leave the fitting of RRB (Inner Root rib section) until after the waist longeron (S2) has been fitted.

With the upper fuselage structure in place, the canopy framework can also be put together in-situ to make for a good fit at front & back. Note that there is an additional glazing frame piece to fit once the existing top piece has been profiled to take the ply skin.


Meanwhile, the rear tail boom attachment, fin & rudder structures have been put together using the supplied laser cut parts. The tail boom attachment slides into the boom and will be glued in due course. The tailplane halves attach using a rear joiner rod & M4 bolts at the front. Long 3/32” aluminium tubes carry the rudder C/L wires from the fuselage pod along the inside of the boom to exit points near the finpost. The elevator servo cables also go through the boom.
It is recommended that the rear boom attachment assembly is fitted with the C/L tubes before fitting to the fin assembly - as the tubes can initially be straight at the rear end, then bent outwards to exit via the side slots when the finpost is added. I have opted to use the boom attachment to help position the fin LE/rib pieces, so I will hopefully still be able to tease the guide tube through the side slots later.

Note: Do not build the fin directly onto the rear boom attachment assembly as shown
The rear attachment assembly must be slid all the way into the boom (till it reaches the fin post) & epoxied in position. Then the fin LE pieces tab into slots made in the boom tube, not onto the rear boom attachment woodwork as shown in the photo. I will have to unpick my fin LE attachments.


The rudder structure has been assembled & still needs to be fitted with Bala support blocks here & there. I will fit a long pin through the 3 Robart pin hinges in order to make the rudder removeable for transport, thus a 3/32” aluminium guide tube will be fitted on the front of the rudder post before the lower LE is fitted (exiting at the top of the fin).


The 1st tailplane half has also been started.
This build does not have building tabs on the stabiliser or elevator ribs, so these will initially need to be assembled with ribs vertical on the relevant spar web.
The 1st bit on the stabiliser is to assemble root rib section with servo tray & doublers. The various tabs make this assembly self jigging.

Peter, I have the canopy here ready whenever you want it.

Cliff Evans wrote: ↑15 Apr 2022, 13:31 Peter, I have the canopy here ready whenever you want it.

Thanks Cliff.
Probably Will not need it until the fuselage & lower canopy area has been skinned/planked and profiled to get edges flush. Also, I expect the canopy assembly will need to be painted before it is glazed, a bit like the Oly.
Peter

Upper & lower fin LE pieces have been carefully removed using scalpel & razor saw to remove the Aliphatic glue line
Tail boom now slides between the rear boom attachment assembly & the nearest fin ribs, allowing it to go right back to the fin post.


The tail boom has also been check fitted in the fuselage as it has to slide through several formers to get to the rear of the cockpit.

Stabiliser halves & Elevator structures now assembled & spars fitted.

I am using the GRP tailboom option on this build & decided to draw up a template of the various rear penetrations to enable more accurate placement & registration. The pic below shows this template stuck in place with Pritstick prior to drilling any holes.

The paper template worked very well & all holes/slot centres were spotted through the template, then drilled & fettled.
Just the stabiliser joiner holes to open out to the correct size now.

The rear boom attachment assembly now slides fully into the boom, leaving notches top & bottom to accept the ends of the fin LE pieces top & bottom. The LH stabiliser securing bolt can also be seen in the photo below (Stabiliser halves have an Aluminium retention plate bolted to the root rib & fixing bolt is immediately forward of the LE at root). Additional slots on the boom side are elevator servo cable exits & the rear side scollop is the rudder C/L guide tube exit.
The Stabiliser joiner hole is between the cable slot & the finpost, but is only a tiny pilot hole at present, hence very difficult to see.
Note that the assemblies have only been dry fitted so far to check everything.

Very nice Peter, can you draw the template out in cad, I will supply it with the kit and plans.

Cliff Evans wrote: ↑20 Apr 2022, 22:47 Very nice Peter, can you draw the template out in cad, I will supply it with the kit and plans.

Already done Cliff.
I will send you a file tomorrow to convert to a pdf. Easily printed onto an A4 sheet.

Whilst waiting for some supplies to arrive, I’ve started construction of the 1st (LH) wing.

The first jobs are to splice up the main spars (tapering the outboard 400mm from 1/4” to 1/8” thickness on inside surfaces only), plus joining the main spar web, LE spar & aileron hinge spar web sections.
With the lower main spar pre-glued to the bottom edge of the spar web (Note that the main spar web assembly goes from the tip rib to R5 only, with a separate section going from the inboard side of R5 to the root), the ribs can be inserted into the spar web & registered using LE web & aileron hinge spar.
Note that some ribs need the lower part of the aileron hinge spar tab slot to be removed before they can be fitted.
(I initially fitted the aileron hinge spar in place using just the ribs at each end to hold it in place, then was able to fit the remaining ribs over all 3 spars).
The building tabs on both the webs & a number of the ribs do a good job at making sure everything lines up & a spare bit of strip wood temporarily clipped across the lower surface of the tabbed ribs ensures that the non-tabbed ribs align at the TE.
I’ve initially fitted about half the ribs outboard of R5, plus the aileron servo plate.

All ribs now fitted, plus TE and main wing joiner, followed by the upper main spar.
Photo shows progress so far, with wing temporarily inverted to fit the lower angled root spar in order that the rear spar webs can be fitted once the wing is turned back onto its building tabs.

Final spar web items now fitted, so only the rear incidence tube & airbrake assembly to fit now before starting preparation for skinning the D box structure with 0.6mm ply.
Only 2 servos fitted in each wing, one near the root for airbrake & one for aileron.
The aileron is separated from the wing after skinning & hinged using flat hinges with cotter pins.

Do you ever sleep?????



BC

This is the very quick part as the laser parts just slot together.
Progress is much slower from here.

1st airbrake assembled & moving ok now - although not yet connected to the servo.
I first assembled each brake vane by glueing a 0.8mm cover to each side of the core, then fitted the 1/8” pins, ensuring each was square & central.
Jilles suggests assembling the brake assemblies, then dropping them into the wing, but I fixed my unglued assembly into the wing & them fixed the pivot tubes in place whilst the vanes were held central in the slot with temporary parking pieces.
Jilles has thoughtfully provided apertures in the spar web at each vane so that the ball-link bolts can be slid through from the front after the brake assembly in in place.
Pics below show the vanes in position & and link pushrod in place, but additional servo pushrod ball-link not yet attached at the inboard end.

1st wing check fitted to fuselage pod to ensure the rear incidence peg lines up ok.

The boom has now been drilled to take the carbon stabiliser joiner tube, so it’s time for a trial rig of the tail feathers to the fuselage pod.
Note that the stabiliser roots have yet to be fitted with curved facings to match the boom curvature.
The boom has to be drilled through for the fuselage pin, but this will be done after the boom/tail attachment has been completed & equipped with rudder CL tubes & elevator servo cabling.

Looking really good Peter.

Brake operation all sorted.

The RH wing structure has been assembled during the past week & is now virtually at the same state as the LH wing (once the joiner tube & top spar has been fitted). The airbrake has already been fitted.

Meanwhile, I have now received stabiliser joiner tube material from Hyperflight & fitted 13.8/12mm tube as the joiner tube & epoxied some9.8/8mm tube inside 11.8/10mm tube to make the joiner itself.
The 1.2m long rudder C/L guide tube has been made up from 3/32” aluminium tube, enabling this to be threaded through the tail boom rear assembly & then this epoxied into the tail boom, whilst fitting stabiliser joiner tube & fin LE pieces. With the balsa facing added to the stabiliser root ribs & then profiled to match the boom external shape, the tail feathers can be check fitted once again.

The tail feathers can now be given their balsa LE infill strips & profiled to provide glueing support for the 0.6mm skins.
The rudder has been fitted with a 3/32” aluminium hinge pin tube & then the balsa LE added ready for shaping. Twin rudder horns will be fitted once the LE has been profiled.

Fin LE balsa infill added (hardwood at bottom where aluminium skid fits) plus additional balsa skin support on fin post, then sanded to follow rib profile ready for skinning.
Rudder LE also profiled & hinge pins fitted so that the rudder could be hung & then the twin horns fitted (retained by 3mm pin down rear of the rudder post).
When check fitted, the end of the rudder C/L tube can be seen inside the rear of the boom. The rudder movement is mechanically limited by the horns hitting the fin post, but the required +/-30 degrees looks to be there.
The C/L end loop will need to be fairly neat on the bushes fitted between the horns as there isn’t much space between the ends of the tubes and the horns at full movement.
Note that the fin skins form a rudder hinge shroud at the rear, the lower part is angled rearwards to cover the tapered rudder LE.


A view of the front of the tail boom, with the 2 C/L tubes & elevator servo cables existing via slots in the lower part of the boom.

A photo of a Super Albatross tail group taken at the South West Soaring museum, Moriarty, New Mexico, by Ingo Warnecke.

Fin & stabilisers now skinned & overall structure fully rigged whilst installing the rear incidence tubes on the RH wing.

Note that whilst assembling the tail boom assembly, it’s probably worth fitting a balsa (or similar spacer) between the M4 Stabiliser fixing captive nuts to keep them in place. Once the rear assembly has been fixed inside the boom, keyhole surgery is needed if the captive nuts should release themselves whilst inserting the bolts!! Don’t ask me how I know this

Also, choose when to install the elevator servo cables.
Easier to do before the boom is fitted onto the fuselage, but you need to be careful not to trap the cables between tube & fuselage formers as you fit the tube.
Remember to pay attention to the plan note about initially installing the boom with tail upside down to ensure that the rudder C/L tubes (projecting from bottom) can safely pass the rearmost part formers.

The fuselage pod is now very nearly sufficiently planked to allow it to be removed from the building board in order to complete the bottom section once the tow release etc. has been fitted.
The ply wing root stubs were fitted prior to planking.
The outstanding upper fuselage section will be planked once the boom has been installed. (The assembly is much easier to handle on he bench without the boom & fin attached!)

As can be seen, the cockpit canopy frame was clamped in position prior to planking as this ensures a smooth fuselage surface transition once the planking has been sanded to a smooth profile & then hopefully the canopy separated using a razor saw/scalpel along the frame/fuselage joints.

Fuselge pod now released from the building board & FEMA wheel check fitted.
A start has been made on adding the hardwood block support around the skid spine in order to provide a firm attachment point for the laminated skid assembly.

hi Peter
Beautiful planking! I think you must have been a boat builder in another life.
Thanks
Mike

Each side of the forward keel is blocked in between each former to fill out the space between the the keel and 0.8mm ply keel side pieces. This solid assembly then forms the seat for the laminated ply skid.
The tow release assembly will be fitted on the rear of the front former (bottom loop entry) & a forward skid attachment block between this and the 2nd former.

Albatross video sent to me to post by Peter shows the elevator movement.

A bit more work done on the RH wing in preparation for applying the wing skins.
In addition to sanding the various areas of wood flush, balsa doublers have been fitted just behind the main spar web at root & tip to support the skins.
An 1/8” Sq spruce spar has also been let into position 30.9mm behind the spar web in the brake area to support the upper skin in this area. (The plan shows this support spar, but no slots in the ribs. I’m sure this will be sorted in further kits).
Also shown below is the aluminium wing retention tongue between the root ribs. This needs to be fitted before the upper root skin is fitted.

As can be seen below, the upper D box skin has also now been fitted. (Possible using 2 lengths from a 4ft sheet)

I have also fitted balsa support blocks at the aileron hinge poisons & epoxied Dubro#257 hinges to these prior to fitting the skin strips over them. (Brass hinge split pins used during fixing, but now removed until the aileron has been separated from the wing).

After a few weeks off to visit family across the pond, I’m back in harness.
First job was to complete the upper skinning on the RH wing (apart from rib & brake vane caps).
With this now done, it’s time to turn the wing over & remove all of the building tabs

A little diversion from finishing off building the first wing to make the tow release mechanism……

This release is based on a short length of 15mm Aluminium U channel section bolted onto the rear of the double thickness front former, with the channel forming 3 sides of a box on the rear side.
The tow loop is fed up into the channel from the bottom of the fuselage, guided by 2 wedges, between two 1/8” steel pins - above which slides an 1/8” steel servo operated cross pin.
Small hardwood blocks support the channel at the 2 attachment bolting points & a third block (mounted on the rear) carries the cross pin running in a brass bearing tube.
Hopefully the attached shots show how it works (angled end of channel at bottom, bearing tube block at rear. Ignore the unsupported hole in Ali ).

1st wing now nearly ready for covering - just requires LE sanding to profile.
(Blue foam blocks attached to root rib in photo are to protect the wing retention tab.)
The 3D printed tip moulding was attached using 2 wire pegs epoxied into the tip moulding & balsa reinforcement blocks fitted inside the tip rib.
The aileron was cut from the wing once the main skin area had been fitted - starting from wide hinge gap on bottom surface & marking top rear of hinge spar for final cut in top skins.
M3 clevises & aileron pushrod used. Hatch fitted in lower rib bay & both top & bottom of aileron servo rib bay skinned.

2nd wing now at same state as the first, with just the final LE profiling to be completed prior to covering.
The 3D printed wing tips were fitted using 2 short 16swg rods epoxied into the moulded tip holes & then corresponding holes drilled into the tip ribs. In retrospect I should have fitted balsa support blocks on the inside of the tip ribs before skinning this area
The tips were about 6mm shorter in chord than the tip rib, so I fitted centrally & sanded back LE & TE to fair in.

The aileron servo bays have been skinned top & bottom, with servo hatches & pushrod exits provided in the underside.


The fuselage pod planking is now complete apart from the area around the tail boom attachment. This has been given an initial sand back & faired in with the 3D printed nose cone.
With the cockpit fairing removed, the 2 temporary former bracing bars can be removed & easy internal access gained to cockpit & forward fuselage, plus the rudder servo area behind the cockpit.
The underside planking was initially extended over the wheel area & then a wheel aperture removed once the planking had been sanded to a curved profile.
Note that the laminated skid has yet to be fixed to the mount. Access to the tow release can be seen just behind the nose cone.


Next job is to fettle the wing roots to achieve a good fit along the complete 22” chord length prior to fitting the tail boom & completing the fuselage planking.

Pilots seat made up & tried for size in the “Office”
I laminated the seat pan from 2off 0.4mm ply sheet instead of the recommended single piece of 0.8mm ply, but either way would work. My reasoning was to more easily achieve the sharp bend at the rear of the curved pan, but pre-soak8ng the 0.8mm with hot water would probably do the same thing.

Tail boom now fixed in place after checking that the stabiliser & wing joiners were parallel - eyeing from one to the other makes this easy to do. Once the boom is in place & aligned, the fixing pin hole can be drilled through, dowel fitted & everything alignment re-checked before the epoxy cures. I used a short length of 1/4” carbon shaft length for the dowel.

The rudder closed-loop cables take a straight path from the forward end of their tubes to the servo, mounted an an angle just behind the pilot’s seat. However, this path goes through cutouts in the centre section brace plate & access to the rear part of this would be a challenge once the upper fuselage planking is in place.
Hence I decided that the C/L cables are better fitted & terminated before the fuselage planking prevents access.
There is limited space at the rear of the boom between C/L tube exit and the rudder horn, so I cut back the tubes as far as possible & terminated the C/L cables in loops which secure to the rudder using M2 bolts - allowing the rudder to be removed, but allowing full rudder movement when connected.
Note that an extended servo arm (made from Epoxy board) has been bolted to the top of a normal servo arm to give a 40mm attachment spacing as for the rudder horn.

With the upper fuselage pod planking completed & 3D printed tail cone pieces fitted, it’s time for another check assembly & balance to see how much lead can be safely put into the nose.
The plan shows the balance point to be 196mm behind the LE at the root.

With the wings pulled back 15mm or so from the fuselage, the model can be check balanced using a couple of hooks locating in the fuselage root ribs at 196mm from the LE (approx. the front edge of the wing retainer tabs).
This showed that approx 1.75Kg was needed in the front fuselage former bay to achieve balance,
After making an allowance for the planned 2off NiMh packs & pilot etc at approx. 1Kg then probably 0.4-0.5Kg can be safely put up front.

Whilst finishing off the elevator/rudder skins/rib capping & sorting out the removeable canopy area of the fuselage, I now realise that the canopy glazing hoop C4 should have been fitted prior to finishing off the canopy area planking. The planking needs to go right up to C4 to avoid a step at the front & enable the surface profile to curve all the way up to the canopy.
Looking closely at the drawing & photographs of the full size replica, the canopy appears to need to be fitted into a narrow slot made in the planking around the edge of C4, thus effectively using C4 as a hidden internal locator.

The pic below shows the amended build, with extra balsa sheet fitted to the top of C5 & shaped to fit up against the outer edge of C4 prior to sanding to give a continuous curved profile up to the top of C4.
A slot will now need to be cut around the outer edge of C4 to allow the canopy glazing to sit in in due course.
(My backup plan is to fit a further hoop to the top of C4, but that would then be visible through the glazing!)

Last task before glassing the fuselage (including canopy section) is to fit registration pins & retention magnets to the canopy frame.

Well, the canopy preparation wasn't as bad as I expected
I first ran a scalpel around the the outside of the glazing frame C4 & then carefully made a 2nd cut 3mm further out. Removing the 3mm wide strip of balsa & cleaning out the slot with the edge of a needle file was straightforward, leaving a slot as below.

The canopy glazing moulding was then carefully cut to size, steadily taking parallel strips off the bottom until the glazing rested on the top frame hoop with the glazing sitting in the slot all the way around.
Then the rear of the glazing was cut to size with the canopy frame in situ.
I’m pleased with the result as long as I can keep the slot as clear during fuselage glassing.
It should then be a simple matter of sitting the glazing in place once the slot has been primed with canopy glue.

The build is now just about done & ready for painting.
Apart from glassing the fuselage, fin & stabilisers, the wings & control surfaces have been covered with Lightweight Ceconite & sealed with a coat of cellulose dope. (Photos to follow when the weather is a bit brighter for fully rigged shots).

Meanwhile, a couple of pics showing the instrument panel installation using a couple of small magnets mounted in ply lugs fitted to the fuselage former + matching magnets on the rear of the panel.

Took a brief opportunity to take some final build shots before painting.

At last, finished the paint job, just have to balance her





Thanks to Barry Cole for decals and paint masks

Very colourful Cliff

So she flies

Who was going to doubt it! A beautiful build and super paintwork too.

Just splendid!
Mike

Some more photos.

Superb!

how does she fly? Any video?

Ell.

She is very easy to fly, just a big floater. Even with 50% aileron differential you need bags of rudder in the turn. But overall, very pleased with the way she handles. Sorry Elliot, no video yet.

Hi Cliff,

I'm just starting to frame up of the POD now here in Australia and I have a few questions.

Love the finished Albatross.

How much did she end up weighing?

How did you hold the canopy hatch on during flight?

Cheers,

Marshy

Ok, all up weight is 13.1Kg. Canopy is held on with magnets. Still no video but it really is a big floater.

With no side surface on the fuselage to speak off might be a reason you need more than normal rudder input
I am a lazy pilot and on all my vintage models I have a rudder mix on the aileron so I us only the ailerons most of the time to turn.
Because the sencus here is that you should not use rudder during the tow this mix is switched on when the tow release switch is to the open position.
That way I do not forget the mix as I did in the past.

Thanks for that info Cliff.

Jilles, That is actually a good idea putting that mix on the release switch as I to have the mix on a separate switch and have forgotten to switch it post release.