THIS BLOG DISCONTINUED

Whisper X build info from here onwards now resides in a dropbox folder. Once you receive your kit I'll provide the link to the folder.

Elevator bellcrank

The bushes are bonded into the fin skins in a position that allows the bellcrank to be as far aft as possible. The limiting factor is contact between the rear face of the bellcrank and the forward face of the rear fin spar. This allows the mass balance arm free movement without fouling the fin skins. Once the position is detemined the cut line for the elevator can be established. Drill a small hole through the fin skins and run a gut line through it from tip to tip of the stab. This ensures a straight cut line. The elevator width should be 210mm at the root (+/-5mm tolerance). Accurately fit bushes such that their axis is in line with that of the elevator piano hinge pin (NB). Bond bushes to fin skins. (At this stage only the right fin skin is attached and the left is held in position with screws).

More details available at http://whisperaircraft.blogspot.com/2009/03/horizontal-stab-fairings.html

Tailplane installation

The tailplane is installed at zero degrees incidence. It is therefore set parallel to the canopy sills. A self levelling laser works well for this. Add strengthening layers to the rear face of the forward fin spar in the area of the tailplane attach pins (6 layers 280gsm at 45 deg 100mm above and below pin centreline). Drill holes for the pins through the spar and insert pin bushes into the tailplane with cotton flox. Roughen the phosphor bronze just prior to bonding. Ensure that pins and bushes are parallel (NB). Tailplane front attach bolt is positioned as far forward as possible. Roughen all bond areas and bond as indicated on pictures.

Aileron pushrod holes through fuselage side

Measure 500mm down from the canopy sills (in a straight line). Measure 40mm aft of the rear face of the carry through spar. Use a 57mm diameter hole saw.

Elevator pulley bracket

Cut a rectangular hole and drill 1/4" holes to mount the pulley bracket as shown.

Fin ribs

Roughen bond areas thoroughly and apply cotton flox.
Hold ribs during bonding using 4mm pop rivets.

Ensure that rib faces are perpendicular to the split line mark on the front fin spar. Ensure also that the ribs are exactly parallel to each other or slightly further apart at their front points. This will allow for easy fitment of the horizontal stab later.

Fin skin (right hand side)

Roughen all bond areas thoroughly and apply cotton flox. Attach right fin skin using 4mm pop rivets. Attach left fin skin using screws. Ensure that fin is not twisted. A plywood template like the one shown is useful here. Use the middle stab hot wiring template to assist in making the plywood template.

Fin Spars

Assemble the fin skins, ribs and spars on the fuselage using self tapping screws in the pre drilled jigging holes provided. Level the fuselage and get both the spars vertical. Make sure that the front spar is not at all twisted as this affects your measurements a lot!
Once absolutely sure that both spars are vertical drill 4 holes to attach the front spar to its bulkhead. The 4 holes will ultimately be used for the M5 / 3/16" "chicken bolts" which you'll use during bonding. Drill the rear spar for 4mm pop rivets to be used during bonding. Disassemble everything, roughen bond areas, apply cotton flox and re assemble just the spars. Install the "chicken bolts" to hold the front spar and the pop rivets to hold the rear spar. Once cured drill out the pop rivets. Remove the chicken bolts (or if a chicken like me - leave them in!). Roughen and apply layers of 280gsm around the spars, pulley mount area and tailspring clamp attach area as shown.

Cockpit edge longerons

Make a trial fit of the longerons (cockpit sill/edge mouldings). Trim as required for a good fit. Thoroughly roughen all bond surfaces and apply cotton flox. Hold in place using clamps and pop rivets.

Undercarriage - main bolt

Level the aircraft (a self levelling laser is very useful for this)
Insert the two undercarriage legs as far as they will go into the steel housings (the curved edge faces forwards)
Retract them 5 mm (for clearance)
Determine and mark the position of the top hole. Confirm that both marks are at the same height (the laser is useful for this). This measurement will ensure that your aircraft will stand straight and not have one wing lower than the other!
The hole position is midway between the undercarriage bulkheads (fore/aft measurement)
Drill 3/8"
Fabricate suitable mild steel load spreaders as shown. Suggested material is 50 by 50 by 5mm mild steel angle cut down to 25mm width and shaped as shown. Radius the outer edges to snugly fit the corner fillet.

Temporarily bolt the legs on.

Also shown is a dolley to assist in moving the fuselage around.

Undercarriage bulkheads - phase 3

Cut:
280gsm (500mm wide) strips at 45deg 6 off (full roll width)
500gsm UD 150mm wide 1700mm long 4 off
280gsm at 45 deg (200mm by 300mm) 20off

Note: 410gsm (same total mass) can be substituted for the 280gsm but it is slightly more difficult to drape into such a deep trough.

Sand thoroughly.
Apply cotton flox in the sharp corners and into the holes in the steel
Start with a 280gsm and alternate with the UD (The UD lies in the bottom of the trough only whereas the 280gsm goes up the sides as well.
Add 10 pieces of 280gsm (200 by 300mm) each side as indicated in red in the pic above

Finish with peel ply

Undercarriage bulkheads - phase 2

Repeat the same process for the rear undercarriage bulkhead as used on the front bulkhead

Top engine mount points

Invert the fuselage and support on the canopy sill edges.
Remove peel ply as required and sand thoroughly.

Cutting list for both top mounts (share between left and right)
410gsm (140mm wide) 1300mm long (roll width) 20 pieces
500gsm UD (125mm wide) 1000mm long 20 pieces 
500gsm UD (125mm wide) 1200mm long 10 pieces

Start with a piece of 410 going 100mm up onto the firewall and as far back as its 1300mm length extends. There is a kink near the front edge of the canopy which the 410 can go around.
Next is a piece of UD (1000mm long) going 100mm up the firewall and straight back onto the fuselage side as shown in the pics. UD cannot be kinked.
Third is a piece of 500gsm (1200mm long) overlapping the other UD and extending back to about 150mm past the aft edge of the canopy sill as per the pic.
Avoid letting the layers climb onto the underside of the canopy sill as this will clash with the longeron moulding to be attached there later.

Continue in this order. Finish with peel ply. Work slowly ensuring that all bubbles are removed - this is a critical part of the structure!!. Also ensure that the glass onto the firewall is centred over the pilot hole. Making a dark circle with a felt tipped pen around the hole helps.

Undercarriage bulkheads

Shape 3 pieces of chipboard to fit as shown. Apply packaging tape to the front side of these. Tack in place with polyester bodyfiller. Once cured remove peel ply and thoroughly roughen the bond area on the fuselage skin. Cut the following fibreglass:
1) 350 wide 410gsm (5 off)
2) 150 wide 500gsm 1200mm long (6off) - one piece on vertical face, one piece on fuselage
3) 100 wide 410gsm 1200mm long (4off)

alternate 1) and 2) and finish with 3)

Peel ply whole area

Undercarriage humps - tacking in place

Thoroughly grind all scale off the outside of the steel. Cut away just enough steel on the outboard ends of the humps if they ride up onto the lower engine mount strengthening layers. Apply packaging tape to the inside of the humps so that resin and flox does not go through the holes. Clamp suitable straight edges as shown to ensure that both humps are in plane. Position of humps is as shown (measured from centreline and from aft face of firewall plywood. Once happy with position tack the humps in place using some flox around the edges. Form a small fillet all the way around using your finger.

Lower engine mount strengthening layers

Cut 10 strips 1100mm long of 410gsm cloth 140mm wide.
Cut 10 strips 750mm long of 410gsm cloth 140mm wide.
Cut 10 strips 1100mm long of 500gsm UD cloth 140mm wide (UD strips are cut using a sharp blade between the roving bundles).
Cut 10 strips 750mm wide of 500gsm UD cloth 140mm wide
Above cutting list is enough for both lower engine mount points (share between left and right)

Mix about 300g of resin at a time or a bit less if weather is warm (to avoid exotherm) and using a brush and squeegee laminate as follows:

All layers go up onto the firewall plywood by 100mm.
Start with the long strips first.
Alternate between UD and 410
Shorter strips last
Finish with a layer of peel ply
Strips pass just outboard of gear cutouts and kink slightly at this point to become parallel to longitudinal axis of aircraft. Squegee out all bubbles and work slowly to avoid any dry spots.

Make sure that the lower fuselage is not deformed at all during curing...support it aft of the area where the strips go.

All "resin" mentioned in this manual is either Ampreg 22 (mix ratio 100:28) or Ampreg 21 (mix ratio 100:33). Both come with different cure rate hardeners. Typically "extra slow" is used for very thick lay ups such as spar caps and "slow" or "standard" is used elsewhere. "Fast" is only used for small tacking jobs and mixing filler (microballoons).

Engine mount attach strengthening - preparation

Mark out and cut undercarriage slots in positions shown. Remove peel ply as shown and thoroughly sand the area. All bond areas and areas where additional layers are to be added must be sanded until all shiny spots are removed and the area is completely white. This applies throughout the construction and will not necessarily be repeated again in the manual. Remove dust with a vacuum cleaner and new brush. Do not use compressed air as it may contain oil. Do not touch the bond area or contaminate it in any way.

Firewall - marking out engine mount attach points

Mark vertical centreline on plywood from scribe line on top fuselage half to the scribe line on lower fuselage half. Dimensions are to hole centres. Drill pilot holes.

Fitting firewall plywood

Cut out the firewall to the shape drawn out on the plywood. Carefully sand it until it fits snugly in position. The front face of the plywood must be in line with the start of the cowling joggle. Remove peel ply in the area where the plywood rests. Because the fuselage is tapered towards the nose it is difficult to keep the plywood in position...to assist I drilled a few 2.5mm holes and temporarily inserted nails to help position it. Once happy that the firewall is perfectly in position mix some cotton flox and apply this to the outer edge of the plywood. I chose to only "tack" the firewall in place in this first phase. In addition to the flox I also applied a few pieces of 20mm wide 280gsm (cut at 45 deg) between the nails.  Once cured I will apply the further layers.

Fuselage - preliminary work

Yesterday I fetched the fuselage and a few other components from the factory. I will assemble the first Whisper eXpress at home under typical "homebuilder" conditions. The fuselage halves are bonded together in the moulds at the factory thereby ensuring that everything is straight. We have added a scribed centreline down the top and bottom of the fuselage which will aid with many measurements to follow. The front fin spar differs from the motorglider in that it now consists of two pieces; a circular bulkhead pre bonded at the factory and a fin spar that you bond to it. The bulkhead just aft of the baggage compartment is also pre bonded for you. The firewall and other bulkheads are done by the builder. So far I have just pressed the firewall plywood bulkhead into position. I plan on starting work on the fin assembly and then the firewall.