Main Construction Page

Next Archive

February 05


The fin web is jigged for glue clearance and glued in. Some small parts like cow horns are made to help connect the main bolt bearing to the upper fuse shell. The bearings themselves are wet laid with carbon twill, cured then ground to fit so the glue thickness is small where the main bolts go through. Although a laid in situ bearing would have some good points I felt the precured block would have more even resin content and less voids. Some carbon uni and extra glass layers distribute load from the main bolt bearing areas.

November 04

The buckling analysis with the JAR22 landing loads told us to add more thickness to the wheelbox and some of the bulkheads.
The undercart bearing areas were redesigned for more strength and stiffness also. The old bearings were ground off and rebuilt as shown with precured carbon blocks. Then the bulkheads and wheelbox were glued in and most of the tape joins done.

From Oct to Jan there were some distractions from the workshop. I had to review loads and design for the major internal parts.
A buckling analysis was needed for the wheelbox and fuselage bulkheads. The calculations for the wing main bolts and bearing areas in the fuse were reviewed. A more detailed FEA showed some peak stresses.
I looked again at tail loads that were sizing the fin structure, which lead to a revision of all the tail load cases with reference to CS22.
Then a detailed look at stick forces for the control system redesign. Some interesting results from Xfoil showing the non linearity in the hinge moment coeficients.

September 04

The demoulded, partially finished parts. The cure temperature may have affected the finish or release materials on the forms/moulds - surface release was really poor and some revision of shape would also help release.
The main bulkheads and wheel box are clamped together to show how it all fits.

August 04

Layup of spar bridge box. General idea with these internals was to have
balanced glass twill at 45/0/45/0.......
The 45deg twill on this plastic carrier film has only one diagonal joint, but to interleave the 0/90 fibres we ended up with several crosswise joints. Unfortunately the box form was not stiff enough at the
joints and we have to do this one again.

August 04

There was some review of FEA and calculations for these internal structures
(Structural web page will be updated around this time).
The fin spar web is also the closing element for the fin section in
torsion, so it is a carbon sandwich for continuity. The plywood bearing
blocks on the wheel box double as panel stifeners for the side loads. We'll
put a picture on the structural page that makes it clear how
this all goes together. We should be using purpose made super stretch
bagging film for these shapes but we are just using plain
50micron clear film, with a lot of informal pleats and folds to avoid any
surface tension on the bag. We occasionaly get a wrinkle or
inclusion on the outer fibre layer if it is too wet.

August 04

The moulds were strengthened and several flanges added. The spar bridge box
form is designed to come appart inside the
part. There are fillets of bondo at the end joins with tape to seal the
joins so the vacume won't suck resin into the gaps. Same idea
for the front plate of the main wheel box form. Each face of the wheel box
has an air outlet in case we have difficulties with
release. Most surfaces were finished with Duratech, sealed with TR glaze
and waxed with some old Epiglass wax. Sofar this
release system has worked on cedar and MDF end grain ok.

June-July 04

The forms and moulds for the major fuselage internals are made. Release tape is put locally on the fuselage shells.
About 1.5-2mm of glass cloth is laid in the location of the final gluing flanges. It's thickness represents the glue thickness for the actual parts later. MDF board is used to define the planes of the bulkheads etc. It is glued to the glass cloth first on the starboard then port side. Because of the risk of prerelease, the method of closing the moulds to accurately set the final glue gap was not used. Insteead we used the plane of symetry, and for the fin spar (too floppy) we used the Klause measuring device to adjust the height when gluing the MDF on the port side.
The spar bridge box and the wheel box are male forms, the rest are female moulds. Some finishing required and some extra laminate required to beef up the flange part and it's joint to the MDF.

June 04

The fin spar caps are wet laid onto a strip of twill weave in the trench in the PVC.
This fin spar becomes an oblique bulkhead that intersects with the bulkhead for the rear wing spar. Inner laminate is laid up on the fin. The joggle (on the starboard fin) will have carbon uni inside it to form a cap for strong axis stiffening.

June 04

Starboard fuselage is laid up. Location of the regestration pin holes refered to before is shown.

May 04

The port fuselage is laid up. The fin is a carbon PVC sandwich, the fuselage is a solid glass shell with some carbon uni.
The wing root fillet is quite deep at the trailing edge so that bit was laid up first and a shaped "wedgie" of PVC was glued in the space to make an easier contour for the main layup.

April-May 04

The canopy sill insert mould is made and fitted to the fuselage mould. Fits good. For the prototype it is just held in place with hot glue.
Preparations are completed for the fuselage shell layups.
Alignment and regestration of all the internal bulkheads geometry is checked and marked on the moulds.
There are two holes for regestration pins at the cutout for the spar bridge so that locating the main bulkheads after the fuselage layup is easy. Location of all internals refers to that. The rudder cutout and gear door locations are marked.
The gear doors are laid up, trimmed and held in the moulds so the fuselage layup goes over the top.

April 04

Some forms and rough moulds are made for the root ribs. We may leave the tip ribs and tip joiner till later.
The shown method has some problems- instability and weakness of the poured urethane mostly.
Better and easier methods will be used on the fuse bulkheads, fin spar. We'll report on success of that soon.

March-April 04

The wing shear webs are being glued and taped to the upper shells (the shine on the spar bridge is just plastic film).
They were first held in the glue flanges on the lower shells with cardboard packers and tape, then the
moulds were closed to effect the gluing.

Main Construction Page

Next Archive