Carf-Models Ultra Lightning Instruction Manual page 15

range of turbines and it is, therefore, a compromise - but has already been used very success-
fully with several different turbines including JetCat Titan, P160, P180 and AMT NL Pegasus HP
types. If you find that you have a warm fuselage after an extended idle period, then you can
increase the cooling air around the outside of the outer tube by making a couple of small addi-
tional air inlet holes in the bottom hatch (see photo P19). Although the exhaust tube is pre-
assembled for you, we recommend that you check that all the securing bolts and nuts are tight-
ened and Loctited before installing the duct in your fuselage.
Install the tube in the fuselage, fitted onto the bypass cone tightly. You may need to make 3 small
semi-circular cutouts in the rear bulkhead to clear the nuts on the outside of the tube. The alu-
minium outer exhaust tube should be a tight fit over the back of the carbon cone, but you can
sand this if it is a bit tight. It should push over it by about 5 - 6mm (photos P12 & P14.)
The tube is held in place using three M3 x 12mm bolts,
washers, T-nuts and 3 small ply blocks on the front face of
the rear bulkhead (photo P16). Make up the 3 plywood
blocks using the 12mm wide 3mm thick ply strip supplied.
Because the rear bulkhead is angled slightly in the fuse-
lage, the blocks at the lower side need to be thinner than
the top side. Normally you will need one block of 6mm thick,
and 2 blocks of 9mm thick.
Glue together with CA, and drill thru' 4.5 mm Ø to accept the
M3 T-nuts on the back face of the blocks, against the bulk-
head. Drill 3mm holes in the tabs on the exhaust duct for the M3 bolts and washers. Rough sand
the back face of the T-nuts, and bolt the blocks to the exhaust duct tabs. Install the duct onto the
bypass cone and push into place. Install the upper bypass and bolt in position.Trial fit the fibre-
glass tailcone onto the fuselage to check that the exhaust tube is centred. When all is aligned,
glue the blocks and T-nuts to the bulkhead with slow epoxy and milled fibre, aligned as shown
so that you can access the upper bolt with an M3 ball-ended wrench.
Bottom Hatch
The large bottom hatch is 95% completed for you, and only needs the fixings installing. The
front is retained with three 6mm Ø carbon pins, and the middle and back of the hatch with 4
allen bolts (M4 x 25mm) into T-nuts glued into the fuselage. The plywood support plates for the
bolts and T-nuts are already installed and reinforced with fibreglass cloth.
Important: Please do not modify this hatch fixing in any way. The hatch must be fixed onto the
fuselage securely to give torsional stiffness to the rear of the fuselage, and if it is not fixed
properly it could result in terminal flutter of the fin and stabiliser.
The 3 carbon pins must be glued securely into the front of the hatch, and the plywood bulk-
head inside. Drill the 6mm holes in the front of the hatch first, one on the centreline, and one
about 135mm either side (photo P17), with the centres about 8mm down from the outer sur-
face of the hatch. Make sure that you drill the holes in the hatch parallel to the fuselage centre-
line. Transfer the hole positions onto the fuselage (P18).
Drill the holes in the fuselage a bit small to start with, about 5mm diameter, and then open up
with a round file to fit. Work on one pin and hole at a time. The carbon pins must project out of
the hatch by at least 9mm (3/8") so that they pass through the fibreglass lip and the plywood
bulkhead in front of the it. Don't forget to prepare the gluing surface of the carbon pins. Finally
Laminate 3 blocks from the ply
strip with thin CA, for exhaust
mounting to the rear bulkhead.
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