Hi shipmates,

Thanks to reading jbkiwi's water jet mods I have been lucky to find two contra rotating props (one left handed and one right handed) at 40mm diameter in my prop box, both 4mm centred and dog fitments.
only 2 bladed,

Using a pillar drill I inserted the short 4mm shaft into the chuck, gave it a spin and used a sandpaper sheet glue to a block of wood to grind them down to size.

These will replace the original 25/26mm propellers in the two 28mm jet units, that were a bit small and a poor design as blades were blunt.

Added second sheet of ply skin to the hull.

Kind regards Roy

Hi Ship mates,
Props changed and modified to fit the two jet pumps,

Some close-up of the jet pump nozzle and reversing bucket arrangement "Kamewa" style, uses a flexible cable for operation, as it needs to be able to move when the nozzle turns.
Please note: Will need some 'polystyrene cement' to glue the reversing mech to the nozzle.

It is said that if you rev over 16,000 rpm the pump will cavitate. so keep an eye on your brushless motors kv and running voltage.

A picture of the real thing 'Rolls Royce Kamewa 90SII waterjets of a Hamina-class missile boat'

Regards Roy

Hi Ship mates,

Needed to square up the bow underside which had too much of a curve in it where it joins the bow ramp, added two short strips of 4.5 square which will be carved to shape.
Put on base of the Bow ramp, the final ramp will be stuck on this as it will protrudes above the deck line.

Photo showing side bow profile:

Regards
Roy

Hi Ship mates,

At the end of the day, added support rails to the bow flange to hold the 1mm ply covering port side only covered (upside-down to the deck).

Added keel as per original craft, the central area of the keel will be twice as deep, was not sure about the keel, as it will slow the boat a little, but may help manoeuvrability.

Regards Roy

Hi Ship mates,

Another update, tidy underside of Bow, pic1.
Add two more layers to the keel, pic2.
Keel semi finished, pic3.

Now to complete the inverse chine on the outer edge of the hull, so the secret material is used, yes ! 'Matchsticks' extra long, to provide a 10 degree inverse, Pic4 and 5.

I hope it works?

As mentioned before I only have a side view, and a top down view, plan from the manufacturers brochure, so front, rear and bottom view are not available.
Thus using the under side of a CB90 for the arrangement of the hull bottom, pic 6.

Regards Roy

Hi Ship mates,

Decided install the jet drives, I have initially put them in with silicon sealant, to provide some vibration absorption.

I thought it would be better to fit them before putting on the side skins

Annoyingly had to change angle of the jet heads to keep them up right, as jet unit is mounted on the chine which has a low dead rise, should have made the stern flat it would have been easier to install.

The motors are mounted low just able to get water jackets on!

Waiting for silicon to cure, then I'll bolt the motors and the other head in position.

Later I will epoxy-resin the two in place as silicon is not the greatest at fixing plastics.

Regards Roy

Hi Ship mates,
Installed outer jet heads to transom, ensuring they were upright and not at the angle of the jet units.

Then turned my attention to the inlets on the underside (or on top as boat inverted) cleaned up and shaped to help with water flow into the units.
Noted a flow trap where the propeller tube comes into the drive. So add as mall amount of plastic padding to smooth the obstacle and sanded to shape, painted the area.

Now to add the inlet grills, here I got a bit confused (often happens), I'll try to explain, the recessed holes for the screws, seem to be on the side of the grill which meant if you put them that way round.

1. The contoured shape which would help the flow of water into the units was upside down?

2. The grill protrudes higher (into the water)

So with this in mind I put the grill in upside-down.
May be wrong but I think it will be better that way.

Regards Roy

Hi ship mates,

Built a stand from a HK kit from eBay and a wooden Shower tray grill.

Added a own design flow guide for the jet intake.

Have used epoxy resin to seal and fix the jets in position, hopefully no leaks. at a cost of added weight.

Regards Roy

Hi Shipmates,

Added small fillet of wood behind the intake grill to assist water flow over the grill. Did not make a ride plate as this would have prevented reversing.

Added 2 trim tabs, while side skins are still off, the job was quite fiddly and took some time as bolts were M2 and needed washers both sides and a nut.

Tidied the shed, and put the boat back in it, the utility room returns to normal.

Please note have removed the water cooling output from the jet pump outlet and filled it, I will collect water a different way as this method wastes pump pressure.

Regards Roy

Hi Shipmates,

Reinforced stern quarter to facilitate the addition of hand rails at a later stage.

Worked on Control linkages, but this is going to be difficult due to jets being a part by some distance that a standard double servo arm will not span the gap between linkages about 3.5ins.

May have to use two servos for steering, and two for reverse.

Had a bit of a revelation when I found a large (95mm) double servo arm on Amazon, and with a combination of hanging the servo upside down (that way I can get the right height).

Regards Roy