Just having a play with an idea for a model of a early Russian KS 100D general purpose work boat. These were used for river work towing logs etc in shallow rivers . The water jet is unusual, as it has a rear shute with twin rudder type deflectors, and rear hull side ports for reverse (independent controls for each port). Someone on the site mentioned a steam powered water pump driven ship from the 1800s ? a while back on the site which used a similar principal.

The boats were made by the Yaroslavl shipyard, and were very common in the late 50s till (I think) the 70s. Not much info on them but a few guys have rebuilt old ones for pleasure boats. They have a speed of around 16-18knts and used a Yamz 170hp V8 diesel. I've contacted (YT) a guy who has rebuilt one of these boats, and he has fitted the V6 version of this engine.

My attempt is not like the original, as there is no info on the complicated internal deflector system, so I've gone with the next best thing using modified electrical conduit fittings with flap valves. Seems to work ok, but not sealed yet so leaks like a sieve. I'd use a 26mm jet unit for the pump in front of the unit. I'll have to reduce the diameter of the side outlets to get more force behind the jets. Might have to fit the unit in a waterproof tray with a bilge pump. as I think, even though it will be sealed, it will still leak slightly round the 3 shafts.

MK 2 version started now which should be an improvement. Has 3 internal flaps, rather than them being outside on the bends, which should make the shafts easier to seal as there are only 3 shaft exit holes. Might be able to use a smaller box, depending on where the screw pillars are located, as they could interfere with the shaft placement. Jet unit will hopefully be bolted to the front of the box. This version is narrower than the MK 1 which gives room to play with the reverse outlets.

Finished the flaps, -except for a few bits of tube for spacers to stop them lifting up in the box) All seem quite airtight now with the thin sponge seals, so will get another test soon. Looking a lot better than the MK 1.

A diagram showing how this system works (for anyone scratching their heads )😁 Three flaps,- 4 operations

JB

Started fitting the servos, also sorting out the programming on the 9X TX, Unfortunately it's not clever enough to mix 2 Aux channels with the L&R pump outlets for single stick steering in reverse (like flaperons) I've worked it so 2 pots operate the 2 reverse nozzles independently, flap switch operates fwd flap, rudders on aileron ch and normal throttle ch.

I tried mixing the 2 rev nozzles (using the pots), with the rudder channel - switching the mixing on and off with the 3 pos sw on pos 1, but it will only operate one servo on one aux channel. You can't add pos 2 on the sw for both servos,- probably has to be on another channel. I can get both servos operating together for reverse, but it's not much use for steering.

Would have been nice to have it on one stick but it would need a non centering rudder stick, then you could add flaperons, (switched on with the 3 pos). My 9XR would probably do it all, but that's set up for planes.

I've ordered a 26mm jet unit to modify,- hopefully I can bolt it straight onto the front of the box.

Finally got a chance to give the MK2 version a test after spending the morning doing car repairs. Going to have to be seriously waterproofed and screwed together, as the box is a bit flimsy on high pressure with all the valves shut (to be expected) I have center lid screw pads glued in which will help hold the center of the lid in place. Will have to make sure at least one of the valves is open under power. Better than MK 1 at least

I Might see if I can find a small adjustable relief valve which can prevent over pressurising. All the outlets will be reduced in diameter to help with pressure. Won't know how it will perform till the jet is bolted to it and tested in water. Getting there slowly, but needs perfecting before committing to a boat to put it in.

Jet unit arrived from Ali Exp in record time,-6 days ! Drilled out the end of the box and fitted the 26mm jet unit to the front end. I'll need a spacer or 2.5mm O ring to fill the gap, as the box is only 2mm thick. Modified the jet the same way as the Hartley model, by drilling and tapping the lower body screw holes for M3 machine screws, (bit of dremeling required) and the drilling the motor mount lower screw holes and plate for M3 x 10mm machine screws and nuts. The cheap self tapping screws are rubbish and will rust easily, making them impossible to remove later. Stainless cap screws would be even better.

The end of the motor needs supporting with these, as the mount plastic is thin and flexible. When I modified the previous unit, I filled the slot with resin to beef it up a bit.

Have also glued internal tabs and now can screw the center of the lid down, as it was bowing under water pressure. The unit will have to be glued together once everything is ready, as I don't think silicone will be enough of a seal. Easy enough to get apart if necessary. I found a couple of tiny O rings (from an old pressure sprayer trigger) to go under the servo arms (need 1 more) which should stop any leaks. Where the flap shafts go through the box at the bottom, I've glued plates over them.

The bottom screws on the jet inside, were accessed by drilling 5mm holes in the exit end of the box for a long shaft Philips screwdriver, and will be sealed once everything is ready, (plastic plate glued on the inside, re drilled if necessary for service).

The impeller will need modifying as well and the shaft will be grooved for a circlip where it exits the front bearing, to replace the coil spring. The coupler will go in the bin, (sloppy fit) and I'll make one of my own again. Intake grill will be remade as well with vertical bars.

If anyone is interested in the mods, they are all on my Hartley build blog. Worth doing, as they make a big difference in performance.

Hopefully the jet will move enough water for this to work, if not it's plan B.

Have added another mod to the jet unit to give it more go, as I did with a previous model. First thing was replacing the small self tapping screws supplied and replacing them with 3mm machine screws (as described in the last post). Next was the prop which is just a std 3 blade 26mm with round tips and a .6mm tip gap. This is useless for jet efficiency, as half the thrust is lost round the tip clearance. This was replaced with a cut down RH 30mm racing prop which has a better rake. It was drilled to 4mm from a 3mm shaft hole to suit the jet shaft.

The prop was fitted to the shaft and placed in the unit, and the blades marked for the diameter. They were them carefully cut and sanded for a close fit. When this is done, the flow correcting vanes needed cutting back to miss the blade tips, as well as sanding the front of the hub to gain a bit more clearance. A circlip or collar is needed at the front of the shaft to prevent any movement backwards.

There is also an important mod for the flat strip intake grill, (ie make a new one),- as this restricts and disturbs the flow a lot (see the mod in my Hartley blog if you are interested) a bit of work but well worth it. With the mods, the jet loaded 30A on the motor shown (last post) Surpass F540 36/50 3000kv brushless) in the Hartley model, which weighs around 6kg,- a lighter boat will draw less). Before the mods it was around 20A and no real performance.

To get the best from these cheap jets you need power, around 3000kv, 36/50 motor or similar on 2/4s LiPo, and a few mods. Smoothness and speed of flow is king. Another mod I'd like to try, is making a ball end for the output to fit into the steering nozzle, as these units lose efficiency with the huge gap, (draws in air and aerates the flow,- you need a solid flow not foam). There should be a minimum gap there as well, especially when in reverse, as a lot of water gets lost there.

Had a sudden surge of electrons in the grey matter while looking at a spare fitting, a few nights back, and now there is the flow director MK3. Half the size now, - 60x70mm (as small as it can go) and looking like having a better reverse flow with everything closer together. The 2 'T' pieces are glued and filled back to back, with the bottoms inside milled flat for the flaps, and channels milled in the sides for the shafts. A bit of external filling was required, as it was necessary to mill through the body in places to get it all flat, due to the small size.

I made a one piece 4mm Perspex lid for it, as the 2 original lids were a bit thin, and radiused where they needed to be flat. I've left the lid a bit oversize, as I may need to screw something like pushrod guides on later. The idea is, that this and the jet will be mounted on a ply base, and incorporated into the hull (as I did with the Hartley cabin jet model)

The whole thing cost around $6, and around a day mucking around with it, so a very cheap experiment. Will give it the hose test once it stops raining here.(if it ever will)

Glued on the sponge flap seals today and gave it a bit of a test with the hose (no vid sorry as it was drizzling all day) and it all works well. As mentioned , I'll only know how effective it will be once I get it sealed and try the jet on it. I'll also have to play with nozzle sizes for the best effect.

I decided to try the glass on foam approach for the hull, as It's a lot quicker than a built up one to do. I did it with a 40" tug about 1980 and it worked very well. Picked up a 2400x1200x50mm sheet of polystyrene from the hardware,($36) and had the basic hull form done in about an hour for a cost of around $3 and still have 1-3/4 half sheets left for more projects - (or a stand up paddleboard for a rescue boat😁)

2x 36"x11"x 50mm sheets were laminated using polystyrene safe contact glue and surformed and sanded to shape. The hull will have pre drilled and shaped ply inserts for the jet/diverter and jet rudder box and a ply transom fitted before fiberglassing, and any cutouts made above the jet/motor plate etc made at that stage (will save trying to dig the foam out later). The hull will have a good coating of PVA and maybe tissue to prevent the Polyester resin eating the foam. The whole hull and deck will be glassed, with cutouts made under the cabin (cabin will be balsa) later for R/C gear etc.