The moment of truth!
Weather has improved, decided to try the unfinished hull with an open water test.

The home made reverse & steering nozzle performance was disappointing. They function in theory and move significant amounts of water. The dimensions of the model though restrict the range of movements necessary to ensure full steering and reverse operation.
These restrictions cause significant disruptions to flow impeding performance and manoeuverability.

JBKIWI offered some words of advice and suggestions following his experience with waterjets. Spent some time trying to figure out how they could be incorporated, but the size restrictions still restrict performance unacceptably.

Have decided to install bucket style nozzles to get some testing in over the summer. Might resurrect the original nozzles next winter and experiment with the necessary modifications.

The flow is much better with these nozzles and a plane can be easily achieved. The hull sits level at rest, but at speed the bow lifts excessively. The performance is good.

Considering the forces generated by a waterjet. The input flow tends to pull the stern down, lifting the bow.
The bow on this vessel is higher than the stern, probably due to its military heritage. This is exaggerated in the last picture, as does the perspective. Think it needs to be lower though.
See pictures

Going to experiment with some simple, fixed transom flaps to increase the upwards force and level the hull

Nice spot, used to sail my Merlin Rocket there in the olden days!!

The hull is now fair and prime painted. Decided to try it in a water tank to test for leaks, check ballast, waterjet impeller and reverse operation.

The usual adjustments quickly concluded the ballast and jet rotation questions. There was a couple of leaks around one jet mounting. Easily resolved with silicon seal.

The clamshell nozzles do not to give as much reverse thrust as the bucket style.
As the test tank is very limited in size and shallow, not sure how they will operate in open water.
The ice is now retreating on the Lake Ontario so hope to find out shortly.
The inner jet outlets are also directed towards the centre of the transom, reducing their effectiveness.
At least am now forewarned of the problem and can fit bucket style reverser units if required.

Decided a hull of about 30” O/L should make a nice model, based upon my Visby experience.
Had plans printed using drawings from the web and, although somewhat pixelated, they are usable. Made the hull as a typical frame and strip style with a thin plywood skin.
It presented no unusual problems, made up using various plywood thicknesses and basswood strip.

The deck edge support strip was made up of ¼” square basswood up to the area when the bow curve begins. Have done this before, not usually very well.
Decided to try to laminate this forward section using a 1/32 bass wood strip and, whilst the wood still requires bending, it turned out superior.
Did most of the bending by saturating the wood in ammonia. Shaping around a curved pattern, followed by drying with a heat gun. Once the shape was achieved laminated the next strip to it with CA glue. This proved much easier than trying to bend a full section strip.
The finished result has the correct curvature and is robust.
Find the ultimate test of bow curvature is to turn the hull over and see if both sides fit the plan. To my relief they did!

Once the outer skins were fitted and blended into a smooth shape, was unhappy with the chine.
This vessel has a chine strip onto which the bottom and upper skins fit. The strip has a land (about 3/16” wide) on the outer underside, the outer corner of which blends into the upper skin.

This is similar to the one on my Daman 4207 model. Seems to be a development of the traditional chine strip. However, it is difficult to obtain a sharp corner as it is easy to round off the edge with the repetitive sanding needed to make a clean land.

Decided to try another approach. Once the skins were fitted and the land established, CA glued a thin metal wire onto the lower corner of the upper skin.
Could then blend the wire into the bottom skin using epoxy, leaving a clean corner on the upper skin. This has the added benefit of truing up the corner. The pictures show the general idea.
Not sure how robust the wire edge will prove to be, but it is nice and sharp.
So far, has survived much emery cloth smoothing without any separation!

The Interceptor and VIP vessels have slightly different chines. The Interceptor does not have one, but there in a small one on the VIP version.
As have decided to build that version, added a thin styrene strip to inside of the wire chine edge to reproduce it.

Have found several water jets with steering and reverse capability, using buckets. Have not found one, in this size range, that offers “clamshell” type reversers with steering.

The clamshells are mounted separately from the steering nozzles, unlike the bucket style. So, when the nozzle is steered with the clamshells lowered, the water is directed towards that side of the nozzle. This can give the vessel good manoeuverability.
Decided to try see how these could be replicated.

After the usual scratting around with offcuts of plastic pipe realized, using regular copper plumbing fittings, the basic layout could be achieved. When the excess copper was cut away, the shape was replicated. The remaining pieces were then soldered together to form the clamshell unit.

Mounted this to the waterjet nozzle, which had earlier been fitted with a swivelling copper pipe reducer to form the steering nozzle. All the functions were then replicated.

The final picture shows the complete unit on a dummy half transom. Still needs some fettling and the linkages working out. The general idea is evident though.
Having made all my mistakes on this first unit, making the second was a pleasure!

Once the hull is made, will fit two of these units to the stern. Can then apply the final touches, install linkages and all should work - Inshallah!
If it does not, will revert to the bucket style as have spare units.

Readers of my HSwMS Visby blog will be aware the model is complete and operating well.

Was quite happy spending last Summer just sailing models; that was until JBKIWI wrote a forum entry introducing the Swedish CB90 class of waterjet propelled fast assault class! Sparked my imagination.

After some research, found the base hull has been developed into a number of forms, including attractive “Interceptor” and VIP vessels.

The hull is of a hard chine style and should not present any unusual challenges. The waterjets are not the same as the Visby, in that the reverse/steering function is different. From experience with the Visby, consider a reverse capability essential.

Decided to use the same base 20mm waterjet units as the Visby. They power a hull in the 30 – 40” O/L range nicely. My preferred size. They also work well and do not leak. Problems friends have encountered with other units.

This offered two approaches, one use “modellers license” and fit the same bucket style units as on the Visby. The other was to use the base waterjet unit, but make up the correct Kamewa “clamshell” style reverse /steering units. These were not available through the jet supplier.

I am struggling to bend stripwood for the handrails for my current build. The boat is 1/24 and at least two of the bends are quite sharp.
I have been struggling with 3mm x 5mm mahogany and holding in a jig after both steaming and soaking in very hot water. I achieve the required bend but after a few hours the wood springs back significantly.
Walnut has been suggested as it has a better "memory" than mahogany which has no "memory" at all.
Please any suggestions.
Regards ChrisG
Hi Chris,
My suggestion is once the plank is steamed it must be fastened in place immediately or as you said it will straighten out.
Trev

I have had similar problems and found the best solution is. Once, the wood is saturated and bent, dry it with a heat gun.
Mahogany will retain a shape similar to the bent shape. It can then be CA glued into place. Working it to final shape as the glue sets
Rowen

I am struggling to bend stripwood for the handrails for my current build. The boat is 1/24 and at least two of the bends are quite sharp.
I have been struggling with 3mm x 5mm mahogany and holding in a jig after both steaming and soaking in very hot water. I achieve the required bend but after a few hours the wood springs back significantly.
Walnut has been suggested as it has a better "memory" than mahogany which has no "memory" at all.
Please any suggestions.
Regards ChrisG
Hi Chris,
My suggestion is once the plank is steamed it must be fastened in place immediately or as you said it will straighten out.
Trev

I have had similar problems and found the best solution is. Once, the wood is saturated and bent, dry it with a heat gun.
Mahogany will retain a shape similar the the bent shape. It can then be CA glued into place. Working it to final shape as the glue sets
Rowen

I am struggling to bend stripwood for the handrails for my current build. The boat is 1/24 and at least two of the bends are quite sharp.
I have been struggling with 3mm x 5mm mahogany and holding in a jig after both steaming and soaking in very hot water. I achieve the required bend but after a few hours the wood springs back significantly.
Walnut has been suggested as it has a better "memory" than mahogany which has no "memory" at all.
Please any suggestions.
Regards ChrisG
Hi Chris,
My suggestion is once the plank is steamed it must be fastened in place immediately or as you said it will straighten out.
Trev

I am struggling to bend stripwood for the handrails for my current build. The boat is 1/24 and at least two of the bends are quite sharp.
I have been struggling with 3mm x 5mm mahogany and holding in a jig after both steaming and soaking in very hot water. I achieve the required bend but after a few hours the wood springs back significantly.
Walnut has been suggested as it has a better "memory" than mahogany which has no "memory" at all.
Please any suggestions.
Regards ChrisG

From experience, my Brave Borderer blog recounts how this was gained:
The tubular glass fuses blow immediately their capacity is reached.
That is fine for brushed motors, but brushless can have high transient currents that cause instantaneous failure.
Have found the automotive blade type handle these currents and still offer protection. They have "slow blow" characteristics.
With brushless, I always power each motor independently to avoid a single fuse taking all the load.

Looks great Roger
R

Hi Nick,
That sounds like my problem as cannot reply to you.
Anyway, not here yet. No problem though. Just received an envelope from Cornwall MB, ordered and shipped in October!
Think Canada Post has met its
match with the GPO
Thanks again
Rowen

Used a garden spray pump, 6V and self priming, controlled by RC switch. Works well
Used it on a twin waterjet model that was difficult to seal.
Even then, not that much water ingress so unsure worth the trouble.

Have previously finished hulls with a layer of glass fibre cloth and epoxy. Then smoothed it all down.
What are the groups thoughts on this technique as will be doing another hull shortly?
It is very labour intensive.

Had a Flysky i6 for several years and now has 13 models on it.
Has proved fairly easy to program and easy to use.
Would recommend it

When you have done that a coupler is still preferable.
Have experimented with several types, the one on the extreme right shows the most promise.
The one next to it with the spiral cut works well, but is bulky and the shaft must be slide out to fit.
This one can be assembled is situ, is robust and allows a small amount of misalignment and vibration thus cuts noise down. Available through our friends at Aliexpress and Bangood
The others all have failings. The traditional Hookes joint style vibrate, wear and are noisy

Steven,
If you can send me a message so can get your correct address have a GA that I used for mine.
Built 2762 a couple of years ago and there is a full blog of it.
Made the mast from a mixture of brass tube and styrene, even made it removable.
There are several picture on the net that amplify the drawing.
Rowen

Sounds realistic, typical Russian stealth vessel!

My last post slipped out prematurely.
Meant to add:
Think it would be interesting if members identified the type of components they have had success or failure with.

Doug, they work well.
Have been using a “no-name” brand from Banggood.
They come in a variety of sizes from 30 to around 60A. No programming so happy with them.

No Garth, it was at Tillsonberg. Well out of the range of your camera!

Nothing like the stench of a burnt out Turnigy ESC!
Hangs around for ages.

Doug,
Think I might have beaten you to it!
Retrieved my Seaforth Conqueror in 2016 after she sank on her maiden voyage. Somebody took a picture of my palid, frozen body in underpants.
Do not have a copy to make you jealous though!
Hull sprang a leak.
Had to move the ice aside to get in the water.
Funnily enough a few days later, after drying out all worked well. Drop of araldite and good as new.
Think the award should resemble a cork life belt!

Admire your fortitude!
There should be a special award for modelers who have had to swim to retrieve models.

Thanks Nick, will have a shufti tomorrow as we are forecast freezing rain

Hi Nick,
The smaller one looks ideal for one on my projects.
Going to try the software you suggest. Hope can manage it!
Another OAP but in Canada
Rowen

The helicopter was straightforward.
Cheated by buying a Revell AW109 kit and converting it resemble the Swedish forces version. Fastened it down with a central restraint to mimic the “Bear trap” helicopter landing system. Modified the blades to allow them to fold rearwards for storage, as is done with most ship borne helicopters.

The more powerful bow thruster motor had now arrived. This motor is slightly bigger so the gears no longer mesh. Wanted to purchase a new set from KK Produkcja, in Poland where had purchased the original ones. Tried to place an order, but they ignored my several messages. Eventually ordered through Aliexpress.

In the meantime. Rummaged through my stock of defective servos to see it there were any gears that might work. Came up with a pair that fit quite well and seem to mesh properly.
Doubt this bow thruster will ever have enough power, should have chosen the larger version. Also replaced the ESC with one that can be modulated so removed the extra electric switch.
Pity cannot test these modifications until winter passes. My wide dispensed with our indoor test facilities last year!


Antennas

There are two antennas fitted to the front of the superstructure. Made these up from old wound guitar strings, with mounts made from old plastic model bits. The strings are flexible yet substantial. Once painted they look realistic.

The model is now essentially finished. Did one last bench test of electrical systems and all checked out.

This entry thus closes the blog. This project was my introduction to the use of waterjets. They do present some challenges and advantages compared to the traditional propeller layout. Have decided they are worth persevering with, my next model will be equipped with them too.

Was dreading making the rear deck railings as, using brass tube (for the most robust installation) requires much structural soldering.
The railing can be operated to both vertical and horizontal positions to facilitate helicopter operations. This means a system of hinges is required.

Determined the sizes of brass rod required and made up a crude jig to locate components as needed.
The first railing (stern as the smallest) turned out quite well, but none thereafter!

Had changed the soldering iron tip to a new, pointed one as the earlier spade shaped one was worn out. After much messing around and resoldering finally arrived at the combination that worked. My objective was to leave a shiny, small gob of solder on each joint. This is much harder that it sounds!

Thought a pointed tip would concentrate the heat, then used a max. setting for maximum heat. That it might well do, but does not give a good joint. Often came apart with poor adhesion and left a poor surface finish.
Eventually determined, for this 1/32” rod and 1/16” tube joints, the best combination turned out to be;
With a 60w soldering iron. About half heat (250 C), a new tip with chisel end and very thin multi-core solder. The tip was cleaned frequently to remove contamination.
Once arrived at this combination things moved quite well. Did not require as much cleaning up either to remove excess solder. The components are held together and the solder flows into the joint. The chisel tip also helps to hold the joint together as the solder flows.

Made the hinges out of styrene, cut them into a “C” shape so the bottom rail could be slotted into the groove allowing the rail to rotate. The railings go all around the three sides of the rear deck, as they are shaped around the stern corners the side bottom rails can be inserted into the rear, forming a discreet stop.

Next, tack soldering brass mesh into the frames to resemble netting proved another challenge. First attempt was to cut small pieces of mesh and tack into the apertures.
This looked unsightly, any tacks that were not perfectly symmetrical looked awful when painted.
Next tried to CA glue the mesh in. This also looked unsightly as any CA residue leakage then blocked adjacent mesh holes and, when painted, looked odd.

Found the best way was to cut a strip of mesh and cover all the apertures at once. Then used CA glue to hold the mesh in place. Appreciate this is cheating to the purist.
Either that or hurl these railings and convert to a conventional stanchion and rail design. As used on some of the earlier vessels.

All fitted and looks acceptable.

Nice model, not sure how can compare with real thing as have absolutely no plans to visit Russia in the foreseeable future.
Particularly admire the sound unit that captures the sound of a 1960s Russian diesel so well!
Best wishes
Rowen