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    H.Sw.H.S. Visby
    20 Posts ยท 6 Followers ยท 50 Photos ยท 85 Likes
    Began 2 years ago by
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    ๐Ÿ“ H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 184 Views ยท 4 Likes ยท 18 Comments
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    ๐Ÿ’ฌ Add Comment
    Been trying to find an interesting model for my next build and was intrigued by the articles on a semi-scale waterjet powered Finnish stealth corvette in the Model Boats magazine. Thought that a similar model would be an interesting introduction to the world of waterjets.

    Quickly discovered that to make a scale model with a manufactured glass fibre hull (my preferred construction), would have to find a similar vessel as nobody offered a GF hull for that ship. The author of the article had made his semi-scale model by adapting another hull.

    After searching around, discovered then decided on the Swedish Visby class. This was an early version of a stealth corvette and has had excellent reviews in the various defence forums. Was waterjet powered and of similar dimensions, meeting my requirements.

    Concluded this would make a nice project, so started to accumulate the necessary parts.
    Researched the class in more detail and found Swedish naval vessels are also know as โ€œH.M.S.โ€, but in Swedish! The Swedes have a proud naval tradition and use a similar nomenclature to the British. They are referred to as โ€œH.Sw.M.S. XXXโ€ amongst the Naval fraternity.

    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 159 Views ยท 0 Likes
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    Thanks Dave,
    Had already decided to use a "coffer dam" approach, good to see it reinforced by an authority.
    The suggestion to fit the unit to the bottom of the hull first is a good one. Was going to fit to the transom first, but if this works for Dave, will emulate it.
    Thanks Rowen
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    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฌ๐Ÿ‡ง dave976 ( Captain)
    โœง 170 Views ยท 0 Likes
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    Hi Rowen
    Spoke to Dave to-day and he has a similar unit to yours. As expected he researched what was available and how others had fitted their units. As a result he has no water ingress.
    Basically he made a coffer dam round the unit where it joins the hull bottom. This was fibre glassed to the hull. He then used a sealant between the hull and the unit that dries hard but remains flexible. He has no problem with the transom connection. In discussion it would appear that a glued joint fails over time due to vibration. I believe I will use a similar system but fit a metal plate to the outside hull and bolt this to the flange on the unit. We are really in the realm of the submariner and they always use bolted fixtures to seal anything exposed to water.
    Dave's instructions also advised fitting the unit to the hull and then cutting a hole to size. Dave used some mastic to seal the residual joint line.
    Hope this helps and looking forward to your buid
    Dave
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 168 Views ยท 1 Like
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    Thanks Dave. Would be interested in Dave Ws advise and thoughts, he is one of the modellers whose work astounds me.
    Rowen
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฌ๐Ÿ‡ง dave976 ( Captain)
    โœง 183 Views ยท 0 Likes
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    Hi Rowen
    Looking at the Ali version it appears to be well made and I suspect they used stainless for the metal fittings. A magnet will not attract and reveal if it is stainless. It was several years ago when Brian had the problem and I am sure the later versions have rectified the issue. My waterjet units use plastic flanges where the unit fits to the stern and there is a machined joint from the internal waterjet to the output unit. I have not progressed my build so cannot say if it will leak but I have not heard of any problems from others who have fitted and used the exact same unit. My friend Dave Wooley has installed waterjets in his recent model so I will ask if he has found this to be an issue.
    Dave
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฉ๐Ÿ‡ช RNinMunich ( Fleet Admiral)
    โœง 176 Views ยท 2 Likes
    Flag
    "put wings on her and she's not unlike a stealth bomber"
    Not surprising Nerys, same principles are used.
    Minimise the area of surfaces which reflect radar waves back the way they came, especially vertical surfaces. I.e. Scattering. Thus reducing the size of the echo. Allegedly the Visby, and similar small ships, look like innocent small fishing boats on radar plots.

    Reckon cannonballs from close range could have punctured her hull๐Ÿ˜ฎ, it's built using composites I believe.
    Stay safe U2,
    Doug ๐Ÿ˜Ž
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฌ๐Ÿ‡ง Nerys ( Fleet Admiral)
    โœง 180 Views ยท 2 Likes
    Flag
    No Doug, to my eyes there's nothing ship shape about her at all, put wings on her and she's not unlike a stealth bomber, but at least the cannon balls would roll off those near vertical sides.

    Cheers, Nerys
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฉ๐Ÿ‡ช RNinMunich ( Fleet Admiral)
    โœง 176 Views ยท 0 Likes
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    "Unlike the KMB, where the outlet slides into the nozzle, there is a dual flange with O ring layout. "
    Rowen; as I understood from the KMB site (Hooray, got it right๐Ÿ˜€) they supply an alu flange to go between the two parts? But wadda I know about water jets๐Ÿ˜‰
    Alls well that ends well I trust ๐Ÿคž
    Cheers, Doug ๐Ÿ˜Ž
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฉ๐Ÿ‡ช RNinMunich ( Fleet Admiral)
    โœง 176 Views ยท 2 Likes
    Flag
    Hi Nerys,
    Not quite 'ship shape' eh Nerys๐Ÿ˜‰
    I reckon first thing Jacky Fisher would have said is
    "Where are the bloody guns?"
    Second
    "RADAR, what the bloody hell is that?"
    Trust you and the worthy Alice are keeping well๐Ÿคž
    All the best, Doug ๐Ÿ˜Ž

    PS: Sorry Dave, got me typing fingers in a twist. Don't know me Ks from me Ms ๐Ÿ™„
    Oo's bin muckin aboot wiv me keyboard? ๐Ÿ˜
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฉ๐Ÿ‡ช RNinMunich ( Fleet Admiral)
    โœง 176 Views ยท 0 Likes
    Flag
    "Cannot vouch for the quality, ..."
    Never mind the quality Rowen!
    FEEL the width! ๐Ÿ˜‰
    Perhaps it's just as well then that KMB was so unresponsive.
    Cheers ๐Ÿ˜Ž
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฌ๐Ÿ‡ง Nerys ( Fleet Admiral)
    โœง 179 Views ยท 3 Likes
    Flag
    Interesting shape ship, don't know what the designer of HMS Dreadnought would have had to say about her.

    Nerys
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 175 Views ยท 4 Likes
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    Hi Dave,
    Cannot vouch for the quality, although the construction looks sound.
    Think the body is 3D printed and the impellor aluminium (optional). The shafting looks stainless steel. The motor is additional, but fits straight up to the mounting flange.
    Unlike the KMB, where the outlet slides into the nozzle, there is a dual flange with O ring layout.
    I understand this is an area of common waterjet leakage, so the O ring idea might be better.
    Not wanting to reveal too much of my next blog, but the KMB would not have worked anyway!
    Rowen
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    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฌ๐Ÿ‡ง dave976 ( Captain)
    โœง 187 Views ยท 0 Likes
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    Hi Rowen
    I hope they are similar. A fellow club member used a Graupner type which he had to strip after every use as it seized with rust.
    I haven't even started this model but have attached brushless motors to each unit and have Esc's and many of the bits including the hull. I think yours will be finished before I start.
    Dave
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 176 Views ยท 2 Likes
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    Hi Dave,
    That is the company. Have still got the jet units and they look fine. The ones I got from AliExpress look almost as good.
    Will not know until the model is on the water. Maybe next Summer
    Rowen
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฌ๐Ÿ‡ง dave976 ( Captain)
    โœง 187 Views ยท 2 Likes
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    Hi Rowen
    Sounds interesting.
    I have a Shannon to build using twin waterjets. I got mine from

    https://kehrer-modellbau.de/en/KMB-JET28-Rev.-3/?p=1
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฉ๐Ÿ‡ช RNinMunich ( Fleet Admiral)
    โœง 182 Views ยท 3 Likes
    Flag
    Hi Rowen,
    Thought the Aussie option would be too expensive with freight an all๐Ÿค”
    Look forward to the detail of what and where you find the alternative.
    What scale will she be?

    Ref the folding gun! (Better than a smoking one I guess๐Ÿ˜ฎ)
    Would be cool if you could cruise along the shore in stealth mode ...
    then suddenly unfold the gun ...
    and blast the unsuspecting spectators with a pulsed water jet salvo
    ๐Ÿ˜๐Ÿ˜‚
    "Problem is the long, narrow hull ..."
    Perennial problem with warships Rowen. The high length to beam ratio (generally around 10:1) increases the max speed achievable for a given power plant.
    One reason why the engine rooms and boiler rooms / generator rooms are staggered on warships with 3 or 4 shafts; carriers etc. Another being damage control of course๐Ÿ˜‰
    But you aren't going BB gun battling. ARE YOU?๐Ÿ˜ฎ

    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 181 Views ยท 3 Likes
    Flag
    Thanks Doug,
    Recently became aware of them. Have already placed an order though with another company.

    Your question on the gun is germaine, have not thought much about that yet. Whilst the vessel has little vulnerable and fiddly detail the internal hull layout is challenging.
    Problem is the long, narrow hull leaves little room for Waterjets and their control linkages- watch this space for future blogs!
    Thanks again for your efforts with KMB
    Rowen
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฉ๐Ÿ‡ช RNinMunich ( Fleet Admiral)
    โœง 182 Views ยท 2 Likes
    Flag
    PS: You can get a 1:72 scale hull here (101cm x 14.5cm) ๐Ÿ˜ฎ

    https://southerncrossmodels.com.au/index.php/corvettes/53-swedish-visby-class-co
    ๐Ÿ’ฌ Re: H.Sw.H.S. Visby
    2 years ago by ๐Ÿ‡ฉ๐Ÿ‡ช RNinMunich ( Fleet Admiral)
    โœง 182 Views ยท 2 Likes
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    Excellent choice Rowen๐Ÿ‘ not too much external detail to worry about ๐Ÿ˜‰
    Are you going to make the 57mm barrel fold into the turret like the original does?
    Have fun, looking forward to following๐Ÿ˜€
    Cheers, Doug ๐Ÿ˜Ž

    https://en.wikipedia.org/wiki/Visby-class_corvette
    https://www.google.com/search?q=visby+class+corvette+model+plan&client=firefox-b
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    ๐Ÿ“ H.Sw.M.S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 155 Views ยท 4 Likes ยท 2 Comments
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    ๐Ÿ’ฌ Add Comment
    Decided the Visby class would make an ideal project so started to accumulate the necessary bits.
    Another modeller donated a pair of used KMB 28mm waterjets, but missing the reverse / steering nozzles. After this stroke of luck, turned to obtaining the missing nozzles. Thought getting a pair would be easy!

    Made innumerable attempts to make contact through the KMB website. Then E mails and even telephone calls from Canada to place an order, got absolutely no response.
    Finally, in desperation, thought as โ€œRN in Munichโ€ lived in the same country and speaks German, perhaps he would be able to make contact locally. Doug gave his usual generous support.
    After many attempts - nothing (thanks again Doug โ€“ now I know what Fleet Admirals are for!). Fortunately, we both gave up.

    By now had obtained some scale GA drawings and printed them off at the appropriate size. Discovered that the KMB jets were too big to fit in the stern recess anyway!
    Searched for alternatives and found there are many different sizes available.
    Through AliExpress, found a 22mm jet unit made by MSQ. With some trepidation, ordered a pair.
    These arrived quite quickly and were nicely manufactured. Think they are 3D printed, but not sure. Anyway, they look good and robust. With minor modifications, they will be fine. The KMB are the black and the MSQ white in the photo.
    With the wisdom of hindsight, it might be easier to install an even smaller unit, but too late. Anyway, the 22 mm should move more water than a smaller one.
    As the original vessel could do some 35 knots, this should make max. speed more realistic.
    The challenges of squeezing these units into the available space do not look insurmountable. Rather too late anyway as now have them.

    ๐Ÿ’ฌ Re: H.Sw.M.S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 155 Views ยท 0 Likes
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    Thanks Chas for your offer and interest.
    In a nutshell - no, never got through to them.
    Anyway, the 28mm unit turned out to be larger than could get into the space, so they would not have worked anyway.
    I opened an account, with Canada as the address, it made no difference. Then Doug tried from Munich, he could not place an order in Germany and then ship to Canada.
    Think he heard K.M.B. has changed ownership, so these might be start-up troubles. Doubt Brexit is the issue.
    The MQT units I finally bought were not much more expensive for the whole assembly, including KaWeMa style reversing/steering units. They look as if they will fit too (that was not KMBs fault, just mine).
    AliExpress and Bangood have a range of waterjets on their sites. Some look good, others maybe not so.
    Was thinking could adapt one of their steering/reversing units to a K.M.B. body, but never got around to trying.
    Thanks again,
    Rowen
    ๐Ÿ’ฌ Re: H.Sw.M.S. Visby
    2 years ago by ๐Ÿ‡ฌ๐Ÿ‡ง RC-Modeller ( Recruit)
    โœง 150 Views ยท 0 Likes
    Flag
    Hi,
    Have you managed to get your reverse for your KMB jets?

    I live in the UK, and since Brexit when we left the EU Market, they won't send to the UK. It's a shipping company issue at the moment.

    I like you tried to contact them several times with no luck. As I had purchased from them several time before, I just changed my delivery address to my Son's in Germany. He then sends stuff onto me.

    I have purchased from KMB for several years with no problems, and still buy from them via a different route.

    I've checked their website, and They do ship to Canada, so I think you will have more luck if you just open an account, then just go ahead and buy them online.

    The - KMB JET28 KaMeWa-like steering and thrust reversal system, is the better of the two reverse units at 21โ‚ฌ each.

    If you need any more help, pse PM me.
    Regards
    Chas
    ๐Ÿ“ H.Sw.M.S. VISBY
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 152 Views ยท 3 Likes
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    ๐Ÿ’ฌ Add Comment
    Original idea was to try and combine the twin nozzle reverse and steering linkages to avoid drilling too many holes in the transom. The MSQ units also have a water-cooling tapping, but in the outlet nozzle, making another set of transom holes necessary.

    Decided that as the waterjet installation would be congested, making up a simple jig to resemble the transom mounting face would help. This would also help trial the installation of control linkages and the cooling circuits. Cut a plywood sheet to the same dimensions as the scale transom and fitted the jet nozzles into it.

    Many of the earliest installation ideas were then quickly dumped! The top link on the nozzle reversing bucket also fouled the underside of the deck above the waterjets. Removed this linkage and determined a straight pull linkage required very little extra force. This linkage installation could be further simplified if a flexible joint was introduced.

    Thoughts to combine the two nozzle reversing linkages were shelved. Much simpler to run them separately through the transom.
    It does not look feasible to combine the two steering linkages either. Will need to leave them separate through the transom.

    Spent several hours trying to mock-up the nozzle layout to experiment with various control arrangements. Concluded that the permutations in working in 3D, along with vagaries in the drawings, have decided best to wait until have an actual hull to work with.

    Once the waterjets are fully installed, will investigate combining these two sets of linkages, but closer to the operating servos inside the hull.
    That will be sometime in the future though.

    Had a stroke of luck! During the vessel research found the Australian Group โ€œTask Force 72โ€. This has two members who have built this model. They are a font of knowledge and very willing to share it. Will incorporate their experiences and advice into the build.

    ๐Ÿ“ H. Sw. M. S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 149 Views ยท 5 Likes ยท 5 Comments
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    ๐Ÿ’ฌ Add Comment
    Started to assemble the other major components.
    The use of a 3D printed bow thruster was suggested on this website. Purchased one from Shapeways, it duly arrived and looks good.
    Was apprehensive when it was shipped by UPS that would be stung with an extra โ€œBrokerage feeโ€, as is levied by DHL. Fortunately, not.
    Just need to obtain the motor and gears now. The requisite items are usefully listed by Shapeways.

    Accumulating the necessary servos, fuse block, Rx, BEC items etc. so these are ready when required. One of the problems with buying from the Orient is extended delivery times. The impact can be minimized by planning and purchasing ahead.

    Placed an order for the hull so, apart from getting fully prepared for the project, am planning to hold off building until all my other projects are complete.

    Will restart this blog once building commences.
    Until then, a Merry Christmas and Happy New Year to all my readers.

    ๐Ÿ’ฌ Re: H. Sw. M. S. Visby
    2 years ago by ๐Ÿ‡บ๐Ÿ‡ธ pressonreguardless ( Rear Admiral)
    โœง 111 Views ยท 0 Likes
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    Only in America, Land of Opportunity๐Ÿคฃ๐Ÿ˜‚๐Ÿคฃ๐Ÿ˜‚
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    ๐Ÿ’ฌ Re: H. Sw. M. S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 140 Views ยท 0 Likes
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    Could well be! My stuff comes by air, allegedly. When tracked it usually flies direct to Toronto so avoids the US.
    No reason why that problem could not arise here though. Rather more of a challenge to throw things out of an aircraft!!
    ๐Ÿ’ฌ Re: H. Sw. M. S. Visby
    2 years ago by ๐Ÿ‡ณ๐Ÿ‡ฟ jbkiwi ( Fleet Admiral)
    โœง 138 Views ยท 1 Like
    Flag
    Hi Rowen, perhaps this is why the postal service is slow up your way ?


    ๐Ÿ’ฌ Re: H. Sw. M. S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 144 Views ยท 1 Like
    Flag
    Hi Toradog, hope you feel better now!
    Am likewise fed up of shipping companies. In Canada they have now included the โ€œfloods in BCโ€ as another reason for delays, even if your package is airfreight!
    The legacy of COVID will be milked for years.
    Glad you enjoy the blog, most of my projects are coming to a halt as parts are in the mail!
    ๐Ÿ’ฌ Re: H. Sw. M. S. Visby
    2 years ago by ๐Ÿ‡บ๐Ÿ‡ธ ToraDog ( Captain)
    โœง 144 Views ยท 2 Likes
    Flag
    Rowen,
    Looking fantastic. I hope you will allow me a short rant.
    DHL is now charging a "breakage fee"? Shapeways dded a processing and and handling fee that is a percentage of the order, UPS and FED EX no longer guarantee delivery by stated dated, and the US Post Office has gone back to the Pony Express. Not to mention that every company is using COVID as an excuse not to fill orders in a timely manner.
    Besides the lives lost, which will never be overcome, we have not even begun to realize how much this pandemic has, and will forever, change our lives.
    Sorry Rowen, Keep your build flowin'.
    ๐Ÿ“ H.M.Sw S Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 131 Views ยท 2 Likes
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    ๐Ÿ’ฌ Add Comment
    The hull is in transit, have also found a set of drawings that show the stern details more accurately. There is a recess in the stern between the nozzles and had hoped to be able to fit linkages through this, above the waterline. Did not previously know the dimensions.

    The drawings enabled taking the wooden former had previously mounted the jet nozzles on and add horizontal top pieces straddling the recess. Now had the principal items of the installation. Was apparent these waterjets could only just be squeezed in, so made the top pieces out of Perspex to observe the various layouts.

    Photo # 1 shows the stern side elevation; # 1 is the stern face, # 2 the top horizontal piece and # 3 inclined stern face. Photo # 2 shows the nozzles mounted on the wood stern face and Photo #3 with the Perspex top pieces added.

    The steering linkages look straightforward and expect to be able to link each nozzle to opposite sides of a single servo crank. The servo will be fitted forward inside the hull. The links will be above the waterline and sealed simply. Photo # 3 mocks this up.

    The reversing mechanism is another matter! Whatever link arrangement is fitted it must allow adequate lateral movement to allow the nozzles to swing easily for steerage.

    The crank mechanism on top of the nozzle originally fouled the underside of the horizontal piece. Had already decided the crank could be dispensed with by using a direct acting link. Unfortunately, there is not enough space for this link without drilling holes very close to the waterline, leaving insufficient space for an effective seal.

    Next idea was to mount inverted, individual servos on top of the horizontal piece. The shafts would protrude through so could fit a servo arm that acts on the short link to each nozzle.
    Not enough space for this. The nozzles fit too closely to the underside surface to allow an arm to be installed and to also move freely. This can be discerned in the closest (Port) nozzle on Photo 3.

    Only straightforward idea, as these nozzles are longer than the original, is to lift the crank rod and drill through the rear face, mounting a servo on the inside. Rather like the outboard (Stbd) nozzle in Photo 3.
    This would add a visible external link, not to scale. It would considerably simplify the installation and maintenance.
    ce though, also lift the linkage holes so they are well clear of the waterline. The links will also be under the stern, hidden from most observers.

    There are several permutations on each of these ideas, but until can try on the hull will not modify anything.

    Has anybody any other suggestions?

    ๐Ÿ“ H.Sw.M.S Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 142 Views ยท 3 Likes
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    ๐Ÿ’ฌ Add Comment
    The hull is now in transit, also found a set of drawings that show the stern details more accurately. There is a recess in the stern between the nozzles and had hoped to be able to fit linkages through this, above the waterline.

    The drawings enabled taking the wooden former previously used to mount the jet nozzles and add horizontal top pieces straddling the recess. This gives the principal items of the installation. Was apparent the waterjets could only just be squeezed in, so made the top pieces out of clear perspex to observe the various layouts.

    Photo # 1 shows the stern side elevation; # 1 is the stern face, # 2 the top horizontal piece and # 3 inclined stern face. Photo # 2 shows the nozzles mounted on the wood stern face and Photo #3 with the clear top pieces added.

    The steering linkages look straightforward and expect to be able to link each nozzle to opposite sides of a single servo crank. The servo will be fitted forward inside the hull. The links will be above the waterline and sealed simply. Photo # 3 mocks this up.

    The reversing mechanism is another matter! Whatever link arrangement is fitted it must allow adequate lateral movement to allow the nozzles to swing easily for steerage.

    Had three basic ideas to do this:
    1) The crank mechanism on top of the nozzle originally fouled the underside of the horizontal piece. Had already decided the crank could be dispensed with by using a direct acting link. Unfortunately, there is not enough space for this link without drilling holes very close to the waterline, leaving insufficient space for an effective seal.

    2) Next idea was to mount inverted, individual servos on top of the horizontal piece. The shafts would protrude through so could fit a servo arm that acted on the short link to each nozzle. Not enough space for this. The nozzles fit too closely to the underside surface to allow an arm to be installed and to then move freely. This can be discerned in the closest (Port) nozzle on Photo 3.

    3) Only simple idea, as these nozzles are longer than the original, is to lift the crank rod and drill through the rear face, mounting a servo on the inside. Rather like the outboard (Stbd) nozzle in Photo 3. This would add a visible external link and not be scale. It would considerably simplify the installation and maintenance though, also would lift the linkage holes so they are well clear of the waterline. The links would also be under the stern, hidden from most observers.

    There are several permutations on each of these ideas, but until can try on the hull will not modify anything.

    Has anybody any other ideas?

    ๐Ÿ“ H.Sw.M.S.VISBY
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 140 Views ยท 4 Likes
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    Happy days - hull arrived, looks good.

    Can now fully explore the waterjet installation. Had decided to buy waterjets that were fully functional with both steering and reverse to emulate the real vessel.

    The smallest could find was 22mm dia. For some reason was thinking as 28 mm jets would fit, 22 would also fit. Quickly established that as 28mm will not fit a 1:72 scale Visby class hull, neither will a 22 mm!

    So, could either sacrifice full functionality and buy smaller jets without the reverse function, or modify the hull to accommodate the 22mm jets already purchased.

    After reviewing the jets and comparing them to the hull, decided that with some courage to tackle the hull mutilation, 22 mm jets could be fitted. The body of the jet unit is fitted under and forward of the stern, so it would not be readily apparent.
    This class of vessel also has a recess in the nozzle mounting bulkhead forward of the stern. By enlarging this, the jet and associated linkages looked as if they could be squeezed in. The side profile would be unaffected, hiding these modifications.

    Carefully marked the hull to determine the areas that required cutting out. As this became apparent, became more confident in the planned modifications.
    Using a Dremel tool started cutting, well inside the perimeter of the area marked.
    After each cut offered the jets up to the hull, to ensure the cuts would be extended only by the minimum.

    The final picture shows the modified hull. The flat panel above the nozzle apertures is now removeable and gives access so the linkages can be maintained and adjusted from above. The rear bulkhead, where the nozzles will be fitted remained much as it was, so buoyancy and stability are not be affected.

    ๐Ÿ“ H.M. Sw S. Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
    โœง 150 Views ยท 6 Likes ยท 1 Comment
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    The moment of truth!
    The first of what will prove to be several trial installations. Will not bore readers with a description of all, but jump to the final version.

    The hull mods described previously both allow the jets to operate in steering and direction; they also provide access to the operating linkages through the removable cover panel. This proved to be a godsend as can now make linkage adjustments without jet removal.

    First step was to locate the water jets onto the stern bulkhead. Because of the size of the jets experimented to see where they would fit. Due to the hull and linkage layouts the range of choices was limited. They very much fit where they fit!
    Fortunately, this is very close to where the drawings show them.

    Had been advised the jet units should be fitted to the bottom of the hull first, then into the stern bulkhead. Once located, the bulkhead can be drilled to accept the nozzle. The mounting hardware holes in the bulkhead and the hull can now be drilled.

    Drilled the holes, located the jets and bolted them in position. Continued to install more bolts in the hull and stern until the jets were firmly located.

    Fitted the steering and reversing actuating linkages next.
    Started with the steering, as shown on the attached picture. None of the rods supplied with the jets were long enough for my installation. Used scrap bicycle spokes, suitably reworked, instead.
    A used sail winch servo was considered to have enough torque to handle both steering nozzles, was installed between them.

    Used a couple of smaller servos, one to operate each reversing bucket. These were wired in parallel, so could use one Rx channel to control both. Again, used modified bicycle spokes as actuating rods.

    The bucket must remain capable of being moved by the steering control. To allow this, cut the reversing bucket spoke and inserted both ends into a flexible nylon sleeve. Movement for steering and reversing can now take place simultaneously.

    After observing a number of dry runs, concluded the linkages work with the minimum of deflection and can control both functions.
    Used the Tx โ€œEnd pointโ€ range limiting function to ensure all the servos โ€œbottomedโ€ electrically, not by mechanical interference.

    The pictures show the installation.

    ๐Ÿ’ฌ Re: H.M. Sw S. Visby
    2 years ago by ๐Ÿ‡บ๐Ÿ‡ธ pressonreguardless ( Rear Admiral)
    โœง 141 Views ยท 0 Likes
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    Looks Great. Very anxious to see her in operation๐Ÿ‘๐Ÿ‘
    Trev
    ๐Ÿ“ H.Sw.M.S.Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
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    Now confirmed the waterjet controls operate properly.
    Removed all components to reinstall the waterjets with sealant.

    Fitted a flexible pipe to direct cooling water from each nozzle fitting into the rear of the hull. This flexible tube can be seen at each side of the nozzles and then through the stern bulkhead and into the ESC. The coolant then continues to each respective motor.

    Have not puzzled out the outboard discharge yet. There are several discharge points available on this model, am hoping to use one per side. If the coolant flow is inadequate can incorporate a pump if needed.

    This would be the last opportunity to ensure all the supporting structure was fitted properly and to install the wiring and electrical system. Much of this can be removed if required in the future.

    Plans are to get the hull into the water this summer. The planned test runs should reveal any issues which can then be resolved before the finish is applied.
    Will then park the hull to become my next winter project.

    As this is my first venture into waterjets, am impatient to see the model on the water.
    The attached picture shows our favourite sailing location. Easy to appreciate that the next blog instalments may be some time off!

    ๐Ÿ“ H.Sw.M.S Visby
    2 years ago by ๐Ÿ‡จ๐Ÿ‡ฆ Rowen ( Captain)
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    My wife noticed me trying to check for leaks using a wallpaper tray to partially immerse the hull. Our indoor test tank had been replaced with a shower recently.
    Was offered the use of a large, plastic underbed storage box. This is deep enough to allow the waterjets to be properly immersed to check for leaks. Horror! Water entered in an almost continuous bead from the joint between one jet intake and hull.

    Originally had built up a bed of silicon around each jet to hull joint. Was hoping the silicon would cure around the jets to create the seal. Suspect the retention screws had relaxed as the silicon set, slightly releasing the joint. Water then seeped through.

    Did not want to remove the jet to reseal it, so searched my local auto store for ideas. Permatex make a โ€œFlowableโ€ thin, clear, silicon sealant that is designed to run into joints by capillary action, cure and seal them. It is really intended for windscreen and similar applications. Hoped it might work here.

    A bead was run around all the hull / jet joints, inside and out, and left to cure. On retest, the major leak was solved, so now searched for any lesser ones. Water was seeping up some of the retaining bolt threads and coming out around the head washers. Treated them with thread sealant and retightened. Almost no leakage.

    Decided to retighten the nuts a final time and retest. Water now seeped in from one of the jet bodies!
    Closely examined the installation and discovered a hairline crack in this 3D printed item. The body has right angled surfaces, which mount to the stern and hull bottom.
    Think my tightening induced a bending moment, thus the crack.
    Did not consider the fasteners were overtightened, but perhaps they were. Wonder if 3D items are not as robust as more traditional components and need careful installation. Thoughts anybody.

    Removed the nozzle and worked flexible silicone sealer into and around the crack- it sealed. Relaxed the fasteners on both waterjets and retested. Overall seepage is minimal.
    Think will watch what happens and, if necessary, change the damaged jet body next winter when the project will be completed.

    Feel confident now starting the open water program once the lakes open up.
    Also noticed the jets move considerable amounts of water and that the cooling system works. Do not need an extra pump and can plumb directly overboard.
    The hull rides stern heavy and bow light, all within โ€œtrim balancingโ€ expectations.

    This experience reinforces a decision made after an earlier model had sunk on the maiden voyage. ALWAYS fit a water alarm until confident the model performs safely.
    Not a bad idea to leave it fitted permanently either.

    To be continued when open water is available.

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