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    HMAFV SEAL
    by RHBaker ๐Ÿ‡จ๐Ÿ‡ฆ ( Lieutenant)
    ๐Ÿ“ฃ










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    5 Posts 14 Comments 0 Photos 36 Likes
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    ๐Ÿ“ HMAFV SEAL #5
    6 days ago by RHBaker ( Lieutenant)
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    After several open water runs concluded the drivetrain and rudders work well. Parked the hull awaiting for winter, when could start work on fitting out the hull and adding the deck.

    Most of this follows the processes used on my Brave Borderer on the Model Boats website. That blog should be consulted for details. Will only describe features here where the two hulls differ.

    First step was to cut out the door in the transom. There are limited details of this on either the drawings or from on line. The best illustration is one taken at the launch of HMS Sea Otter, a sister ship. From these pictures the dimensions can be estimated and the hole cut to suite.

    Proceed then to make up a opening door with the necessary operating linkage. This is controlled by a servo and uses a transmitter channel.

    Readers might question the relevance of this door on a model. It was used to recover air-launched weapons or towed targets. These were then winched into the rear hull for storage and removed through the large upper access hatch.

    Building a scale model Shackleton, Nimrod or Sea King to launch these weapons is beyond my skills, so cannot envisage ever using it. Just felt if it were needed would be much easier to add it now than once the decks were finished.
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    ๐Ÿ’ฌ Re: HMAFV SEAL #5
    6 days ago by Scratchbuilder ( Warrant Officer)
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    Hi.
    This is excellent craftsmanship to a high standard.
    Regards Bill ๐Ÿ‘
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    ๐Ÿ’ฌ Re: HMAFV SEAL #5
    5 days ago by Joe727 ( Lieutenant Commander)
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    Hello,
    I really like your linkage and mechanism design. Nice photos as well.
    Joe
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    ๐Ÿ’ฌ Re: HMAFV SEAL #5
    5 days ago by RNinMunich ( Fleet Admiral)
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    "Building a scale model Shackleton, Nimrod or Sea King to launch these weapons is beyond my skills, so cannot envisage ever using it"
    I can lend you a 1.5m span Catalina if you like Rowen๐Ÿ˜‰
    You could always use the door for minelaying!!๐Ÿ’ฅ๐Ÿ’ฅ๐Ÿ˜ฎ
    Cheers, Doug ๐Ÿ˜Ž
    PS Don't back up too fast with it open!๐Ÿ˜ฎ๐Ÿ˜ญ
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    ๐Ÿ’ฌ Re: HMAFV SEAL #5
    5 days ago by mturpin013 ( Captain)
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    Nice detail well executed, most mechanisms on our models are never used but are really appreciated by everyone who sees them
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    ๐Ÿ“ HMAFV SEAL
    14 days ago by RHBaker ( Lieutenant)
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    The hull was now watertight with the powertrain fitted; time for trail tests on the local pool. This blog tends to jump around chronologically as wanted to get the hull sailing properly before adding the superstructure etc as a winter project.

    Using 3 S Li-Po batteries found the performance adequate. Nice bow and wave patterns, similar to the actual vessel photographs.

    The forward / aft trim looks OK, although was surprised by the draft. The model weights about 6 lbs and is already close to the waterline. Added ballast weights to see what would be needed to bring the model down to waterline. This shows that rather less that 3 lbs is available for the deck, superstructure and detail. Going to have to watch my weight again!

    Decided to increase the top speed by overpowering the ESCs using a 4S battery. The Quicrun ESCs must have a high voltage limiter as they cut out. From a box of bits found a voltage reducer and installed it. Providing the voltage is adjusted to below about 14 volts, the ESCs operate fine. Settled on using 13.25 v to give a slight margin.

    The increase in voltage gives a marked increase in performance, decided to use this set-up permanently. Think the model is slightly overpowered, but at least it can be quickly moved out of conflict situations!
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    ๐Ÿ“ HMAFV SEAL
    18 days ago by RHBaker ( Lieutenant)
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    After the shafts were correctly located, the motor mount position was established. Made up a mount using wood and aluminium plate. The motor shaft spacing is determined using the shaft centre lines. The longitudinal location can be measured from the shaft slope and height.

    Two brushed, 550 type motors were then fitted to the mount, followed by the shaft couplings. The mount location can be fine tuned by slightly sliding the mount around until the motor and shafts could be rotated with the minimum force. The mount was then glued into place.

    The shaft couplings used are steel, which tend to be noisy. Find that if a rubber or plastic sleeve is pushed over the coupling it quietens considerably. The inner coupling cavity/sleeve can also be filled with grease to ensure the joint is lubricated. Had earlier installed โ€œoilerโ€ fittings to the shafts for periodic lubrication.

    Decided to try the Quicrun 1060 series ESC on this model, one per motor, to improve control. So far they work well, although the installation would be eased if the wires were longer.

    Made up rudders by wrapping styrene sheet around a flattened brass rod and gluing together. The doubled over sheet is then be cut to the rudder side profile and the section sanded to shape. Once compete the shafts were lubricated and inserted into the tubes.

    The rudder servo fitted with a control linkage made up using old bicycle spokes and tested.

    Set the radio up to the โ€œelevonโ€ control sequence and tested the systems. Nice thing about brushed motors is everything usually works right the first time! No programming of ESCs etc needed either!
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    17 days ago by Martin555 ( Fleet Admiral)
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    You are to a great start.
    Keep up the good work.

    Martin555.
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    ๐Ÿ“ HMAFV SEAL
    28 days ago by RHBaker ( Lieutenant)
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    Checked the relevant dimensions. The drawings for this class are limited, but every measurement checked was correct. Fortunately there are a number of photographs on the net, so establishing details is possible.

    The hull upper edges followed the contour of the deck and bulwarks, with a trimming allowance of around 3mm. This must be removed to allow the hull height dimensions to be correctly reproduced on the model.

    Using a combination of spirit level, steel rule and various other measuring tools marked the bulwark edge; then carefully removed the allowance by sanding and a Surform โ€œscraperโ€.

    Once the deck & bulwark lines were dimensionally correct, turned to the propeller shafts and rudders. These are all straightforward and follow accepted practice. A wooden block was glued into place inside the lower rear portion of the hull to hold the rudder shafts and sleeves vertically. The cranks and servo will be installed above this block.

    Fitting the twin propeller shafts accurately proved the usual challenge, but with care and patience it was completed. The only โ€œtrickโ€ used to simplify this was to fit the shaft outer tubes into thin-wall brass sleeves where they go through the hull. This means that the three dimensional alignment needed to locate the propellers accurately can be simplified into two. The slope and parallelism of the shafts and then the horizontal protrusion.

    Once the first is achieved and the shaft sleeves glued in place, the shaft can be slid in/out of the sleeve to the correct horizontal position. After that is established each shaft is glued into place in its respective sleeve.
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    27 days ago by Martin555 ( Fleet Admiral)
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    You are off to a good start.
    I am looking forward to your future updates.

    Martin555.
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    27 days ago by nasraf ( Chief Petty Officer 2nd Class)
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    I rather like your idea of fitting a positional mounting tube for the prop shaft assembly. I think I will do the same for my HSL but only with one shaft, bit too complicated with two and the real boat had three.
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    27 days ago by RHBaker ( Lieutenant)
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    Thanks.
    I find the more the number of shafts the better this idea works. It separates parallellism from protrusion, so each requirement can be adjusted independently.
    Used it on my 3 screw Brave Borderer (an earlier blog) and on my twin screw RAF RTTL (current build).
    Both were much easier then my earlier twin screw installations.
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    ๐Ÿ“ HMAFV SEAL
    1 month ago by RHBaker ( Lieutenant)
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    My last project, H.M.S. Brave Borderer, was an interesting and enjoyable build. It was based on a glass fibre (gf) hull from MTBHULLS. Have decided that purchasing a gf hull gives an excellent base for a scale, robust model. Have previously experienced minor issues of micro-cracking on wooden models, gf avoids that. From a cost perspective, the hulls are probably little more expensive than building from scratch.

    MTBHulls was planning to produce a hull for the R.A.F. Seal Class which would be available in time for my winter 2019 project. The Seal was the last class operated by the R.A.F. Marine Branch, but as a LRRS (Long Range Recovery & Support) launch. They were significantly larger than the traditional ASRL, offering much greater range and capability, albeit it at a lower speed.

    At 1:35 scale the overall length would be 41.25โ€, just about my upper limit for transport.

    Ordered the hull and it duly arrived well packaged and safely, rather earlier than expected! At least it gave the opportunity for installing and testing the running gear before winter.
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    1 month ago by RNinMunich ( Fleet Admiral)
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    Hurrah!
    Dimly remember helping with research back then Rowen.
    Pleased to hear the project is underway at last.
    Looking forward to further instalments immensely.
    Pics of the hull?
    Cheers, Doug
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    1 month ago by RHBaker ( Lieutenant)
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    Hi Doug,
    Patience is a virue!
    All will be revealed in the fullness of time.
    Rowen
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    1 month ago by RNinMunich ( Fleet Admiral)
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    "Patience is a virue!" ?
    Virtue or virus Rowen?๐Ÿ˜ฎ
    ๐Ÿ˜
    Whatever! Expecting good things from you, as ever๐Ÿ‘
    All the best, Doug ๐Ÿ˜Ž
    PS: Croatia is open for visitors again!๐Ÿ˜‰
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    1 month ago by Martin555 ( Fleet Admiral)
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    I too would like to see this build.

    Martin555.
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    1 month ago by Scratchbuilder ( Warrant Officer)
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    I would like to follow this interesting build
    Bill ๐Ÿ‘
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    ๐Ÿ’ฌ Re: HMAFV SEAL
    1 month ago by MouldBuilder ( Captain)
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    I will be looking too.
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