Hi all,

just posting a summary of (mainly) previously posted pics to kick off this build log and show progress to date since I first started researching the building of this 'leviathan'😉 last year.

I'm currently at a stage where I have acquired the necessary propshaft/tube/propellor assembly and awaiting delivery of my chosen powertrain. The timber for most of the build has been sourced, so now I have finished other projects, all that really remains is to get on with it!!😁
1)The plan...
2)Drawing bulkhead and keel templates from plan
3)Bulkhead paper shapes stuck to 3/8 ply - I chose to make the bulkheads slightly thicker for extra gluing area and because I need to have ply-skin joins across certain bulkhead positions as standard modelling ply lengths do not go to 54". Some of these may have lightening holes cut in them for better internal access to equipment - haven't decided yet.
4)bulkheads cut out and trimmed/notched for stringers. Waiting for keel cut out, as a couple of issues regarding installation of the prop tube into the keel pieces have arisen; I need to accommodate the two oilers somehow, and the original keel pieces need to have another piece added to support the prop shaft all the way to the prop bearing - I'll post details when I've sorted it out...I hope🤔
5)Original 10mm pine keel pieces cut out and assembled over plan - not yet glued up as an extra piece still required
6),7) & 8) Lots of spruce strips!! - spliced together to make up pieces approx. 70" in length for 3/16x3/8 chine stringer laminations, 1/4sq. sub-stringers, 3/6 sq spray rails and keel doublers.
9)18" 3-bush 3/8dia prop tube with oilers/tubes at two bearing positions, 3" diameter 3 blade propellor fashioned from 1mm brass sheet to be fitted to M5 thread on 3/16 steel shaft. I had this specially made up by Bill Nordmeyer who owns SAB Model Boat Fittings - thanks Bill!👍👍

The brushless motor and speed controller should be arriving in the next week or two. When they do, I intend to set up an engine/propshaft test to see what the performance specs are like prior to installing the tube in the keel. Once this has taken place I'll be able to post again.

Until then , best regards,

Nick

Hi to all again!
Sorry no post for a few months, but I've been rather busy on other projects; my younger grand-daughter's first train set for Christmas which still needs work (one has to plan these things well in advance otherwise time runs out....been there, done that😉), shown in the first photo, and some building work for a seating area next to our pond, 2nd photo.
A recent bout of awful weather meant we had an indoor weekend where I was able to focus a bit more on Vivacity's keel assembly which was actually started back in February. Constant referral to this large-model boat plan reminded me a great deal about what it felt like scratch-building David Boddington's 102" wingspan Centurion a few years ago, probably the pride and joy of my current airfleet (photo 3). With models of this size, NOTHING is as straightforward as it looks on the plan, as many of the oversized parts are actually sub-assemblies needing to be fabricated from more than a single piece of material. This means every piece requires some fettling to fit satisfactorily.

And so it has been with Vivacity's keel assembly;
4)15FEB2026 - initial gluing up of 10mm pine keel centre pieces using PVA glue - every attempt made to keep keel straight/flat. Note powertrain components, details to follow.
5)Once glue cured, position of tube drawn on in preparation for cutting and filing out circular section groove for tube to seat snugly within keel piece.
6)&7) 08JUL2026 - Powertrain test rig assembled and tested with 4s lipo. After much deliberation weighing up a brushed set-up vs brushless, then choosing brushless only to find the only way I could get a low enough kv motor for the 3 inch prop speed to be acceptably low was to use an aero motor, I finally settled on the following; - Surpass C5055 400kv outrunner, a 50mm brushless fan unit to draw air across the motor, a Flycolor 120Amp brushless watercooled ESC, a Spektrum AR410 receiver which will be mounted as high on the superstructure as possible, a double universal coupling to iron out any shaft alignment discrepancy. Max RPM for a 75mm (3 inch) prop is only about 3200, and this set up with 4s gives double that, but I figure that it will reduce significantly under the load of water immersion, and I probably won't be using full throttle all the time anyway. If it is too high for this prop, I can always down size the prop, or move to a 3s set up, although I would prefer to keep it at 4s, as otherwise the current draw really starts to climb for a given power output. As a matter of interest, this motor is meant to be good for about 1600 watts! - that's drawing nearly 100amps with a 4s battery - hopefully I'll only need a fraction of that as the original Vivacity used a 34cc JAP motor producing 1/3 hp at 3250 rpm with a 3inch brass prop...food for thought, eh?!🤔
8)After filing circular section groove into keel pieces, prop tube roughed up on outside to help key in epoxy, then glued and taped into position, left overnight to cure.
9)09JUL2026 - remaining keel pieces epoxied around tube and splinted in place with popsicle sticks and tape to keep flat while epoxy cures overnight again.
10)10JUL2026 - keel centre assembly offered up to plan - note slightly reduced length of skeg as brass propellor hub requires the extra room to bring prop blades into correct position - this may of course change the blade position if a different prop is used. Another problem encountered by the oilers being present, meaning doublers require cut-outs to clear oiler assembly.
11)-13)25JUL2026 - 5mm plywood & spruce keel doublers measured up, carefully cut in matched pairs and glued into position. Exterior-grade PVA used. Care taken to keep keel flat while doubler-glue joints cure to ensure keel kept true.
14)26JUL2026 - keel assembly with doublers fitted laid over plan - note datum line drawn under keel at right angles to bulkheads. This is done in preparation for next stage of build, where a jig will be assembled to allow keel to be held vertically so bulkheads can be tailor-fitted into position and glued.

A question for anyone reading with more experience than myself (just about all of you I suspect😉) - with a model this size, upright assembly of hull, or inverted? - any thoughts/input gratefully received and considered.

Until the next few stages are completed...

Best regards to all of you,

Nick