I decided to start this following a suggestion from one of you on this website, that the smaller Lesro designs such as the Sea Urchin, Sea Nymph and Fast Patrol Boat would perhaps be able to be sailed relatively safely on my backyard pond with reduced power settings.
As I have most of the plans for these designs, it stood to reason that my severe building addiction could be somewhat satisfied in the background whist trying to solve arising issues on another much larger build I had already embarked on but which had stalled for the time being (namely Vivacity).
So here goes with just a few pics to set the ball rolling;

1) 20FEB2026 - measuring and transferring shape of parts onto paper templates and balsa - I decided to use balsa for most of the frame as I had plenty, and I find it much easier to work with on smaller boats. And the model was for modest electric power, not small diesel, so it should be plenty strong enough if the outer hull is covered with tissue, as on the Knocker White Tug model completed earlier.

2)&3) Keel and bulkhead parts cut from 3/16" balsa. Keel doublers glued on first side using exterior grade PVA, all excess 'splurge' immediately wiped away using damp rag - I cannot stress enough the importance of this, as it really minimises/eases the 'fettling' required to fit bulkhead/other parts as the build progresses.

4)Keel assembly turned over and propshaft 'slot' cut away/filed.

5)Remaining keel doublers glued with PVA, as well as 5 minute epoxy around prop shaft/keel/doubler sandwich.

6)Bulkhead shapes reinforced with scrap 1/16" balsa crossgrain at edges where slots are to be cut, creating a sort of 'liteply'.

7)Keel assembly completed with proptube reinforcement and bow doublers glued. Bulkhead slots for cabin sides/keel cut.

8)Fettling and test fitting bulkheads to keel - and a celebratory glass of Henkell Trocken to mark the progress to date - 01MAR2026.

More to come once I've done this weekend's property jobs!

Best regards to all reading,

Nick

9) 02MAR2026 - 3/32 hardish balsa cabin sides cracked and glued at 'crease' line shown on plan - propped up at approx correct angle and held with weights.

10) 3/16 balsa breasthook glued to keel assembly and checked for squareness.

11) Bulkhead 1 glued to breasthook/keel assembly.

12)&13) Bulkhead 2 glued to keel and checked for squareness, and alignment using centre markings and mark one eye-ometer - I think it was good...🤔

14)&15) Remaining main bulkheads attached and checked over plan for general alignment while glue still 'pliable'.

16) Cabin sides slotted into place after some keel length adjustment to ensure better fit to transom slots.

17) Top and bottom inner chine laminations added from 3/32" x 1/4" strips. NB the original plan shows 1/4" x 1/8 hardwood or spruce chine stringer pieces, but as I was using balsa, I chose to use 2 laminations of 3/32" balsa, as I felt it would be easier to bend into shape in 2 stages, and strong enough with it being laminated. The notches in the bulkheads had been cut accordingly. As it turned out, I probably could have got away with 2 laminations of 1/16" balsa, as laminated balsa is remarkably strong and stiff for its weight - a lesson learned in several of my vintage model aircraft builds.

18)&19) Outer chine layers added.

20) Lower chines sanded flush with bulkheads to seat hull bottom sheeting.

21) Reinforcing 3/32" strips glued around cabin window frames and cabin front added - I made a mistake with the front cabin window piece, which should have had a curve to match that of the roof hatch - I later had to add a piece to the top and sand it to shape once I had made up the roof hatch - see later.

22) Bulkhead B3A glued in.

23)12MAR2026 - prior to adding hull bottom sheeting - starting to look like a Sea Urchin!

Best regards,

Nick

So far I'd got the basic shape/frame completed - onto the hull sheeting. As I was using balsa, I chose to upsize the thickness to 3/32 sheet and orientated the grain to assist with matching the chine curves.

24) 20MAR2026 - 3/16" square section rear hatch supports glued into place.

25) & 26) 3/32 balsa sheeting makes up the hull bottom.

27) Rear hull sides started, then paused so open sides around the cabin ease motor-mount installation.

28) 1mm aluminium sheet motor mount bent into shape using hammer and vice 😉, drilled for mounting screws, then epoxied to RE360 motor. Coupling from flexible gas tube with narrower piece of silicone fuel tube inserted in one end to cater for disparity between shaft diameters (2mm motor to 3.2mm shaft). Decided against universal metal coupling at this size of boat, also hoping any slight misalignment might be 'absorbed' by the flexibility of the coupling. This type of coupling worked well in the Knocker White tug.

29) Rudder assembly made up from 0.5mm brass sheet soldered to 1/8" piano wire shaft, tiller from same brass sheet soldered to 1/8" wheel collet. Shaft is to be secured to transom using 1/8" undercarriage straps.

30) 1.5mm ply transom sheet glued to balsa transom - this is not shown on the plan, but I chose to add it as the rudder assembly mounting screws needed something a little denser to screw into, as well as covering up the ends of the chines. Another piece of ply was glued on the inside of the balsa transom to create a ply-balsa-ply sandwich. A groove was then filed into the ply transom on the outside to allow free movement of the rudder shaft despite being 'clamped'.

31) - 34) 3/16" motor mount bearers slotted onto keel, then trimmed for correct angle of 3mm motor mounting ply plate. Motor attached to prop shaft using solid coupling to align before ply plate glued with 5 minute epoxy (the epoxy fills any gaps if the bearers are not quite right😉). With the solid coupling also providing lateral alignment between the two shafts, screw hole positions can be marked in the ply plate and drilled.

35) And finally for this instalment, setting up the RC gear to test before doing a 'dry run' of the installation in the boat prior to finishing off the side sheeting. This RC set up was very similar to that used in the Knocker White tug, which made the tug perform like a speedboat(!?!) and get on the plane before it was properly ballasted;
- a cheap metal geared 10gram servo for the rudder, salvaged from a crashed RC plane, 5-cell NimH battery pack for motor and RX power, 10Amp brushed ESC from Ali Express, and Spectrum AR 410 4ch RX. Wires were soldered to the motor and everything wired up and switched on to check it all worked prior to installing into the boat - we're up 02APR2026.

Best regards,

Nick

36) & 37) 03APR2026 - battery box for 5-cell AA pack built up over the keel from scrap balsa to fit under the rear deck.

38) Scrap spruce blocks glued in to mount steering servo. Brass tiller arm drilled for connection to servo, hooked up using z-bends in standard 'soft' 2mm servo connector wire.

39) RC electrics test fit-out completed, cutting holes for wires where necessary. Installation energised to check throttle and steering response, before removing for remaining side sheet to be fitted.

40) Cabin roof hatch frame constructed from 3/16" balsa scrap.

41) Cabin roof sheet from 1/32" ply bent over frame and glued.

42) Once cabin roof hatch cured, rear hatch cut from 1/16" ply & trimmed/sanded to fit over rear well.

43) By this time, I realised I really needed a stand for the Sea Urchin, so this was constructed from 5mm foamboard I had. My technique for assembling this is to make mapping pin holes along the lines of contact between the pieces before liberally applying PVA glue and pinning while the glue cures. Excess glue removed with damp cloth.

44) Sides sheeted with vertical grain 3/32", then sanded to fit chines.
1/16" ply foredeck cut, trimmed, then glued/fitted into position and held with masking tape.

45) Sea Urchin with hatches fitted awaiting side deck pieces and rear servo compartment covering.

Best regards,

Nick

I mentioned earlier that I had made a mistake with the shape of the cabin windscreen former, so...

46) 12APR2026 - a shaped piece of 3/16" balsa was glued to the top of the windscreen and sanded to provide a neater fit with the underside of the roof.

47) Remaining 1/16" ply deck pieces glued and steering servo removable access hatch fitted held with 4 small screws, then all sanded flush with sides.

48) Steering hatch hole carefully cut/filed out and servo with linkage re-fitted - note groove filed into transom to allow rudder shaft free movement.

49) Steering gear re-fitted and tiller drilled to accept linkage arm from servo.

50) - 53) I wasn't initially convinced I could use rubbing strips from 1/8" sq. as per plan as I thought they would snap when drilled for fixing screws.
Decided to used 1/8" x 1/4" bass; first these were soaked in warm water for an hour or so, then drilled at intervalswith 1.5mm pilot holes for some very small (10mm x1.5mm shank) screws I got through my work place. A 'dry run' fitting was carried out, piercing the balsa sides with a mapping pin through the pre-drilled holes to ensure a good, snug fit all along the length of the strip. When satisfied, and after waiting a few hours for the wood to dry out, screws were removed and the resulting shape checked. PVA glue then applied and strip re-screwed into position.
This process was repeated on the other side, taking care to mirror the position/curvature of the first piece.
The process was repeated for the spray rails after testing whether the 1/8" square bass could be similarly drilled without snapping - I only snapped them once! (honest😉). Once glued, excess glue was carefully removed with a damp cloth, the rails/rubbing strips left overnight to cure.

54) The following morning, all the screws were removed and screw-holes filled with a light multi-purpose wood filler. Once dry, this was sanded down to blend all the surfaces to surrounding wood areas.

55) Sea Urchin's basic woodwork is now complete, awaiting final sanding down before sealing with several coats of thinned dope sanded back between coats, then tissue on the balsa parts of the hull, followed by more dope until nice and smooth - then comes the painting/fittings etc.
We are on 20APR2026, bringing us to approx. present day.

More posts to follow once I've started the finishing - starting to get excited about seeing her on the water...😊

Best regards,

Nick

56) 24APRIL2026 - 50:50 Dope/Thinners to seal wood inside and out, cut back between coats until smooth.

57) 3-days - Tissue doped onto hull and trimmed. 3 coats 80:20 dope:thinners to fill tissue, lightly cut back with 240 grit between coats.

58) White gloss paint two coats inside hull.

59) - 61) 3-coats of nautical blue paint on cabin roof and upper hull. 3 coats gloss white on lower hull. Decks painted two coats matt light brown to cover wood filler but retain wood colour.

62) & 63) Deck planking carefully drawn on with fine permanent ink marker. Inside of Window frames also 'painted' with permanent black marker.

64) & 65) 2 coats polyurethane varnish on deck/cabin surfaces to seal in matt wood coloured paint and decking lines.

66) Glazing from food packaging epoxied to inside of cabin sides.

67) Final refit of electrical components - some amendments to wiring. Wireless receiver positioned as high as possible in cabin.

68) - 71) 16MAY2026 - Sea Urchin on the stand & in the water awaiting maiden voyage.

I have a couple of short videos to upload also, although my first attempt to do this failed due to file size restrictions.

Sea Urchin performs well, as expected considering she was deliberately fitted with a modest power system due to the confines of my backyard pond. She actually performs best at a couple of notches below full speed, The motor got a little warm, but as the cabin doorway is open, there is room for some cooling air circulation.

I may post a few more pics in the future, as I still have to manufacture and fit some fittings such as grab rails, cleats etc, as well as a carry/storage case

It's been a very enjoyable build, and although the Vivacity build needs attention, Sea Nymph and Fast Patrol Launch plans are beckoning!

Thanks to Fireboat's efforts, we are now able to upload videos up to 1GB in file size, so here are the two short videos of my Sea Urchins maiden voyage on 16MAY2026.