1:25 wally tango build log (in progress)

This project aims to create a 1:25 Wally 100 Tango model: LOA=1219mm, beam=288mm

Covid crisis and minimal ressources: a 28″ screen, openSCAD, some paper, two block of styrofoam, 3mm plywood… and a lot of “week-end” time.

Choices made:

  • composite hull because we are in the 21th century … and to keep the weight low
  • fiberglass Vs carbon to be more easily repairable
  • one hull is needed, I go for the lost (not really) mold method – The plug is used to build the final part directly. It is lower cost, faster and avoid me to store the mold after… the time saved on sanding/finetuning the plug will be use on the final part
  • full scale sail plan
    2020, April 4-12: my openscad design: Hull / waterlines
    24-Deg angle: waterlines look correct. Single rudder ok, still immersed, everything seems ok.
    45-Deg angle: waterlines look. hum… I have a doubt about the single rudder here.
    We will see;-) I am planning to make it larger than a real scaled one.
    And heeled now, buttock lines.
    2020, April 18-19: Covid-19 == no 3d printer here. Old school but efficient method.
    Calibrate the screen size and copy over each bulkhead with paper.
    Mirror the imprint on the plywood and cut with a manual scroll saw.
    2020, April 25-26:
    40mm styrofoam cuts to reach the 120mm spacing stated between bulkheads.
    3 blocks of styrofoam and one bulkhead glued together and fixed on the support.
    (The bow has a lower number of styrofoam layers (two and one on the last bulkhead)
    reduced result before heavy hand sanding
    After sanding

    2020, May 2-3:
    Nothing much to do, still waiting for the delivery of fiberglass cloth. packing tape and mold release wax applied.

    2020, May 6:
    Hull lost mold fiberglassing.

    • 2 layers of 160gr/m2 sergé fiberglass cloth
    • Slow epoxy resin
    • Epoxy black RAL 9005 pigments
    The second layer of fiberglass is set at a 45 degrees angle from the first.
    The color is useful during fiberglass impregnation, it helps to make it even. It creates also a base for the hull final color, perhaps allowing less paint job.

    2020, May 9:
    lot of sanding (reducing a bit the previous fiberglass layers), epoxy putty to level properly the surface, sanding, the structural finishing double 160gr/m2 fiberglass layers, ultra light sanding, epoxy putty and final sanding!

    2020, May 10:
    Here’s come my 1200mm wally tango hull ! 😎
    Resin/Pigment/Putty/fiberglass total cost: ~50 Euros.
    Weight of the untrimmed hull: 720gr.
    I still have to trim a big part to the deck limit. I will probably land around ~600/650gr which is not bad at all considering it is a 1200m stiff hull with at least 2 layers of 160gr fiberglass. It should be able to take some rough hits.

    Trimmed! 610gr

    Borders: Light bulkheads with 3mm plywood and border are shaped with 3mm balsa. It aims to provide a light structure easy to finetune. I will see if an added G4 primer will provide enough strength or I will simply fiberglass the wood…

    3mm Balsa custom insertion

    Trimming and sanding

    Second layer of 3mm balsa on top and bevel

    Rudder and fin

    The rudder is 4 layers of 160gr/m2 fiberglass encapsulated between plywood and shaped. The middle fiberglass is for stiffness and leading/trailing edge hardness. 19cm, 30gr

    The fin is from center: 4 layers of 160gr/m2 fiberglass, balsa 3mm, 2 layers of 160gr/m2 fiberglass covering and fixing the middle shaped carbon tube of 8mm. The middle fiberglass is a bit for stiffness and mainly for leading/trailing edge hardness. The carbon tube has two purposes: stiffness and holding top/down brass knurl nuts.
    40cm, 7.5mm thickness, 87gr, bending 17mm with 1600gr bulb.

    Keel box is built on the fin: unidirectional carbon 200gr and multiple layers of fiberglass.

    Keel box settled in the hull, rock solid and light weight: epoxy glue against the hull, high strength unidirectional carbon 200gr stratified web over the box head and bulkheads, one layer of fiberglass 160gr over the seal (box / hull). I used black pigment in my resin to ensure visual control of the epoxy resin covering, it looks a bit messy but still very useful.

    The front is prepared and reinforced to hold the jib stay and possibly a classic headsail like the real 1:1 tango… but I will probably finish with a classic RC jib boom.


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