Building a scale Maxi - RC Groups
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Jan 29, 2018, 05:08 AM
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Daniel Gut's Avatar

Building a scale Maxi

Approximately two years after my first online enquiries and subsequent contact with Wick Smith, 2 of his gorgeous looking 1.7 Meter hulls landed on my workbench. The hulls have seen some racing and have a few Sea Miles under their belt. Since there is no class here and I am not looking to squeeze the last 1/8 of a knot out of the performance, the aim of the project is a good replica of the maxi Esimit Europa 2, including the colour scheme.
I have done some research on the scaling down of boats and learnt a few interesting things that I would like to share, I think it will help some of you in your decision making for the scale projects to come.

When scaling down length, width, draft and height, it can be done in a linear manner, sail area will be the square root of the original, while scale mass and volume are approx. the cubed root of the real thing. At 1.7 meters long, model has a scale of 1: 17.5, the sail area 1:306 and the mass 1:5360. The loss of righting moment, if I built the underwater to scale, would be a factor of 17.5. (sail area to ballast and ignoring the fact that the original has a canting keel). Wind resistance/pressure increases exponentially with increased velocity, so that when the real thing is still sailing unreefed in 20 knots the model, with less righting Moment, is starting to struggle with a third or more less wind.

Esimit Europa 2 is 30 meters long and 5.3 m wide that equals a length to width ratio of 1:5.7. The model has a ratio of 1:5.8, so all good there. I have a Walicki profiled mast that is 2.45 meters long and is within mm of being scale. The original keel for the Model is 430mm long and supports 7.3 kg (16 lbs). I have a Bantock 10 Rater keel fin lying around awaiting its conversion to the Maxi class. It is not quite as sexy as the skinny ones, but the fin has more than proved its class on the racing stage. I am increasing the Fin length to 630mm and reducing the Bulb weight by about 800g. All in all the righting moment should increase by about 20 %.

First up is a deck modification and the installation of the Winch sheeting system for a RMG Drum winch, possibly two if I decide to have a boomless foresail.
Enough for now, I will post pics and comments as I go
Last edited by Daniel Gut; Jan 29, 2018 at 09:39 AM.
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Feb 13, 2018, 03:21 PM
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Daniel Gut's Avatar
Not really much to tell, other than that I have been changing the deck slightly and constructing the coach roof. RMG can only send the new winch in about 5 weeks so I cannot close up the foredeck yet ( don't want to actually)
In order to have stanchions and the tack of the jib down on the deck, the jib will have a slightly higher clew like the one on the 2nd picture of EE2 above. The jib will there fore have a small boom attached approx. in the middle of the foredeck ... well that is the idea for now, but it could change again
Here is the progress.

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