Building a scale Maxi - RC Groups
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Jan 29, 2018, 04:08 AM
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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 08:39 AM.
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Feb 13, 2018, 02:21 PM
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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.
Mar 06, 2018, 04:06 AM
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I have now raised the deck at the stern and installed the self-tensioning line for the closed sheeting system below deck. The RMG 380EL winch has arrived and will be installed soon, the ruder servo is a Futaba 3070 HV with 6.5 kg of torque … that is ample for the narrow high aspect rudder.

The 7.3 kg bulb now weighs 6.6 kg and will lose a few grams more when I reshape it. The keel fin has been cut to length, attachment "bolts" for the bulb are in place and the attachment fin to hull is being shaped. I have thought about putting in a approx.. 4:1 kicking strap system on both jib and main that is adjustable (see sketch) I like the idea of being able to depower the top of the rig and the system is not too complicated. More on that later.

The mast is a Walicki carbon, profiled and tapered section and a real work of art. I am very glad that I still managed to get one of these a few years ago before Mr Walick passed away. I have not given the rig and spreaders to much thought yet. I have a piece that is 2.1 meters long and another approx.40cm that needs to be added to the bottom. The mast is going to look fabulous on that hull.
Last edited by Daniel Gut; Mar 07, 2018 at 04:05 AM. Reason: Spelling
Mar 06, 2018, 05:51 AM
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Nice work Daniel


Hi Daniel,

Great idea,....

Thank you for your postings.


D

P.s.,....who made your Rubin sails?
Last edited by Derusha; Mar 06, 2018 at 05:52 AM. Reason: Add p.s .
Mar 06, 2018, 12:42 PM
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Hello Derusha

The kicker idea? or building a maxi

The Rubin sails came from a company called Latsch in Germany. Not cheap but lovely.

also D
Mar 06, 2018, 01:48 PM
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Quote:
Originally Posted by Daniel Gut
Hello Derusha

The kicker idea? or building a maxi

The Rubin sails came from a company called Latsch in Germany. Not cheap but lovely.

also D
Both!

How much for the sails?

DJD
Mar 07, 2018, 03:59 AM
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If I have done my sums correctly, about $260

The RMG winch is a brute and has loads of travel. My biggest headache at the Moment is creating a workable System for the Job, that looks scale and functions simply. Here is my initial thought on that.
Mar 07, 2018, 10:54 PM
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Why not run the radial jib boom at the front like Wheelers do out here in California? Works really well and looks cool. Ryan
Mar 08, 2018, 04:22 AM
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The Jib


I have never liked the look of the jib high off the deck and would therefore like the Jib tack to be on the deck. With a slightly higher cut foot/ clew a shortened boom will clear the stanchions and still make for a jib that works well and looks good. The IMOCA 60s and VO65s also have Systems for moving the sheeting Point outboard. The System on the Wheeler does look very nice though. Thank you for the Input.

The RMG winch is going to be a tight fit and will require a bit of fiddling to get it right

Regards from a slightly springy Zurich
Mar 08, 2018, 11:36 AM
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Quote:
Originally Posted by Daniel Gut
. Here is my initial thought on that.
If you draw the top view of the jib arc and the short boom arc you might see when the jib is out for downwind the short boom is not long enough.
I think thats why the radial boom pivot is under the front of the jib.
Mar 08, 2018, 01:32 PM
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Quote:
Originally Posted by huzway
If you draw the top view of the jib arc and the short boom arc you might see when the jib is out for downwind the short boom is not long enough.
I think thats why the radial boom pivot is under the front of the jib.
I understand that, but since I am not racing and prefer reaching to the flat downwind courses that the racers sail, it is a compromise (a small one) that I am willing to make. I am looking for a good balance between aesthetics and efficiency. Getting that right is not going to be easy

D
Jul 08, 2018, 03:34 PM
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Daniel,

these look amazing! i am currently in the process of build a 1:14th scale tp52, and am in the same position! just looking for realism!

so excited to follow this thread!

Michael
Jul 10, 2018, 12:46 PM
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Just a thought...

As mentioned way back in March, with regards to radial jib pivot position, at the point of sail you prefer, the jib will be very full (baggy) and not very effective. Also, try to keep the centerline of the pivot about the same angle as the head stay. I know you say that scale looks are important, but poor performance on the water will likely result is not enjoying to sail the boat, and that would be a shame. It's a great project.


Dave
Jul 11, 2018, 02:39 AM
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Hi Dave

The effectiveness also depends on the point of sail. Flat downwind I agree with you, my system would have a little disadvantage if I were racing and if the course were a windward – leeward one. A fuller jib when reaching downwind is a good thing and with the adjustable kicking strap system, I can set up the slot between main and jib to suit the twist in the main sail. If the boom is about 2/3 as long as the jib it will also not get too full.
The project is taking a summer break at the moment, the weather is great and I have been testing how cold my gliders get at altitude

Thank you for your thoughts


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