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Dec 12, 2019, 11:48 AM
rshousha's Avatar
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Frank Paine’s 1935 "A" J-class (Currently “Topaz”) in 1/16 scale

Hello Everyone and welcome to a new build. After the design of the 12-meter Liberty, I am starting the design of a new boat for Spinnaker225, who has several builds in various places on this forum, notably, in the "J-Class" thread.

This is going to be interesting as this design is a team effort. Generally, I do all the design work based on ideas that are discussed with a builder. In this case, the builder has done much of the development work himself and has asked me to build the 3D model, and cut the parts, based on his design. We hope that this will reduce the total amount of time I have to spend in CAD.

As a Solidworks user, this is interesting because, as the builder works in Autocad, it allows me to mix different types of software to arrive at an accurate end result.

Three things concern me even before starting. Hopefully, these issues will be easy to handle.

First, I am concerned that the files I receive with .dxf extensions do not open at precise locations in a Solidworks part file and none of the lines are fixed with reference to an origin. I will have to think of a strategy to fix the appropriate lines in space and also fix the parts with respect to one another. More on that later, as we get into the project.

Second, I am concerned that the .dxf files do not support splines easily. This means I will open files as combinations of lines and arcs, instead of splines. Are the parts going to be smooth? Will this slow down the laser? Will the part files, when converted to Solidworks, be large? We will see.

Finally, I am concerned that the arcs and lines are not guaranteed to be tangent to each other throughout the parts. Depending on the number of lines in each part, this may, or may not be, an issue. Again, we will see.

So, let's get to the design!

Here is the starting point:

"J8 is an unbuilt 1935 Frank C Paine A design. Frank Paine had previously designed the yacht “Yankee”, which was built by Lawleys in 1930. She is the longest waterline J Class designed, with the highest keel aspect ratio, combined with the lowest wetted surface area. Frank Paine had already calculated in the 1930s that it was better to take a penalty on an increased waterline length in a trade off against sail area and displacement.
LOA: 42.7 m (140’)
BEAM: 6.75 m (22’2”)
DRAUGHT: 4.72 m (15’ 6”)
WEIGHT: 175.0
MANUFACTURER: Holland Jachtbouw. Hull built by F. Bloemsma Aluminiumbouw

Scale model dimensions ; scale is 1 :16
 LOA: 103’ 1/16”
 LWL: 68”
 Beam: 16 5/8”
 Draft: 13 7/16” (actual would be 11 5/8”), with the inclusion of a 2" allowance for the J-Class.
Last edited by rshousha; Dec 12, 2019 at 11:50 AM. Reason: spelling
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Dec 12, 2019, 12:53 PM
Classic wooden RC sailboater
SeattleRCSailor's Avatar
Cool project. I'm excited to watch, especially to see the 3D model.
Dec 12, 2019, 12:55 PM
rshousha's Avatar
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Great, thanks. I can smell that popcorn from here.
Dec 12, 2019, 10:09 PM
rshousha's Avatar
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Here we are at the end of a steady day of work and I have to say that this idea is working out nicely. Here's a picture of a few bulkheads inserted at the correct spots. Once all the bulkheads are in place, I will make the offsets, the cut-outs, the notches, and the then the drawings for the laser cutter. And, of course, the parts for the T-rail.


As for specific issues I found in the transition between file types, there was only one so far. Because the original parts are not aligned in any way with an origin, I had to create planes for each of the bulkheads that I could then use to make the relationships in the main assembly. That should work easily but it's not always obvious that all the planes are perfectly perpendicular to each other. One should be aware of when creating planes on parts.
Last edited by rshousha; Dec 12, 2019 at 10:11 PM. Reason: redundancies eliminated
Dec 13, 2019, 11:50 AM
rshousha's Avatar
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Most excellent work by Spinnaker225 on doing all the design work in advance of the 3D work. Inserting the bulkheads in place has taken much less time than I would have expected. This is great, thanks!
Dec 13, 2019, 06:52 PM
Registered User
Curious questions regarding ballast ...

After the 3D files are completed ... assuming the next step is to produce the frames as laser cut wood frames ...

I am curious if the intent for this design / build to be planked for a plug-mold ... or ... planked and used as a yacht directly ???

If planked and directly used as a fully functional RC yacht ... what method will be used for ballast - internal or external ?? ... especially since the internal frames will make installing INTERNAL ballast challenging to get the ballast as low as possible... considering the large wood keel and wood frames occupying the limited same space where ballast should be.

Will the method of ballast be considered in the final 3D files used to create the laser cut wood frames ??

Really interesting to watch this project develop ...
Dec 13, 2019, 07:03 PM
rshousha's Avatar
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Hi slo.ca6,

This is another boat for Spinnaker225 so the method will be the same as his previous constructions. Check out the J-class thread on this forum and you'll see the links there. Hmm, let me see if I can get the link for you:

I'm not sure if this is the way to connect a link here but this is supposed to go directly to his link for this model, once he gets the parts.

And here is a link to the previous boat I did for him;

Now, I will "submit reply" and see what happens. Exciting.
Dec 14, 2019, 11:49 AM
Registered User

Thank you for the reply regarding my curious ballast question ...

Indeed understand this is a joint project - where your part is the 3D CAD model for generating the frames to be laser cut ... the next part and rest of the build is going to be done by Spinnaker225 ... great to see such collaboration of skills.

As to my curious question(s) regarding internal framing and ballast ... seems this will be addressed by Spinnaker225 and how he did his previous projects ... as you noted in the forum links you provided.

Thank you Rick for the links ...

Indeed there is some up front PLANNING regarding frame layout needed to account for the method of ballast (internal VS external) ... seems Spinnaker225 has several different ways he has approached this in previous builds.

UPDATED added 12-14-2019 2:30pm
It can be seen (link to photos) from your link provided to Spinnaker225 build blog ... showing internal build frames removed to provide room for internal ballast. This must be challenging to remove frames in confined space.

Thank you again Rick for your reply ...

Looking forward to seeing this project progress ... especially the 3D layout and laser cut frames you will produce for Spinnaker225.
Last edited by slo.ca6; Dec 14, 2019 at 05:56 PM.
Dec 14, 2019, 04:15 PM
rshousha's Avatar
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Thanks for the note. This is what I call the "virtual factory". Each specialist does a part of the job and passes the project on to the next. I think the scale model industry is heading in that direction and I am interested to see how the big players are going to adapt to this new reality. I enjoy doing these 3D designs and I get better at them with each new design. The fellow who is now working in the 1:20 scale America seems quite pleased with the results.

Here is the next step in this project; to make the offsets to take into account the modeller's particular building method. This offset is discussed with each builder. Again, this becomes part of the idea of the "virtual factory" where a kit is only manufactured at the request of a builder.

You can see in the picture, the first few bulkheads are smaller than the others. Eventually, they will all be adjusted for the planking.
Dec 14, 2019, 06:18 PM
rshousha's Avatar
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Next step is to open up the bulkheads. Although most of them will be removed after the planking is done, it's important to make the openings to allow for clamps to be used easily during the planking process. I try to make sure all the edges are the same size so it's easy to remove clamps from one bulkhead and place them on another without changing the adjustments more than necessary.

In the picture, only a few of the bulkheads have been opened up. All the edges are 1".
Dec 15, 2019, 12:02 AM
rshousha's Avatar
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Next comes the keel cut-out.
Dec 15, 2019, 11:30 AM
rshousha's Avatar
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So here's something fun about working in 3D before cutting. As I started on the notches in the keel, I could see that some of the spaces in the bulkheads were too big. I have three solutions; reduce the spaces in the bulkhead openings; lengthen the notches; reduce the width of the keel piece. Now, if I have used Solidworks correctly, I should be able to fiddle with the width of the keel without having the rest of the model blow up on me. We shall see.
Dec 16, 2019, 06:21 PM
rshousha's Avatar
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Basic bulkheads completed. Next, we need to add an intermediate bulkhead to increase the support on the mast.
Dec 19, 2019, 12:23 PM
rshousha's Avatar
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Greetings! Sorry for the delay. I drove across the continent a couple of weeks ago to help one of my daughters commute from Montreal to Nelson, BC. She's a ski instructor there and I thought it would be fun to drive across with her.

Well, it turns out a sixty-year-old back doesn't do well sitting in a car for fifty hours and I haven't been able to do much work since. I flew back in good airplane seats but the damage was done.

Fortunately, I can ski better than I can walk and I did get to ski a few runs at Whitewater, where she is teaching. It's an amazing place, getting an average of 500 inches of snow a year.

I have to say the drive was amazing and I was struck by the beauty of the continent and the commonalities we all share, from one end to the other. Everyone should get a chance to make this drive once or twice in their lifetime.

OK, so here is the hull with the addition of the extensions to the bulkheads. These are needed in order to place it upside down for planking.

Next, is to add the t-rail parts.

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