Greetings!

This is a scratch build thread for a modern 10 rater design. While I've built numerous radio control airplanes and gliders, this is my first attempt at building a high-performance racing yacht. Growing up near the ocean, I've always been interested in sailing and the similarities between sailplanes and racing yachts got me thinking. I've been doing quite a bit of reading so hopefully I won't butcher the nomenclature too badly.

Frank Russell made this very easy for me to get started. I purchased the plans from his site and the next day I had a PDF document waiting in my inbox. The plans are very detailed and have 1:1 scale drawings of all of the hull cross-sections so it's simply a matter of printing them out, gluing them to some lite-ply, cutting them out and sanding them to final size.

This is an interactive build and I welcome any and all creative criticism, questions, thoughts and course-correction nudges along the way,

Mike

The first step was getting my little shop space sorted out and building a simple torsion box out of MDF as a platform for the strong back.

Thinking ahead to the layout of the sail winch and other controls, can someone explain to me in layman’s terms what’s going on in here?

Is the blue servo for trimming the jib?

6 hours ago, mdeleo said:

Thinking ahead to the layout of the sail winch and other controls, can someone explain to me in layman’s terms what’s going on in here?

Yes, its an AI generated image and makes no sense at all :)

I like the fact that it only has shrouds on one side - a proa perhaps? Your plan shows the winch drum above the deck. I haven't seen a boat like this in years and would highly recommend having the drum below the deck as it is so much easier to keep the water out like this. You will need to choose between a continuous winch line and a single ended winch line and whether to have the winch line (and the tensioner) above or below the deck. The latter looks better but is so much harder to repair at the lakeside. On my 10Rs I use 2 winches with single ended winch lines exiting right at the stern and these pull the sheets directly. This saves the friction (and expense) of turning blocks. I tension the lines with fishing pole elastic that runs in a loop to the bow and joins the two winch lines. There are many other ways of doing it and I seem to be in a minority of one in using two winches.

I'd like to see a picture of that layout.

5 hours ago, Austin said:

Yes, its an AI generated image and makes no sense at all :)

Hmmm, yes I'd be doubtful to take that as guidance/gospel. I know nothing about 10r exoticity (real word...), but I did notice the carbon-encapsulated battery....? And the servo which seems to operate an athwartships lever (adjustable keel cant?). Oh, and isn't screwed down... Two un-enclosed pcbs (extreme weight saving?)...

A pretty pic, but looks a bit too lovely

Edited August 11Aug 11 by Colin Helliwell

I really stepped in a pile there, didn't I... Thanks to all of you that took the time to think about that nonsense and respond. I really appreciate it.
A possible takeaway for novices, like myself, that may be following along: If you don't have enough domain experience to catch AI-generated nonsensical answers to your questions from ChatGPT, Claude, Gemini, et al, then you need to tread carefully. I'm starting to notice this phenomenon ("whiplash") in my line of work where I do have the expertise and am responsible for reviewing others' work. Not trying to be a Luddite, rather suggesting that you ask before trusting blindly.

11 minutes ago, mdeleo said:

I really stepped in a pile there, didn't I... Thanks to all of you that took the time to think about that nonsense and respond. I really appreciate it.
A possible takeaway for novices, like myself, that may be following along: If you don't have enough domain experience to catch AI-generated nonsensical answers to your questions from ChatGPT, Claude, Gemini, et al, then you need to tread carefully. I'm starting to notice this phenomenon ("whiplash") in my line of work where I do have the expertise and am responsible for reviewing others' work. Not trying to be a Luddite, rather suggesting that you ask before trusting blindly.

I've used chatgpt a few times recently, and found it pretty useful, if only to collate and summarise things that actual human beans have said somewhere. But retain or start with your own knowledge first where poss. I've sometimes responded to ai with "but surely that doesn't make sense because xyz", and it responds "yes, you're right, good catch". I've even had "ah, yes, your solution is better than mine". And smilies.... very creepy.... Skynet/Terminator here we come! It can be useful, but use with care, never forget the A in AI ;)

Edited August 11Aug 11 by Colin Helliwell

Started on the strongback today. The local FedEx office was able to print the plans and cross-sections for me. Nice attention to detail on Frank's part by adding a 100 mm legend in several places that you can use after printing to verify the scale of the printed pages.

Nothing surprising here. Just cut out the cross-sections and glued them to the 1/4" lite ply in a somewhat material-saving pattern. Hard rolled the paper to make sure the edges stuck down to the wood. Then it was off to the races with the band saw and disc sander. Maybe two hours of work for both of those steps.

Then it was just a matter of aligning them along the center and station lines on the torsion box. It's already starting to look like something.

And the rest of the images...

One thing I found useful was to make a set of 'outside' templates. Once you start fairing the mould it's amazing how far out of true you can get, particulalry between stations. If you hold the larger template between stations you can judge the eveness of the gaps. For the last one I made a cradle of outer templates on the strongback to hold the hull true while a put in the keel box etc. The bare shell is very flexible and easy to twist and distort if it is not properly supported

Thanks John. That makes a lot of sense.

Divinycell H80 cut into 10mm strips and spliced to create full-length planks. Strongback formers protected with packing tape.

And the planking.

And more planking.

Added carbon reinforcements and 4 oz structural glass outer layer. West Systems 105 epoxy and 209 hardener readily available and forgiving for this type of hand layup.

A light shaping/sanding layer was added after the glass layup got tacky to the touch.

This has become a bit of a monologue but I’ll need some help once I start arranging things inside the hull.

Thanks again for following along,

Mike

The usual “sand most of it off, add more and repeat” process. Pleasantly surprised that the first go-around wasn’t too bad.

Round 2.

And a sneak peak at the insides. Not a lot of extra Titebond or epoxy wicked through.

Things went pear-shaped when I went to add the glass and carbon cloth to the inside of the hull. A test run was done with dry cloth in the vacuum bag but the sides of the hull bowed in a bit so that wasn’t an option.

The backup plan was to do a hand layup and that led to too much epoxy and a lot of extra weight.

The Divinycell core material is great stuff but this was just the wrong use of it. I made a test deck and transom with it and they came out light and strong.

All that said, the hull is now a plug that molds will be made from. If you’re wanting to build a P4, I would suggest planking the hull with western red cedar or one of the other proven materials instead.

Edited September 15Sep 15 by mdeleo

And lots of filling and sanding.

Edited September 15Sep 15 by mdeleo

Sorry to hear about the difficulties. If it makes you feel any better I am now sailing my 6th attempt to build a competitive 10R. Two of these were rejected for performance reasons (I am using my own designs) but 3 were failures in the moulding process.

I had assumed you were using glass because you didn't have access to a vacuum pump, but as you obviously do, I wonder why you are not using carbon throughout? The very lightest carbon cloths (<100 gsm) are very expensive but myself and another (who builds boats semi-professionally) have successfully used a single layer of 200 gsm carbon with carbon/kevlar strengthening at strategic points. You have to work quite hard to reduce the number of pin holes, but a light watertight hull can be produced with a little surface finishing.

Edited September 16Sep 16 by John949
error high tow is not correct

Thanks John. Again, I truly appreciate the experience and advice you've been providing. It's invaluable, especially the "sailing my 6th attempt..." comment.

Re carbon, absolutely the best choice for something competitive. There are a couple of determining factors that are in play for me right now:

1) My wife was diagnosed with interstitial lung disease (ILD) two years ago which forced us to relocate to an area where we could get the best medical help (UCLA in Southern California) for her. Thankfully, she's in much better health now than when she was diagnosed but I'm much more appreciative now of what I breath in than I was before her diagnosis. I've done a considerable amount of aircraft composite fabrication and was probably less cautious back then when working, particularly sanding, exposed carbon fiber. As you pointed out, if done correctly there should be very little sanding of carbon part that comes out of a mold. Wet sanding obviously mitigates a lot of the carbon dust creation as long as it's done outside of your shop.

2) The expense of the materials, specifically the lighter weights of carbon cloth, for these early hull experiments is prohibitive. Not to say that I won't use them once I get my molding process sorted out and a few benchmark hulls created from less expensive materials. Frank, you will be getting royalty checks for these.

I wanted to be open and up-front about the successes and failures in this build. Hopefully someone following along will be able to not make the same mistakes or at least learn from mine. The plug for the mold gets a coat of 2k epoxy primer today, 24 hours to rest, and probably another coat after that and then the mold-making can begin. I'm excited.

Mike