Keels RG 65


The Model Yachting Magazine, 165 issue, from the American Model Yachting Association, AMYA, is dedicated to the RG 65 Class. A very important contribution for the RG 65 Class.

Earl Boebert, Eric Rosenbaum, Bill Hagerup, Jim Linville, Bill Worrall, and others, gives  important contributions to help peoples do the RG 65.

Knowledge that I took 2 years to get were kindly shared by these enthusiasts for all the people who loves radio controlled sailboats.

Thanks to Mauricio Dantas, Eric Rosenbaum shared to me his articles to put in this page and in the others pages.

We greatly appreciate Eric Rosenbaum for his kindness in sharing through us highly useful knowledge.

It was a great and hard work of everyone who contributed to the magazine and if someone can also share his work, we would be honored to publish them.

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Keel Construction
By Eric Rosenbaum

One way to make keels and rudders is to use cured sheets of carbon fiber (CF), which are bent around a core of some type.  The method described here simplifies the build by replacing a shaped core with a central CF spar or tube.  For the RG65, the finished keel weighs between 30 and 38 grams, and it will not deflect more than a few millimeters with the bulb attached and the keel then held horizontally.

The basic dimensions of my RG65 keels are these:
60mm – chord at hull
40mm – chord at bottom
Max thickness 4mm (1.5-2.0mm at leading edge – rounded, sharp trailing edge)
The portion of the keel inside the keel trunk has its trailing edge angled forward 15-20mm to insure a tight fit.
Weight – 30-38g depending on CF layup (once cut to size)
Overall length of 40+cm to allow for the keel top (in keel box) plus a keel length below the hull of 28-34cm

This keel uses a tapered top that fits into the keel box.  The top should be 2-3mm shorter than the box, so that the retaining screw will pull it tightly into place.  If the keel box is to go all the way to the deck, then make sure you know the correct measurement before cutting the CF skins for the keel.


This is the completed keel with a bulb attached.  All photos by Eric Rosenbaum.

I make a CF sheet on waxed glass (12” x 18”) using 5.6oz CF cloth and get a finished keel weight of approximately 30g.  If the CF cloth is backed with a 3.7oz fiberglass layer, then the finished keel weighs 8g more.  It is also a bit stiffer with the FG layer.
Wax the glass using Meguiars Mold Release #8 wax or equivalent.  Polish to a high shine since this is the surface you will have on the CF sheet.
Brush on a smooth, thin layer of epoxy directly onto the glass work surface.  Try to leave no dry spots while keeping the thickness to a minimum.  The epoxy will soak into the CF cloth, but not well.  You need enough epoxy on the glass minimize pin-holes.
Lay a piece of CF cloth down (11’x17”) and wet out / spread the epoxy with a plastic spreader or fake credit card from some piece of junk mail. (Tip: lift the glass and look at the wetted surface from below.  If there are dry spots or obvious pinholes, dab at the CF cloth with the brush to force epoxy through the weave.)
Optional step:  Add a piece of 3.7oz fiberglass cloth, and smooth /wet out as before.  Excess epoxy should be scraped off with the spreader.
Add a piece of peel ply, and then some absorbent material – paper towels or breather cloth.  The breather cloth absorbs the extra epoxy that comes through the peel ply.
Top the pile off with another sheet of glass, and then add about 25 pounds of books or other weights.
Once cured (24 hrs), the CF sheet pops right off the glass.

Step 2 – Cut out the Skins



The skins are traced on the CF sheet, and the tpe covered bars are ready to keep the edges straight.

Cover the good side of the CF sheet with masking tape, trace on the fin shapes (port and starboard sides).
Carefully cut the skins out with a sharp #11 Exacto and a steel strait edge.  The two matching pieces are sanded to exact mirror images.
I leave the masking tape on to avoid messing up the high-gloss CF finish while building the fin.

Step 3 – Assembly

Here are all the parts that go into making a keel.  A little CA and thickened epoxy will hold everything together.

The CF bar used to thicken the leading edge is 1/16″ by 1/4″ and 1” longer than the leading edge of the keel.
The central tube is a 1/8″ CF tube – either round or square.

For a removable keel, use a 1/8” brass tube tapped with a 4-40 thread.

An 1/8” brass tube is tapped with a 4-40 thread and used as the retainer if you want a removable keel.
Sand and wipe clean everything that will be epoxied.
Lay out the parts and then tack the central spar and brass retaining tube to one skin using CA glue. I draw a line 20mm back from the leading edge.  The spar is just forward of the line, and the brass tube is just aft of it.
Tape the leading edge of the keel together with the CF spacer bar in place, and then place on the table with the pieces opened like a book.  The CF bar will stand vertically stuck to the tape.


The central spar and retaining tube are tacked with thick CA.  The retaining bolt is taped and inserted to keep epoxy out of the tube.  The leading edge CF bar is in place and stuck to the tape – it is difficult to see as it looks like part of the top skin in the photo.

Use epoxy thickened with colloidal silica (not micro balloons) to wet out the forward 7-8mm of both skins as well as the central spar and brass tube.
Fold the keel back together – the tape will hold the leading edge in place and prevent epoxy from squeezing out.
Temporarily tape the trailing edge shut to help align the skins and shape the fin.

The trailing edge is taped temporarily, and the leading edged is epoxied and clamped using tape-wrapped steel bars.

Clamp the leading edge using two strait metal bars covered in Mylar packing tape.
After the epoxy has cured, remove the bars from the leading edge and use them to glue the trailing edge.  The tapered fin top that goes into the keel trunk is taped shut.  The top and bottom are left open for now.
After this epoxy cures, wipe a little thickened epoxy into the open top, tape and turn upside-down until it cures.
Remove all tape, and sand the edges to finish the keel.  The leading edge should be rounded, and the trailing edge should be fairly sharp.


This is the keel after the tape is removed.  Some finish sanding on the leading and trailing edges, and you are ready to paint or use as is.

Rudders can be made in basically the same way.  The only change is that the central CF tube and brass tube are replaced with the solid brass rod that connects to the steering system.
Supplies needed for CF sheet:
I buy most of the items here:  http://www.acp-composites.com/home.php?cat=4752, although there are many other sources including EBAY retailers.  CF cloth, in particular, can be much less expensive when bought from an EBAY supplier.

5.6 Oz Carbon Fiber Fabric: 50″ Wide 2×2 Twill
WF-19-1    $41.00 / yard    Enough for more than 15 keels and rudders
3.7 Oz. “S-Glass”
S-2 Fiberglass Fabric    WF-15D    $10.00 / yard    Same as above
Peel Ply: 60” Wide – White
V-18    $4.50 / yard
Breather Cloth: 60” Wide
V-22    $5.00 / yard    Can substitute paper towels
West System Epoxy w/ Fast Hardener
105 Resin and 205 Hardener    $50.00 for the Quart kit    Widely available, but not at ACP

Matching Keel Trunk
To make a matching keel trunk, wrap a layer of Mylar packing tape (very slick brown tape) over the top portion of the keel.  Secure the keel with its leading edge up, then drape two layers of 3.5-4.0 oz fiberglass over the top portion of the keel – overlapping the actual finished size by 2 cm to allow for trimming later.  Clamp the cloth together tight to the trailing edge using tape-wrapped sticks, and pull the cloth through the clamp to remove excess or wrinkles.  Wet the cloth out with a thin epoxy resin (like West Systems), scrape off extra resin, and let cure.


Here is the taped fin with two layers of fiberglass cloth secured by the clamps.

Once cured, remove and trim the aft side of the layup to match the trailing edge of the fin.  Flip the fin over so that the trailing edge is now up, put the cured keel box part back on, lightly sand it, and then repeat the glass and epoxy steps.  Once cured, remove and trim to final size.  You will have a stiff, light and watertight keel box that is open at the top and bottom.  I epoxy some scrap from the cutoffs to enclose the top.

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13 Responses to Keels RG 65

  1. Bob Wells says:

    just how stiff should the cf sheet be? I am able to bend the one i made quite easily. Will it stiffen up when fully cured. I used the cf twill and a layer of fiberglass cloth

    • Fred Schmidt says:

      Hi Bob, unhappy I do not have experience in cf, I suppose that 200g/m2 cf will be stiff.
      Regards

      fred

  2. Barrie says:

    Fred

    Here is a link to my “how to fit a Keel Bulb” it is a downloadable PDF file, feel free to use it.

    http://modelgraphics.wordpress.com/how-to-guides/how-to-fit-the-keel-bulb/

    • Fred Schmidt says:

      Good job Barrie.
      One more help to assemble the keel and bulb in RG 65.
      Thank you.
      Cheers
      Fred

  3. Barrie says:

    After many experiments with RG-65 keels I have now moved onto using a balsa core skinned with 200 g/ms plain weave carbon fibre this is time consuming having to sand the profile of the keel, I then cover with a well wetted sheet of carbon fibre cloth then a layer of peel ply, making sure that the cloth has made good contact with the balsa core then I vac bag the whole thing. Vac bogging is not a necessity as I know that not every one has access to this equipment, it could be held in place to dry with bulldog clips or spring clamps as long as the cloth is held tight against the core. Once cured the peel ply is removed lightly sanded to remove the texture of the peel ply. this method gives you a very light strong keel, it should work for IOM but I would use 2 layers of carbon cloth for extra strength. you only make it once so the extra time and effort is worth it, you can make your rudders in the same way.

    Keep up the good work Fred.

    • Fred Schmidt says:

      Good idea Barrie. I’ll try.
      I greatly appreciate your blogs. Good job.
      A hug.
      Fred

  4. Benson Or says:

    Brilliant Fred. Good timing as I have just ordered a Noux65 from rcsails. The keel bulb construction guides are easy to follow and good for an amateur boat builder and also the links you provided have got a lot of useful and practical information. I have learnt a lot from you and other authors who are willing to share their boat building experience. I salute to all of them. Next time when I go to a furniture shop, I will look for a timber torpedo to be used as a keel bulb mould.
    Keep up the good work!
    Many thanks

    Benson

  5. Fred Schmidt says:

    Hi Benson

    Really, Eric Rosembaun, do a great work to help us.
    Your suggestion is accepted and as soon as possible I will put here the bulb manufacture and attachment.
    Cheers
    Fred

  6. dexter says:

    Hello- first of all: Really great site!

    I have a question: is this method usable for making a fin for an IOM ? Its the thickness and stiffness that concerns me.. 2. question, are the CF sheets flexible (do they bulge a little around where the carbon spar is inserted in them)? Do you fill it all up with epoxy & silica/microbaloons?
    *the IOM bulb is about 2 kilos (kg), thats why Im asking.

    ps. how come no contact mail adresses are present?

    Regards,
    Dexter

    • Fred Schmidt says:

      Yes, I myself use fiberglass, four layers 160 g/m^2 woven roving to do my IOM keels, no fill. Only two fiberglas plates with a balsa strip, minimum width to give the keel thikness. How less weigth in keel, better is. Personnaly, I do not know what’s the weights to use on carbon fiber laminate.
      E-mail – fredschmidtnatal@hotmail.com

      Thanks for the words,

      Fred

      • Benson Or says:

        Hi Fred,

        I really enjoy your step-by-step building advice and hints. Pls advise how to make the keel bulb and to affix it onto the keel.

        Cheers

        Benson

        • Fred Schmidt says:

          Benson
          You can see in Construction page how to make a bulb. I hope that helps.

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