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.
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.
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
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.
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.
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.