Bonus, an improvment on my method already.
Thanks Hew
Don
Hi Larry and others,
as promised this sketch shows the principle as to make a mould for fin and rudder. The profile blade is used to shape the white cement or any others plaster or fillers.
Smal imperfections will be repaired with polyester filler as the one used for car body and abravive wet papers.
Once fully dried the cement base will be waxed several times (cement is porous) unless is decided to spray some paints before, in order to get a glance surface first.
I confess I never made one myself, but it is not escluded in future.
IMPORTANT TWO IDENTICALS MOULD ARE NEEDED FOR LEFT A RIGHT SIDES.
The other method is similar to the Bulb mould using the red silicone rubber as per RTV139, in this case a properly finished balsa fin is needed as prime shape to be copied.
Cheers
Claudio
Hew !!! Your blood is worth bottling. I have just sent off an email to the fibreglasssupply.com asking about products and shipping prices. I had spent ages Googling looking all over Australia for FG supplies. And here you go finding exactly what I need. And if I’m not mistaken their prices are ½ of what I have been paying. Their 6oz Carbon Fibre $30.94 per yard. My regular supplier quoted me $85.
Do we have ebay down under??? It’s how we survive. This place is so big and desolate only way we get our supplies.
Thanks again
Larry
Claudio,
as always beautiful drawing and easy to follow instructions. One question — what is White Cement ?? All the rest is simple to follow. I love the metal profile. No guess work in shaping profile.
Ciao
Larry.
Don,
it’s so simple when explained well. I kept visualising just the profiled plug. Forgot all about the framing and building into a proper box. Mixing up the Microballoons into peanut butter thickness I get. I have been using Microlight Filler which is harder to thicken. And also dries soft when mixed that much. Hence my other misconception about insides pouring out.
My major problem now, based on your directions, is that I have to find a wife! Someone to borrow candles and a hairdryer from :~)) Kidding… I have them left over from the divorces.
Recently I was clueless as to where to begin. Now thanks to yourself and Claudio, I have 2 methods of mould making. Now just need prices on carbon fibre from Western Australian company.
Thanks again
Larry.
PS Don, you’re on Vancouver Island. Am I jealous. I saw a travelouge of the island years ago. Will never forget how fantastic it looked. Small, friendly and isolated. My next yacht may have to be scaled at 1:1 so I can sail over.
Larry just so simple using google : http://www.google.fr/search?hl=fr&q=white+cement&sourceid=navclient-ff&rlz=1B3GGGL_frFR364FR344&ie=UTF-8
claudio
Hi Larry - Britten was one of the one of the pioneering composite motorcycle builders, he was from your part of the world. He was a brilliant designer. His work was inspiring in both cutting edge design and innovative methods and had worldwide influence. Unfortunately, he was working before the health ramifications of working with resins and composite fabrics were fully understood. He died of cancer fairly young. Google him to find out more. I’m sure there are others down under following in his wake.
I cast my M class and 36/600 keels in two part press molds. With my keels I cast integral threaded inserts in both ends of the keel, one in the base for attaching the bulb and one in the root at the top of the fin that fits into the keel trunk. I use epoxy for my molds, polyester is not strong enough to resist the pressure I use to evacuate air from the casting and to achieve a very high fiber to resin ratio. I use a post cure two stage epoxy which needs to be heat treated to effect the B stage. My lay-up pattern and hi-pressure system give me very professional results. The time involved in putting together a top quality system is significant. Just making a basic keel mold takes less time and will probably yield okay results but as they say, you get out what you put in.
I was under the impression that you were interested in a one off keel. If you want to learn more about composites, resins, and mold making then you should probably get your hands on the, “Boatbuilder’s Manual”, edited by Charles Walbridge, from Menasha Ridge Press. This book is actually an expansion of Mr. Walbridge’s thesis on composite lay-up schemes for whitewater canoes. It is an old book (from the late '80’s) and comes in and out of print. But it is well worth the search because it is the most thorough treatment of this niche of boat building that I’ve found. John Sweet Co. here in the US is where I got my copies years ago, they might be a place to start looking. You could try contacting the publisher but I don’t know if they are even in business anymore, what with the contraction in the book publishing industry (thank you very much internet).
Hi Larry
I think I would go with Claudio’s method. It looks pretty reliable. I think “white cement” is what I would call “Plaster of Paris”. Can someone correct me if I’m wrong. Do you know where the picture you posted is? It’s obviously on the west of the island. Long Beach maybe? I’m in Campbell River on the east so we don’t get as much rain but we don’t have the rugged scenery. I was born here so I like the wind and wet.
Claudio
Does your mould making device(Claudio’s Gadjet II) lend itself to tapered fins? It looks like it would. If you are making a tapered fin does the profile change as you slide down the fin? I guess it would but does it matter? Sorry I’m thinking while I’m typing. It’s funny how a new idea can get the jiuces flowing. I suppose you could use wax instead of white cement. Wouldn’t be as durable though. Off to the shop.
Don
Niel
Can you elaborate a little more about this method, mostly the two-part press mold.
Thanks
Don
I find this method interesting. I printed out some different airfoil sizes and rotated a small on inside a larger one (the method would have the trailing edge move higher as you go down the taper) and the results indicate a tapered foil would be fine, but the pivot point should be the leading edge, so you might need the pattern to have a complex curve on the leading edge guide. Cut out the patern so that only the point of the leading edge touches the side of the form, with a concave section above. The part that rides the rail should also be curved so as the patern rotates up the point of the leading edge stays at a constant depth. I don’t know if it is possible, I will have to try.
Mike
Hi Mike
If you cut the part that rides the rail so that it fits nicely when it’s on the narrow end of the fin then it will rise as you scrape towards the wide end. As long as you hold the scraper against the leading edge you should be OK. I think maybe two patterns. One a little smaller to rough it in while the plaster(cement) is wetish and another for the final shape. This might keep you from cutting too deep. We need an answer on the white cement/plaster of paris question. I did a google search and it seemed to indicate that they were different but the white cement they were describing sounded too hard to scrape nicely.
I’m thinking that the rails would be better made of plexiglass or something with a very uniform thickness to keep the fin a straight as possible.
Don
Don,
I’m going the traditional route. Claudio’s Gizmo#2 bit too experimental. (I used his Gizmo #1 for about a year before I built a sailboard; also following Claudio’s plans.)
Making a plug - original profiled fin shape. Today I bought a bottle of ViSE Polyurethane Glue. Says it’s “sandable, waterproof and super strong”. What I plan is to sandwich balsa sheets together thus - 2.5/2.5/1.5/2.5/2.5 - 1.5mm sheet in middle will have black edges to show centreline. Gives ma a fat 11.5 mm thick sandwich. Planks will be layed between some 15mm thick heavy glass panels I have, to keep dead flat while glue sets. 3 - 4 hours.
Then start hand sanding till I get correct profile. Is there a better way to sand than just using sandpaper glued to flat board? I’m going to make profile slightly “fatter” than final fin to allow for thickness of CF. Approx 8mm chord final plug for 6mm finished fin. I also insert a 3M threaded bolt into top of fins to screw to deck. Bolt head filed flat on 2 sides as a key lock buried inside fin. So want to retain fin thickness at top, inside keel box.
I found some really high quality 1mm thick wood sheet that I use for decks. It cuts with exacto knife and has perfect edge. This I’ll use for the 'parting board". I have some plasticine, modelling clay. So after I finish my plug, I surround it with the parting board. Stick plasticine all round to fill gaps. Make smooth face. Wax then PVA release and then 3 layers 4oz fibreglass cloth. Let cure. Flip and repeat. Drill holes in corners for registration and separate finished mould. Oh yeah, glue timber strips along edges as supports. Forgot that bit.
Does all this sound kosher? I haven’t used dripping wax or DS tape or a hairdryer. Have I missed something?
Larry.
There are some great ideas passing through this thread!
White Cement, as per Claudio’s google search, is the same thing as regular old gray Portland cement… just white. Nothing special about it except color!
How about getting some shaper blades cut to a profile shape, and running a piece of MDF through the shaper. You could even wedge one end up a mm or so, to get a tapered foil cut. Then soak the MDF with epoxy, to seal the surface, wipe off the excess, and let cure. Run through the shaper again to cut the final shape, and polish up the molds. I know some of the airplane guys do this with a CNC shaped wing plug.
Hi Larry
Unless I’m misunderstanding. It sounds like you’re setting yourself up for a lot of unnecessary sanding. You should make the blank just 1mm thicker than the plug. No sense wasting time and effort sanding stuff that doesn’t have to be there in the first place. About the thickness, I’m confused. If you are making a plug to make a mold then the plug should be exactly the same as the finished fin. If you are making a core and are then going to skin it, then the core needs to be smaller than the finished fin.
You can use a piece of black cardboard for the center lamination instead of the 1.5mm piece. It’s thinner and will be more accurate. I’m going to try to attach a picture of one side of my mold. It’s not a good picture but maybe it will show you something.
Don
PS the picture really is crap. What you are looking at is the edge showing the fiberglass mold and the piece of plywood it’s glued to. Three layers of 4oz cloth won’t be enough. The 1 1/2 oz matt is way heavier than 4 oz cloth. I think cloth is weighed per sq yd and mat is measured per sq ft. Someone correct me if I’m wrong please. The finished fiberglass should be at least 1/8" thick, 1/4" would be better. You need the stiffness to get a true fin
OK. Now I have to re-think this. I thought the idea was to pour the plaster(cement), let it set a bit and then and then use the profile as a scraper to arrive at the final shape. Portland cement would be too hard I think. Am I missing something? Most likely. The reason I was thinking Plaster of Paris is that it is still scrapeable when set so a person could sneak up on the final shape slowly(hopefully accurately).
I like your idea of shaper blades but I was thinking of this as a quick way of trying different profiles. Getting blades ground for every profile could get pricey.
Don
I was thinking the idea was to have a material, on its way to setting, that was still soft, but would hold a shape. Cement that has stiffened up enough to write your initials in 
but no too loose, as it will flow back out. A few experiments are in order to look at a few materials. Plaster, cement, Clay? For plaster, the scraping idea might also work.
Don - Originally I used a metal frame with an I beam that slides up and down. The I beam has a 2 ton car jack below it that is jacked up to apply pressure to squeeze the two halves of the mold together. Very simple. Harbor Freight has a frame that is adapted for this. Look up do-it-yourself ram presses. Since I use a post cure resin system the molds were made with integral heating wires that attach to a reostat to control temperature stages. Another boat builder in my club had a similar press that was mounted in an insulated metal closet that functioned as an oven. Same concept.
There are vents in the flat edges of the mold to evacuate excess resin. The female half of the mold is in a pocket with fairly steep sides. The sloped sides act as a locater for the male, upper half. Extraction is with compressed air.
Thats about as far as I will go with this.
Larry - Don is right, if you want the mold to stay true and not deflect I would go thicker than 1/8th. Also, I start with an epoxy gelcoat slurry of Graphite Powder (8 + parts roughly) and Colloidal Silica (1 part). This should be mixed to the consistency of whipped cream just before its whipped (so that it spreads easily but doesn’t run). Gradually keep adding the powders in roughly this ratio until you get to this consistency. Be patient and stir thoroughly, the silica takes some time to expand. Colloidal Silica is a thixotropic agent (a thickener that keeps resin from sagging on a vertical surface) that will make any filler (like Microlight) much tougher (and also causes lung cancer so be careful when mixing and sanding). This, combined with with Graphite Powder, gives the mold a hard, slick, smooth surface. This gelcoat should be about 1/16th inch thick, but at the proper consistency you want to spread it on so you just lose sight of your keel blank, that will end up being around 1/16th.
This is the first step which is followed with progressively heavier weights of fiberglass. Start with 6 layers or so of sheathing glass, 1 oz. or there about. Then 4 layers of 4 oz., then 4 of 6 oz., then 2 layers of 10 oz., finished off with another layer of sheathing glass to help avoid fiberglass splinters when handling the mold. I back this up with about an inch and a half of multi-core plywood, but if you are just going to clamp the mold shut then it doesn’t need to be as beefy as mine. The reason for the graduated weights of cloth is to avoid “printing”, or the cloth weave from showing through to the mold’s surface.
I would use Claudio’s method for creating the keel blank, and make a real mold for casting fins from. Rather than using white portland cement which has sand in it and doesn’t screed smoothly I would use Hydrostone or Ceramical. Both are cement/gypsum mixes that are much harder than plaster and not quite as strong a cement but have working properties close to that of plaster. I use mesh reenforced Hydrostone for my bulb molds. One thing to note, Hydrostone takes at least half an hour of constant mixing before it is ready to pour. It also has a shelf life of about six months so buy only the amount that you need.
Hope this helps.
Here in USA (and probably Canada) there are a variety of Home Repair/Design TV shows. I recall one where the guys were building replacment plaster cornices, mouldings, etc.
A box is made, plaster is added, and the worker slides a wooden shaped piece of plywood along to create the shape of moulding desired. He keeps moving it along multiple times until final shape is achieved, and the box is set aside to dry out. After most moisture is gone, I recall they “fired it” (???) and sent to building job site to install. The one I watched was on refurbishing crown moulding in old home. There has gotta be a YOUTUBE video out there somewhere. Using the female shaped plywood shape would create a male shaped plaster “plug” - then just go from there.
Hi Guys,
I have made fins using the scraper method, both ways - 1st way was to make a male plug from polyester filler & then take a female tooling off it.(Same process as Neil described)
The second time I used a material nick named Chemi-wood. Tool and pattern makers use it all the time and carved the profile directly into it.
However my main reason for posting here is that the scrapers do not need to be expensive. All I have ever used are the 19mm thick 100mm long "snap-off’ blades ground to shape… they work perfectly as long as your fin isn’t wider than 100mm!
I Would also consider using a old or cheap plane blade for wider profiles…just use it on its side.
There are some very interesting ideas on this thread, I really enjoy the talent that comes together on this site…so Ithought I would throw another concept into the mix on fin building. I am presently building a set of moulds for a Mini 40 trimamaran and wanted to build a bunch of fins but do not have the skills to ensure a perfectly symetrical fin freehand.fascinating to see Claudio has developed an idea not dissimalr to mine, the key difference is Claudios concept produces a female mould, mine produces a male plug.
I figured that while chord and profile were key features of a good fin, also a fin with good symetrics would be just as important…so 4 months ago I developed the following idea, so far it has worked perfectly and very easily ( and quick).
I should point out I would have preferred to build tapered fins but could live with parallel trailing and leading edges, maybe some one smarter than me can can up with a way to use this idea to produce a tapered fin??.
First off I wanted a set of female moulds that I could produce multiple fins with…
So my first pic shows a foil profile a cut into a small peice of angle aluminium…this was very easy to make…just trace the required section onto the aluminium and file it out, ending with a fine metal file and then wet and dry sandpaper leaving a very sharp knife edge on the cutting profile.I then screwed this onto a couple of small blocks of wood at 90 degrees true to the wood blocks.These blocks act as the slides.
Next step was the board to form the shape on, because I wanted a board that would stay true and not twist or deform or swell with moisture (especially after wet sanding), I used a pine board which had been laminated in strips, found this at a hardware shop sold as shelving.
I choose to use polyester filler to scrape the profile with because it is very quick to harden, its cheap and when it is just gelling off it goes rubbery which makes it easy to slice off with a sharp blade any excess left on the board after each swipe.
I then sealed the wood board with wood sealer to help the filler adhere.Polyester filler can lift and curl when very thin, to prevent this I drilled a series of “foundation holes” around the inner perimeter of the fin. Then fitted two aluminium angle sections down the length of the board to act as guides for the cutter slides to run down.
When scraping the filler on to the board I took around 5 swipes at it, each time builiding up the height, waiting between swipes for the filler to harden and cleaning up the blade with acetone to keep it sharp.Because polyester filler does shrink ( ands get very hot when layed up thick), I found it better to build the profile up in layers.
The final result was a plug which required zero shaping, only a very light sand to fair smooth and then paint in preparation for building the mould. A couple of pics here show a few I made in the ready for paint stage and a couple with a fresh coat of Duratec surfacing primer/ Duratec Clear being readied for final wet sanding/ polishing/ waxing.
A couple of final points about this concept. I filled the foundation holes before scraping on filler…and the recess slots I have routered in to the plugs for the shafts actually need to be male but because I could not locate a straight half round to use for posts , I will lay stainless rods into the plug before laying up mould and this will give me a perfect “post” female in the moulds which will mean I can laminate and press the posts into the two final halves of fin…make sense??.
I do not expect the final fins to be 100% perfect forms and will have to do a little tidy up on the trailing and leading edges but at least I know the symetry of profile will be true on both sides …Sorry for long winded post, couldn’t find a way to put this in a nutshell!!.
Cheers…Gary