Canoe Mold

From what I can tell, you want to make a mold off your canoe, make another plug from that mold and then fair that up good and make another mold off that plug.?. If that's right, it is something you could do, but it's a bunch of extra time and money, and you end up with an extra mold you probably won't have a use for. If you don't have much room, it becomes a nuisance to store these things, they are bulky.

You get the plug ready for molding, all faired, shiny etc. Then you erect a parting board all along the centerline of the canoe. Mine was thin ply about 3" wide, painted and waxed, any seams in the ply covered with cellophane tape. That is somehow stuck to the mold, I used 1", 90 degree angle corner braces, with one screw into the plug and one into the back of the parting board to hold it upright. I plugged the gap between the board and the plug with modeling clay from a toystore and then cleaned the extra off flush with the face of the board.

Take care to get the corner where the plug and board/clay meet as sharp as possible, in that you don't want any fillet at all there, since when you finish the first half of the mold , you remove the parting board and lay the second half up to the first half, and any little fillet on the first half will create a knife edge on the second part, which will chip off and create problems in future molding.

You have to put "registration" points in the mold flanges so when they bolt together, they align up perfectly. The bolts themselves won't work as the bolt holes can wear and allow movement. You can add some kind of lumps to the board or make some kind of pit in it. Every 12" or so I made shallow holes in the board with a counter sink so the first half of the mold ended up with short cones which the second half molded around to form the registration points.

Next you wax up the first half of the mold and the parting board and then apply the tooling gelcoat. You don't want to use any hot mixes on the mold, you want a slow cure to minimize shrinkage or distortion. After the gelcoat has set, you apply a layer of 3/4 oz mat and let that set. You don't want a lot of gelcoat or resin in the corner between the board and the plug as that leaves a resin rich corner that is also prone to chipping, so instead of running one piece of mat from the plug up the parting board and creating a small, bubble filled or resin rich fillet, put one straight edge of the mat into the corner and down over the plug and the edge of another piece of mat into the corner and up the face of the board. You let the first lamination set completely, like overnight, then do another layer of 1 1/2 oz and let that set. Then next maybe two layers and so on until you get 3/8" or more built up.

Take off the parting board, clean up the clay, clean up the flange created by the board, plug any holes, wax it all and repeat what you did on the first half.

Before you take the mold off the plug, drill holes every 12" or so for 5/16" bolts to clamp the two halves together. Also, make some bracing and glass that to the mold. Let it all set for a day or two and then remove.

Steve W, 1000 boats is a bunch of experience. I never worked with more than 3 people and never where regs and restrictions were very worrisome. The last was ten+ years ago. The price difference between epoxy and poly was a lot bigger so epoxy wasn't used. What hoops would a real small operation have to jump through nowdays? What are some of the up to date methods and materials used for plugs and molds and finished products?

 

you can also set your canoe on a level table and find center and do your measurements and basically loft your boat using measurements then get a university student taking a engineering coarse to put them on a program for cnc duplication. Or use exsiting boats for plugs and or start again using plywood strips with resin and glass but you will still have to take measurements from your exsiting designs to keep measurements accurate and make master plugs. I personally would start again useing my canoes for measurements only, this will allow u to use your exsisting boats for demo boats. This also reduce the amount of waxing and glassin you will have to do and will make good use of your exsisting strong back. split stern is the easyest way to go for demolding perposes. Only requires you to take a piece of arbright and center it on the stern hot glue and wax both sidesand layup to top of arbright make sure you give at least 3inches of height min. Only needs to cover stern to bottm of hull, have two canoe molds just like this. Also with this process it will allow u to put a flange on it for vaccume bagging the best way to go for a far supperior product.

 

Clamps for two piece mold

Any ideas on what might be used to clamp a two piece canoe mold together other than bolts?
Is there a quick-release kind that you know of?
Also, If you use bolts, what would be the best way to protect from the wearing/friction damage around the holes drilled to receive the bolts?

By the way, that was some very good two-piece mold info, so thanks!

 

"providing they are symmetrical". - CNC can take the defects out.
"Do they even make a cnc mold?" Yes. And you could probably pull five or six canoes out of it without anything but release agent. Call Janiki, http://www.janicki.com/ , the one I know.
As far as two-part molds are concerned, this is where machined plugs really come into play - everything lines up!

 

RE: CNC Machine Work

Hi, I am a retired plastics injection mold maker who also spent several years as a model maker and CNC operator. I can (unfortunately) assure you that you do not want to consider the cost of machining a plug that large, however there are still some good options avail. to you.
One that I just watched on a PBS special used no plug. It was a small company in upstate NY who used a female mold and a type of inflated bag which squeezed the fiberglass to the sides. While this was taking place, they vacuum bag the entire top half of the mold (including the air filled bag) and let it cure. All that was left was to remove the bag. What I don't know is if they produced this inner bag or if they had them made somewhere.
If it were up to me and I was really that concerned with accuracy, I would do the following. Find someone who can draw the plug on a CAD system and segment it at intervals from on end to another. Print out cross sections and use the prints to make gauges at different intervals along the plug. Your cad segment prints can transferred to something like thin plywood or Plexiglas that can be cut at home with simple tools without the cost of any machining.Thin Plexiglas works well because you can tape the prints to one side and trace the design on the other by using a small perm marker. Use the templates to carve a soft (and inexpensive) material which can later be use to cast a perm plug.
If I haven’t lost you, Rough out the core by eye, then use your new gauges at the distances you make on both sides, which are the same as the CAD drawing. The more gauges the more accurate. The same can also be done with the length of the core by transferring prints onto thin wood , Plexiglas etc. to make one large gauge for the length. I have seen this method used on a 22ft. sailboat and was amazed at the accuracy given a little TLC. The boat I saw constructed used cardboard templates stiffened with strips of wood glued to the sides. It was cheap and worked very well.