Layers of fiberglass

[Mrdennis]

Im new to boat building, but my plan is to build a 10 1/2 ft power boat. I have one already that I got used but needs some repairs. I want to make a mold from the hull that I have. But I dont know how may layers of fiber glass I should use to make the mold. Also, I want to know how many layers I should use to make the hull itself, also the topside of the boat. Any info would be great.

[alan white]

Hi Mrdennis,

Molds are pretty heavy, and reinforced with female molds made from such as plywood, steel, etc.. A mold is a production item. Why would you want to make a mold, when it is a very time-consuming and expensive project? Are you interested in selling a few boats?

Alan

[Raggi_Thor]

What about the copyrights?
If the boat is still in production you can get in trouble if you copy it.

[Mrdennis]

The long term goal is to produce my own boat/boats. I guess my idea was simply to build the mold, and make a copy or two. So I would familiarize myself with the building process, without having to go through the research and development of starting from scratch. As for the copyrights, the boat's design looks very dated, like from the early 80's. But I havent a clue as to who made it. But i dont really plan on making money on these, its mostly for the experiance. How much do you think it would cost to set up a mold?

[alan white]

Your money's going to be in the mat and resin. Your time will be far in excess of the eventual layup of a finished boat. It is certainly a good experience to go through, and you'll learn a lot. In that sense, it's all positives. There are books others could recommend, ways to avoid common pitfalls.
Be certain you've chosen the right boat to create a mold from. The shape of the boat will determine whether the mold bolts together or is a single piece. Tumble-home, reverse transoms, and so forth will require two halves. Such a small boat should not need a liner, nor decks or motor well. This simplifies the process. If the boat hasn't reversing shapes as mentioned, a single mold is all you need.
A good compressor and spray gun will be required as an initial investment, along with quality breathing apparatus (for two, since you should not do the layup alone if at all possible at the start). Again, others here more qualified than I can tell you what minimum spray rig will suffice, and what breathing masks are best. The rest are common items such as fan, lighting, cloth rack and cutting table, etc..
My guess is you'll spend a minimum of $1500.00 if you shop around and buy used equipment. Some here may have just what you need, if they've upgraded along the way.

Alan

[ratrace2]

Originally Posted by Mrdennis

Im new to boat building, but my plan is to build a 10 1/2 ft power boat. I have one already that I got used but needs some repairs. I want to make a mold from the hull that I have. But I dont know how may layers of fiber glass I should use to make the mold. Also, I want to know how many layers I should use to make the hull itself, also the topside of the boat. Any info would be great.

Let's get started:
(a) flip your boat up side down.
Your current boat is your plug
_____________________________
(b) with some 1000 grit buffing compound and a power buffer, buff the
boat hull until you can see yourself--mirror finish.
(c) with some 1500 grit polishing compound, polish the boat until, you got it,
untill it is perfectly smooth and shiny.
_______________________________________________________
______________________CAUTION___________________________
(d) Wax the plug--your boat hull. (if you get this step wrong your boat is done--ruined, wrecked, got it) Get "MOLD RELEASE WAX"....google it.
(e) wax the plug--your boat--three (3) times by hand.......read the directions
_____________________________________________________________
(f) Gel-coat: for a 10ft boat, get a gallon of gel-coat and brush/roll it onto the hull. Coat the plug three (3) times....nice and thick....read the directions.
____________________________________________________________
(g) Mat/Resin: get 1 ounce CSM (chopped strand mat) at Mahogany Co. Mays landing NJ that's where I shop). OK: get a 4'x8" sheet of plywood and build a table, cover the table with a sheet of polypropolene. Also, buy an aluminium roller, look in their online catalog....Get some 20 ounce Roving, too.
________________________________________________________________
(h) let's use some Polyester..... LAMININATING... Resin. Mix up about a 1/2 gallon.(this is best done on a warm summer day 70 degrees or better)
Cut some Mat about 2ft by 3ft, or what ever size you are comfortable with.
Lay the mat on the table and pour on some resin and roll the resin into the mat....until it looks completley wetted out......See You Tube for "wetted out"
Then: Lay the wetted out Mat on the Plug and roller it down with your roller....get all of the air bubbles out
_____________________________________________________________
____________________________CAUTION___________________________
_________Your plug cannot have a postive slope or you must make a two part mold. For example, An ice cube in an ice tray slips out because the slope is negative, if an ice try were spherical and deeper than 50 percent of the volume of the sphere then the ice would not slip out, you would need a two part mold.
____________________________________________________________
(i) cover the whole plug (your boat) with three layers of Mat. (One layer a day)...read the directions....done do to many layers at once ....too much heat. too much heat is bad...warp.....warp....warp
________________________________________________________
(j)ROVING: lay down one (1) layer of 20oz Roving...whole boat....
________________________________________________________
(k): Mat and Plywood strips: laydown a layer of mat, and embed 1/4 plywood strips into the wet mat. I like to cut 1"(inch) by 4' (ft) plywood strips to reinforce the mold...90% of the boat.....
____________________________________________________________
(l): lay down a layer of Mat and One layer of Roving...whole boat....
______________________________________________________________
_______________________CAUTION________________________________
(m) Jack handle: if you are going to ever seperate the mold from the plug, you have to build a jack handle into your mold or you will never get the two apart: get two (2) 12 ft 2"x4" and Mat and Fiberglass them into the bottom of the mold about 2' (ft) apart. They should hang over the bow and stern about 1' (ft). This is your jacking handle.
_____________________________________________________________
(n): let the whole mold cure for 72 hours......Since you used Laminating resin, your are going to have to seal the mold with either finishing resin or some sort of top coat......So, lets use finishing resin. Brush some finishing resin over the whole mold....this removes the sticky feeling from the resin....
________________________________________________________________
(o): Jack the mold off of your plug( your boat).....done......