Building 1 time use mold. input?

Dave Hirshberg · #1 12-26-2003, 08:49 PM

I've been commissioned to build a Livewell for sportfish. It will measure roughly 40" wide by 24" high by 16"deep. And it will be visible on three sides and the top, backing up to the transom on the cockpit of the boat. I plan on building a one time use 3 sided custom mold for the job. First I plan to make a template out of wood for the top and bottom roughly in the shape of a capitol D if you were looking from the top down. I then plan to lay-up a rectangle of 1 1/2 ounce mat and resin over gelcoat on a flat waxed melamine board and form it(gelcoat side in) around the top and bottom plywood boards while the fiberglass is still relatively green or before it completely hardens, using screws thru the thin fiberglass laminate into the plywood to hold the shape. I then plan to beef up the outside of the form and lastly lay-up my three sided part in it. I'll add the bottom and back of the well afterwards. the only thing to come from the mold will be a shell with a front two sides and a top. I'm good with glass and paint but I'm wondering if there isn't another material out there that lends itself better to bending a tight radius like the two rounded front corners without breaking. I'm sorry if this looks like Greek to you all, I just know some of you have used some West Products and epoxys which i have no experience with. Any Suggestions are appreciated

strick · #2 12-27-2003, 01:57 AM

Hi Dave,

I like your idea and have been thinking kinda along the same lines for my boat however I want a live well that sits behind the leaning post.
Per your description the back and bottom of the finished live well does not need to be finished because they will not be seen. And I guess the inside of it does not need to be a smooth finished surface as well? So it sounds like you have a good plan. I've only worked with epoxy so I do not know how long a working time you have with polyester. You can use a slow cure product to give you more working time to get the wrap around the plywood. It may get a little messy if you start too early in the wrap process if the epoxy or polyester has not kicked. I worry a little about buckeling of the material in places in between the two pieces of plywood. If that happens you may need to add capital C piece of plywood to support the outside middle of the mold. You can use very small finish nails (the ones with no head)to hold the piece of fiberglass to the middle piece of plywood. If done carefully you will not need to putty over them. I've used formica and hard board for my molds and I really like the hard board as it is cheap and easy to work with. It comes in two sizes at Home Depot... I think 1/8 and 1/4 inch and has a very smooth surface. As far as how long it will take to make the throw away mold? Hard to say but i'm thinking no more then 3-4 hours max if you have all your ducks in a row. I'm thinking that for my boat I will buy a Kodiak live well and just build a mold for a cover that goes around it as part of the leaning post/live well combo. I dont trust my ability as a plumber so I prefer to buy a tank with all the fittings attached already. Below is a pic of the stern of my old boat. The middle hatch is that of a Kodiak tank enclosed in the stern of the boat. Hope some of this helps.

Strick

John R · #3 12-27-2003, 10:46 AM

Strick - did you make that Leaning Post? Curious what plans you have for your custom livewell/leaning post

70s - I have a question / thought and don't know if it would work... What are the chances you can core it with some kind of closed cell insulation - instead of plywood? You won't need the structural benifit of plywood, right? So what other materials can you core with? As for closed cell, are there any panels that are flexible enough to be the core? Or another thought, if you made up a mold of something flexible (vinyl for instance) could you pour your core of closed cell
insulation and then lay up the glass around it... Just something I've been bouncing around with in the tiny mind

Next - I'm not sure about the baits you suthnern guys use but some of the ones we use up north, herring and mackeral, need to be able swim around a tank with no corners. If there are any corners, they tend to collect there and eventually not get enough circulation thru the gills and go kaput...

Dave Hirshberg · #4 12-27-2003, 10:56 AM

Thanks Strick,
I was hoping you'd chime in.
I agree with you on that middle part flexing . After I posted last night I thought about Laying up the flat skin on the hardboard in three sessions. First the gel coat on the entire part. Then a skin coat of 1/2 oz glass and 1/4 inch coreboard in three peices( sort of like a tri fold wallet. I believe that this would stifen the three sides and still leave a thin layer of glass to bend around the radius on each side. Then finally a layer of 1 oz in each of the radius before tacking it to the plywood mold.

jw · #5 12-27-2003, 11:18 AM

Dave,
You might check out some baltec core material, it is scored for making radius'sssss. I believe you can get it in foam or balsa, and in different thickness'sssss. It may be a bit more work, but the coring material my help insulate the live well, and you can still gelcoat it or paint it.
A buddy of mine enclosed the windows on his 31 Bertram, he used this stuff, if you know a 31 bertram you know the weird curves on the front outboard windows.

Hope this helps,
JW

Dave Hirshberg · #6 12-27-2003, 12:49 PM

John an JW,
You must have been posting the same time as I was.

I hear what your saying and i'm planning on using a coring material in three places on the outer skin of the mold. Leaving two 3 inch gaps between the sections that will form the corners. The coring will be running vertical to the top and bottom of tank. I'm hoping this will stiffen the three sides and prevent buckling while allowing me to bend the still green fiberglass around the D shaped base and D Shaped top (3/4 Ply) and form the two radius curves in the front before it completely kicks. I then plan to add core board to the radius to keep it from trying to lay flat after the base board is removed. This is just going to be a flimsy single use mold to lay up the actual fiberglass part . As I lay up the part itself I may use some coring material as well to stiffen and insulate. We pretty much bottom fish here with Shrimp, Pinfish, and grunts. All pretty hardy baits. I find that good water flow is the most crucial, they don't tend to bunch into corners. however, I plan on forming a clay radius on all corners of the mold before laying up the actual part.
Keep the input coming, I appreciate it.

EBEACH · #7 12-27-2003, 07:01 PM

Dave,
An easy way to do it would be to use a plastic container from someone such as Rubbermaid. Home Depot, office supply, and toy stores might be a good place to look for your mold. Wax the container then use a non-waxed gel coat and coat the inside. Then just glass it. You can add core material as well for insulation.

Great thing about the rotational molded plastics, they have a taper built into the part, and your piece should pull right out. If not, just cut it off. Further more, the plastic totes and garbage cans come in all shapes and sizes, even stating the volume in gallons . They have relief’s in the sides that will add to its strength.

You’ll have a great looking fish box in no time at all. [img]images/icons/wink.gif[/img]

Jim

John R · #8 12-28-2003, 01:37 AM

Cool - if you can, can you document with pics how you do it?

Thanks,

John

Dave Hirshberg · #9 12-28-2003, 10:36 AM

Good Idea Jim,
But I'm very confined to the size and type of well I need . It has to cover or blend to a nonskid outline already on the dck of the boat. I bought the Melamine board yesterday and I'll photo the process for better or worse to show how it comes out. I'm considering doing one the sixe of a shoebox to see if and at what point the laminents will bend. I'll keep you posted.

strick · #10 12-28-2003, 04:44 PM

Dave- Sounds like you got it figured pretty good and it's probably going to work just fine. Looking forward to the pics. The only thing I would do different is make the flexable part of the mold out of hard board rather then using a laminate espically if you are going to throw it away when you are finished. I think it would be quick and the 1/8 inch hard board would bend very easily around the plywood has a smooth shiney surface and is easy to cut.

John- I made the leaning post out of a piece of plastic bent at a 90 degree angle. then I laminated two pieces of plywood at a 90 degree angle slightly narrower then the plastic base. The Vinyl cushion is attached to the plywood backing and then it is bolted to the plastic base. There are some handles on either side of the leaning post that are hard to see in the pic. It's a quickie job and I've always thought that I would add a tackle center to the underside rear of the post but never did. Not sure exactly what I'm going to do on the new boat as of yet.... still thinking about the stern [img]images/icons/smile.gif[/img]

Strick

Strick