My 12'6" splash mold process.... here we go.

[supuk]

Looks great are they stiff enough without any real support? Are you going to use just wax for the parts or pva as well or a semi permanent ?

[bef]

I haven't moved them around much, but they are pretty rigid.  With the mold sitting on three of the four supports, I do not notice any twisting.  Not like it is settling into place.  Which gives me a thought:  I should make a single point mount for one of the table ends.  Three points define a plane, so if the mold is supported by two points on one end and a middle point on the other end, it should provide no twisting force for the mold trying to settle into place.  Bolting the halves together when bonding would straighten it, but then you are flexing the molded part and who knows how it will relax once bonded to the other half.

I am going to do the test layup first section with wax / pva.  See how it releases.  With epoxy I should be fine doing it with just wax.  Still, the molds are fresh so if I set them out in the sun a bit to bake, it would help finish curing the gelcoat.  If I try a polyester one, I will PVA the mold for that.  Epoxy should be fine though.  They really did come apart easy.  I had adhesion issues with the primer on the nose, I didn't clean the wax off that section well enough from doing the bottom mold.

 

[SUPflorida]

We use to use a product called "Freecoat 44" a bit pricey but never had a part fail to release easily...and some these parts were 200 + sq/ft. That was with epoxy. Application was much easier than wax and touch up for the next part was super easy as well.

[bef]

We use to use a product called "Freecoat 44" a bit pricey but never had a part fail to release easily...and some these parts were 200 + sq/ft. That was with epoxy. Application was much easier than wax and touch up for the next part was super easy as well.

Thanks, will look that one up.  I learned in the job shops back in the late 80's, so I know a lot has changed since then.  I have seen several of these apply once and easy part removal products, but have never researched them.  I have used a couple good ones for urethane resin casting, but I have not with standard molds and epoxy resins.

Brian

[bef]

Been awhile since I replied.  Been busy trying to finish the new bottom on my 1963 hydrodyne and also camping season has started.

Update on Top Mold.  Yesterday  I finished wet sanding out the top mold and waxing it up so it is nice and ready to go.  PVA put down in the middle few feet for a test section.  Going to paint the urethane today on part of it and do the glass layup tomorrow.

Bottom Mold:  This is what I wet sanded and waxed up first, so I have been using it for the test layups.  People said things wouldn't work, I believe that they wouldn't work, but I am just stubborn that I have to know "why" they won't work.  My main issue is what core to use.  I know, Divynicell <sp> is preferred, but I am too cheap and low performance, so looking at other options.  To be honest, I had to try the expanding foam and I think it would work.  IF you had way more patience than me or if you paid the money for an inject-able foam sprayer.  So I laid up a section of skin with one layer of 6.5 oz glass.  Way too flimsy, should have used two.  Then I removed that from the mold.  I then laid up a section with two layers of 6.5 oz glass.  First picture shows the top piece in the background behind the two ply outer skin.  I glued some 3/4" strips of EPS foam in them and then epoxied the removed skin back in as shown in the second picture.  It was actually pretty easy up to this point.  With the inner skin only one layer, it was also easy to cut little holes in the skin, fold the flap back and poor in foam resin, see picture 3 and 4.  The top skin did bow too much, but I think it could work, picture 5.  It is really stiff and pretty light, but pouring a small section at a time is a pain.  No way I am doing that for 6 - 8 boards!  But I wanted to report that I was stubborn enough to try it, show results and admit defeat!  Foam was 4 lb density.
   

[bef]

So I also did some experimenting with more cork sheeting.  I had some 2mm cork, so I did a test layup, no vacuum using the same area of the mold along the edge.  Two and three layers of 6.5 oz glass on each side of 2mm cork.  Went pretty well and was strong.  Problem was the cork wanted to spring back, so vacuum bagging is needed just for that if nothing else.  For the test layup, I did weight the cork sheet first overnight so it would kind of take the shape and not pull up from the resin, this did really help in the layup this time.  I did this test at the end of the day and did not have much time, so I just set a bag full of something on it and let it cure up (plastic down first).  I also did a small section with a self leveling urethane topside marine paint that I am using on the Hydrodyne hull.  It seemed to turn out well with good adhesion, so I am going to try that also.

After seeing how well all that turned out, I decided to do a full width test section 24" long.  The bottom is half painted with the urethane to compare that to a resin finish.  A couple of these I need to be strong and heavy that will withstand being left out in the elements and sun all summer long.  I am putting down two layers o 6.5 oz glass, 3 mm cork sheet, 2 more layers of 6.5 oz glass.  Polyester resin for this test.  I still need to layup the side joint pieces from the board, but will show that later.

For the top side, I am going to go with half urethane paint again and then two layers of the 6.5 oz glass.  i am going to try some 5 mm plywood that I bought in the standing area.  Any standard foam that I try, will compress under my weight, so I am going to try the plywood.  The plywood will have one layer of 6.5 oz glass covering it and then vacuum bagged with a peel ply.  Once sanded, I am going to make two 8' long stringers out of 1.5" XPS and epoxy them down to the flat standing area of the board.  These will be glassed over with epoxy strengthening the boards and the standing area similar to my illustrations earlier in the thread.

The two halves will be positioned for joining, the outside joint will be glued and at the last minute, 3 pound foam will be poured in two strips along the bottom section right were the stringers will mate up.  This 4 pound foam will take up the small gap between the bottom and the stringers, giving good support to the bottom skin of the board (I hope)!  We will see how this goes and it should show by doing a 24" section first.  Plus, i can stand on it and actually show a true cross section of what I am making.  Should be interesting.

[bef]

This is a pretty basic test.  Notice no peel ply, no breather.  So not really worried about removing resin or crushing it in really tight.  The vacuum varies over the laminate depending on how far from the vacuum source it is and the no peel ply will mean sanding is required for epoxy or foam bonding later.  Quick and dirty test, no big technology here.  Better later with each edition.

[surfcowboy]

Dude, this is looking good. Also, it makes me feel better for doing my current longboard restoration. Never again will I refurb a board. Lol. PITA

I'm ready to see you pop a board out of there man.

[bef]

So i have updated my cross section to what I am going to try as discussed above.  Not sure on the plywood, I think the 4x8 sheet I bought weighs about 18 lbs, so an 8' deck section might weigh in at 5 or 6 pounds.  Would be strong, but might be too much weight.

Also, the first board will not have a center handle.  i am going with external handles like a kayak since this is pretty experimental and it will just sit pond side.  i still need to go over the method of installing hardware which will be done in the mold.  Probably just show pictures when I do the first layup. 

Since the expanding foam core did kind of work, I think I am going to try it to fill in the raised rails on the deck.  To do this, the outer skin will be laid up.  The ply deck installed.  A single layer of 6 oz glass over the deck done.  The cork core along the side rails installed and then the whole thing vacuum bagged.  Once cured and the bagging removed, I am going to mix and pour in the expanding foam into the rail and just lay a piece of waxed plastic on top of the ply core.  The foam will expand up to it and then out the side seam which can be trimmed off.  The plastic piece will then be removed.  Hope that makes sense.  While the expanding foam for the bottom was too big of a task to do, a single rail that is 8' long, just under 1" high and about 3" wide should be much more doable.  Even if I do that in 4' pours, that is only 4 pours per board, should go pretty well and give me a solid top rail with easy glassing.

[bef]

So I just figured out my deck core for the first one.  I am going to start 30" in front of the tail and make the core 6.5 feet long (2 meters) long.  That is a pretty big standing area, but I am thinking on a pond I can easily see two people on this paddling it around.  The core ranges from 17" wide to a max of about 21" wide.  Will end up being about 11 square feet of area and the piece of wood will at 6 to 6.2 pounds.  Pretty heavy, but we will see how it goes. 

The deck area is flat enough for plywood, so i could easily substitute a 5 or 6mm high performance foam core for mine.  Instead of 6.5' long, it would just be made from one piece of 24" x 48 Foam.  4' is plenty of space for me to stand on and move around some.  The lighter boards will be made later.  Start heavy and go from there.

I thought about it, and many on here have posted how much like they like the PE rotomolded boards.  Huge, wide and heavy, but very stable and indestructible.  They weigh 50 lbs and are slow, but somedays that is what you want.  Well, what happens if I built a 50 pound 12'6" touring board?  how strong would that be?  I do not want to lug it around, that is what the lighter boards are for.  But for leaving pond side and for the kids to use as a float?  So what, they will have fun. 

So my goals range from a cheap and strong board that is heavy for multiple riders and kids play toy, to spending more on raw materials and getting a solid board that will support me yet be under the 40 pounds that my original board was and is already failing.  Pretty wide range of what I will be building, so it will be interesting.

[TallDude]

Something I've experienced with a few molded race boards I've paddled is they creak under foot when I load the board during a stroke. I weigh 240 lbs and they were well used boards, but the creak creak with every stroke drove me a little crazy. You might want to consider some sort of more durable expanding filler (Gorilla Glue) under the stringers. Some of the typical pour and expanding foams will break down pretty easy under pressure.   

[bef]

Something I've experienced with a few molded race boards I've paddled is they creak under foot when I load the board during a stroke. I weigh 240 lbs and they were well used boards, but the creak creak with every stroke drove me a little crazy. You might want to consider some sort of more durable expanding filler (Gorilla Glue) under the stringers. Some of the typical pour and expanding foams will break down pretty easy under pressure.

That is a good point.  Will have to look at that.  One reason I am doing it this way, is the stringer is glassed to the deck and solid.  The foam joint is on the hull bottom, has a compression width below the stringer of 1.5".  3 lb foam is what I will try first and it has a compression strength of 60 psi, or 90 lbs per linear inch of each stringer.  For my experiment above, I used 4 lb foam which pushes 90 psi compression!  If you go with lighter or cheaper foam that number falls off pretty quick.  I have been amazed at how strong 4 lb foam can be. 

In this application it is supporting the outer skin.  Given good expansion of a few inches and two stringers, that is  well over 500 square inches of support area. 

2 lb foam is often used for weight savings and flotation.  While it is rated at 30 psi for compression, it is suprising how unstable it is and how fast it can change shape.

Thank you for the tip

[bef]

You might want to consider some sort of more durable expanding filler (Gorilla Glue) under the stringers. Some of the typical pour and expanding foams will break down pretty easy under pressure.

Thought about this more over the past several days and thinking of other options.  completely unrelated, I have been following a couple of Formula Festec threads over on Offshoreonly about liner adhesion problems from the early 2000 range of boats.  Plexus is an adhesive that eats into the fiberglass and would do what you are describing.  Fill the gap, squish out and then set up.  Typically the joint fails by ripping the fiberglass apart.  But it still gives a gap filling option for easier and less precise manufacturing.  The other one I wonder about is 3M 5200 sealant / adhesive.  I have used that on my Formula and it is some really tough stuff.  The good thing about building some cheaper "pond side" boards first is I have a chance to learn and try them out, then adapt.  If I was going right to full on race manufacture like SUPUK did on his molded board years ago, I would be a lot more nervous. 

Reading about the boardroom thread and layups of 3x top and 2x bottom of 4 oz glass over 1.5 eps, I still want to try that with expanding urethane 3 lb foam.  I know, heavy and questionable.  But the urethane should be strong enough, add a deck patch section in, maybe some cork and another layer of 6 oz.  But layup and bag two layers of 6 oz in, then cork the deck area, another two layers of 6 oz over the cork area.  just not sure how to get the foam in without a new mold or cutting a hole in it?  Or join the two halves and remove the deck mold.  Cut an access hole in middle of deck area.  Prop up bottom mold/board assembly with the nose pointing up.  Pour in some foam, drop the deck mold back on, clamp and wait.  Keep repeating that until it is about 40% up to middle.  Then change it to drop the nose and do the front cavity.  Seems like a pain after my deck trials.  Still, 3 lb urethane foam with a vacuum bagged skin might not be too bad.  about 27 lbs of foam though, not light and doesn't seem easier to do.  Just talked myself out of it.....

[Arany]

I used to build wind surfer for make money  when I was young and we made them  like you try but after we put urethne the noise that  come from the mold  show allot of presher  inside the mold mast be very strong.

[bef]

So I am running behind on this project.  Mainly due to kids and trying to finish up the bottom of my 1963 Hydrodyne so i can flip it back over.  But it is starting to look pretty smooth and shiny (pic attached)

So this is where I sit now.  I got the top test section laid up and bagged.  The 5mm plywood I have is about 0.54 lbs per sq. foot.  I cut a section to give me a 6.5' standing section on the board.  That is pretty big, but with the first one being a pond board / kids raft, I figured heavy duty might not be bad. That piece of wood trimmed up weighs in at 5 lbs 13 oz.  Yeah, heavy.  I had some left over 5 mm cork also, and it weighs in 4.8 oz a sq. ft.  So that same area in the 5mm thick cork would weigh 3.2 pounds, not a big weight savings for using the cork over the strength of the plywood, so i am going with the plywood.  The 3mm cork I have as the bottom core is a good deal lighter at 1.92 oz per sq. ft.  It is amazing how much of a range you can get in density of cork.  3mm cork in that same area would add only 1.3 pounds to the board.  So I might try that in the future. 

Anyways, in this test section I used scrap cutoff pieces of plywood.  It will show me how it turns out as well as allowing me to put in a plywood seem and a cork seam.  See if there is any issues with them once they are removed from the mold.  I did forget to add my cork to the side rails of the deck piece.  So I am going to change my stringer layup a bit.  Originally  i was going to sand the poly so I could cut a 2' long EPS stringer and glass over it with epoxy.  Sanding the poly would give the epoxy a good bond.  But now I need to add in a thin strip of cork along the rails with poly, so I am going to use some of the 1/2" foil face urethane foam sheeting I have.  I will glue three layers together and set them in place, then glass over that with the 6.5 oz glass/polyester and add the cork to the sides with two layers of glass over it at the same time.  Will also glue in the rail reinforcement / joint extender pieces to the bottom section of the board at the same time.  Tomorrow it should be ready to glue and join the halves together!

I know, wordy post.  it is a flaw - remember I am an engineer.....