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Old     (surfdad)      Join Date: Sep 2004       05-17-2008, 6:46 AM Reply   
Bondo - the mold makers best friend! :-) You can use it to take out imperfections in your mold, or to shape out undercuts. I glued up the pieces of my mold and used wood screws to "clamp" the pieces in place. I am using Bondo to fill in the indentations and a few places where the wood ripped out.

Old     (bigshow)      Join Date: Feb 2005       05-17-2008, 6:49 AM Reply   
I'm sure Jeff knows this, but...Make sure that you use fresh filters. A filter that's rated for VOCs will deteriorate over time. These filters come from the factory in tightly sealed wrappers.
Old     (surfdad)      Join Date: Sep 2004       05-17-2008, 7:27 AM Reply   
Good point Ed, safety first.

I am not well-versed with the use of Bondo, but I do know that it can be worked while hardening and that it sands/feathers well after about 20 minutes of cure time. I was only orried about the area of the mold that will be used to form the PU foam - the inside of the curve.

Sanded through 400. I will be applying a few more coats of paint and the next stage is 5-7 layers of Partall Paste #2 (wax). Molding isn't for wimps! :-)

Old     (surfdad)      Join Date: Sep 2004       05-17-2008, 7:27 AM Reply   
First "next" coat of paint.

Old     (surfdad)      Join Date: Sep 2004       05-17-2008, 9:37 AM Reply   
Partall makes a full line of mold relase products. Partall #2 paste is a paste wax that will help seal the porousity of the mold surface and also prevents most resins/foams from adhering to the underlying mold. Fresh molds, like this where it hasn't been used previously, needs a lot of wax and release film. After it has been seasoned with use, a single coat of wax "can be" enough for a few castings. I only wich to get 4 parts out of this mold, so I don't have a supply budget to be concerned with :-) I'll wax the heck out of it each time. :-)

Old     (surfdad)      Join Date: Sep 2004       05-17-2008, 9:41 AM Reply   
Huh I just lost a post - oh well. #2 contain petroleum distallates - use appropriate safety measures also, make sure that your mold surface is compatible and fully cured.

My elbow exercise cream:

Old     (surfdad)      Join Date: Sep 2004       05-17-2008, 9:44 AM Reply   
Paste #2 will dry quickly...within a minute or two. You'll want to only do a surface area that you can easily apply and buff out in that time. If you wait too long the #2 is tough to buff out.
Also treat it like waxing your car. Not in direct sunlight or if the surface is too hot. I'm pretty much done for this morning - too hot the wax turns to liquid upon contact.

I tried to get a picture of the result you want - notice the shine compared to the area immediately to the right. You'll want all interior mold surfaces to have this shine.

Old     (surfdad)      Join Date: Sep 2004       05-17-2008, 5:14 PM Reply   
My buddy Dennis was helping Capitol Marine on the boat show/demo day so we got a chance to do a demo! :-) It was on Folsom, first 100 + degree day so the water was a bit rough.

The perimeter stringer board worked pretty well, I'll reserve judgment for decent water, but it seemed to have a great deal of snap.

Old     (bigshow)      Join Date: Feb 2005       05-17-2008, 7:05 PM Reply   
Jeff, for all of the varied build methods that you've tried in what this last year how do the different methods rate?
Old     (surfdad)      Join Date: Sep 2004       05-18-2008, 8:13 AM Reply   
That is such an expansive question, Show. I think that of the tools I have employed, the vacuum and rocker table/bed allow for exceptionally light, strong boards with virtually identical production of multiple parts. I love those tools.

I think that the composite sandwich offers the greatest level of customization of a board. The drawback being that it also offers the greatest number of variations or maybe combinations of materials. When you start combining different materials, the results are often different than the expectation. If I won the lottery tomorrow, I would love to set aside a few million to test every concievable material combination and board shape, with the understanding that it would yield, maybe, one or two worthwhile prototypes! :-)

I think that one of the reasons that we haven't seen much development in this regard is that it is so expensive and there isn't solid science behind the construction of surf or wakesurf vehicles.

Corecell is too stiff/brittle IMO. Rohacell is almost fragile and so expensive that it's scary to work with. The two pieces I have are more expensive than the cost of a board! :-) Divinycell offers the broadest range of application.

The hollow carbon/balsa was a joke. :-) Heavy, stiff and expensive. Not many virtues in there. :-)

Honestly...I believe that foam with some bits and pieces to help performance is, IMO, the best combination of materials that I have experimented with. The jury is still out on this springer concept, but the perimeter stringer concept is solid.
Old     (bigshow)      Join Date: Feb 2005       05-18-2008, 8:23 AM Reply   
That's about what I expected. Of the techniques you’ve tried the parabolic rails are maybe to most promising.

I think the reason is that you want a springy board. You want a board that will swim forward when you flex the board. By swim I mean like a dolphin kick. A center stringer will do that for you but that stringer is half a board width from the wake. Putting the stringer in the rails puts the spring where it can do the most work.

The Vernor/Stixx V boards tide the edge of the board to the stringer with an I-beam (T-beam really). That system make sense too and you’re reports indicate it works.
Old     (surfdad)      Join Date: Sep 2004       05-18-2008, 9:05 AM Reply   
Vernor's suspension system is that T beam like you say or an inconguent I beam if there is such a thing. :-) The stringer down the middle of a board does offer resitance to lengthwise flex, as you point out Ed, but offers nothing to prevent rail twist.

This picture of James shows where an increase in resistance to rail flex can be beneficial.

Old     (surfdad)      Join Date: Sep 2004       05-18-2008, 9:14 AM Reply   
The term that is used by surf folks is "squirt". Where the board squirts forward, either by fins or flex return in the tail. If you look at the side profile of many surfboards - and CAskimmer eluded to this with the skim build, the tail is thinner and this allows for some flex in the tail.

I think that I have some opposing forces that need to be balanced. One is that I need the fins to be SOLID in the box so that the only flex is in the fin itself and at the tip. Placing the stringers out at the rails prevents the box flex, but also prevents some of the tail flex because I have TWICE as much stringer material. This requires thinning the tail more than usual.
Old     (surfdad)      Join Date: Sep 2004       05-18-2008, 11:45 AM Reply   
I have so many things going on in this post! :-) Back to my rail foam mold. I have sealed all the seams with simple painters caulk, for a few reasons. I'll be using pour foam and as that expands, it will want to find the path of least resistance OUT, sealing the seams will tend to cause the foam to travel up the mold, which is what I want. Also, angular surfaces tend to make demolding tougher. I use a generous amout of caulk in the seams to round these areas and ease demolding. I'm not really concerned with the appearance as I will be shaping all areas of the rail foam, except the inside curve. The other thing I want is for the caulk to demold with the part. I'll need to rewax the mold for the remaining 3 parts and I don't want to dig the caulk out. Leaving a rough surface will tend to make it stick to the foam.

Obviously this mold could be refined to provide a finished shape that required no further labor...which is really the biggest benefit of using a mold. Perhaps one day I'll undertake that project. :-)


(Message edited by surfdad on May 18, 2008)
Old     (surfdad)      Join Date: Sep 2004       05-19-2008, 7:59 PM Reply   
I poured one rail this evening. Pretty painless.

After all the waxing, I like to apply a film release. Normally I use PVA, but in a test, this didn't work well with the Polyu foam.

Old     (surfdad)      Join Date: Sep 2004       05-19-2008, 8:01 PM Reply   
I opted for Synlube 531 which is a wax based mold release and that did fine in my test. I sprayed all mold surfaces before final assembly.

Old     (surfdad)      Join Date: Sep 2004       05-19-2008, 8:04 PM Reply   
I used 4 lb foam from US Composites. It is a two part 1:1 mix. If you look carefully you'll notice that there is no net wt or volume marked on the can. You have to carefully estimate the volume and convert the expanded volume to get the amout to mix.

Old     (surfdad)      Join Date: Sep 2004       05-19-2008, 8:08 PM Reply   
When working with pour foam, you have about 15 seconds of mixing time and 45 seconds before it starts to foam. Get organized first! Measured components and a final mixing bucket.

Old     (surfdad)      Join Date: Sep 2004       05-19-2008, 8:10 PM Reply   
This pour foam is an ugly brown color, so I decided to add some color - well Black pigment to the foam. You mix this in with either the a or b side by hand before combining the two components together.

Old     (surfdad)      Join Date: Sep 2004       05-19-2008, 8:13 PM Reply   
By mixing the pigment with the foam, the entire piece will be colored black, I'll be able to shape it and the underlying foam will be black. For folks that are artistically talented, you can mix up several small batches of foam and color each one separately, then as you pour the separate batches the part will have differing colors running the length of the part.
Old     (surfdad)      Join Date: Sep 2004       05-19-2008, 8:15 PM Reply   
The part demolded - I have a little more mold cleanup than I care for, but it's not bad. You can see the clean molded inside that will line up with the boards perimeter stringer.

Old     (surfdad)      Join Date: Sep 2004       05-19-2008, 8:18 PM Reply   
This is what I hoped would happen - the painters caulk transferred to the part and pulled off the mold.

Old     (surfdad)      Join Date: Sep 2004       05-19-2008, 8:20 PM Reply   
With these steps it's possible to make molds for polyu blanks, rails or even high density fin inserts for low density foam builds.
Old     (surfdad)      Join Date: Sep 2004       05-21-2008, 8:56 PM Reply   
I always love first posts by folks. :-) In an effort to avoid getting involved in the drama, I ran out and made a new mold! :-)

You can use latex for making molds and it won't require a release agent. It takes several layers and then after that a layer of 'glass to give the latex a bed.

Old     (surfdad)      Join Date: Sep 2004       05-21-2008, 8:57 PM Reply   
Three layers of latex

Old     (surfdad)      Join Date: Sep 2004       05-21-2008, 9:02 PM Reply   
While latex is a quick and easy solution for making molds it suffers in terms of longevity. I want to try and mold another 4 parts and that is no doubt the extent of the life of the mold.
Old     (jstieg)      Join Date: Apr 2007       05-21-2008, 11:57 PM Reply   
ok i finally got 2 free blanks from my work and i started the shaping of a 5'5" high performans fish. (ocean board) i have been surfing nothing but my wakesurf in the ocean. surfed rincon 3 days perfect waves and people were lookin at me all crazy cuz my board was less than half the size of all theirs and i was still zippin down the line faster than any one
Old     (surfdad)      Join Date: Sep 2004       05-22-2008, 5:28 AM Reply   
Sick Johnny, post up your build! I can imagine the looks you generated on your wakesurf at Rincon! :-)
Old     (surfdad)      Join Date: Sep 2004       05-22-2008, 8:41 PM Reply   
5 layers and counting :-)


I finally got some C-5 boxes, FGS was out and told me a week later! :-)

Old     (jstieg)      Join Date: Apr 2007       05-23-2008, 12:35 AM Reply   
yea i had cody take some pics while i shaped it. dave let me use his shaping bay so my board came out perfect. i cant wait to ride it. 5'5" quad hp fish. im goin out tomorrow to seal the blank and glass.
Old     (surfdad)      Join Date: Sep 2004       05-23-2008, 8:51 PM Reply   
Post 'em up Johhny. 5'5"? You're more wakesurfer than anything these days! :-)

I got tired of building my latex mold, so I decided to make some dinosaur cake. This is white frosting over a teradactyl clavicle. Bake your clavicle at 350 degrees for 35 minutes or until a toothpick inserted into the middle comes out clean. Allow the teradactyl clavicle to cool before icing a minimum of 3 days. A generous supply of icing is needed, at least 2 pounds per foot of teradactyl clavicle. Serve with ice cold milk and present on a lovely serving tray of 1/4" plywood. Serves 82.

Old     (surfdad)      Join Date: Sep 2004       05-27-2008, 7:42 PM Reply   
After 10 coats you have to allow the latex to cure 24 hours. If you compare the picture below with the picture above, you'll notice that the latex has cured to a "tan"'ish color. The 24 hour time doesn't start ticking until ALL of the white has turned to tan.

Old     (surfdad)      Join Date: Sep 2004       05-27-2008, 7:46 PM Reply   
Next I will build up a solid foundation around the latex. This foundation will be 'glass and it supports the latex when casting. A heavy or expanding casting medium can deform the latex mold, so the 'glass foundation prevents that deformation.

I use a viel or 2 oz glass as the first layer to get the corners and other details correct. Subsequent layers will be built up with chopped strand matt.

Old     (surfdad)      Join Date: Sep 2004       05-27-2008, 7:47 PM Reply   
Oh! Don't forget your pleats in the corners! :-)

First layer wetted out.

Old     (surfdad)      Join Date: Sep 2004       05-28-2008, 8:34 PM Reply   
The next layers are chopped strand mat. The CSM is a random oriented fiber mat. The mat makes up a pretty thick and stiff structure after saturated with resin - this layer took almost 30 oz.

A close up of the CSM


Cut sections of CSM ready for laminating


All resined up :-)

Old     (surfdad)      Join Date: Sep 2004       05-29-2008, 8:09 PM Reply   
Second layer of CSM.

Old     (surfdad)      Join Date: Sep 2004       05-31-2008, 5:15 PM Reply   
The rigid base is finished, now it's time to demold the plug and the latex mold from the 'glass rigid base.

The latex doesn't stick to the cured glass, but it can be stubborn to demold. My secret: a garden hose. Once you get one corner started, you can force water between the latex and the rigid typically pops right out.

Old     (surfdad)      Join Date: Sep 2004       05-31-2008, 5:20 PM Reply   
This picture shows the latex mold as I've partially separated it from the rigid base.


The Latex mold inside the rigid base ready for the pour foam.

Old     (surfdad)      Join Date: Sep 2004       05-31-2008, 5:25 PM Reply   
Smooth-on makes arts and crafts products, including this 5 pound density urethane pour foam. I did a quick test and it is an exceptionally fine cell structure, it shapes well and without large voids in the foam.


I decided to try red foam rails for this part

Old     (surfdad)      Join Date: Sep 2004       05-31-2008, 5:29 PM Reply   
It mixes up painlessly - smooth-on offers kits in various sizes. I used the one pound size for each rail.

The expanded red foam still in the mold.


I hacked a piece off to see what the granularity was like, it's exceptionally fine.

Old     (surfdad)      Join Date: Sep 2004       05-31-2008, 7:14 PM Reply   
First part demolded. The pour foam is tack-free in about 20 minutes and takes about 5 minutes to to demold.


Second part in the mold. It takes about 10 minutes to mix the materials and pour.


Once the mold is built, the processing is pretty straightforward and quick. In a production environment, I would estimate that one person (unskilled labor) could manage three molds and roughly produce 6 parts an hour.
Old     (surfdad)      Join Date: Sep 2004       05-31-2008, 7:59 PM Reply   
Part two demolded, it does get a bit easier as the mold seasons. This is how the two parts will be oriented when I attach them to an EPS core.

Old     (surfdad)      Join Date: Sep 2004       05-31-2008, 8:04 PM Reply   
The latex mold is a tool and I like to care for it, as such. I dry out the rigid base if I've used water for demolding. Then I spray the inside of the latex mold surface with mold release before putting away inside the rigid base.

Old     (surfdad)      Join Date: Sep 2004       06-01-2008, 7:52 PM Reply   
Test fitting the core and the HD rails. Hopefully I'll glue it up this week.

Old     (surfdad)      Join Date: Sep 2004       06-04-2008, 7:33 PM Reply   
Red rail glue up

Old     (surfdad)      Join Date: Sep 2004       06-05-2008, 8:27 PM Reply   
Shaped this red rail blank this evening. The polyU on the rails made shaping this a dream.

Old     (surfdad)      Join Date: Sep 2004       06-05-2008, 8:33 PM Reply   
I've heard folks talk about pour foam leaving all sorts of voids and I didn't experience that at all.

I shook both components up well and then mixed the part b with the dye for about 1 minute with a hamster wheel that may have something to do with it. A cross section of a cut.

Old     (christopher)      Join Date: Jul 2006       06-18-2008, 10:26 PM Reply   
How's this bad boy coming along?
Old     (surfdad)      Join Date: Sep 2004       06-19-2008, 5:41 AM Reply   
Hey Chris that one is done. Our boat blew up and we've been bumming rides with other folks, so I don't think I have any pictures riding it. I'm pleased with the potential of the tech - the green board is an early iteration of this tech:

Old     (bigshow)      Join Date: Feb 2005       06-23-2008, 3:59 PM Reply   
James killed it at the TWC on the green board. Front side air 3!!!


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