I have another board under construction. New rocker templates created and close tolerance blank hot wired. The objectives of this project are 1. to produce a more lightweight method of construction than my blue spyder foam/epoxy board board 2. develop a method of building suitable for restricted environments with no workshop. 3. Improve on the shape of my professionally made custom pt break tri fin (made with conventional PU/PE materials. 4. Use materials that are tolerant to my awful glassing skills. My blue spyder(hi density xps) board is successful in that it is rock hard due to the double 6oz top and double 4oz bottom epoxy/s-glass over spyder foam which can withstand 60psi compression. Its not a very light board though. Spyder foam is 3.3 lb/cu ft so I’ve been considering other options. The type II beaded eps is lighter at about 1.5 lb/cu ft, but only copes with 15psi by comparison – I don’t know about Clark foam. XPS is incredibly hard to find in N Cali though and I can only get 2” thick sheets. So I sanded the skin off a couple of small pieces and put it in a G-clamp with some elmers glue to see how it would bond. Exact same results as Eric J – after 24 hrs incomplete setting of glue, although reasonable bond. I could still break it apart at the join. I’ve glued white eps with elmers and it sets fine. This illustrates that the xps is very water resistant and explains how I am able to put my blue xps twin fin in the car early morning, put the heater on for the 45min drive and then place the board in the cold N Cali water and get no perceptible absorbtion thru the many pinholes of my badly blown thru home grown glass job. I’ve even tried pressing my thumb against the pinholes after coming out of the sea and could see no water. Trouble is my blue xps does have some flex, don’t notice it when riding but if I thump the nose while I’m sitting on it I can feel it shudder. So if I’m going to reduce the weight then a thinner glass job will result in too much flex I think. The conventional solution is to add a stringer. Does this really make much difference? I suppose from looking at my conventional PU/PE with basswood stringer pt break tri-fin, its single 6oz plus patch it does seem to be effective. Its not just the longitudinal stiffness of the basswood I’m told but the vertical stiffness which makes it an I-beam. Keeps the top and bottom laminates apart. The grain makes the stringer weak vertically but the foam supports its sides. I suppose the classical I-beam construction is Paul Jensen’s Hollow boards. He uses Luan plywood which I can easily get. Plywood has more vertical stiffness than straight basswood too. The carbon Paul Jensen reinforces it with would help the vertical stiffness even more. In fact he has I-beams running in both directions as the ribs in his board would be I-beams too. It then occurs to me that all surfboards are I-beams even my blue xps – here the foam itself provides the vertical support uniformly for the entire top and bottom surfaces. I consider a lighter foam with this sort of structure, or same spyder foam with just luan plywood and lighter glass job. Even luan on its own is going to give me indoor shaping problems, so I consider the construction of the only magic board in my quiver. My definition of a magic board is one whose performance exceeds my expectations – like most surfboard enthusiasts I always have fairly high expectations. I have 4 very good boards and the one magic board in my active collection. The magic board is a mini-tank designed by Donald Takayama, I’ve admired its hull contours and noted that nothing unusual is going on. It has belly throughout most of its length running into panel V in the tail. I don’t have a rocker stick but it seems to have as much rocker in the rear half as the front half (ignoring the slight nose flip). I’ve described the performance of this board before, but the sort of thing I’ve been able to get this thing to do is sideways air-drops on a bowl section I sometimes encounter on south swells and tail slide during the recovery part of a cutback (on the gently sloping long walled NW swells that Cali enjoys in winter). I can’t produce such moves at will and at times I’m more of a passenger than a pilot, but I consider it to be a magic board. Of course this board is magic for ME. Others will require different float for their boat. Mr Takayama’s design is obviously to my tastes for that sort of board, but I think its construction helps too. Its got an EPS core, no stringer and a hi density pvc foam/epoxy glass sandwich skin. Designed in Hawaii (I hope) but no prizes for guessing where it was produced. The result is a board which is lighter than a conventional PU/PE board of similar size yet fairly stiff. So what makes this stringerless board so stiff? Considering a cross section thru it, it is in fact a triple I-beam construction. Bottom skin consists of epoxy glass/pvc sandwich I-beam. Top skin is another identical I-beam. The two bottom and top I-beams then sandwich the eps core to make a third I-beam. After considering all my construction options I’ve decided to go for stringerless triple I-beam construction. So I’m now trying Dow wallmate for the core which has 25 psi compressive strength and lighter than spyder but similar weight to type II eps. The blank was made from 2” thick Dow Wallmate, supposed to be 1.6 lb/cu ft. Incredibly hard to find in N Cal but I found some in Bob’s foam Fremont. Rather expensive so I balked at buying 2 sheets and got some beaded EPS Insulfoam from Home Depot. The insulfoam is only about 1lb/cu ft type I and not strong, but its cheap. Quite likely I’m going to mess up on my novice attempt at this construction so use of the eps will keep costs down and maybe I might even end up with an interesting flex. I’m quite aware that I’m running the risk of a leaky boat as the eps will absorb water. I can always try building another one in 100% xps if this one doesn’t work out I tell myself. For the sandwich skin I’ve decided on 1/8” divinycel – hi density pvc. fiberglasssupply.com sells it, but they say cutting the sheet into a 4 ft length is necessary for shipping. Despite being reassured that I can butt join the pieces I really want one complete piece for the top and bottom skins so I go and get something similar from fiberglass Hawaii in Santa Cruz. They have CoreCell which is a SAN foam suitable for sandwich building. A boat building website tells me that SAN is the weakest of the sandwich skin foams when comparing similar densities. The makers of CoreCel however publish conflicting data which shows their foam is the most impact resistant. Naively I turn up at Fiberglass Hawaii without any specific means of transporting the 8’ x 4’ sheets. I mistakenly thought they told me they were 7’ x 2’ when I phoned them. However a Stanley knife down the center splits it into 8’ x 2’ and it can easily withstand a few undulations to compress it into the back of my Mercury Sable station wagon. My latest toy is a vacuum pump complete with pressure gauge and decompression tank mounted on a piece of chipboard. This vacuum bagging system came ready assembled and part of a bagging kit from ACP 45 min north of the Valley. They have done me a deal which gets me a bigger nylon bagging tube (9’ x 36”) which will accommodate a surfboard and extra lengths of peel ply and breather material. However I am having a re-occurrence of resin setting anxiety again. For those who didn’t read the description of my last project, resin setting anxiety is the condition where novice builders experience apprehension with getting their resin mix to set. Polyester novices laminating tend to add a few extra CCs of catalyst, frequently with disastrous results. I couldn’t do this with epoxy but found stirring with a spoon for 3min guaranteed a set. My latest bout is brought on by reading that the vacuum bag can exert so much pressure that the resin will be squeezed too thin to bond and I am going to have to laminate my 2” polystyrene foam into a thicker blank. Unlike my last blue project where I launched straight into the construction without any sample test laminations I’m going to do a bit of testing first before attempting the board. So I mix up a batch of epoxy and divide the mix. In one mix I add enough micro-balloons to make up a mayonnaise consistency (lets call this micro-mayo). According to one of the epoxy manufacturers anything between mayonnaise and peanut butter can be achieved with micro-balloons. I stack 2 pieces of xps separated by micro mayo, 4oz cloth squeegeed with epoxy and ,a smaller piece of corecell, a piece of peel ply to cover the exposed glass where the smaller corecell doesn’t cover and finally wrap it in bleeder fabric held in place by masking tape.Lets call all this the stack. The whole lot goes in the vacuum bag. One of the problems I’m facing with the sandwich construction is how to get the stiff corecell to wrap the rails. I don’t have specialist heat moulding equipment to curve the corecell. I’ve spent a lot of time going thru Anthony’s excellent board building links, I found myself spending far more time at the kite building, sailboard building and alternative surfboard construction websites as well as searching for boat building websites. Boat builders use PVC and SAN foam a lot. I find it helpful to consider methods that don’t resemble what I’m trying to do – helps get my mind off the beaten track. So Paul Jensen doesn’t attempt to wrap the wooden deck and hull skins around his rails so I’m not going to either. I’m going to take the bottom skin up to the edge of the hull and only partially wrap the top skin over the rail curve and allow the polystyrene foam to be exposed and covered in glass only. Sandwich construction requires a minimum of 2 layers of glass to sandwich each corecell skin. So with the top and bottom skins I’m going to get 4 layers of glass overlapping on the rails. I’m hoping that this will be enough glass to produce a durable rail and that the separate top and bottom corecell skins will add I-beam stiffness to the low density stringerless blank. Back to the bag: I put a quick lock seal on the open end of the 9’ nylon tube which dwarfs my test stack. Turn on the pump and nothing happens ??? After a few moments the bag starts to move – the pump doesn’t seem to move large cubic feet of air per minute. However I understand it to be a good pump coz it has plenty of power and is able to achieve 28 hg or about 14psi of atmospheric pressure. Every time the pressure drops a couple of hg the vacuum switch turns the pump on. With my setup I understand that I have a good seal with the pump cycling only every 30min. The next day I remove it and peel off the bleeder and peel ply. My test stack has had a rail band and rail roll and some dome shaped into it and the corecell did take on shape of this dome, although as mentioned before I haven’t attempted a complete rail wrap. I have an exposed 4oz lap which is far neater than anything I’ve been able to achieve with squeegee alone. However it seems to have squeezed a fair bit of resin out of the layup and the single 4oz lap feels fairly soft when pressed with my thumb. The corecell has not been given a final laminate on its top surface, but feels rock hard by comparison. The xps to xps bond using the micro-mayo cannot be broken apart at the join – so no reason for any resin setting anxiety with this method of laminating sheets of xps. Now for some real stuff. I’m not going to attempt to bend the sheet of 2” xps and 2” eps into a rocker like Eric J. Instead I’m going to stack them flat and wire cut – that way I will get top and bottom rocker tables from the offcuts. I also don’t have easy means of bending the foam either. To get my 5 ½” of nose rocker I have to stack foam in the following order: 2’ x 7’ eps, followed by 2’ x 7’ xps followed by 2’ x 1’ of xps on the nose end only. I have a go at pre-cutting the stack before laminating but give up on the nose section when I find this method too fiddly. So I’m going to bond the stack first and hope the wire cutter can get thru the micro-mayo glue. At this point I read some instructions on how to vacuum bag a model airplane wing. It says that the blue foam can take full pressure, but the white foam will require only 8hg or it will be crushed! Phew that was lucky I spotted that. Upon returning to my task I test a piece of white insulfoam under full pressure. Instead of cycling every 30min the pump cycles every 10min. Slowly but surely the life is being crushed out of the foam and ruts start to develop where the individual beads of foam meet each other. Over a period of hours it starts to deform. So I now adjust the vacuum pump to 8g and spread a micro-mayo mix on one surface of the xps and put the stack in the bag. This operation is performed on two tables arranged lengthwise to accommodate the 7’ stack length. The next day the stack is removed and …what’s happened? I have some springback. This is ridiculous, Eric J bent his sheets and anticipated springback but didn’t get any. I’ve layed mine flat and got a noticeable bow! I realize what has happened. The vacuum has slightly compressed the insulfoam but not the xps. But I’m not at all concerned…. Shaping goes smoothly, I rented another planer from homedepot. I’ve taped a vacuum cleaner bag on the exhaust port and the flow is powerful enough to inflate the bag and it greatly reduces foam dust. Glassing the blank, positioning the corecell, wrapping it all in peel ply and bleeder wrestling the whole lot into the bag and vacuuming without any wrinkles in the bag seems a daunting task. I think a dry test-run is needed first. I’ve devised a scheme where short strips of peel ply are taped on to the corecell edges only. Followed by strips of bleeder. The corecell is non perforated and I don’t believe I’m going to get any resin penetration thru its surface so only the rails need peel plying and bleeder. This will be more economical use of the disposable bagging materials. I set the stopwatch and pretend that I have laminated 4oz of glass. I have already taped the peel and bleeder fabric strips on to the edges of the corecell sheet and I carefully position it centred on the hull. I fold over the peel/bleeder and use more tape to hold it in place. While pulling the bag over the wrapped blank the masking tape doesn’t stick very well and catches on the vacuum bag. Bits of fabric start falling off the rails – total failure with this method, but at least I’ve avoided a real life debacle. After some thought and experimenting, I’ve modified the scheme to use a complete sheet of bleeder which will cover the peel rails strips and wrap this all over the board and then wrap masking tape around it to hold it in place. This is the procedure: 1. Lay the vacuum tube on the rocker table first. One end of the tube should be sealed the other end should be open. 2. Put the corecell and peel/bleeder in place on top of the bag. The corecell should take on the curve of the rocker table. 3. Lifting the blank off the glassing stand and putting it on top of the corecell. It will sit quite nicely in the curve of the rocker table. 4. Wrap vacuum fabric around the rails. 5. Pick up assembly and slide it into the vacuum bag which has been carefully layed flat in the curve of the table. The alternative method of pulling a heavy nylon tube over the assembly requires some fairly rough handling and seems to be a bad method. A dry run after setting my stopwatch is completed in 17min. This will easily accommodate the tolerant setting properties of epoxy even if I had used up all my pot life during lamination. I’m rather nervous of the actual process but it goes well. A small piece of masking tape catches on the bag when sliding in the assembly, but it doesn’t cause any problems. I pick up some of my heaviest books and place ,it on top of the sealed bag. The board is lying in my wire cut rocker table and the blank glue up. Springback is completely removed by the weight of the books. If I wanted to I could even adjust the rocker with this method by bending my rocker table. Forgive my self indulgence but at this point I am gloating. I have a completely sealed sandwich lying on my dining and folding table. I’ve attached a plastic tube onto the exhaust port of the vacuum pump which is fed out of the window. With the balcony door open and the laminating fumes swept away I can now sit down and watch tv glance over at my incubating creation with no smell whatsoever 
Unwrapping the board the next day is exciting. The vacuum process does a great job of smoothing out my limited squeegee technique. Its completely flattened out the lap. No spikes of glass, no air bubbles, hardly any smoothing out with the surform tool required. However at some point in the process the corecell sheet has moved and one of the rails near the tail has a bit of a step. Ah well I’ve got an asymetric Micro Edge board, I’m not going to worry about it. I then shape the square edge of the corecell to conform to the tucked edges as planned. A surform tool was able to shape the corecell easily. The deck is done in a similar manner except this time I’m using the deck rocker offcut sheet and I don’t bother to weight the assembly with books. Deck shape has slightly changed the rocker anyway and the laminated hull skin has stiffened the board and retains its shape. I had already beveled the edges of the corecell before laminating it. I do a bit more shaping with the surform again. I’m not attempting to remove the ridge where the top corecell skin meets the xps, nothing wrong with having this if some ppl even put rail channels for stiffness. The fluffy bleeder fabric when wrapped around tends to cling to the hull corecell which is good and I wasn’t happy with the way the masking tape was prone to catching on the bag so I’m stitching up the bleeder with dental floss and a big needle instead. The floss can pull the stretchy non woven bleeder fabric reasonably tight and smooth. But got to be careful not to pierce the vacuum bag which is placed underneath ready to receive the assembly. When the assembly is in the nylon vacuum tube and the tube starts to collapse from being evacuated by the pump it is necessary to arrange the tube such that it is pulled tight against the laminated surface and all wrinkles gathered onto the non laminating surface instead otherwise the wrinkles will be put in the glass too. The pump can be temporarily switched off to help smooth out the wrinkles. I also recommend the use of quick lock seals (long plastic clips which came with my vacuum kit). I tried the sealing tape during one of my tests and it is like chewing gum and cannot be peeled off without ruining the part of the bag it clings to and also is much harder to get a nice even seal. The nylon vacuum tube is fairly stretchy under atmospheric pressure and will conform to rail shape. The bleeder is easy to manage too. However the peel ply is fairly tightly woven and I cut slits into the overlap every foot or so – a bit like what would be put into glass cloth when glassing tight outline curves. This method of getting the peel to wrap the rails without wrinkles worked well. I’ve been recording the weight of the 6’ 9” board as it progresses: 1.9 lb cut blank (profile and outline). 1.6 lb shaped blank 2.96 lb bottom lam 1 4oz + corecell 4.57 lb corecell both sides + 3 lokboxes the rest is over the limit of my kitchen scales. But I feel it rapidly got heavier with the application of the final glass. Resin consumption record: 4oz/1.7oz micro mayo for glue up – plenty. 2 oz/0.9oz micro mayo1.5 for sealing the thirsty eps prior to laminating first layer on hull – not quite enough, had to really scrape up every drop and get only a sparse layer on. lam 10oz/ 4.4oz , discarded plenty of surplus = 4oz roughly top lam 10/4.4 oz, surplus = 3.4 oz top final 6oz cloth, brush under laps 10/4.4 oz NOT ENOUGH!!! Had to really scavenge with the squeegee. Reverse lapped final hull layup with 4oz cloth, double fin patches 10/4.4oz barely enough. I found that by the time I got to wrap the laps the epoxy was already going sticky and slightly reluctant to wrap and stick and that brushing a thin coat of resin on the foam under the laps before pouring on the resin on top allowed the lap to squeegee much more smoothly. When looking at the above I was surprised that the final laminations required so much resin when I was discarding quite a lot with the corecell laminations. I initially thought that the 6oz cloth needed more than I thought, but the final 4oz on the hull seemed to need more too. My conclusion is that corecell despite being closed cell is thirsty – next time I should give it the micro-mayo sealer treatment like I did on the eps surface. Also looking at the above it seems that despite not giving the eps a really good coat of sealer it was effective, with the eps lam absorbing slightly less resin than the unsealed closed cell xps top lam.
Michael - Whew! That sounds like a hell of a project! I can only imagine the high anxiety that went along with it. I give you a lot of credit for figuring it all out. I’ve often wondered why you couldn’t cut profiles (think side view of a stringer) out of panel(s) and laminate them together creating a multi-stringer effect. You could design any rocker and board thickness you want and no springback. It might take an extra panel or two to do it that way. The video linked below shows how a guy builds sailboards using vacuum bag techniques. He uses an adjustable rocker table to avoid tweaking the blank under vacuum. He also does a fair amount of rough shaping after the high density skin is applied but before the glassing is done. If you can, I’d advise viewing a copy of the tape before doing another as it could help streamline your process. I’ve looked into vacuum bagging myself but the costs of the peel/perf ply, absorbant backing, etc were quite high considering they were basically a one time throw away application. http://www.victoriavideo.com/board.shtml
Hey Mr. J, you are all over it! I have a few questions though… Are you saving those offcuts for a set of variable rocker tables for future boards? What is the final weight of the board? This sounds like a consuming project for sure, but is it a reasonable building method for one-off’s? What kind of hours overall went into this project? Bagging is of interest to me, but I’m considering it for fins (as a fin mold compression method). As for laminating I’ve found I actually enjoy the traditional way, albeit with epoxy or solarez. Best, Eric J PS: Elmers will work for an xps glue up, but you have to give it 2-3 days to cure. would seem better, & more quickly, done with epoxy since you don’t need the air to set epoxy off. Elmers seems to need some exposure to air for curing.
Hello John, thanks for that link, I think it would have definately been a good idea for me to see that vid before, the more knowledge the better, but I don’t have a vid player. Will be returning to australia which has a different electricity voltage and vid format. I’ve figure that the low power consumption of my vacuum pump can be easily rectified with a step down transformer so I will be transporting this to Oz. There is however heaps of free information on the internet about vacuum building. Like all methods of construction there are a million and one variations which can be done and mine is just one way and after getting thru 75% of one board I don’t have the best method. Of most use for the actual process has been Eric Hertzen’s kiteboard building site. Although I’d figured out the “open edge sandwich” method which avoids the problems of getting the hi-density skin around the rails before I saw his site, it does resemble his “plyfoam” technique. Although his method really works only for flat hulls and mine allowed the corecell to conform to the double concave bottom. I believe the open sandwich definately reduces the labour involved and I couldn’t easily get the more pliable airex skin that the sailboarder’s use anyway. Yes, the blank could have been laminated vertically but coz I was using a combination of low density eps and hi density xps I wanted the stronger xps to be on the deck surface to resist denting. My last project was built out of a solid 5 1/2" thick spyder foam blank which didn’t need laminating. there seems to be no avoiding the wasteful and expensive discarding of peel and bleeder cloth. There are vacuum builders who seem to have devoted themselves to finding cheaper alternative vacuum materials, but each time something is substituted the process seems to get more inconvenient and harder to control. Polythene from hardware stores can be used as the bag but its not guaranteed to be pinhole free. Dress making cloths aren’t necessarily cheaper than peel ply and harder to remove than the release treated one I used. the bleeder I used is already recycled and nice and drapable, only the edges get soaked in the initial corecell lams and I could have tried salvaging the middle and stitching it together but it smells of epoxy amine when removed so I decided it was more healthy to throw it. http://www.kiteboardbuilder.com/index2.htm
Hello Eric, its a time consuming process. What is reasonable one-off construction time is subjective. I’m just trying to build a better board and have fun. I spent at least as much time searching for info too. And in fact the reason why i’ve just been typing notes into a word document and posting it all in one hit is coz I only just had enough time to do my day job, build my board and get some surfing, knew I wouldn’t have time to reply to any questions. I’m on vacation in Australia right now and board construction has halted at the “hot coat” stage. A single lamination takes one day, with the peel, bleeder and corecell being cut and prepared in say the evening and lamination the next morning before work.I didn’t want to risk trying to pull the peel off on the same day anyway. The lamination of the glass is no different from normal glassing except that it has to be wrapped up in layers of vacuum material afterwards. A Norwegian builder does a regular lam without vacuum and then glues on the skin with micro balloon mix under vacuum later. I suppose the method I chose of placing the skin on the wet glass job, then putting the whole lot under vacuum is faster. The rocker table offcuts are specific to that blank profile only and seeing as a table comes for “free” every time a blank is wirecut its not necessary to save it. It is possible to make small rocker adjustments in the middle part of the board by propping up the ends. the board seems rock solid, similar weight to my PU/PE but I think i can improve on that with sealing of the corecell next time. just a thought but it might be a solution to your cold winter building problem. You could heat your shed, do a lam, wrap it up in the bag. Clamp off the end of the vacuum hose, put it under your arm and transport it into your warm house for curing. Probably best to reconnect the pump in your house. You could even put a layer of reusable release film on top of the fluffy breather and then another layer of breather as insulation which could be re-used if you were concerned about it cooling down during the journey from shed to house. i’ve recently aquired a digital cam, so when I return to the US I’ll post some pics. cheers, Mike
Mr J, Soo much to read I skipped over it. If you can bag it, you could probably infuse it. Less waste, gets rid of the bleeder schedule. Sluggo