DIY Board and Design Spreadsheet

Finally finished my second homemade board and thanks to some great tips from other board builders on seabreeze it was a big step forward from the first, very dodgy board I made last year.

Its 133x39cm, 4.5cm continuous rocker, 5mm concave. The core is 2x6mm PVC foam (Klegecell) with balsawood veneer over the top. 2x6oz e-glass (one at 45/45 degrees), 1x 4oz s-glass on each side of the board.








To help design this board I put together an excel spreadsheet that lets you create the outline, rocker and concave templates for the rocker table and estimate the weight of the board. It came in pretty handy and if any other DIY board builders want a copy you can download it free from the link on this page.

www.boardbuilders.co/2011/05/my-first-plagarism-free-board.html

It was put together in MS Excel 2007 and doesn't open properly in earlier versions ( the chart series get dropped for some reason). It contains a VB macro for generating the splines used to get the smooth curves used for the outlines so you'll need to enable macros.

There is a very very beta board flex model in the workbook which attempts to predict the flex of the board under different loads. Its currently way off the mark but I have left it in there in case anyone with some background in the area can help me refine it.

Thanks RayQ.

Regarding flex it seems that it is a lot better to thin the core rather than the reduce the glass to get the flex you want. This seems to work because stiffness reduces much more rapidly than strength does as you reduce the thickness. Brokites (the absolute masters!!!) make a board with a 6mm foam core and use stringered carbon which is usually very brittle and end up with an increadibly strong and very flexible board.

I am keen to have a go at a wood core and was thinking about it this time but for me there were two issues that swayed me. One is weight and the other was the ease of controlling the rocker and concave in a backyard set up. Even taking into account the reduced amount of glass (about 200gm per layer of 6 oz glass) wood core boards are a lot heavier. The best of it seems to be Paulonia but it is still at least 3 times the density of foam and plywood is about 10x. The other issue was the amount of spring back in wood cores that aren't CNC cut is big and unpredictable. I've heard figures in the order of 25% +/- lots and I wanted to have more control over it than that. If you laminate the layers of foam core on the rocker table you can have near zero spring back.

Some time in the future I'm going to have a crack at a foam core with a wood stringers to see if that finds a good middle ground.

Cheers
Matt

Hey djdojo. Thanks very much.

I used epoxy resin (R180 with standard hardnered) from FGI. It gives about 45mins-1 hour of working time. For the bottom I used the same resin but mixed white pigment with it. The footstrap insert are just standard stainless steel flange nuts pushed through the middle of a plastic washer cut from scrap ABS plastic. Last board I used stainless steel t-nuts but they are really hard to get hold of where I live and the benefit of using flange nuts (which are just ordinary hex nuts that have a 1-mm thick 'washer' already attached) is that they are only 6mm high so you can use them in thin baords.

The rails are 5mmx10mm ABS plastic strips that were cut as straight strips then I heated them on a gas BBQ till they where soft and then bend them around the outline of the board. When ABS is soft its really easy to shape like this. Although I haven't tested this yet I have read that to make epoxy stick to ABS properly you need to scratch them up with really rough sand paper and flame them (again I just used the gas BBQ and ran them back and forward through it). Apparently this oxidises the surface of the ABS and creates a better chemical bond with the epoxy. The scratches act like 'grab handles' for the epoxy. That said, the much easier solution to the rails seems to be to just rout a channell around the outline of the board and fill it with the same epoxy you use for laminating. You can add milled fibres to stengthen it and pigment if you want to colour it. Then you have no worries with the laminate sticking to it. The downside (I think) is that poured rails aren't as impact resistant as ABS which is awesome ( hits a rock on a 20 knot day and cracked the fibreglass but not barely dented the ABS rails).

If you'r interested I've documented the whole process in detail on my blog www.boardbuilders.co/
including all the stuff that went wrong.

The spreadsheet 'Boardoff' that you can download from the blog has the outline, rocker and concave profile of the board as one of the saved boards if you want to muck around with it.

Hope this helps.
Matt

Adding to the material discussion. Some experience gained working with fibre reinforced plastics in the aerospace and oil/gas industry over the last few years:

Alternative rail materials:
I don't understand why everybody uses ABS (as said it is difficult to bond). Some thermoplastics which bond well to epoxys and which are tough enough for rails are: HTPE, TPU, PA11/PA12, PSU, PES, PEI, PEEK. (in order of price left->low, right->high). HTPE and TPU shuld do the job and are easy to bend using a BBQ . For a high-end board maybe PA11. The others are hard to bend as Tm/Tg to high - for BBQ.

UV resistance:
UV resistance of epoxies are poor however the effect over the lifetime of a board is small (maybe some yellowing) – more of a problem for boats which are outside 24/7.
The industry standard seems to be to use PBT film to protect the board from UV. On top of that PBT is easy to print. I think for “home made” PU top coat would do the job too.

Inserts:
Would be interesting to try non-metal inserts made from some of the plastics mentioned above using "plastic screws"…

Should have written HD not HT (HD=High density) -sorry

PU vs. Epoxy: The only advantages of PU is the lower price, slightly higher toughness, better UV resistance and mixing ratios can be varied. However, I think epoxies are still the way to go. Mechanical properties are a lot better, bonding is easyer and modern epoxy formulations have significantly increased toughness. In addition and maybe the most important point when doing it at home (if you have girlfriend, wife, etc.) is that epoxy are odour less- most PUs smell horrendous…

To all DIYers (and epoxy using businesses too), bear in mind that while epoxies are pretty much odourless, they do let off chemicals that have serious long-term effects on your immune system. Sure, the odd pot of 5 min araldite won't hurt but ongoing exposure has cumulative and irreversible effects including hyper-sensitisation to other chemicals. Steve McGeary (of Speed Sailboards, 80s and 90s) got to the point where he had a major reaction to things like shampoo and beer.

Please minimise your exposure by wearing appropriate gloves and respirator, using ventilation, and generally minimising the amount of toxic stuff that you use in the first place.

Perhaps epoxy manufacturers should include an offensive but harmless scent in resins to give people an immediate incentive to take care?

Nice!

What sort of cost are we looking at?

Matt

You are the master sourcer! I have recorded all those links that you put up on the home made board post a few weeks back and there is some real gold among them.

Thanks for sharing all the good info.

Cheers
Matt

Sweet board

Where would you recomend getting foot pads/straps, and fins?

Thanks for the info,
last time I went out at pazza I came back with only three fins. My mate has made a couple boards now, just not sure if I am willing to put in the effort required.......

Thanks mate.

The convention used in the spreadsheet is that yellow cells are the ones that you update. The OutlineParameters tab lets you save your outline data in the columns of yellow cells on the left and then you load it byentering the template number into the "Template Selection' cell. Heres a screen capture this comments on this tab which I hope helps. Once you've got a template selected just change the numbers in the selected template (in the yellow cells) and you'll see pretty quicly what they do. The RockerConcaveParameters tab has 2 options - continuous rocker ( i.e a arc of a circle) or 2-stage. Again the yellow cells are for updating. Again, best thing to do is change something and watch what it does in the corresponding charts. I'm putting together a bit of a user guide so keep an eye out on the blog www.boardbuilders.co/ over the next week or so. Also, feel free to ask questions on the download page for it on the blog so that other users can see the discussion.




The board templates with names have been traced off pictures of the baords with those names. Board #1 was my first attempt and wasn't good.
Board #2' is the this board.

Cheers
Matt

Hey suface2air. I didn't do a lot of research on resins but when with the recommendation from the guys at the shop where I got all the material (FGI). I used FGI's R180 Epoxy resin and for my first attempt I used slow hardner H180 because I thought that my first attempts to wet out the fibreglass would be slow but it was more straight forward than I expected so didn't need the extra time. Now that I know and because its colder here I use the standard hardner (ambient temperature makes a big difference). One thing to keep in mind is that different speed hardeners can have different (dis)colouration.

West System is another brand of epoxy that I see very regularly spoken about in boat and board building forums. One tip, get the pumps on the resin so you don't have to stuff around with weighing it.

Cheers
Matt

you guys sound like you are all over it but there are some neat ideas and advice re epoxy , glassing on wooden boards etc on www.swaylocks.com/ and woodensurfboards.blogspot.com/ and www.paulowniaparadise.com.au/surfboards.htm
mainly surfboard stuff but glassing is pretty universal.....

another interesting site if you are little handier with a welder and wiring
www.mechmate.com/forums/index.php
would love to have a go but know SFA about welding
great job on the board stikflik

the 2 piece mould is a nice idea, I was stuffing around with a one piece silicone mould a few years ago, very crude, and it was hard to feed fibre glass into it before filling with epoxy,
For threads, I wraped a wetted out strand of fibre glass around the thread of two stainless screws and pushed them into the soft resin, works great.
My bigest problem was bubbles in the finished fin.
All glass fins are manufactured by CNC these days, cut from a layerd up sheet.
I went over to getting fins made up for my boards

Hi Fossil you wont need release agent, the screws came out pretty easy, they snap loose once the resin has cured, I think as long as you dont roughen up the surface of the screws you wont have any problems, actually you may have problems with the coil if its not marine grade steel, give the fibre glass wrap a go.

Ray