Sick looking boards. I personally like how the thruster came out too, the color looks great with the grain. Looks like things are coming along nicely since I met you last summer. I wanted to get in touch anyway, I finally got that Mandala 6’1" bonzer. The one I ordered LAST March! It’s a sicky and I remember you were saying you’d like to maybe steal the template. Maybe we can meet up one of these days. I’d love to get another look at your board making process now that I know a little more about the whole package. PM me with you number again, or when you have some free time if you like.
Am I right in thinking that you use RR epoxy? We have an importer in the UK now, and should be getting some in about a month. Can’t wait, should make the whole process much easier with the additive F.
I also use the Chinook vents, but use the 1" ones designed to be glassed over, I put gthose 5/8" ones in some early boards and people didn’t like the idea of anythink standing proud of the deck. I get mine from Fiberglass Supplies in Bingen Washington.
This is my 2nd (and 3rd) time of preforming the skins separate from the board and I’m really becoming a big fan of this approach. The skin is incredibly tough (for only being 2 oz, balsa, 2 oz) and lays so flat and filled that I’m not going to hotcoat it.
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should make the whole process much easier with the additive F
I’ve only worked with Greg’s stuff with the additive F, but its so cheap that I wouldn’t consider doing it without it.
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I also use the Chinook vents, but use the 1" ones designed to be glassed over … from Fiberglass Supplies
After jjp’s recommendation I went out and ordered some from the same company. The vents are the only parts that I’ve ever had fail (on 2 out of 4 boards), so I’ve decided its time to break down and buy premade ones.
Do you vac the outer glass onto the skins on a table, or are you hand laminating?
Do you have any trouble with pinholes? I guess if you hand lam it’s not a problem. I vacced a 4oz onto my balsa on my rocker table on one board and was less than happy with the result.
I suppose you then tape the rails?
Can’t wait to get the RR, it will make all these proceedures more user friendly I am sure.
I am a big fan of vaccing the whole skin in one go because using the resin (sp115) that I do at present, it is the most time efficient way of doing it, and I don’t have to bother with sanding laps etc.
I vac it onto a flat “cookie tray” made from 1/2" steel electrical conduite with XPS taped in the middle. On top of this I put a piece of formica. I slide the whole thing into a bag and pull 25 inches of mg. It comes out beautiful.
I pre-glass on the exterior glass. I’m a little worried now after hearing of jjp’s board breaking. On my current 9 footers I’m going 2-balsa-2 on the bottom and 2-balsa-4 on the deck.
Thanks for the reply, I wasn’t very clear there, what I meant was when you vac the glass on, do you put down the glass first then the balsa, then formica, or
balsa, glass, formica?
Might sound pedantic, but it does make a difference.
I have been putting 2 balsa 4 on the bottom of all my boards (7’ 2" is the longest though!!) and 2 balsa 4+4 on the decks, average weights around or under 6lb incl fins and boxes on a 6’6".
Balsa 3mm on decks.
They are still a lot stiffer than Berts boards. I have jumped on a couple upside down and they do bounce back but no where near flatten out like the pics of Bert’s boards. I am going for thinner rail balsa for my next one.
The last kneeboard I made myself was 1 3/4" thick and had the deck concaved! that was nice and flexy!!
No pressure dings and no breakages yet!
jjp’s board was tested way harder than any of mine though!!!
What I do is to lay out the balsa the way I want it for the skin then run long strands of tape (on what will end up being the inside of the balsa) to hold the whole thing together. Next I flip the balsa over so that the outside of the balsa is facing me. I remove the glass from my wetout table (I find that it works best if I wet out the glass so that it is rolled like a 1 foot wide tube). As I unroll the glass on the exterior of the balsa I smooth it out with my gloved hands (I tried using a squeege but the 2 oz is so light and uses so little epoxy that hand smoothing it was the only way that worked for me). Now that the glass is looking good I flip the balsa/glass combo over so that the glass is on the formica. I remove the tape from the back, put on some shade cloth as a breather, slide the whole thing into the bag, and go to 22 inches (I know that its a lot of pressure but I think it helps the glass lie better and helps eliminate dry spots).
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I am going for thinner rail balsa for my next one.
On
my current boards I’m building I went 5/8" with the springer on one and
3/4" on the the one without the springer. I’m thinking that
boards need to have X amount of strength form a certain wave
size. You can get the strength from the rails, the springer, the
balsa skin, the glass job, or a springer. If you take away
strength from one of these variables then you need to give it back
somewhere else. For instance more glass will give greater impact
resistance, but will make the board to stiff . To compansate for
the extra glass you need to weaken one of the other variable in order
to maintain balance (I hope I’m right or I’ll have to boards heading to
i have tried that method a few times… works pretty well except for the air bubbles I get. they fill in really easily with the hotcoat but you said you were not going to hotcoat so you must not be getting the pin holes? so my question is what do you do after you bag the preglassed skins on? rough em up and glass just the rails?
my take on the balsa rails is that the balsa itself dosn’t really add that much strength… i think it adds to stiffness and springyness but balsa snaps sooooo easily when it is unglassed that i really doubt it has a huge part in the preventing breaking. try snapping a piece of 1/4 balsa and then a piece of 1/4 ply… i think it is really there to hold shape, stiffen the rails and provide spring…
dan your next board sounds like it should be feather light… should be fun. i am scared to put 2oz on the outside, it just seems so weak, but as we know there is one person who does it all the time…
I have used 2oz on the outside of a board, but worry about sanding through as it is so thin, I guess by prefabbing you dont need to sand as much because its so smooth, the one time I did prefab though it looked good from a distance but had loads of pin bibbles between the weave so I put it on the inside!!
I have been keeping my rails at 15mm (3x5mm) for consistancy, but am going for 3x4mm (1/2")when I get some more supplies.
I tend to put less glass on my own boards, but go for the 4+4 on the deck for other people erring on the strong side as people are so amazed by the weight anyhow.
I think that your method sounds much quicker than the way I have been doing it, prefab the skins by laying out the planks and joining with 5 min pu glue and temporary tape, tke off tape, quick belt sand with 120 grit and then vac to the blank. I can glue up in 20 mins or so, but it takes about the same to get it all onto the table and vacced down.
Think about this - how and why does unglassed balsa break? Get a peice and slowly bend it until it breaks. Try peices of different widths and thickness. What you’ll find is that the tension side always gives first (the side away from which the ends are being bent). If you can find a peice with unbroken grain to sacrifice you’ll see quite clearly that this is a result of wood fibers parting. This is normal for all timbers - wood is far stronger in compression than tension. Now, even the lightest layer of glass bonded on will strengthen the tension characteristics a great deal. So the glass enhances the natural characteristics of the timber itself. That’s why the point of composite construction is to use the right material (or combination of materials) in the right place.
markyv,
I see that as one of the advantages of pre-fabbing the skins. It also seems less fiddly in a lot of ways (the way I envision it anyway). For me it jells with the way I “see” the board being build from the ground up. Still having some conceptual issues with the deck, but I’ll get them worked out
I’m still working out the details of how to progress, but here are a couple of pictures of what I’m talking about. These have been out of the bag for a week or so and have picked up a lot of junk laying around my garage. Like the red line… It was my most resent learning adventure. I drew a red line down the middle of the formica (with sharpy) to help orient the balsa then put on 5 coats of mold release. I couldn’t see how it could possible transfer but it did… TWICE. I wanted the boards to be twins of each other so I didn’t bother to erase the line. Now they’re both equally messed up! By the way, the flecs on the board are foam dust.
dan i got the red line using a red posca pen, six coats of wax over it… it still showed up after 4 pulls… black posca pen did the same thing, but not nearly as bad. i haven’t seen the black run yet so maybe the wax is doing something to it…
At least I feel better that its happened to somebody else! I finally found a use for the acetone I had laying around. It was the only way to remove the sharpie from the formica. I didn’t want to recreate that “feature” on the deck.
PM me with you number again, or when you have some free time if you like.
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