Jonrezz’s Build Log

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MadRussian
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Re: Jonrezz’s Build Log

Post by MadRussian »

Are you using heat blankets only on one side? Sure way to get surprise camber or reverse camber.

On your temperature controller. Research "line voltage thermostat" 110v or 220v simple and effective plug-and-play some of them included thermocouple. I've been using one of those for years
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vinman
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Re: Jonrezz’s Build Log

Post by vinman »

When edging bases, lay the base so the abraded/ bonding side is down . Lift the base to apply the glue and then clamp. This way you can see if there are any gaps between the base and the edge.
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Jonrezz
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Re: Jonrezz’s Build Log

Post by Jonrezz »

Thanks for the tips guys! I'll give your method for the edges a shot. when I did it that way I crouched under the base and pointed my phones flashlight at it to check for gaps haha.

I did read on another thread a while ago about unpredictable camber with one sided heat. My thought here was try a ramp/soak controller and program a gradual temp profile instead of just blasting the heat full throttle up to setpoint, hopefully reducing the unevenness. if my little experiment fails I will have to duplicate my heater like you're suggesting. either way I'll update the thread with how it goes, my buddy's coming to visit this weekend we're going to attempt our first layup! The main reason I didn't start with double sided heat was because I was nervous to have to run the wires out from inside the vacuum, risking a leak or ruining the table.

some pics of the installed setup, just wired it back to the breaker panel today!

side note - yes I did staple the dangling wire in the background to the ceiling after taking the photo ;)
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JSquare
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Re: Jonrezz’s Build Log

Post by JSquare »

Jonrezz wrote:
Tue Oct 06, 2020 6:49 pm

I did read on another thread a while ago about unpredictable camber with one sided heat. My thought here was try a ramp/soak controller and program a gradual temp profile instead of just blasting the heat full throttle up to setpoint, hopefully reducing the unevenness. if my little experiment fails I will have to duplicate my heater like you're suggesting. either way I'll update the thread with how it goes, my buddy's coming to visit this weekend we're going to attempt our first layup! The main reason I didn't start with double sided heat was because I was nervous to have to run the wires out from inside the vacuum, risking a leak or ruining the table.
It's not about ramp times-- sure you can calm the ramps down and minimize the thermal gradient, but the gradient will still be there. Think of it this way. When things come down from a high temp, they shrink. If the temp is higher on top of the board than the bottom, than the top will shrink more. You'll lose camber and the base will be convex. If the bottom is hotter, you get more camber and a concave base. For skis the concave/convex things matters less since you cut them out down the middle and 1/2 the problem.

Slower ramps can help soak the heat in and distribute it-- this is true. Lower temps will mean less gradient probably as well. The game you play is to either minimize the gradient, offset your molds to accommodate for the known change, or unbalance your fiberglass layup with different weight glasses top/bottom.

Plenty of folks have top heated with vac bag presses before. It can be done. We use one blanket-- it makes the whole wet layup a little lighter for picking up and putting into the press. Also we made ours and it took a few tries to get a nice one.

And yes-- just charge ahead! Take good notes and measurements.... do that a few times and you'll arrive at your recipe that works for you.

I'm very much enjoying your thread. I like your approach and how clean things are coming up thus far. I'm excited for you.

Jonrezz
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Re: Jonrezz’s Build Log

Post by Jonrezz »

Thanks for the insight and encouragement!

After having power restored on Saturday due to a storm taking down the power line at our house a couple days ago, we decided to press one simple ski layup on Sunday to get some notes /data regarding what works well, what needs improvement, etc. in our process. the layup is 22 oz fiberglass top and bottom with a nylon topsheet and wood core with poured sidewalls. we used one of our old, kind of messed up cores that was laying around (didn't want to mess up the good ones on our first press attempt ever). We skipped the graphics so we can look for internal defects through the clear nylon topsheet.

we used double sided tape and mold release wax around the tape to hold the base to the aluminum sheet
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Here's an action shot while the ski was pressing. we noticed right away the need to ventilate the room when the vac pump runs - smoke from the oil vent was coming out pretty fast and actually activated the smoke alarm at the top of the stairs.. the idea will be to get a small 50-100 cfm exhaust fan and duct it out the basement window. if we can get the air inlet close to the oil vent, problem solved I think.
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This was a big mistake - the epoxy flowed into the bottom of the mold and pooled up in there. the silicone sheet was in contact with that pool of epoxy. my suspicion is that the heat from the curing pool of epoxy damaged the silicone sheet. fortunately it isn't torn or anything, but it looks permanently deformed. I'm hoping it'll spring back to some extent, but I'm also ordering a spare sheet of silicone in case I need to swap it out. Also - i didnt notice at the time but we shouldve cut the fiberglass to length instead of letting it overhang the front like that - now the fiberglass is epoxied to the mold! whoops!
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here it is right before we ripped it out of the mold - in total for this run we did 4 hours of heat - 1 hour ramp from 80 degrees to 180 degrees (deg. F), 2 hours at 180 F, then 1/2 hr ramp down to 140 F before pulling it out.
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cutting out the shape on the bandsaw - we did the tip and tail shape with a jigsaw and belt sander
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Rough shape cut out
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as jsquare mentioned - we are going to have to play the game of exaggerating the mold camber to get the correct ski camber. in this run we had 9mm of mold camber, and the ski has 3-1/2" of camber when it's resting under its own weight. the unweighted camber is closer to 5mm.

topsheet is pretty flat, we have one minor crease near the tip though.

as far as internal defects, the ski looks clean - fiberglass has no dry spots and lamination seems secure. no complaints there. One issue (we knew we had it going in but proceeded to layup anyway as a learning experience) - the base warped when we glued the edges on. going to need to experiment with ways to keep the base secure while doing the edges to avoid that. a couple posts back there's more details on how we did the edges and my guess at why it warped is because we didnt have the base secure to something stiff when we spun it around to put on the 2nd edge. we're thinking of double sided taping the base material to the aluminum cassette, cutting the base shape on the cnc, then applying the edges without ever removing the base from the aluminum? the tricky part is we dont have a base mold like a lot of other people use for this process, since it's all cnc cut.

Here's the aftermath of the pooled epoxy issue we had before. not sure if there's a way to patch it or if we should just replace. leaning towards replacing though
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looking forward to next steps and trying again! those include the exhaust fan, experiment with an adjustable camber mold, fix our base warp issue, figure out a sidewall beveling jig, experiment with some better edge bending solutions, start experiment with graphics/veneers, figure out how to protect the silicone sheet better during layup..

gav wa
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Re: Jonrezz’s Build Log

Post by gav wa »

That sounds like a lot of smoke from your vac pump. You should include a needle valve so it doesn't pull so hard. This will help lengthen the pump life. Once you have it all pulled down the pump shouldn't be moving too much air so shouldn't be venting much at all. You should have a couple of settings on your pump to adjust how much the oil is moving around it while pumping.
When I was working on large vac insulated gas equipment we would only adjust the pump vent to max maybe for an hour a day and with careful adjustment of the inline valve to make sure we didn't lose any vacuum.
I would also look at skinning your mold so your silicon mat doesn't pull into the grooves so much, might help it last a little longer

JSquare
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Re: Jonrezz’s Build Log

Post by JSquare »

gav wa wrote:
Wed Oct 14, 2020 9:16 pm
That sounds like a lot of smoke from your vac pump. You should include a needle valve so it doesn't pull so hard.
^What he said. The way i typically see this done is that there's a cross fitting going into the pump from the bag. T-d in there is a vacuum gauge and a bleeder valve. You shouldnt need full vac. I can't remember what pressures we ran at, but prob like 3/4 of at atm is my guess. others might comment on this. Your pump should have a also filter/muffler on it its exhaust. Among other things, it keeps crap from getting into the pump when its stored in the shop. Smoke shouldn't be a thing at all. I'm a little worried about your pump. If its overfilled maybe it could mist. But i've run a lot of vac pumps on the day gig for different pieces of equipment and filling a room with smoke doesn't sit right. Crossing my fingers your hardware is OK.


Do you own a shop vac yet? Put some sanding filter bags in that and hook it up to that bandsaw when you're cutting stuff. You'll love it.

SleepingAwake
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Re: Jonrezz’s Build Log

Post by SleepingAwake »

For a lot of the cheap pumps a lot of smoke is completely normal. Run i hose out the window or run it through a filter. You don't want to breath that not want you to have oil mist on anything you want to bond afterwards...

Jonrezz
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Re: Jonrezz’s Build Log

Post by Jonrezz »

Thanks for the Responses! interesting suggestion - is the needle valve supposed to reduce the airflow in the pump thus less smoke? When I did this run, the pressure was at -28 inwc. I did a bit more research myself and am wondering if I should put an "oil mist eliminator" on the exhaust port.

I do have a shop vac! I'm going to try your suggestion. I do have a dust collection drop at the bandsaw, but all of my blast gates have clogged with sawdust and dont close all the way so the bandsaw inlet is just taped up for now so I can still collect dust when the CNC is running. at some point I'm going to replace them with the "self cleaning" blast gate type.

This weekend I sketched up my concept for an adjustable camber mold! it's designed to sit right on the table I'm using, and allows quick camber changes by inserting the correct sized "ribs" in the racks that go lengthwise. The basis of material is 3/4" sheet wood or mdf. The tip and tail molds are held in place with threaded rod and there's going to be holes spaced every 50mm down the length, and five holes spaced 10mm at the tail, allowing any length in 1cm steps . The tip and tail molds will still need to be created for each ski / board style, but I'm hoping this will cut down tremendously on the amount of mold making to create various camber/rocker / length boards and skis for my friends & I. here's the sketches:

Assembly drawing with parts list. Part 22 and 23 are mcmaster carr part #s, one's a washer and one's a nylock nut:
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The dimension for each rib is just how far it sticks out the top of the base - so add 12.7 to each for the full height of it..

Base "rack" detail:
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The radius in the bottom of each slot is just because the CNC won't be able to cut a 90 degree inside angle so it allows room for the bit to create a flat surface for the rib to sit on.

Jonrezz
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Re: Jonrezz’s Build Log

Post by Jonrezz »

Was also contemplating this idea instead since it’s more simple, more smooth so less wear on the silicone sheet, and would not require thicker aluminum over the top to smooth out the ribs in the last design - which I’m not really sure what thickness that’d be to get a smooth but flexible enough cover for that

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The only drawback I can think of for this is I’d need a new camber mold if I wanted to do a different setup like how some snowboards have rocker in the middle - as opposed to replacing some ribs in the last idea. Also I’d need to redo the camber mold if I decide to add bottom heating since this design has exaggerated camber for top only heat.

Jonrezz
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Re: Jonrezz’s Build Log

Post by Jonrezz »

Decided to go with a second version of the first idea above where the rack collapses on itself, this way no extra prongs stick into the silicone sheet. here's the assembly:

https://i.imgur.com/FKBA4at.mp4

some progress I made today:

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and here's a timelapse of the CNC goin at it:

https://www.youtube.com/watch?v=4js66HuEXL4

Jonrezz
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Re: Jonrezz’s Build Log

Post by Jonrezz »

here she is! length is adjustable by removing the camber ribs and sliding the base of the mold in and out, and the camber is adjustable by replacing the camber ribs with different height pieces:

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time to get the first non-test pair of skis prepped for layup! 8)

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chrismp
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Re: Jonrezz’s Build Log

Post by chrismp »

I really like that mold design! You might want to do a bigger round over on the tip/tail mold pieces to put a little less stress on the vacuum membrane.

Jonrezz
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Re: Jonrezz’s Build Log

Post by Jonrezz »

Thanks!

Yeah, I'm probably playing with fire there. especially with my silpoxy patch near the tip block lol

the other thing is I want to close the gaps between the tip and tail pieces to avoid another scenario like my test run where epoxy pooled in there and burnt the membrane. I'm thinking maybe a simple piece of mdf as a "skirt" that comes off the front and back at an angle. could kill two birds with one stone.

one thing I'd also be curious about, does anyone protect their vacuum mold pieces with some sort of epoxy resistant coating? I read online that packaging tape and plastic works, maybe I should just wrap the whole mold in plastic? if epoxy does spill off the aluminum sheet I'd hate for it to epoxy my mold components together. wondering if there's something I can like dip each piece in and the resulting coat won't bond to the epoxy? should I wax all of my pieces with mold release or something?

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Dr. Delam
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Re: Jonrezz’s Build Log

Post by Dr. Delam »

When attaching your edges, put both on at the same time. This will keep them under equal tension and symmetrical.

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