I have some of that stretchlon 200 as well, may try it. I think the standard film can make the curves just fine I just lost vacuum pressure while the epoxy was setting.
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Also from @DerelictRobot these 4p 21700 PCBs, only because I had the space for them. As recommended, they were spot welded and soldered to the nickel strip. The substrate on the PCB is pretty thin so I spot welded them about 10 times per side to make sure the nickel was held to it in many locations and tightly bent against it. My malectrics spot welder was set to half of what I normally weld 0.2 nickel to cells at
For a flexy pack, I also like that these take the connection points off the nickel. Depending on how much flex exists, the moving series connections will transfer some of that flex to the nickel to cell connection, and this eliminates that. To finish them off ill add a touch of glue under the edge of the PCB essentially locking the cell, nickel, pcb into one unit. Theyāre pretty cheap so buy yourself an extra to practice on and get a tear test done with the nickel youāre using
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Itās a tight fit for sure! This damn heatsink made this all a lot more difficult
Now that the last battery section has been poured with urethane the next step is to figure out how Iām handling the tail section where the wires will come through to the rear motors. Likely going to cut some of the MK3 channels back.
Then Iāll paint the enclosure with a textured bed liner
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I very much admire how you got that heat sink so nicely in place. Whatās the total weight of the board?
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Dunno yet on the weight. Iāve only added about 1 lb with all of the rubber inserts but tbh, I forgot to weigh out items before and after.
Iāll get a total weight when itās built and will be able to compare it to original components.
The heat sink is honestly the source of most of the issues. The height it added caused problems, locating it was difficult with 12S etc.
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Whatās the depth of your enclosure?
Edit: if you still have the part you cut out, may be you could get rid of the heat sink if it causes too many problems?
Oh no, everythingās being built to work out. Itās been a lot of fun working through these problems and not limiting myself on solutions. A lot of time, sweat and money has gone into this but Iām excited to see the finished product.
I couldāve cheated with a thick gasket and used a D140 and gotten away with it I think. Still wouldāve been tough with the heatsink.
Getting some ideas about motor phase wire routing. Too much length on the maytech motor sensor wires so Iāll shorten them
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I see a build of the year contender here!
I always look forward to that battle, specially with this much love for the builds this year!
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Figuring out if I can mold MR60s into a tail gasket to seal off these channels. This would have the motor phase wires plugging in from the outside, although the distance is really short so they may have a tendency to get tugged out
May have to just stick with bullet connectors
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I would epoxy male (with pins, not holes) MR60 in there.
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Itās gonna be a tough area to form and pour this urethane or epoxy too because itās pretty runny. Might get some of the brushable stuff they sell which is much thicker. Donāt really wanna make a whole mold for this and then glue it in.
Thereās a rate of return on all of these products thatās rapidly diminishing. Like a $40 bottle of urethane to make the gasket is getting excessive. 
Iām also considering fiberglassing an end cap with the MR60 plugs sticking through for a lot less effort and cost then making a big urethane plug for the tail.
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Making plans to keep approval from @b264
Rather than a whole rubber plug, Iām going to fiberglass an end cap on the tail cable channel which Iāve cut down quite a bit now.
Worth going to a GX12 or something similar for sensor wires or should I stick with a grommet for those? Iāve seen the haggy plugs, but the overall connection gets pretty long
lol hopefully the finished product is straighter
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Iāve been following this with great interest Bwah! There are many new techniques that I havenāt seen anyone do before here, potting the batteries with urethane, fucking genius! Looking to essentially build something very similar with the Sportster and this has been an extremely valuable writeup <3
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Mistakes were madeā¦humbled update
After waiting for new fiberglass materials, I was able to get a good layup of fiberglass reinforcement for the bottom. I used 4oz cloth from the ends into under the foot areas and covered the entire bottom with two layers of 2oz over all of that. Dried perfectly, trimmed it up, and got ready to layup the final top layerā¦
Then I decided to bolt it to the trucks and do a little flex test to see how much the flex had changed after the FG. Bounce bounce everything feels good and thereās a noticeable addition to rigidity but the board feels good still. I stepped off the board, mulled around for a bit, and came back to it. This time recalling that I had bounced on the deck once and the center touched the floor. Someone posted a video of the Sportster doing this as well. I gave it a light bounce to get an idea of what it would take and i bounced with both feet dead center of the boardā¦ an audible POP! let loose from beneath my feet. As the sound faded it became a chilling rush down my spine that sent icicle daggers into my soulā¦
In hindsight, i think the guy that did just this on his Sportster was on 90mm wheels. Thinking back, I might have done it with 110s, or it may have just been sitting on top of two wheels on their sides. This time, im on 110s and adjustable TKPs that add 13mm ā so essentially the effective diameter of 136mm wheels. WTF was I thinking. It would never have flexed like this in real life, especially once the enclosure and final top layer were attached. Regardless, I sort of didnāt expect it to fail.
The fiberglass layer on the bottom split from one edge to 25% of the way through at the bottom of the flex. This was dead center on the deck under my feet. The reinforcement layers around the edge and below the FG there cracked. At this point, I knew I wasnāt going to move forward with the deck and the consequences were final. I hopped again to explore the failure location and do some more investigation, it continued to split at the center. The original deck only split on one edge from the original crack, through a bolt hole and does not appear to have split the whole width.
Observations: I took a bit more off of the deck in the original cut than I had planned to but still very minimal. I also couldāve made the pocket slightly smaller. This will make aligning the pocket location within a few mm per side a little bit of a pain but worth it to reduce the pocket size. Other than the failure I caused, no layer separation or other issues.
Moving onā¦
So this was a $200 mistake. Not only did I need to buy another deck, but I also needed to buy more maple veneer from roarockit because I had run out. Insult to injury, bustin didnāt have a labor day sale so the deck cost me $20 more than the original one.
New sportster came in two days. Maybe I just havenāt seen it for some time in its original state - but the new sportster feels different this time. Definitely stiffer, the colors along the edge are different and the overall color looks different. The logo is also black now and not just laser engraved on
I contacted Bustin and asked if they would make a deck with extra layers and they said that they couldnt. I reached out to Roarockit and had a great conversation with the owner about what I was working on. He understood the challenges getting the material to meet some of the complex curves in the bustin (the evo deck was a piece of cake to get the wood conformed to), but made a few suggestions:
My technique of spraying the maple with water and vacuuming against the deck to āpreformā it was definitely helping with getting the contours tightly matched. However, he thinks that pre-wetting and drying likely contributed to some stiffening of the maple. It expands when wet and when it dries after that it becomes much more brittle. Something looking back now I observed while doing this.
He also recommended pre-cutting the panels to shape match the board before hand to reduce splitting and hopefully help with the contours. This means ill be using paper templates to trace the deck shape and then applying to the veneer and cutting out. Theyre thin, so i clamp them to the bench and cut out with a utility blade.
I was a bit defeated by this setback and in addition, my current board died and Im throwing together this falcon 36 quickly so Ive got some transporation. Bustin took the back burner for a bit.
Plans for this go around.
Similar 4 panel layup for 6mm of additional clearance. I wont be doing the FG layer between the deck and the new veneers this time because the epoxy doesnt soften the wood like titebond 3 does. I need the water based glue to get the wood to bend properly.
Since Ill be pre-cutting the veneers to shape, Ill also be cutting out the majority of the battery compartment so I wont have as much material to remove later on. For this go, Ill avoid cutting into the original deck at all - if possible.
Lastly, dont jump on the center of it - its not a vanguard
More to come in the next week or so. A few quick pictures below.
Iāll add some more of the work ive been doing to the enclosure, which has required a lot of re-work in the tail section to get the connector interface I want. Coming along good.
Iām not feeling too far from finished, but school has restarted so my free time has gone down a little
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Yeah idk what to make of this as well. I also saw the same video as you did of the person flexing the deck to the ground, but the sportster I got for my little brother is quite stiff, very comparable to my Switchblade. Wonder if theyāve changed something in the manufacturing process 
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They may have. This new deck is definitely different from the first one I had in appearance and I āfeelā like its stiffer. But hard to compare now.
I was actually pretty surprised that it cracked where it did. This was not the weakest area of the deck in theory after the cutting I did.
However, theoretically, I stiffened the ends and that may have put more of a bend point on the center. Regardless, the flex seems to have exceeded the elongation/tensile strength of the FG layer on the bottom. When that popped, things failed beneath it. Given that observation, I think I just exceeded the amount it should have flexed. Measurement currently on the wheels and TKPs to the floor is 3.25", so it was quite a bit of distortion from where it started to reach the floor, especially over 35" in length
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Extra reinforcement layers this time?
The strengthening you did wonāt have changed the fact that the highest bending load on the board is in the centre. Nearer to the trucks, loads are resisted more in shear, rather than bending. Additional strength for reinforcing layers or (as well as) thickness between the layers will help resist bending loads.
@rosco, theoretically, the extra re-inforcement should be laminated to a mostly untouched original deck. For this go, it will be 4 layers with the center pocket removed from them and the original deck will remain untouched. Thats 6mm of additional material that will only border the majority of the board but will fully cover the ends. That makes the ends stiffer and leaves the center much less affected. Ill be adding a FG reinforcement layer again to the entire bottom after the veneer layers are on top lock the whole thing together.
I think last time I removed slightly more matieral than I had intended and I flat out overstressed the deck trying to achieve too much flex.
Even after speaking with the roarockit founder, the wetting of the maple may have made those more brittle. So the FG might not have broken under tension, the reinforcement veneer may have cracked and caused the FG above it to split.
With the necessary space I need for the battery, I cant leave a reinforcement ridge down the center of the deck. Currently though, Im not planning to add more than 4 layers (6mm) unless I have to. I know going into this that ill need to get the majority of 10mm of clearance to fit the bms - hopefully the 6mm addition and a thick gasket once compressed will achieve that and I wont have to remove any of the original deck. If I do need to, ill consider an additional layer of reinforcement or a thicker gasket rather than cutting into the deck. Especially since the deck is only 12mm thick.
the newer deck is definitely much stiffer. For my weight (130lbs) it does not flex.
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Think thereās a typo there b-wah.
Assuming you are using FG or CF reinforcing, itās tensile strength you are adding and that is best placed where the tensile loads exist on the deck.
In normal use on a longboard that is the underside. (Roadside) Like on this diagram of a structural beam. 
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