Comments sought on new build: A CNC Router for RC Gliders and Planes

[njhussey]

Cheers, yes the draught excluder went on fine. I did give the rails a good clean with thinners first and they stuck to the rail like s*^t to a blanket...so to speak!

[njhussey]

Well I spoke a little too soon. I did press them all down firmly before pouring and still had a couple of leaks. As soon as the epoxy finds a leak path it lifts the draft excluder. Spent 1/2hr chasing 2 leaks...managed to stop them with some blue paper towel and masking tape. After 1/2hr the epoxy is slightly more viscous and stops running (famous last words) as much. Going to check in another 1/2hr to make sure no more is leaking out.

I used 1kg (mixed) for the rails and the gantry. I'd guess the rails are 4-5mm thick and the gantry 2-3mm. The large container (like an ice cream container) I used was ideal as the epoxy didn't get warm at all after mixing. I was quite vigorous in mixing and there were quite a few bubbles but the 7mm hole I drilled in the side of the container coupled with pouring it from about 12" high eliminated nearly all the bubbles. So if you're pouring it do it from a height so it pours in a really thin stream and it gets all the air out. Pics below.

[EddyCurrent]

Pity about the leaks, someone posted a video of using epoxy and the idea was to pour a thin layer first, this would both find and plug leaks for the final layer.
The 7mm hole works great, anyway it looks like a great job, nice and flat and clear. Remember to give it plenty of time before bolting the rails on, you don't want it compressing slighty like mine did after 3 days.
It's a great feeling when you've passed this stage of the construction, it's like getting past the foundations when building a house and the epoxy is the damp course.

[njhussey]

Pity about the leaks, someone posted a video of using epoxy and the idea was to pour a thin layer first, this would both find and plug leaks for the final layer.
The 7mm hole works great, anyway it looks like a great job, nice and flat and clear. Remember to give it plenty of time before bolting the rails on, you don't want it compressing slighty like mine did after 3 days.
It's a great feeling when you've passed this stage of the construction, it's like getting past the foundations when building a house and the epoxy is the damp course.

Given more time I'd have done it in a couple of pours and spent more time sealing and doing the moat. I'll be leaving it all week to cure (if I can curb my impatience) before doing anything more to it. I've got to cut all the linear rails to length as the X axis are 100mm too long (now wishing I'd extended the rails 100mm further forward but next time...) and the Y & Z are in one length at the moment so that will keep me busy for the next few lunchtimes.

I'm feeling like real progress has been made now the epoxy has been poured. Should be able to get it home and start working on it in the shed after the Honeymoon. I discovered that I can run my pillar drill from my inverter and shed's solar power so I'm happy with that, free (apart from the set up cost) electrickery!!

[EddyCurrent]

I knew someone who used to have batteries and DC lighting in his shed, but he just kept taking the batteries to work to recharge them.

[njhussey]

I knew someone who used to have batteries and DC lighting in his shed, but he just kept taking the batteries to work to recharge them.

That's cheating but I like his style! Just checked the epoxy and it's stopped leaking as it's now got too viscous to freely flow/run/dribble. It's a nice 24°C in the test bay so should go off nicely...

[Wobblycogs]

Nice work Neil. Would have commented sooner but for some reason I've not been getting notifications of new posts.

Glad to hear the leaks have stopped.

[njhussey]

Just realised (when checking how it was curing in my lunch break) that I have made a total and utter f**k up on the epoxy.... I've only used half the hardner that I needed to. Now considering it's pretty simple maths to halve 800g of resin to get 400g of hardner my brain decided to stop pouring the hardner at 1000g.....WTF, did I decide that I liked the look of 1000g better than 1200g, was it too early in the morning for my brain to be working (was 7am when pouring so was up and out the house for 5.30am) or was it simply that I'm fecking stupid......!!!! I know what my money's on...

So looks like I'll have to try and scrape the epoxy off and start again as it's never going to fully cure. Out of desperation I'm putting it in the drying oven of our local contract painters over night (40°C - 50°C) to see what effect that has on it, however I'm not hopeful as it's been in a building that's about 24°C for the past 2 days and has only got to the stage where you can put a nail mark in it and it'll dissapear in 10 minutes. ARGGGGGGGHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH......... ....

[charlieuk]

the epoxy will never cure unfortunately it is the wrong type of chemical reaction you are best to strip it all off now clean up the mess and start a fresh. I made a similar mistake on my first surfboard i made! you will only do it once. I make sure i always zero the scales before adding the hardener as it saves simple mistakes. The other time this can happen is if you do not mix the two parts well enuff but sounds like you know were the problem came from.

[Wobblycogs]

We need a Homer Simpson "Doh!" emoticon for just this situation.

That's a real shame as it seemed to be going so well. It's going to be an pretty awful clean up job as well I'd reckon. I hope the drying oven works but I can't believe it will, your epoxy wouldn't achieve anywhere near it's maximum hardness anyway.