HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Nov 08, 2012, 01:13 PM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
5,731 Posts
Well I did a bit of a rush job last night as I had some spare time, and tried a fuse.

What an eventful night!

Highlight had to the the compressor blowing up (literally!!!) and smoking out the garage and cutting the power to the whole house.

So bladder didn't really do its job. Seams have not pushed flat as well as you would like, and the fin hasn't joined at all, but that was because I forgot to splooge it around the edges after the lay-up! DOH!

Also fuse stuck in the molds a little, left paint behind in areas.

Moral: Do not rush these things! But I knew this one was going to be a "throw away learning exercise" whhich it certainly was.

I am now going to to put the regulator on the "blow" side of the vac pump to get pressure for future bladders.
ALEX HEWSON is offline Find More Posts by ALEX HEWSON
RCG Plus Member
Reply With Quote
Sign up now
to remove ads between posts
Old Nov 08, 2012, 05:38 PM
R.I.P
josh18's Avatar
Australia, QLD, Toowoomba
Joined Jan 2010
3,584 Posts
Nice one Alex, at least youve got your first one out of the way. I find fuses are the most stressfull part of a build by far, as there are so many steps to be done right first time in such a short time frame. If you havn't already, try some slow hardener, I find it just lets you take your time that little bit more.
josh18 is offline Find More Posts by josh18
Reply With Quote
Old Nov 08, 2012, 05:56 PM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
5,731 Posts
I used slow hardener. Probably didn't help that it was 28 degrees C in the garage lol

Mixed up three lots of resin
ALEX HEWSON is offline Find More Posts by ALEX HEWSON
RCG Plus Member
Reply With Quote
Old Nov 08, 2012, 06:16 PM
AvB
Wind, hill, ... I'm keen ...
AvB's Avatar
Australia, QLD, Woody Point
Joined Nov 2006
4,697 Posts
Alex, well done. Sounds like the average effort in the shed for me.

The Germans have a saying "you need to do it 3 times to get it right". Keep going!
AvB is online now Find More Posts by AvB
Reply With Quote
Old Nov 08, 2012, 08:23 PM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
5,731 Posts
I want to try PU in the tail of the next one
ALEX HEWSON is offline Find More Posts by ALEX HEWSON
RCG Plus Member
Reply With Quote
Old Nov 08, 2012, 10:50 PM
Twisted and Confused
flyonline's Avatar
Joined May 2003
4,353 Posts
Alex

I'm using an el cheapo compressor and I can get the pressure down low enough for a non-reinforced mold layup @ ~10psi.

Might be worth investing $100 as they're useful for other things too

Good luck ahead, I've been down that road and have been tempted to re-kit a mold at times from frustration!!! Getting it right though and a tight seam is well worth the effort.

Steve
flyonline is offline Find More Posts by flyonline
Reply With Quote
Old Nov 09, 2012, 02:33 AM
Where is the inspiration
wdeighton's Avatar
Moira
Joined Feb 2006
831 Posts
I picked up what could be a top tip the other day at a composite expo.
When laying up resin, let the resin start to go green before winding up the pressure / vacuum. go for about half an atmosphere to start, keep some resin in a tub on the side. When this starts going green wind the pressure up to the max. it improves the consolidation of the resin and stops getting all the little air holes.
wdeighton is offline Find More Posts by wdeighton
Reply With Quote
Old Nov 09, 2012, 02:57 AM
AvB
Wind, hill, ... I'm keen ...
AvB's Avatar
Australia, QLD, Woody Point
Joined Nov 2006
4,697 Posts
For light fuses I'm the opposite ... I want to crank the pressure up early while the epoxy is still runny, to squeeze as much excess out as possible. As long as you have cloth overlap covering the mould join all around, the bag won't pop and leak.
AvB is online now Find More Posts by AvB
Reply With Quote
Old Nov 09, 2012, 05:41 AM
R.I.P
josh18's Avatar
Australia, QLD, Toowoomba
Joined Jan 2010
3,584 Posts
Thats what I thought too. I reckon unless you're really good, most layups will be pretty green by the time you close the moulds anyway. Andrew, do you run a bead of splooge around your seam before closing the mould?
Cheers
Josh
josh18 is offline Find More Posts by josh18
Reply With Quote
Old Nov 09, 2012, 06:46 AM
AvB
Wind, hill, ... I'm keen ...
AvB's Avatar
Australia, QLD, Woody Point
Joined Nov 2006
4,697 Posts
Josh, I "covered that" in my enormous long post on the previous page - haha! I write so much stuff it's overload and people can't take it all in!

No I don't use any splooge. Basically, as long as the bag is big enough, and doesn't have any leaks itself, it won't leak at all if there are no gaps for it to have an aneurysm and blow/pop into the gap. Splooge can just get pushed thru a small gap easier than the plastic bag, so it won't prevent the pop. But any amount of cloth overlap covering every bit of the mould join will completely prevent any popping. A common place to pop is the nose tip because it's hard to get the overlap right there. So I cut a circle of floppy satin cloth and wrap it over the tip of the bladder, like a small parachute, so that as you inflate it, it pushes the cloth into the nose tip and seals off any gaps.

Adam (Wyowindworks) has moulds that are so absolutely perfect and tight sealing, that he can pump up to 60psi. I've gone up to 30 but generally it's overkill.

At the end when putting the bladder in, If I have some epoxy going sticky, I'll dab it here and there on the bladder to help tack it down to itself while I join the mould.

When you say layups will be green by the time you close up ... keep persevering. I was like that but honestly even with my klutzy pfaffing absent minded old fart behaviour, I've got it quite fast now. The things that helped me most were working out a pattern of cloth pieces that fit together like a jigsaw in the mould (overlapping of course) then making good templates for them from thin MDF. It's not as easy as it sound and I'm onto Templates Mark 3 now. Do the mould release and do the cutting of all the cloth pieces, strips of tow etc, and lay them out in piles (top half and bottom half) and have every piece cut and ready before you start.

I cheat by laminating a layer of glass over a layer of Kevlar stuck together with a light misting of Super 77. I then treat it like one cloth. I use all the MDF templates to mark the shapes on the glass side with a pencil according to the pattern. Depending on the required weight/ strength, each shapes gets marked out one, two or three times. Some with overlap, some without. Then cut them out and set them out in piles ready to go.

Once you've done it with exactly the same shapes a few times you get quicker. I've been rather surprised how quickly I got the latest ones done. But the Scratcho doesn't have a fin built into the fuz ... that probably helps.

Oh, and remember just before you close the mould to have a look back where you had the cloth bits ready! More than once I've thought I was finished and closed up and there were bits still waiting ... !
AvB is online now Find More Posts by AvB
Last edited by AvB; Nov 09, 2012 at 06:52 AM.
Reply With Quote
Old Nov 09, 2012, 03:26 PM
PB of 733kph
ALEX HEWSON's Avatar
Christchurch, New Zealand
Joined Jul 2005
5,731 Posts
Great advice guys! thanks a heap!
ALEX HEWSON is offline Find More Posts by ALEX HEWSON
RCG Plus Member
Reply With Quote
Old Nov 09, 2012, 05:01 PM
R.I.P
josh18's Avatar
Australia, QLD, Toowoomba
Joined Jan 2010
3,584 Posts
Thanks Andrew, I have basically tought myself to go the same way as you, with templates and laminating multiple layers at a time then cutting them out. I spend a fair bit of time on the first layer, usually one veil and one six oz cloth, making sure all air bublles are stippled out with a paint brush, especially around the tail area as my bladder doesn't go up there. I think because my layups are so thick and I dont stagger my seam like Adam for wyo there is sometimes too much of a step in the seam to always get a perfect seam. For my next part Im going to run a bead of splooge right around just to make sure ther are no voids.
Chees fellas!
josh18 is offline Find More Posts by josh18
Reply With Quote
Old Nov 09, 2012, 05:30 PM
AvB
Wind, hill, ... I'm keen ...
AvB's Avatar
Australia, QLD, Woody Point
Joined Nov 2006
4,697 Posts
I've given up on the veil as I don't think it does anything, and being so fine it can wrinkle up etc. I use 130gm satin which is quite dense glass but able to slide around shapes a bit. I think thick cloths are a problem as they don't want to follow curves, and multiple layers of thinner cloths work around better. I don't understand what you mean about the seam - not staggering it??
AvB is online now Find More Posts by AvB
Reply With Quote
Old Nov 09, 2012, 05:42 PM
R.I.P
josh18's Avatar
Australia, QLD, Toowoomba
Joined Jan 2010
3,584 Posts
No veil? I always get print through without it. What I call veil is 2oz glass though ,which is not really a veil cloth but works well enough. As for staggering, Adam lays one layer with the seam full at protrusion and each subsequent layer the seam sticks out a little less. This is mirrored in the other mould half and the seam sort of locks together and makes for a nicer seam. Ive never done it because it sounds like a lot of extra work.
I dont think Id have any seam issues if I could pump the bladder up more but by design it is unsupported because I have the tail spar and pins in the mould so the most I dare to pump up to is 10psi or so.
Im so glad there is this network of builders we've got going on here as there are so many different ways to do things and you could never learn them all on your own!
josh18 is offline Find More Posts by josh18
Reply With Quote
Old Nov 09, 2012, 06:31 PM
AvB
Wind, hill, ... I'm keen ...
AvB's Avatar
Australia, QLD, Woody Point
Joined Nov 2006
4,697 Posts
Ah I understand. I don't stagger it ... can't see why you'd bother unless you're worried about someone criticising the internal seam! If I'm using 4 layers I'd put overlaps on the first 2, then not the next 2. Also I used to really try to get the non-overlap side's edge really close up to the corner, but now I leave it a mm or so shy of the corner because it saves so much fiddling around removing those annoying strands that stick out, and which can get caught in the flange. If the overlap is say 8mm then it's gonna cover the whole thing anyway.

To avoid klutz mistakes I have a rule that I sit both mould halves with noses pointing left, and both have the overlap sticking up on the far side, which works. Yes I have done one and found that both overlaps were on the same side!!

It's a shame that you have to keep the pressure down because of the fin. You can squish it so well with pressure.
AvB is online now Find More Posts by AvB
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion 10 in1 servo tester (professional servo tester) flydreamrc Radios 21 Jul 17, 2012 02:50 AM
Alert RT Models Beaver Pre-release build St. Martin Scale Kit/Scratch Built 86 Jun 29, 2008 05:01 PM
Build Log kin'Brilliant Build Pics (PU-RT) wdeighton Slope 30 Mar 18, 2008 03:38 AM
Discussion RT Models MIG-15 Build AeroDude Electric Ducted Fan Jet Talk 34 Mar 02, 2008 05:49 PM
Discussion RT Mig 15 Build nut Electric Ducted Fan Jet Talk 8 Jul 30, 2007 01:17 PM