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Post by sf2 on Jul 17, 2008 16:54:16 GMT 10
As part of my annual clean out I found some old(very old , was a kid when I last saw them)plans of a balsa plane that had a solid hand carved wing(the real meaning of the word plank).So looking at it I figured I'd make a mouldie type out of it with fibre glass and carbon(well for the fuse anyway).With the advent of new materials and ideas and wing sections I thought I'd give it a go. Sadly two days ago I ripped all the tendons around my knee so will need some recovery time(off my feet apparently). So thus far, Aplug out of balsa and covered with fibre glass. URL=http://imageshack.us]  [/URL] [URL=http://g.imageshack.us/g.php?h=389&i=dscf0823kr9. |
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Post by sf2 on Jul 17, 2008 17:00:07 GMT 10
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Post by sf2 on Jul 17, 2008 17:06:44 GMT 10
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Post by sf2 on Jul 17, 2008 17:08:23 GMT 10
when I can drive again(ie when my knee bends) I'll whip up to FGI and gt the stuff i need.
If you click on the photos and go someplace strange sorry, still not quite sure how to get pics in properly yet, even tho I've been shown how.
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Post by sean on Jul 17, 2008 17:45:45 GMT 10
Looks great D1ckon, looking forward to seeing it progress  . Sorry to hear about your surfing injury! |
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Post by sf2 on Jul 25, 2008 17:26:49 GMT 10
ok I'm off to Fgi to get some gear, the missus feels sorry for me and will drive me, so long as I don't spend to much time standing up she's ok with the building  . She's at work during the day so i can do lots(teehee)  |
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Post by sf2 on Jul 29, 2008 16:22:03 GMT 10
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Post by sf2 on Jul 29, 2008 16:50:28 GMT 10
Having spoken to the guy in the shop, he suggested 1.5% hardner for the gel coat, so using 250ml I used about 3ml of hardner. This actually set the gel off a lot faster than I thought, and I wasn't really prepared for that.(oh yes don't brush when it starts to gel, it's a mess )
Subsequently maybe 1% would be better. Obviously the better you do the gel coat the better the fibre glass will be. Also not not knowing what sort of matt(chopped) I needed , again I went with the guys suggestion of 6oz. This I think was to heavy and somthing a bit lighter in varying layers might of sufficed.
To help with the glassing I used some car filler bog to ease (?) the sharp corners on the side of the fuse and partition board.
Getting the air bubbles out was a drama mostly I think cos of the poor gel coat application, and I'm not sure if the fibre glass stuck to the gel in several spots.(we'll see)
Using a vinyester resin & having suffered fast setting gel i then used less hardner, I used a litre to do the matt and used 3/4% hardner, figuring the heavy matt would need some encouragement to soak up the resin.It seems to have set well enough but will see how it looks tomorrow.
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Post by sf2 on Jul 29, 2008 21:08:52 GMT 10
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Post by sf2 on Jul 30, 2008 11:52:23 GMT 10
well the process worked ok, the mould came away from the plug and looked good, until I turned it over. About 99.9% of the mould was ok, but where I hadn't brushed the gel well enough onto the plug, it had a few wrinkles, so the initial mould has to be scotched, binned, chucked etc. will post pics when camera charges up
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Post by sf2 on Jul 30, 2008 11:59:17 GMT 10
oh yes and having looked at the quality of the mould I thought I'd done ok, but a turn in the light showed some very minor defects  . Things like the line I drew for a centre line to lione it up in the seperation board took the gloss off the plug, hence the shading on the gel was different. A couple of areas on the plug which I couldn't feel showed very slight cloth pattern, this came out on the mould to . I guess you could give the mould a sand down with really fine wet and dry tho. A finger print also appeared from some place  , so when the plug is ready to go into the seperation board use a cloth or cloth gloves and dont touch it again till the gel has set on it. |
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Post by jirvin4505 on Jul 30, 2008 12:28:21 GMT 10
well the process worked ok, the mould came away from the plug and looked good, until I turned it over. About 99.9% of the mould was ok, but where I hadn't brushed the gel well enough onto the plug, it had a few wrinkles, so the initial mould has to be scotched, binned, chucked etc. will post pics when camera charges up Don't bin it yet. Depending on your requirements the mould sounds very repairable. I have previously used polyester (in the dark ages) to make moulds. A little repair here and there with car bog - some sanding with wet and dry and then a polish with cutting compound covers a lot of defects ;D If you are painting the model after moulding then your base mould can have plenty of blemish's. Are you following any moulding threads to do this - the advice you got from the shop on cloth use was  . Takes me back to when i was first building molds - wasted a lot of money in glass shops untill I found some modelers doing molds and then i was on my way. cheers Jeff When using polyester I build up the first layers with glass tissue (looks like very fine chop strand mat) and then go with the next heaviest stuff after the 3-4 layers of tissue have set. |
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Post by jirvin4505 on Jul 30, 2008 12:42:17 GMT 10
I see you have TR wax - how did you get the PVA onto it? Brush - spray?
I have TR but only use it with epoxy layups when I don't want to use PVA - usually a painted in the mould finish.
I often have trouble with it when it comes to getting a nice fisheye free coat of PVA onto it - you have done well to use it. I have resorted to Caera wax when PVA is being used.
JOKE...How do you know you are getting good advice from a fibreglass shop? You end up with 5 different brands of wax sitting getting old on the shelf.
You remake a mould 4 times due to worms in the gel coat (wrong gel coat / wrong mix ratio) - I must have been keen and determined once!
You make a mould out of polyester - then it twists and warps so that it is unusable after a year or so... I could go on - However I do enjoy moulding.
Keep pluggin' away there - you are onto a good thing. I haven't flown a balsa model for nearly 20 years - all foam and fibreglass- most out of my out of my own moulds.
cheers jeff
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Post by sf2 on Jul 30, 2008 18:11:49 GMT 10
the plan was to paint in the mould, but however it best works out at this stage. Yes followed several(jarts etc and Steve W is helping from rc groups), nobody ever mentions weights ratio's etc, so I'mkinda on my own, per instances I didn't even know there was such a thing as glass tissue( but now I do). The first attempt at the PVA was ok, but cos the mould wasn't so good I'm having another go, and now I've got runs in the pva so will probably have to take it off(Any Bright Ideas) Keep pluggin' away there - you are onto a good thing. I haven't flown a balsa model for nearly 20 years - all foam and fibreglass- most out of my out of my own moulds.
little pun there, haha ;D , any way here the pics  |
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Post by sf2 on Jul 30, 2008 18:28:02 GMT 10
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. Sorry to hear about your surfing injury!
. She's at work during the day so i can do lots(teehee) 
[/URL]
. Things like the line I drew for a centre line to lione it up in the seperation board took the gloss off the plug, hence the shading on the gel was different. A couple of areas on the plug which I couldn't feel showed very slight cloth pattern, this came out on the mould to 
, so when the plug is ready to go into the seperation board use a cloth or cloth gloves and dont touch it again till the gel has set on it. 
. Takes me back to when i was first building molds - wasted a lot of money in glass shops untill I found some modelers doing molds and then i was on my way.
