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General Aircraft: Tips & Techniques
Discussions on specific A/C building techniques.
Canopy - sprue connection fix
slodder
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North Carolina, United States
Joined: February 22, 2002
KitMaker: 11,718 posts
AeroScale: 305 posts
Posted: Saturday, October 11, 2008 - 10:24 AM UTC
Ok, first off - I've looked through the features, and done a site search and came up pretty dry.
My question is how do you fix that little spot where the sprue connected to the canopy and you have a 'dot' that doesn't look close to transparent. I can't rely on the canopy frame to 'paint' over it; it's an F16 bubble canopy. No hiding it.

My 1st thoughts are to use a really fine grit sand paper/stick and sand as much down as possible. Then use a drop or two of future to fill it in.
I'm curious if this is the right direction or not??? Help please - thanks in advance.
alpha_tango
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Germany
Joined: September 07, 2005
KitMaker: 5,609 posts
AeroScale: 5,231 posts
Posted: Saturday, October 11, 2008 - 10:56 AM UTC
Hi Scott

I am not sure if i understand your problem the right way, so please forgive my if I get a little too basic.

Clear sprues are much more brittle than the coloured so it is best to cut the parts off the sprue with a razor saw ... at least do not cut close to the part. if you have those fine cracks in the clear part there is no way to get rid of them! I clean the area with a scalpel until I think it is flush (cutting and scraping). Some sanding is also possible. All manufacturers I came across so far put the sprue attachments in an area that is later painted. So here I am probably missing your point.

When you have mold seams like on F-16 canopies it is best to remove it (some scrape it with a scalpel and sand then others sand immediately) an the polish it out with a polishing set (e.g. the Master Caster set is very nice, also Micro Mesh is good) .. if you do it right you get to an absolute perfect finish this way. Some like to give it a dip in Klear/Future for the final touch .. IMO it just looks better that way (clearer and thinner), even a perfect canopy from the kit does.

all the best

Steffen
slodder
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North Carolina, United States
Joined: February 22, 2002
KitMaker: 11,718 posts
AeroScale: 305 posts
Posted: Saturday, October 11, 2008 - 02:50 PM UTC
No problem on the questions for clarification.

This time its a small one piece canopy by Hasagawa - Egg Planes to be exact. The canopy is about 1inch long and .5 inches wide. The canopy was connected right at the front tip with a very short sprue stub. I did cut it with a razor saw but was unable to leave no damage. I tried to shave it down with a new hobby blade but the plastic was sooo brittle it just crumbled when I shaved it down. There is a small 2mm round 'hole' about .5mm deep where the sprue was. If it were body panels I would putty it and be done. But it's clear canopy, So I thought I'd ask how you guys who build AC do it.

Thanks again.
TedMamere
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Moselle, France
Joined: May 15, 2005
KitMaker: 5,653 posts
AeroScale: 4,347 posts
Posted: Saturday, October 11, 2008 - 06:18 PM UTC
Hi Scott,

You could ask for a replacement part if it is really too bad. Another thing that may work is Clear Fix from Humbrol.



It's some kind of thick glue/varnish that remains transparent when dry. Maybe you could tone down the damaged area with it a bit but I'm afraid the spot won't disapear completely...

Jean-Luc
alpha_tango
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Germany
Joined: September 07, 2005
KitMaker: 5,609 posts
AeroScale: 5,231 posts
Posted: Saturday, October 11, 2008 - 07:57 PM UTC
Hello Scott

I am with Jean-Luc, I do not think you can totally fix it.

You might try to clean the area (maby drill a hole and fill it with clear sprue.

I have tried this on a wing tip light (it was pretty large): Heat the sprue until it starts to get glossy/liquify. Avoid soot i.e. it must stay clear. Then press it into the hole. Cut, sand, polish, ..... even if everything goes well you will still see the circle of the hole

sorry no better idea

all the best

Steffen
PlaneOldMe
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Northern Ireland, United Kingdom
Joined: September 26, 2005
KitMaker: 31 posts
AeroScale: 4 posts
Posted: Saturday, October 11, 2008 - 11:16 PM UTC
Hi Scott,
This wont help fix your problem with the canopy, but it's the technique i used for removing the clear parts from the sprue. I never cut the sprue with a razor saw or snips, this has always left fine fractures in the parts. I heat an old number 11 blade in a candle and melt the clear part away from the sprue. This means there virtually no force applied to the plastic when removing it and you dont get the fractures. I then put masking tape over the canopy leaving only the bit that needs cleaned up unprotected. You can then sand this down with out risk of damage to the canopy hood.
Hope this helps for next time
Dean
slodder
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North Carolina, United States
Joined: February 22, 2002
KitMaker: 11,718 posts
AeroScale: 305 posts
Posted: Sunday, October 12, 2008 - 12:22 AM UTC
Thanks guys, I appreciate the feedback.
I think I can try most in succession, try the glue trick, then if that doesn't work try the hole trick, then if that doesn't work get a replacement and use the melt it off trick (Great tip by the way - thanks).

Thanks