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Old Mar 12, 2013, 12:20 PM
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Knoll53's Avatar
United States, CA, Marina
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It's the microballoons that hurts epoxy. My new epoxy from US Composites is amazing. I put a chunk in a vice and could not break it.

The PU glue is a little more brittle than epoxy, but is perfectly matched to foam.

Kent
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Old Mar 12, 2013, 05:36 PM
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Vancouver, Canada
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PU is good stuff.

When nothing but thickened epoxy will do I use West 404. We used it a lot when I worked in a full scale repair shop.

For RC it is the cats meow.

http://www.westsystem.com/ss/404-high-density-filler



Tony
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Old Mar 15, 2013, 07:23 AM
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Brazil, MG, Belo Horizonte
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Quote:
Originally Posted by Knoll53 View Post
It's the microballoons that hurts epoxy. My new epoxy from US Composites is amazing. I put a chunk in a vice and could not break it.

The PU glue is a little more brittle than epoxy, but is perfectly matched to foam.

Kent
Hello,

For a very resilient epoxi you have to add cotton flocks, it makes the polymer matrix elastic...
Microbaloons are good for light weight gap filling, just that.

André
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Old Mar 15, 2013, 09:31 AM
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United States, VA, Alexandria
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Here is westsystems products guide. Download the pdf's; they have the best uses for each of the fillers and epoxies. http://www.westsystem.com/ss/how-to-publications-2/
Their 404 filler is the best for strength. Chopped glass is probably stronger and carried by some other suppliers.
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Old Mar 16, 2013, 11:01 AM
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Well I think I have the plan for the built up version finished, baring a little clean up for printing. Would welcome any comments.
I have deliberately left off any reference to installation of rc gear and electrics to allow moving and fitting as required.

Martin
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Old Mar 16, 2013, 12:08 PM
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Wow, nice drawings....you've been busy.

I prefer strong wings over light wings so my suggestions would be to use spruce instead of basswood for spar caps, increase the size of the center joiners and make them out of solid spruce and wrap all joiners with kevlar cord or similar.

Kent
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Old Mar 17, 2013, 02:06 PM
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Thanks for the comments Kent.
I think for the type of flying I have in mind with this one the spar will be OK, though I may use spruce- I have bass in stock which is why it's specified. Combined with 3/32 skins and maybe glass finish it should be enough. I will add balsa webs between the spars as well. I am also intending to bind the spar around the joiner areas.

Now to print off some ribs.

Martin
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Old Mar 17, 2013, 02:36 PM
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I can't say until I fly it, but my hunch is that there is something about this plane that just may spur you on to fly it faster than normal....or maybe that's just me. I know some RES pilots that probably never fly over 1 1/2 Gs. Then never do loops and limit there speed to just faster than best glide.

Although I'll probably never DS this wing, I am planning on a fast pull out from a terminal dive.

BTW, by the time you are ready for your maiden flight, I'll have the CG confirmed by flight testing.......good timing on your part.

Kent
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Old Mar 17, 2013, 03:02 PM
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I knew I was missing something on the plan!
Ribs are nearly done so I'm really going to have to clear out the workshop now. Temperature's on the up too so hopefully I can start end of month when I'm on holiday- in-between all the home jobs my good lady has listed.

Martin
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Old Mar 17, 2013, 05:32 PM
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PU as quick filler

As far as set-backs go, I had a good one today.

While final sanding of the foam cores, I had set up a spot light at a low angle to the work surface in order to highlight bumps and dips. Minutes later....I smelled something. The hot spot light 6" away from the LE had melted a sizable chunk of the foam wing ( and bed ). The CF fabric at the LE was unaffected so there was a well defined void. I was hell bent on laying up the top skin of the wing today, so a fast curing filler was needed. PU glue to the rescue.

Applied masking tape to the surrounding area, mixed up a tiny amount of PU and maybe 4 drops of water, mixed for 30 seconds and painted a thin layer over the melted foam. By the time that I had cleaned up and grabbed the camera, it had already started to expand. Maybe 90 seconds. Piccies show time lapse of repair to sanded patch and ready to cover.

Top skin is on and in the oven.

Kent
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Old Mar 18, 2013, 09:57 AM
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Top skin is cured and out of the bag. That is one solid wing.

Surprised by the print through of the CF reinforcement at the yellow paint. This paint was laid on in many layers until it was thick. It was completely opaque when held up to the sun, but when epoxy is applied, it's a different story. Maybe a primer in addition to the paint would help cover.

Kent
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Old Mar 18, 2013, 11:26 AM
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Print through or not,that is a bonny wing.Can you just give a quick rundown on the steps prior to painting(prep of the mylars)This inside out painting thing takes some getting used to.The primer coats go on last?
Stuart
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Old Mar 18, 2013, 11:54 AM
Herk
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Quote:
Originally Posted by Knoll53 View Post
Top skin is cured and out of the bag. That is one solid wing.

Surprised by the print through of the CF reinforcement at the yellow paint. This paint was laid on in many layers until it was thick. It was completely opaque when held up to the sun, but when epoxy is applied, it's a different story. Maybe a primer in addition to the paint would help cover.

Kent
Hi Kent, I think that the standard treatment for light colors (like yellow) and also for the fluorescents is to have a white underlayer.
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Old Mar 18, 2013, 02:09 PM
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Yeah, as Herk says you want to over spray the primary colour on the mylar with white, gloss is good for that.

If you want a deeper surface colour with less pop do the over spray with silver.

Nice wing BTW.


Tony
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Old Mar 18, 2013, 09:38 PM
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Cutting out surfaces.

Quote:
Originally Posted by Stupot46 View Post
Print through or not,that is a bonny wing.
My wing is Boney?.......like Leggy???

Oh BONNY....OH OH yea. RIGHT ! It's a bonny wing mate!

Yes Stuart, mylars are waxed then painted. Yes all backwards. It should all be in the log. Better yet, get your hands on Phil Barnes video "vacuum bagging made easy". It's a must for newbies. This wing is like my 2nd or 3rd try after getting the video.

I'll use light colored paint backing next time.....I'm beginning to think that this wing has a paint job in it's future, but for now it's almost time to fly!

Cut out the flap with a snap off blade knife. WHAT A BEATING ! I used way too heavy of a cloth and foolishly let the CF cloth overlap the flaps. It's like working on a surfboard. Maybe 2 hours to cut out and file the hinge. The foam edge took a beating, but can be fixed later (time to fly) I'll leave the kevlar hinge a little stiff for now....don't want to file all the way through.

Very happy with this hinge. Clean, straight, sealed....will only loosen up in time.

Kent


Plank 2.5 Flap (0 min 0 sec)
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