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Old Feb 06, 2013, 05:33 PM
I don't like your altitude
Stupot46's Avatar
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Slow progress today,but the fin is fixed and primed.
Back to the wing next,attach the l/e and find a way to make some sanding templates to get the profile.
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Old Feb 07, 2013, 05:45 AM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
2,954 Posts
Re the tissue weight thing,I haven't found a definite answer.Nearest is this table-
http://www.modelflight.com/weight.html
Using the lt.Jap.tissue from that(I'd use a heavier one)I've come up with a rounded 21g/sqm.Check my math on that,it was never my strong point
Sanding sealer,heavier tissue,probably more dope than the table allows for,will still bring me home lighter than glass/ epoxy.
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Old Feb 07, 2013, 09:28 AM
I don't like your altitude
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I've been doing a lot of searching on the slope forum,checking out the plank builds.One thing I noticed was the use of hardwood as a leading edge.As I'm going to be saving a bit of weight with the tissue,I decided I could afford to fit some.So,using the same profile glazing bar I roughed out a pair.
To fit them I first cut back the wing beds to leave the front 60mm or so exposed,taped them at the t/e edge and laid the wing in.Clamped each span between two timbers and stood the wing vertical.A couple of packings and it was very stable.
To make sure of a good contact for the glue I wanted to use stranded tape rather than masking.To enable me to concentrate on putting pressure on the tape,and not the alignment,I drilled 5x1.5mm holes in each piece and pushed cocktail sticks through the balsa and foam.
When dry adjusted the clamps and laid the whole thing flat.
Next the coarse permagrit bar.Masking tape isn't strong enough to protect the balsa when using this so I made up a shield from thin plastic sheeting,Once the nose was some where near I changed to masking tape and finer grits.
I still need at least 3 templates to check the profile,I have an idea in mind,I'll post it if it works.
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Old Feb 08, 2013, 05:07 AM
I don't like your altitude
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Leading edges on.I couldn't make an accurate enough template,so eyeballed it .Not bad,and I managed to get a straight l/e.
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Old Feb 08, 2013, 09:32 AM
less is more
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United States, CA, Marina
Joined Sep 2006
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Looks like you'll be flying soon. Do you have a nice slope nearby?

Kent
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Old Feb 08, 2013, 12:41 PM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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Quote:
Originally Posted by Knoll53 View Post
Looks like you'll be flying soon. Do you have a nice slope nearby?

Kent
Not sure about the "soon"bit;the weather is too unpredictable....
I'm right on the edge of the Pennine hills,so no shortage of possible sites.I wasn't aware of it till the other day,but there is a flying area here-



http://www.rcgroups.com/forums/showt...ight=holm+moss
The local slope guys use it,should be excellent on the right day.A car park is also a plus!
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Old Feb 09, 2013, 04:05 PM
I don't like your altitude
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After having a discussion with a certain gent in a shed,I've decided to go with a straight painted finish.I was going to use a primer coat of thinned water based varnish thickened with micro balloons,but tried it on a sample,which promptly curved in a quite violent way,almost to a half circle.Neat varnish produced a similar result.These two were weighted to flatten overnight and painted to compare the surfaces.The thinned micro balloons one is definitely better,much fuller.
The third unpainted piece is coated with a thinned epoxy,thickened with talc.No reaction from the wood;if this dries/sands/fills the grain ok and holds a coat of paint it will form a base coat..
I don't think subjecting the sheeting to the reactions that a water based varnish induce would be a wise move.
Before that I need to give the wing a good sanding.The reflexed area at the t/e is problematic,being slightly concave.What I propose to do is take 3 sections of the wing bed from the root,centre and tip,glue each one to a flat piece of wood and use as sanding blocks.
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Old Feb 10, 2013, 01:07 PM
InceCreations
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Joined Jul 2009
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Same here.
Tried glossy spray the other day, which turned out to be water based ?
Result: curly balsa sheets ...
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Old Feb 19, 2013, 09:49 AM
I don't like your altitude
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Joined Sep 2011
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Not much time or inclination to build lately,apart from making a start on servo hatches.
One thing I have been studying is the hinge line and how to tidy it up after cutting.I came across this on the DS forum-
http://www.rcgroups.com/forums/showt...1824272&page=2 #18.A very neat solution which I am going to attempt to emulate.
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Old Feb 19, 2013, 11:07 AM
InceCreations
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Expecting a good photo report of your hinge work !
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Old Feb 19, 2013, 01:10 PM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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Quote:
Originally Posted by vincent123 View Post
Expecting a good photo report of your hinge work !
When I can find the link again I'll post pics of the hinge system,again cribbed from either slope or DS.
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Old Feb 27, 2013, 01:58 AM
I don't like your altitude
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Joined Sep 2011
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I've had no time at all for building lately,doing some house renovations for a couple of guys.
I wish I'd known about the Kevlar live hinge idea before I sheeted the wing,but I think I can retrofit some.
I'm already planning on inserting a 9mm sq balsa strip at the hinge line,red hatched in the sketch.I found some 14mm x 300gms braided tape(45*)and was thinking about installing it with the balsa(green line)
If I slightly recess the balsa where the Kevlar fits at the sides it should make a good bond.
What do you think?
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Old Feb 27, 2013, 03:42 AM
Deniable plausibility
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Derbyshire, UK
Joined Aug 2008
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Looks like a lot of work you don't need to do. Cut the control surfaces away, face them with resin and micro balloons and make a silicon sealent hinge. Job done.

BTW when facing the wing / control surface, bevel the back of the wing NOT the front of the elevon. That way, when the elevon deflects, the profile is still smooth. For example, take your drawing in post #102 and rotate the elevon about its hinge point until it meets the wing TE. The LE of the elevon now stands proud of the control surface.
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Old Feb 27, 2013, 11:32 AM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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Quote:
Originally Posted by Shedofdread View Post
Looks like a lot of work you don't need to do. Cut the control surfaces away, face them with resin and micro balloons and make a silicon sealent hinge. Job done.

BTW when facing the wing / control surface, bevel the back of the wing NOT the front of the elevon. That way, when the elevon deflects, the profile is still smooth. For example, take your drawing in post #102 and rotate the elevon about its hinge point until it meets the wing TE. The LE of the elevon now stands proud of the control surface.
Thanks for the input Richard.I think I'm going to go ahead(eventually)with the balsa insert thing.Im sure it will make for a cleaner hinge line than trying to fill and sand.
I was going to ask about the bevel.All the pics I've seen of bottom hinged PW51 show the bevel on the elevonerator,which strikes me as odd,for the reason you cite.As you say,it should be possible to cut it(not much upward travel required?) so that the two angles are equal length.
Silicon-not my favourite substance-I've installed too many sinks and baths with it,and removing the stuff is a nightmare.I have some good quality acrylic sealant that I use now,I'll do a trial to see how it flexes/wears.
The Kevlar tape arrived this a/m,again I'm going to trial it to see how it performs before committing.
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Old Feb 27, 2013, 02:33 PM
Deniable plausibility
Shedofdread's Avatar
Derbyshire, UK
Joined Aug 2008
2,307 Posts
Dont bevel them equally - only bevel the back of the wing. Leave the front of the control surface square and cover the gap with a sliding seal (acetate, drawing film, lam film etc) stuck to the wing.

If you draw it and then move the elevon, you'll see what I mean. Never understood why this isn't picked up more...
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