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Old Mar 23, 2012, 07:49 AM
I don't like your altitude
Stupot46's Avatar
Joined Sep 2011
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Jens,the angles are a problem.Raimund supplies a sanding Jig for the bed ribs and wing ribs up to the leading edge.For the ply parts I used this to set up a templet on the chop saw.perfect result.It may be a bit savage to use on balsa,we shall see.And of course with these being segmented ribs I have another two sets of angles on approx 20 ribs to get right.Mini chop saw is what's needed
Stuart
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Old Mar 25, 2012, 07:24 AM
I don't like your altitude
Stupot46's Avatar
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Well I managed to get a little bit more done,after spending too much time following the 3 threads discussing tips and twist etc.You follow a link,look something else up and before you know hours have past and nothing done.Some of the theory(most!) is way over my head,but reading along as you guys bounce ideas around is certainly an education.
Back to the job in hand.One thing this build has confirmed to me is not to trust paper plans.One of the copies I had made is pinned on the wall as a reference.Tight as possible when first fixed,I have had to refix it twice as the weather has gone from bright and sunny(20o in March!)to dull and wet.There is a 4mm difference from centre line to tip in the two halves.Also on the building board the jigs don't want to conform to the the leading edge when the 1st rib is on the centre line.Not much,only about 3mm more sweep measured at the tips.I'm not overly concerned about this,as long as I get both halves identical.I tried to force them into the plan shape,but setting them up stressed doesn't seem a good idea.Safer to let the wood dictate.
I also came up with what I think is a neat solution to my rib sanding problem.Ill post some pics later when I'm sure it works
Stuart
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Old Mar 25, 2012, 09:35 AM
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Hello Stuart,

I hear you with that follow the thread thing ... hours go by, you are likely even more confused and the model is still in pieces But ok ... so do show and tell, I am curious how this wing sanding thing is going to look.

Jens
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Old Mar 25, 2012, 11:04 AM
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Quote:
Originally Posted by Stupot46 View Post
One of the copies I had made is pinned on the wall as a reference.Tight as possible when first fixed,I have had to refix it twice as the weather has gone from bright and sunny(20o in March!)to dull and wet.
Same thing in this country!
I've been a draftsman since the dawn of time and am well of aware of this limitation of paper drawings. The kids learning to draw today start with CAD and probably would not believe your story if you told it to them.
I worked for one designer, decades ago, that would heat his office 24/7 just so that he would not need to re-tape his drawings every morning.

Kent
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Old Mar 25, 2012, 11:17 AM
I don't like your altitude
Stupot46's Avatar
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3,382 Posts
This is the almost complete bed.Still needs a frame along the t/e,but I have left this until the halves are joined so I can do the straight centre piece in one length.
The three pieces of(60/40mm)wood are the sanding jigs.The slots are cut at the angle for each spar,opened up with a wedge they accept the ribs,once the wedge is removed the soft balsa is gripped tight.I have only tried it on one rib so far,I don't want to break all the ribs out until I'm ready for them.The chop saw also does the job ok,but the smaller ribs are too small to hold safely .
Stuart
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Old Mar 30, 2012, 06:26 AM
I don't like your altitude
Stupot46's Avatar
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Bottom sheeting fixed.I made a 2mm depron pattern first,pinned down to the beds on one wing and then used this to get the cuts for the individual sheets.The l/e is sanded straight and square,the ribs have to be set back1.5 mm from this to accommodate the inner section of the l/e balsa.
I have left the trailing edge slightly proud at this stage.Bit of advice needed here.Raimund cites two ways to make the t/e.After thinning to match the rib profile either put a layer of glass between the two,or 0.5mm ply.I favour the ply,having done this before.Any opinions?
Anyway,next job is rib bevel sanding.I may be gone a while!
Stuart
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Old Mar 30, 2012, 12:26 PM
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Originally Posted by Stupot46 View Post
.After thinning to match the rib profile either put a layer of glass between the two,or 0.5mm ply.I favour the ply,having done this before.Any opinions?
Stuart
Since you have a jig to press the parts into, I always favor the soft and gooey approach (FRP), so that stiff materials are not fighting against the intended final form. Or even simplier, my current personal favorite, PU glue that expands to fully fill all voids in the TE joint. Probably the strongest approach would be carbon tow in a bed of epoxy reinforced with milled glass. Fully tape the TE to control glue out flow. If all your materials are balsa, then PU is plenty strong enough.

One reason for the carbon tow is to resist the tension forces that occur at the TE during a hard nose in landing (crash). This tension force is highest at the root area so the tow must be continuous of have a structural joint.

Kent
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Old Mar 30, 2012, 12:37 PM
I don't like your altitude
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Thanks Kent.I'm going to the lhs tomorrow,I'll have a look at what they have.I know ply will be expensive;a piece big enough to do the whole trailing edge will be about 1/3 of the price of the kit!
Stuart
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Old Mar 30, 2012, 12:49 PM
I don't like your altitude
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This bevelling job isn't as hard as I thought.When Kent mentioned spraying black paint to aid his sanding a light went on in the old grey matter.So,black the ends to be bevelled,set in the jig(which is a lot easier with the black line)trim with the knife quick sand and done.
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Old Mar 30, 2012, 12:50 PM
I don't like your altitude
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Forgot the pics
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Old Mar 30, 2012, 01:09 PM
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I know ply will be expensive;a piece big enough to do the whole trailing edge will be about 1/3 of the price of the kit!
Stuart
This is a compelling and often over looked reason to buy a kit. Those little extra parts take time to order and are quite expensive when all costs are added in. I just dropped $57 for plywood stock, for wing skins, for one plane. This for a project that had some wing skins included in the kit. Will I have extra material left over from my plywood purchase? Of course, but some how each new project requires a new plywood order. The extra material left over is handy to have around, but some how is never enough for the work at hand.

The only reason I scratch build is because I like to design. It is certainly not cheaper than even a high end kit. At least, that has been my experience.

Kent
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Old Mar 30, 2012, 02:53 PM
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Hi Stuart,

Thats looking very good so far, I see no dust ... where is the dust ?? They do not supply the stuff for the trailing edge???

Jens
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Old Apr 01, 2012, 12:37 AM
SlingWinger
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[QUOTE=Stupot46 "There is almost certain to be a need for a spare in the future."
Stuart[/QUOTE]

You betcha!
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Old Apr 01, 2012, 03:49 AM
I don't like your altitude
Stupot46's Avatar
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I've been getting some advice in builders workshop about copying the canopy.Some trials with an old one or a slice off a plastic bottle first.
Stuart
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Old Apr 01, 2012, 11:47 AM
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Stuart: In post #25, I see that you have made an angled jig to hold the work for the end bevel, but what part are your beveling?

Kent
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