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Old Sep 08, 2014, 01:32 PM
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As far as the spar being "flat" to the table, the entire surface of the spar will not be flat on the table, but the gap due to the washout will be insignificant, only about .006". It will be a "line contact", not a "surface contact".
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Old Sep 08, 2014, 02:44 PM
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Thank you for your input Don. I am enjoying the build so far. The kit is top notch, and the fit of the laser cut parts is phenominal. Have you considered marking the wing ribs and shear-webs with the laser? It could same headaches for some.
What does the spoiler servos attach to? I don't recall seeing any structure for that on the plans.
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Old Sep 08, 2014, 03:10 PM
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Look at Step 13 on the wing instructions. The spoiler servos are glued to the spar and to the adjacent rib with RTV (silicone rubber "bathtub sealer", hence the old-fashioned bathtub for the glue symbol for it). RTV is easy to cut through if you need to remove the servo later.
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Old Sep 09, 2014, 09:54 AM
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Scallop TE

Thanks for the information on the scalloped TE. I've been searching the forums on flutter and ran across that. A few photos that I found had the scallops on the forward edge of the TE balsa and a straight TE. I don't see any benefit to doing that.

I may add the balsa pieces to the front of my 2m Chrysalis wing and my Chrysalis HL wing as well.

I am going to strip off the top of the tail boom and re-route the cables to the rudder-vators.

Also, can you tell me what you used in the 2M Spectre kits for push rods and the fittings at the rudder-vator control horns?

I've included a picture but can't remember how they were done. I want a similar set -up.
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Old Sep 09, 2014, 11:51 AM
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Scalloping the trailing edge in that manner might help the stiffness/weight ratio of the structure a little bit, although I don't see it as being a big factor in most cases.

The diagonal bracing is just on the inboard panels. The structure of the outboard panel has a sort of "tripod" effect created by the leading edge, spar(s) and trailing edge that gives it some natural torsional stiffness that makes additional bracing less of an issue. For most folks, the natural stiffness of the structure using regular weight covering is enough, but the diagonals add some more, which can be necessary in some situations. the diagonals are simple trapezoids with the front end cut in an arc to match the leading edge dowel. They do not touch the covering. The one in the kit are a lttle oversize so they can be sanded to allow for "manufacturing tolerances" on the wing structure (even with laser-cut parts, the average builders will see some variation in how everything fits together int he assembly).

The Spectre 2-meter, 100 and 120 all used the same yellow plastic tube casings we use in the Chrysalis 2-meter, with 0.025" carbon rod pushrods. We made little end fittings from 1/16" o.d. brass tube to connect to the control horns. We bent the tubes 90 degrees, with a 3/8" leg on one side of thebend and 5/16" on the other. There was enough stiffness in the rod that the end of the fitting could not pull out of the horn, even without a Z-bend. The fittings were epoxied or CA'ed to the end of the push rod, and we glued a brass 2-56 rod end fitting to the other end, and a clevis to connect to the servo arm.
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Old Sep 09, 2014, 02:43 PM
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Thanks for the details and dimensions on the Spectre rods. I may look into this for the Chrysalis 2M

May perform surgery on the wing. Scalloping the TE seems silly.

I have not had that much trouble with flutter on the wings, just the tail.

I am going through all of my old planes and I am going to start flying again; they have not seen the light of day for over a decade!

Got the Wizard set up with a new motor and battery -- Look for a new thread!
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Old Sep 09, 2014, 03:36 PM
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Tail flutter is the result of insufficiently supported pushrods, almost without exception. Make sure they are well supported at both ends, with only the minimum unsupported distance (about 5/8" max, 3/8" to 1/2" is better), when the servo and control surface are at neutral) needed to allow for control travel. A lot of folks do OK with this at the tail end of the pushrod, but forget to support the servo end of it. Also, tin the pushrod wire in the unsupported region with silver solder ("lead free" solder, at Lowes, Home Depot or Radio Shack) to stiffen it.
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Old Sep 09, 2014, 05:23 PM
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These days, there are a bunch of different "lead free" solders which have different compositions. Some don't have any silver at all. Radio Shack does show "silver bearing" solder on their site, but I don't know if this is the same as traditional silver solder. Some of the solders have only minute amounts of silver, some have quite a bit. I have no idea how much silver is required or what other properties the solder needs to have. I can report that some of the "lead free" solders are much harder to use than traditional solder for electronics.

I had URL's for a lot of this stuff, but my computer ate them.
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Old Sep 09, 2014, 07:19 PM
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It isn't the silver content that matters. Some have silver, some have antimony, but in both cases we're looking at only about 4% of the total. The key is that the other 96% is tin. No lead. And tin is a lot stronger and stiffer than lead. Also, the lead-free solders stick to steel alloys much better than electronic tin-lead solder does.

However, typically a lead-free solder uses an acid flux, not rosin flux (which is part of the reason it works better on steel parts). For that reason you should avoid using it for electronics.
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Old Sep 09, 2014, 08:22 PM
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Thanks for clarifying that. I didn't know that was the relevant difference.

RoHS* rules REQUIRE lead free solder in electronics. And I can tell you at least some of them can be a real pain to use, at least when hand soldering. If I recall correctly, the stuff we were using required a higher temperature. That can make things difficult if you're trying to avoid frying components. OTOH, I think I ran across a type of solder with a lot of bismuth in it. That would need a lower temperature, wouldn't it?



*A set of rules in Europe intended to reduce use of toxic substances.
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Old Sep 09, 2014, 08:57 PM
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The problem with using it in electronics is the acid core flux. If you get some with a rosin core (less common, but I have seen it), it should be OK for electronics, but it would have more trouble sticking to steel.

Bismuth alloys can have much lower melting points. At the extreme end is Wood's metal, melting point 158 deg F. One use for it is those trick spoons that melt when you try to stir your coffee with one. Another more legitimate use is to hold or reinforce fragile components for machining, then melt it out afterwards with hot water.
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Old Sep 10, 2014, 01:29 AM
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Some of these lead free solders are meant for electronics and aren't meant for acid flux, or at least are not used with it. I still dislike them and have a pretty good supply of the old 60/40 stuff. I thought one always applied the acid flux separately, but I guess it's not always the case. I suppose it's more convenient that way. Even with rosin core flux for electronics, I often have better luck if I apply some rosin flux from a tube.

I have what I think is a big bar of bismuth someplace. Maybe the attic will get really hot some day and I'll find out just where.

Have been stuck helping s.o. with a rush project and trying to set up an infernal 6 servo sailplane with a motor. Getting back to the Chrysalis project will be relaxing, but the big ALES contest is this weekend and I'm not ready yet. If I do get ready, I have a backup model to fix. Sigh. Maybe after I get the Chrysalis done I'll make an electric fuse and use it for my ALES backup.
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