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Old Aug 13, 2009, 02:55 PM
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Franny B's Avatar
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Goldberg Valkyrie Build

Hi All,

Well, I'm going to take the plunge - right off the deep edge! I have had a set of plans in electronic format that I have been looking at for quite a while and I finally went gown to the graphics place and had them printed out. They are full scale - two pages so both wing halves, fuselage and tail feathers. I also have collected all the articles I could find and after quite a bit of study think I'm ready to give it a whirl. This will be a long build and a little slow getting started as I need to finish up another airplane before the end of the year. My goal is to have it ready by next year's flying season, so here that means about June-ish. I'm just so excited I thought I would start this and get some feedback.

I'll be starting with the wings as I think they are the most complicated and will parley to the rest of the flying surfaces. The fuselage should be reasonably straight forward, but will take a bit of care to keep it straight. That pylon is still somewhat of a mystery but I have some Ideas on a cool wing mount. Wing will be two piece as it is two feet longer than the Cumulus and I couldn't get that in my car in one piece!

For me, it will be electric, around 600W with a nice round spinner on the nose. Rudder and elevator. I'll probably modify the landing gear a tad to add a trailing brace as the original has a single run for each wheel and will bend a bit I bet.

I have a few ideas about how I'm going to get through all this, but I would love to hear your thoughts as you guys have much more experience than I.

I know it is crazy, but what has being subtle ever done for me?

Franny
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Old Aug 13, 2009, 03:17 PM
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Franny B's Avatar
Arvada, Co
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A little dissusion around that 10' wing...

Ok, so starting with the wing... There are 29 ribs and 17 spars - Per half! The first three or so will be solid to accept the dihedral braces (three I think) and probably the last two as they will be under the tip sheeting.

So, after staring at the plans for months and reading through all those articles I was completely baffled on the wing construction until last night... The instructions say to cut all the ribs down the center of the cord and then, set the leading and trailing edge and then place and glue the top of the ribs. That way the wing can be started flat. Then stand the wing up vertically and add the bottom halves of the ribs. Then add the spars and then the cross bracing for each rib and finally the cross bracing between the ribs. That sounds ok on the surface until you try to figure out just how you are going to maintain the curvature of the ribs without the rib truss work. ??? Damned peculiar... I finally figured it out when I was looking at the parts list for the wing. I expected to see about 4mi of 1/8" square 36" pieces. and there weren't that many. And, they called out like eight sheets of 1/8"X3"X36" med balsa. At first I thought that was for the sheeting, but then it dawned on me... What they want you to do is trace out and cut each rib as a solid piece of balsa and then cut out the center leaving 1/8" around the edge. THEN cut along the center cord. Finally, the rest fell into place. I feel like Indiana Jones or something... Anyway, that would work I guess, but it seems like the front of each rib would be cross grain and pretty weak where you need the strength the most. So, here is what I'm going to try... I'll make up each rib from 1/8" sq stock complete with cross bracing and a little sheet piece in the nose to accept the leading edge. I think I can build a straight wing with the TE on the board and the LE raised and blocked. That is how I did the Cumulus and it should work here. My worry is that the spars won't line up correctly if the truss work is already in place. I'll have to make up a couple to see, but my plans have layouts for groups of ribs showing the reduction in size for the smaller ones in the group. The datum will need to be the center cord line from root to tip. Just have to keep my wits about me...

What do you think? Sound like a plan?

Franny
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Old Aug 13, 2009, 05:00 PM
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B'ham UK
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Your right building one of these is the aeromodeling equivalent of building a Forth rail bridge, a once in a lifetime build.......... unless you've got a team of mates you really, really trust............ you did a fine job of the last one so your probably as well prepped as its possible to be...go for it, you have our full attention and admiration.
Clive
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Old Aug 13, 2009, 06:24 PM
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United States, WI, Elm Grove
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Isn't this wing made with "sliced ribs"? The technique is often used with rubber duration models. A metal template is made in the shape of the top arc of the rib. The template is placed on a 1/8 sheet and a razor blade cut is made following the arc. The template is moved down 1/8 (per the drawing above) and another cut is made. The result is a 1/8 deep section matching the top of the rib. A similar template is made for the bottom profile.

The ribs are built up on a jig which has little stubs representing the location of the spars and leading edge. The top, bottom, and cross pieces are added in the jig. The result is matched ribs. Using this method will require threading the ribs on the spars, which might be pretty hard for a wing this large, which is maybe why the technique in the instructions is suggested. Building the ribs in a jig would also require parallel spars.

I'm sure a search on sliced ribs will show the technique, and probably better than I have tried to explain.

Jim
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Old Aug 13, 2009, 07:37 PM
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Franny B's Avatar
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Thanks Jim,

That is what I was thinking... But isn't the leading edge portion of the "sliced" rib a bit cross grained? Also, seems like it would be difficult to maintain its shape without the truss work...

If I can make sure that all my spars will line up properly on the ribs so that the spars are straight from root to tip, I'm thinking I can treat the ribs as though they are solid and notched in a sense.

I'll build a few and see what I have. If my plans are accurate, It *should* work.

Franny
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Old Aug 13, 2009, 09:37 PM
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eastern pa
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This will be something worth tuning into every night. Good luck & know you have our support.
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Old Aug 13, 2009, 09:44 PM
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That's interesting. I can't imagine that I've seen this type of ribs before.
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Old Aug 13, 2009, 09:49 PM
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Canada, ON, Kingston
Joined Aug 2000
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Somewhere I have an old Aeromodeller with a full size Valkyrie on the cover - you are biting off a MAJOR project, but an exceptionally graceful model. I'll enjoy watching this one progress.

Martin
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Old Aug 14, 2009, 12:12 AM
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Gold Coast Australia.
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Quote:
Originally Posted by Martin Irvine
Somewhere I have an old Aeromodeller with a full size Valkyrie on the cover - you are biting off a MAJOR project, but an exceptionally graceful model. I'll enjoy watching this one progress.

Martin
I have that Aeromodeller also. Mid 80s maybe? without looking it up.
From memory the builder shown with the white covered Valkyrie was Jack Humphries(Sp?)
He did a fine little Sporty bipe in an early '50 Aeromodeller.
I think he may have passed some time ago.

It's a lovely model and will I'm sure be well worth the build. There may even be a Youtube vid of the original Goldberg one flying pre WW2.
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Old Aug 14, 2009, 07:07 AM
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It was my understanding that each rib was built up just like a rubber model fuselage, out of appropriately sized strip stock. The story I heard was that Carl built one of each pair of ribs in the morning before going to work (or school, I forget) and the mate that evening.
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Old Aug 14, 2009, 09:00 AM
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Re: the ribs. Yes, I would also be afraid of the cross grain at the front of a rib with such a large chord if sliced from sheet. Maybe that is why the technique is seen on rubber models.

It would seem a jig of some sort would be mandatory. Maybe something like what is used to cap the ribs on a Proctor model. The jig has a sliding top and sliding bottom. The cut-to-length top and bottom strips are put in place and the form is squeezed together with the rib center in between. For the Valkyrie the cross piecs are added, located by the stub spar sections that are part of the base of the jig. The glue is added and the rib left to dry. Another of my convoluted descriptions, but maybe this pic of a Proctor style jig will show the concept.

The crude sketch shows the idea: a base with spar locations established by the little stubs glued on, and a top and bottom slider positioned by some sort of locator bars or pins. The problem I see is how to glue up the rib without gluing to the jig. Plus there needs to be a bit of gap at the spars so the ribs slide on.

Finally, some great planes cribbed from the web.

Jim
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Old Aug 14, 2009, 09:09 AM
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Franny B's Avatar
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More on those ribs

This is what makes this project so interesting - it is a bit mysterious... Lots of different stories and everyone has heard of it. Great fun!

Here is what I was talking about with the ribs... The plans show where to shorten them on each end to accommodate the decreasing cord. I'm wondering about the camber though... I think it needs to be reduced as well, but I'll have to take a look at that and super impose a few ribs to check it out.

Out to the hobby store today or tomorrow for a few hundred feet of 1/8" sq and some 1/8" sheet.

f
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Old Aug 14, 2009, 09:20 AM
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Franny B's Avatar
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Thanks Jim! I'll look into that. A jig may be the ticket as there are so many that need to be built. Great photos too... I hadn't seen the first red-yellow-clear... I looked at the orange one carefully and those ribs have a little solid balsa part in the front so that is what I'm aiming for as well.

f
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Old Aug 14, 2009, 10:19 AM
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Indiana
Joined Jan 2005
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A jig certainly won't hurt.
This is a magnificent airplane!
I'd love to build one myself!!!
Carl Goldberg gave us some truly wonderful airplanes!
I am going to be watching this build!


Ed
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Old Aug 14, 2009, 10:39 AM
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Beaumont tx
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If you get a balsa stripper, you will save bunches of money and be able to match strips for weight and stiffness. I use a midwest (less than $10 last time I looked) and it has worked great for many years.

howell
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