1:4 1928 RRG Professor

[Tom]

So is it going to be ready for Cumberland this month???

What he said! Hop hop!

[JimD]

So is it going to be ready for Cumberland this month???

[ARUP]

All the ribs are attached to the LE and TE. The top surfaces of the ribs have been sanded fair to each other. Next, the outer panel will get pulled off the board so the same sanding treatment can get done to the bottom surface. The next step will be to offer the outer panel to the inner so that the joiner rod and tube can be placed. This will help getting the spars aligned properly over the joiner and tube



That's it for now!

[ARUP]

The ribs were trimmed to the proper width at their noses using the false LE as a guide. So... before gluing them in place each was offered to the false LE then marked (first pic). The rib was then trimmed, top and bottom, using an identical root rib to fair the curve. Sorry that picture turned out blurry. This exercise will save some sanding time. Remember... these ain't laser cut parts and the nose section of the ribs was expected to get cut away anyhow! That's my 'excuse' for them being a little off.





More to come!

[ARUP]

The TE tapered jig was completed as per above and then pinned to the board. The bass TE was pinned to the jig. The ribs were notched at their trailing edges to fit the TE then set aside. The root rib was fixed into position as was a tip rib which had its 'nose' cut off to fit the false LE. Next, a straight edge abutted to the LE of these. Since the straight edge was not actually resting on the board a method needed to be found in order to transfer the straight edge line onto the plan. A small triangle was used so that as the triangle touched the straight edge a mark could be made on the plan. This mark, at each rib station, is to know where to cut the ribs' noses so that they meet the false LE properly. The ribs were then trial fitted to the TE one at a time so that their noses could be cut to fit against the false LE. This was fiddly but my reward was perfectly fitting ribs as they were against the LE. The false LE had a taper cut onto it using the root and tip ribs as a reference. The false LE was then packed to the proper height with the aid of the... you guessed it... straight edge. The pics with the ruler in the background just show various pieces of scrap balsa to pack the false LE to the proper height. The ribs are being inserted and glue is drying as I type. The straight edge was put against the false LE while the gluing process was being done as a second safety measure to insure the false LE is 'dead straight'! (last pic)

[ARUP]

More stuff! This isn't very exciting stuff but stuff that just has to get done! The outer panels taper in plan and thickness. The spars for them will be a composite of spruce at the inner 1/3 section and hard balsa for the outer. A taper jig of about 10:1 ratio was made to cut a bevel to scarf the spar parts together. The picture shows it labeled finer but when trying to cut the wood, the jig wasn't long enough to feed the wood to the saw properly or... the saw was too small! The second pic shows two finished spars in the upper portion of photo and two tapered ends in the lower part of the photo. The third picture shows the outer portions of the spars getting sanded thinner, i.e., a taper was put onto their outer ends. The spars were labeled so that the tapered side faces inward. The fourth picture is of ribs being laid out for cutting on band saw. The previously drawn rib patterns were used. After ink tracing then cutting the rib pairs out they all got sanded fair around their perimeters. A jig was made to hold the TE. The TE will have an aerodynamic wash out but there will be about 5mm physical washout built into each wing by using this jig. This jig needs to be used because the outermost rib is symmetrical (and the next few almost so) and you just can't pin its TE onto the board. The last picture is of the plan waiting for parts!









Hopefully the construction pictures will make more sense than my jibberish!

[ARUP]

Eager beaver? lol

[Tango Juliet]

I'll have to remember that when I get to my wings, and do all my builds that way from here on out.

[lenb]

Your an animal...

[ARUP]

Paper patterns were made to fit the fuselage so the the wing retention pin could pass at the proper depth. Once these were cut from metal they were trial fitted to the wing and fuselage so that their mounting blocks could be made. The front mount block fits between the spars and the rear one nestles in the 'corner' of the inverted 'T' profile spar. The metal connectors bolt to these. The front connector will take most of the loads. The rear one is mostly for alignment of the wing to fuselage. The wing center section will be 1/16" balsa sheeted then skinned with 1/64" ply so the thickness of these layers was taken into consideration. These parts were test fitted multiple times to make sure the wing remained true and square relative to the elevator/rudder and in plan form. Very tedious stuff, especially when you bump the assembly and have to reset things! The epoxy is curing as I type.









Good night!

[ARUP]

Now that the top surface of the ribs are fair the spar and auxiliary spar were offered up to them, taking care to shape the spar slots properly so that the spar nestles straight and flush to the top surface of the ribs. A straight edge was used here while 'adjusting' the slots. Once the epoxy cured the wing was taken off the board then placed top side down so that the bottom surface could get the same treatment. The TE was taped to packing that was pinned to the board. Next, the ribs were pinned to the board at their contact points. The the same process for the upper spars was applied to the lower spars. The auxiliary spar help distribute the load where the wing connects to the fuselage. This will be aided by the struts.







The spars and their packing sandwich the wing tubes. I'll put proper shear webs in place a little later. So... for now the fuselage to wing connectors and their mounting blocks can get fabricated.

[ARUP]

Thanks, TJ! Yeah... if you put spars in first there is a chance the rib noses or tails won't align. There is also a chance the ribs might be 'proud' relative to their neighbors if the spar slots aren't exact or if the ribs weren't pushed down onto the spars correctly. And with the spar in place you have a 'hard' spot' that won't fair to the ribs with sanding. I think I've made all of these errors once upon a time and this technique has evolved as a remedy! It's a tedious process as I've done but gives absolutely perfect results! You can wiggle the 'T' bar laterally across the ribs and see which ones move, i.e., the ones too proud. Then sand along the rib length to level them.

[Tango Juliet]

Never heard of doing it that way, but I guess it works. It's really coming along nicely.

[ARUP]

I like to build wings by dropping the spars in the structure after putting on the TE and LE first. For me, it seems keeping everything straight and square is easier this way. Same goes with fuselage structures that require stringers. I cut the stringer notches after putting the formers in place.

Anyway, here are a few more pictures of the center wing build.





Adios, amigos!

[ARUP]

Jeremy...



The two wing rib patterns were set up with the wing tube to fit two wing tube support blocks that tie the tubes to the spars. These blocks were then used as jigs so that more could be made. The table saw was used to groove the blocks along center to speed up the sanding process. Sand paper was wrapped around a tube and this was used to 'cut' the groove in the blocks. The blocks were carefully glued at the proper spacing onto the spars. These spars, in turn, were used as jigs to glue the ribs to the LE and TE. The ribs were threaded onto wing tube without glue which also helps with alignment. Once the glue dried then the ribs were sanded fair across their top surface and my little special sanding sticks were used to fair the spar slots. All that is left is to pull the wing from the board to sand the bottom surface and true the spar slots then the wing tubes and support blocks with spars can get installed. After that then the sheeting goes on to form the 'D' tube of the wing.







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