Here is the latest on the Lawrence Tech IV development.
I've completed the final outlines for the wings in planview and work is progressing on the ribs and other parts that will be needed for construction. As of now, I have all of the wing rib profiles corrected for sheeting thickness and notched for main and drag spar and leading edge strip. I've worked out the aileron hinge line and have decided to make it fully enclosed within the plywood sheeting to reduce parasitic drag as much as possible along the 53 1/2 inches of aileron.
The leading and trailing edges will be notched to interlock with and jig the ribs parallel to one another. Each rib will also employ a narrow cap strip of the same sheeting material as used on the leading "D" section which will also help with torsional stiffness of the wing.
I have drawn lightning holes in all but the root and tip ribs but am debating whether to delete these. The tradeoff is in the expense of the parts vs. lightness. There are 71 individual parts that make up the rib set in each wing and lightening with semi-scale truss structure will increase the cutting time to more than double and my feeling is that the advantage in performance may not be discernable. Alternatively I could lighten only those that will be under the sheeting to maximize strength aft of the spar.
This will allow more machine time to instead cut the plywood wing skins and include them in the kit of parts - reducing time in construction by making it unnecessary to cut the complex outlines which include gussets at every rib junction.
I've also laid out the plans sheets and will complete the wing drawing details, parts and callouts in the next few days, nesting them as I go. I should be posting a new PDF file to the list with vignettes of construction details by the weekend.
Tom
I owe an update.
The empenage parts for our third scale kit have been checked over once more and nested for cutting. A few small changes were made.
The fuselage has been more of a bear. After receiving an several early photos of the sailplane taken in about 1938-39 from the National Soaring Museum collection, I have better information which helps in correcting some of the issues in the three views. Two of these are also the only photos that I have found that show the sailplane with the original four-pane flat-wrapped canopy. I've also learned now that the sailplane had three different styles of canopies installed at one time or another and here in chronological order - four, then three sections flat wrapped and finally two sections formed. The aft-most of each being the hinged rear section.
At this time I cannot share the images until I get permission or release from John Gallagher at NSM but I can say that the images are signed by Loomis, the photographer and are as clear or more so than any contemporary photos of vintage sailplanes of the day (one you've all seen published on the net).
One of these images shows the sailplane in nearly perfect side view as it is being unloaded from a trailer for an event, most likely on the East Coast but I don't recognize the location. I used this image to correct the side view in my three views.
I've been spending much time on getting the fuselage cross-sections correct and will probably arrive at a final set of parts in the next week and will be sending the fuselage and tail parts out for cutting. Once I have them back here, I will check fit of all fuse parts and build out the tails complete, then proceed to finish up the wing drawings.
There are about nine other sailplanes in the photo taken at the event, you guys can help me determine what they are:
NC1305 - looks like a McMillen Cadet II
A Franklin PS2, maybe another in extreme foreground
What appears to be a third PS2 - Long wing version with slight gull anhedral
NX18474 - wing only seen, high aspect, no struts, undercambered - Bowlus?
__20646 - wing only seen, high aspect dual strut-supported wing
I need to find more photos taken at this meet!
Tom
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