doxilia

My Feedback: (3)

Tim,

Ron drew the core airfoil templates in relation to a 3" foam block depicted by the rectangles around the foils. The root is placed on the block centerline (1.5" up or down). The tip centerline is placed so that the top of the root and tip foils match and are equidistant from the top of the block. In other words, the top of the cores is flat when joined just as they should. This is a nice way to cut dihedral into the cores as joining them is a simple matter of laying the cores in their lower shucks and mating the perpendicular roots. It's sort of akin to how a Kaos wing is built but upside down. The other more typical way of cutting them would be to place the root and tip centerlines on the 1.5" center mark of the block and then angle cutting the roots. This then requires the shucks to be "blocked up" until the roots mate for joining and is IMO a little more tedious. The only issue with cutting the cores as Ron depicts is that the carved wing tips end up having a slight asymmetry about their centerlines as the core tip is perpendicular to the horizontal rather than having the dihedral angle cut into them there. It would actually be a simple enough fix (if one really wanted to not that it matters) to then cut the dihedral angle into the block at the tips.

If I follow you, yes. If I remove the incidence from the wing and stab, it alters the draft of each of these in relation to the thrust line. I saw no reason to change the location of the thrust line so I just left that per plans. As far as locating the chord line of the wing and stab roots, I placed the wing at the draft of the CG location marked on the plan. It would be like rotating the wing downward about the CG (which incidentally would not be a bad location for a wing tube in a plug-in design). The stab in the original is placed such that the extension of the chord line grazes the top of the wing at its thickest point. Upon returning the stab incidence to zero, I left this relationship so the chord line still touches the top of the wing. This kind of wing/stab draft relationship is not uncommon in classics. It ends up putting the wing and stab chords at 2" and 0.8" South of the thrust line, respectively. I just checked Ron's earlier TTI which has a more pronounced upward angle to the lower rear fuse. Guess what? The stab is placed 0.8" North of the thrust line (the wing is at 2.15" from thrust)! A significant change in design approach between the I and III/IV (I haven't seen plans for the III but I suspect the relationship is similar if not identical to the IV).

Honestly though, as with any good adjustable pattern model, the ideal setup would be to have plug-in surfaces allowing one to alter the incidence as well as down/side thrust. Changing the incidence would allow one to experiment with decalage as well as thrust line angle of attack in flight. I plan to do all that with the Brushfire which I designed with plug-in surfaces. I also have a Dalotel which will have both wing and stab plug-in. I like the idea of "tail high" flight but we'll see how this works out. For now, I'm thinking along the lines of a simple no retract, low servo count (7 at most), long stroke YS ship with pipe above the wing along the thrust line. I'd like to try and keep an even mass distribution about the thrust line so the pipe will be on it and the thank will be above it while the wing is below. The fixed gear are the only thing that sort of bothers me but I may consider a conventional retract version.

I don't quite follow you here. What adjustment were you thinking of? Incidence related or draft related? Are you thinking of moving the stab up closer to the thrust? It's too bad Ron is somewhat less reachable nowadays. It would be interesting to hear why the stab came down below thrust from his original. I bet it has to do with rolling maneuvers what with the TT1 being essentially a flat top and a pronounced curved bottom (much more P-40 like) while the TT4 has a more fish-like fuse shape about the thrust line. He might have had no choice but to bring the stab down in such a fuse. Still, it could be flush with the fuse top datum or even higher on the thrust line with a an airfoil shape fin bottom...

Yup, I guess this all makes sense. I suppose I was thinking along the lines of a more extensive removable top (for electric setups) but was concerned with structural integrity in a glow engine setup. The planking makes for a stronger front end than a skinned former approach too and I have removed half of that planking as I don't love that type of building.

Looking at my plans now, I think if I made the wing and stab plug-in structures, the fuse would then be a fairly solid structure even in the absence of a top deck especially if I extend a 1/32" ply doubler into the 3/16" fuse side top extension shown on Ron's plans. I think I'm going to do that regardless and cut the extension from 1/8" balsa and then mate the three fuse sections (top, front and rear) with the doubler. The top would then remove entirely from firewall to F5 along the fuse side top with the deck portion of F5 canted back 30 degrees as typically done with removable tops (and as you were suggesting). The top would then have a 1/8" planked front half and a 3/32" skinned rear half (I decided to switch the skinning from 1/8" to 3/32"). The remainder of the fixed deck potion would also be skinned with 3/32" to match. The front portion of the removable top would also taper upward per the fuse side top extension. Last but not least, I'll use a 1/8" lite ply floor between F1 and F2 which will serve for both an optional nose gear base as well as a battery floor and steering servo mount. With a removable top, this would all be easily accessible including the tank and remainder of the radio which at the moment is all wanting to be mounted output wheels up. I'm thinking one P-P rudder servo in the fuse and two mini (Spektrum 5030) elevator servos in the rear (which will require that battery behind the FW).

Mmmm.... as I'm brain storming it here, the more I'm getting sold on this... Projects always seem to take on a life of their own. So much temptation when designing...

I didn't measure how much I moved the FW forward but I can now see that a nose gear and a 2" wheel would easily fit with a 60 without having to butcher the front of the wing (another building bug I seem to have). Of course, with plug-in wings, this is a non-issue... The retract location and strut length can pretty much be any length desired. Dang, did I just say that! More hard selling seems to be happening to me.

It sounds like the Hyde mount you have is a touch too big for the model. I placed a 2.75" ring (the size of a Dave Brown 90FS mount - 2.74" actually/beam width 1.69") centered 3/16" offset from the FW centerline and it fits without a problem with a little space to spare. In fact, it matches well with the cutout shown on the lite ply cowl ring depicted on Ron's plans near the spinner. The left side (from the front) is vertical as there is no mount there to interfere. It sounds like Pete also got a hold of a Hyde mount of that dimension. Even at 2.9" for the 120FS there doesn't seem to be a problem - it still fits. Is the Hyde mount diameter larger than 3"?

David