|Jun 19, 2012, 04:20 PM|
Tuesday 19th June
Motor Mount/Vertical Stab
I have been thinking long and hard over the weekend whether or not to go with a single or twin motor setup. Single came out on top so forgive me for my deviation from the original plan. The vertical tail stab was cut from 6mm depron. Due to the fact that I have not made a centre keel for this model, the rear portion of the fuselage was missing so I incorporated this vertical section in with the vertical stab. The alignment of the rear end looked really strange, sort of angled up in relation to the rest of the fuz so out came the drawings. After careful checking of various reference lines and measurements, found the tail to be in exactly the correct place! What caused the illusion of misalignment of the tail is the fact that when the fuz is sat on a level surface, it is the exhausts that the airframe is sitting on. The centre reference line of the tail section runs parallel with the wing bottom, not the exhausts (hope this makes sense).
Once I was happy that everything was correct, glued the 6mm rear end side pieces to the rear section. Now I needed to think about the motor mount.
I measured the motor and prop adaptor to work out where the motor needed mounting so that the prop' will present itself in the correct location. Using my balsa saw, chopped off the end of the rear section at the place where the motor mount will be fastened. The plastic motor mount I intended to use was just a little bit too small in diameter to catch the 4 motor mount bolts that i intend to use. I had to make a 6mm plywood ring to widen the mount so that the captive nuts would have something to bite into behind the mount. Again, in an attempt to save weight, hollowed the mount out by drilling 4 holes (useful for cooling and routing of the motor wires).
I cut a 'core' out of the depron tail section to allow the motor mount stem to slide into and then PU glued the mount in place. I have made sure that the motor mount bolt holes are at 12,3, 6, and 9 o'clock positions so that it will be easier to add thrust wedges behind the mount should the need arise.
Hopefully, tomorrow I should be able to complete the ribs that give the correct profile to the tail section and maybe, time allowing, make the rudder.
Bed time for me now so goodnight............
|Jun 19, 2012, 08:35 PM|
Wow, it's really starting to come together. That tail cone sure makes the single pusher configuration seem like a natural choice for propulsion, doesn't it?
Are you building straight off the 3-view, or do you have a set of plans that you've worked up showing your structure? I'm thinking that a half-size (40" span) version would be right up my alley and a nice way to follow my Lancaster as a winter build later this year...
|Jun 20, 2012, 03:01 AM|
You're right, the model does suit a single motor config. As we all know, once the model is airborne, we don't see the prop' do we?. Correct shutter speed on the camera and even the action shots hide the tell-tale discs at the back end.
As for your 40" model, looking at your building ability, you'll be fine working directly from the 3 view. The only problem I'm having at the moment is the sizes of the a0 3view paper tiles. They're a bit unmanageable but on a 40" version, it won't be a problem. The 3 view is quite comprehensive and again, at the size you require, the lines will be far clearer, sharper and therefore even easier to work from. Go for it.
|Jun 21, 2012, 02:22 PM|
Thanks Glenn, maybe Steve would like to take you up on your kind offer - Steve?
Days 9 & 10
June 20th & 21st
Firstly, Apologies for not uploading last evening but after spending best part of 1 and a bit hours writing up the log, I pressed the wrong button and closed down the browser without posting!
So, to summarise, yesterday I managed a few hours and concentrated my efforts on the tail end section and vertical stab.
The rear end of a Vulcan is not straight forward and caused quite a lot of studying and head scratching. I spent quite a good deal of time with the drawings and also studying photos around the internet. There are quite a few 'walk arounds' to be found and this is the one I seem to visit the most.
The 3 view plan does provide a couple of sections through the tail which I used to create the ribs. I cut a couple of extra ribs, the depths of which I 'guesstimated' to fit between the plan ones to offer a bit more support to the skin. Then I simply added vertical spars between the ribs. I repeated the whole process on the other side of the stab. I had already drawn the rudder on the stab and so it was a simple task to cut it out.
Once cut out, the rudder was trimmed at its leading edge by 12mm to allow me to glue in 2 x 6mm face pieces. This additional thickness will allow me to cut the leading edge at an angle and also add some strength at the location of the hinges.
For control horns, I'm using the large plastic type that bolt through your control surface and then into nuts on the other side. To ensure the control horns were fixed securely, I faced an area at the bottom of the rudder with 1/16" ply on each side.
Drilled the holes for the bolts in the ply and fastened the control horn in place.
It was quite easy with the rudder removed to draw around its shape onto 3mm depron for the skinning. In fact, I made this my next job, I sliced a 'nick' in the 3mm depron at the area of the control horn to allow it to pass through when the time came to glue on the skin. I used UhU Por contact adhesive for this job.
The rudder skins went to without any problems. I took this opportunity to mark out the location of the rudder hinges and test fitted 3 of the plastic hinges. They're the clear plastic flat type, the ones that don't have a metal hinge pin. While they were pushed into the rudder, marked their location off on the vertical stab.
With the rudder more or less finished for the time being, I installed my rudder servo. I fitted it as close as was possible within the stab to the rudder's control horn. Simply a tight friction fit into a section of 18mm of depron (a piece of 6mm on each side of the 6mm stab and then cut out to allow a snug fit of the 9g servo).
First thing was to cover the face of a new piece of 3mm depron sheet with adhesive tape. I use sign-maker's application tape which I use at work. The tape comes on a roll 600mm wide so you can almost cover one sheet of depron in one go. It's very much like white paper masking tape and went smoothly onto the 'shiny' side of the depron. This 'shiny' side is always going to be on the outside of the model and the tape does a great job of keeping the Depron smooth and clean whilst the kneading and bending process takes place.
I laid the vertical stab onto the depron sheet and marked around it before cutting the shape out. Then I needed to mark out the location of the servo to cut a small hole in the skin.
The shaping of the depron is quite a therapeutic process and I if care is taken, the results can be quite amazing. Anyhow, the sheets only required a small amount of manipulation to get the desired shape so they didn't take too long to get something like.
Again, using UhU Por, fixed the skins to the vertical stabs.This contact glue is very good if used correctly and the bond is immediate making the skinning job reasonably straight forward - instant grab!
It was at this stage, I managed to break the tail-end keel piece from the rest of the vertical tail section. No big deal because the tail end section can be made as a separate piece and added onto the fuselage section later.
So, rather a long, rambling log update. So many words to describe so very little work! neverthelss. the results are very pleasing.
What next? - not sure. Will sleep on it and update you as soon as anything changes............
|Jun 21, 2012, 02:40 PM|
Photos from today
|Jun 23, 2012, 10:04 AM|
Nice work on the skins. I've still got some wing and fuselage skinning leftto do on the Lanc, and I'll try your "Depron massage" technique.
I'd be very glad to have a set of three views in 40" size. PM sent.
|Jun 26, 2012, 12:41 PM|
Tuesday 26th June
It's been a few days since I updated.......
Yesterday I spent a fair bit of time studying both the tail end and the intake areas. Quite a lot of studying and very little 'doing' I'm afraid.
The tail end section, although rather a complex shape, i managed to skin the top half and also, added the parachute deployment bulge. Now that I'm reasonably happy that I've got the shape of the tail section correct, I'm happy to leave it there until I start finishing the skinning.
So, my attention was drawn to quite an iconic part of the aircraft - the intakes. Again, at the risk of repeating myself, gleaned as much photographic information as I could from the internet to enable me to get it right. OK, the 3 view ensures that measurements are correct and the scale is OK but nothing helps more than loads of pictures from various angles.
The area at the front of the fuselage assembly needed additional ribs and spars cutting to carry the skin around the complex curves that will make up the intakes. Also, additional support ribs were required around the curve of the fuselage to allow the wing skin to meet the fuselage. The intakes are not exactly inline with the leading edge of the wing. By that I mean that they are 'stepped in' slightly. To get around this I laminated som pieces of 6mm Depron to a thickness which allowed me to cut them diagonally. These triangular fillets ware glued into the outer edge of the intake which then enabled me to sand to shape.
To round out the inside of the intake, I used some coarse sandpaper glued to a piece of 1" dowel. With the intakes sanded down, I glued them in place in the fuz with PU glue before adding the extra ribs and spars on top of the inlet. I hollowed these additional bits out before skinning the area.
I found the easiest way of skinning this area was to first make a pattern out of quite stiff wallpaper. Pinning the template in place as I went along, trimming and cutting ensuring hopefully, a good fit when the time comes to cut out the 3mm skin.
I already had a good sized piece of 3mm Depron ready covered with the application tape and so proceeded to draw around the paper templates.
Once cut, I rounded the panels in the areas that required shaping , leading edge etc. (see pic)
I knew how big this model was going to be but I'm still amazed by it's proportions and more importantly, how light the whole thing is!
Slapped a bit of grey acrylic on just before clearing up today, then took another picture. The fuz is close on 6 foot in length.
|Jun 26, 2012, 04:46 PM|
Like you said - we knew it was going to be big, but crikey!
And this is going to be a hand launched model? I know it will be light, but it will be like launching a hang glider! Can't wait!
|Jun 26, 2012, 10:44 PM|
You would think that the title of this thread would set the stage adequately but that thing looks huge all of a sudden.
Nice work again,
|Jun 27, 2012, 07:51 AM|
|Jun 28, 2012, 01:53 PM|
Thursday 28th June
'Depron Legend' ? - Hardly - but thanks Scaledown.
'Born to use this stuff' - Ah, well you may well have a point there! - I'm thoroughly enjoying working with Depron. So much so, although I don't know what my next build will be, I DO know, it will be in Depron!
Today is basically the last day of being 'home alone' so I had to make hay.......
Skinning of the main fuz is my objective and in order to start doing this, I had to route a few servo extension leads within the fuz. I brought home 4 x 1000mm extension leads with the intention of threading them up for use with aileron x 2, rudder, and one for the Esc. However, it's still in my mind that retracts may be a possibility and so used the 4 leads for aileron (x2) and wing retracts (x2).
Being that the wing will be detacheable, needed to make some connection 'pockets' in the root of the wing to house the servo lead connections. (see pic)
It's important I take you back a few days in the build to when I had just cut out the fuselage ribs etc. I forgot to mention then that once I had the wing root ribs and the other ribs cut from the sheet of Depron, I lightly spray-mounted them all together to enable me to plan the area of the wing joiner tubing. Once I had worked out where they were going to be, I drilled through the components on a pillar drill so ensure the tube fitted squarely within the fuselage when the time arose.
Well that time arose and so I connected 2 pieces of 300mm x 4mm ID brass tubing together using some electrical heat shrink (thanks Chris!), then cut it to the correct fuselage width and epoxied it in place. At each stage where it passed through a rib, glued an extra piece of 6mm on to further strengthen the assembly.
There's really not much I can say about the skinning of the top side of the fuz apart from it took the best part of a day to do. I used UHU Por contact adhesive to glue the skin onto the fuz. I find this method works best for me because, the instant 'grab' of the adhesive helps you to lay the depron evenly and smoothly and also, it's an instant result - no waiting for glues to go off.
Hey, it's not perfect by any stretch of the imagination but it's tidy enough to make me feel like I've done a reasonable job.
You know when there's a part of a build when you think "I wish I were working on that bit or I can't wait to see this bit done", well, it happened to me today.
Why on earth I epoxied in the vertical tail stab at this stage of the build, I do not know but I just had to!
The observant of you might notice that I've removed the parachute bulge at the rear of the fuz. It just wasn't right, the shape was wrong so off it came. I'll revisit that one tomorrow maybe.
Here's some pictures for you.
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