|Oct 29, 2011, 05:23 PM|
DLG Project - Volume 2: Zone-V2 airfoils and a new fuselage mold
Guys, it's time for a new plane.
A couple reasons for that:
- I need to test Gerald's Zone-V2 airfoils
- I need a better fuselage with more room for servos and ballast
- My old mold is getting worn out and I'm not satisfied with the quality of the parts anymore
What should the new plane have?
- More room for ballast, the old one had the wing set pretty low that there was almost no room for ballast. I managed to get 50g in, but that's it.
- More room for rudder and elevator servos, I don't want to take the bottom part of the case off to get the servo in.
- The front part of the fuse is higher than wide just because I like the looks of it
- Pylon for a hinged horizontal integrated in the fuse
- Horizontal stab should be detachable for better ground handling
- Vertical tail mount usable for both right and left handers, I don't want to have to align the vertical tail at the required 0.6 deg everytime. The mount should guarantee that the vertical is always precisely positioned.
- The Edge airfoils were OK but for my lousy flying they were too little forgiving. I will try out GT's Zone-V2 series, they seem to be awesome from what one can read about them
Now for the fuselage mold:
- Way better surface finish on the plug than on my old one. I knew almost nothing about surface finish at the time. I just sprayed the paint on, waxed the plug and made the mold. This one gets a glass-like finish.
- Using tooling epoxy as first coat, not regular epoxy with black color paste and cabosil.
- This mold has to be lighter, I'm sick of carrying around that 35kg mold, it's completely unnecessary to make the mold that big.
- No three-piece mold this time, it complicates the process of laying up a fuselage and I didn't get very good results because of the separate wing saddle block.
And there will be a couple of smaller detail solutions that I like to share, I have quite a few of them in my back pocket.
I'd like to post lots of pictures, because we all like them, hopefully some videos, because we like those even more
I'll focus on surface finish of the plug, making the mold, making the parts and so on. I will also use spread tow on both fuse and wings. This is new to me, so we'll see how that goes.
Since my CNC mill is still a long way from completed I have to make this plane still with a bagged wing and a hand-shaped fuselage plug. But I don't see this as a downside. Building a really good and solid CNC takes a lot of time and effort if you're trying to design and make as many parts as possible by yourself. I'll take all the time it needs.
OK, let's take a peek at the 3D model.
I designed it with Rhino, really like this software:
As you can see, the fuselage design is different, the wing is a smoothed ZoneV2 2P by Gerald.
Enough babbling, let's start the building process!
To be honest: I've got a little head start already...
|Oct 29, 2011, 09:49 PM|
United States, MD, Lusby
Joined Nov 2003
Looks sweet, I really like your vertical mount bracket idea! You will like the new airfoils, they have proven very much superior to previously published designs, the number of top-level molded airplanes incorporating them makes that pretty clear IMO!
I hope your CNC progress is less painful than mine, I'm just dealing with a simple foam cutter and it is much, much, much more painful than anything I've dealt with (combining hardware+software is never a good idea)
|Oct 30, 2011, 09:44 AM|
A note to wing and tail design: I've drawn the 2P wing just to have something to sit on my fuselage for the Rhino file. I don't know yet what wing I will build. Same goes for the tailgroup.
Making the plug:
I'd like to show you my method of generating templates for the front part of the plug.
After I completed the design and so that all the gear fits in and that I like the looks I extracted the top and the side view:
Both top and side view are being extruded:
Intersection of each surface with the other creates these yellow lines:
Top and bottom are made into surfaces:
Unrolling both surfaces makes them planar:
Along with the sideview (which is NOT unrolled) I now have the templates for top and bottom and the sides:
|Oct 30, 2011, 09:58 AM|
Unfortunately I didn't take any pictures of the rough shaping of the plug.
I will try to describe the procedure:
Grab a piece of MDF. Print out the templates. 3M77 the sideview template on the MDF. Cut it out with a hacksaw, band saw, whatever. Shape the sideview accurately by hand, make sure the top and bottom surface are rectangular to the sides. When that's done draw a centerline on both top and bottom surface. 3M77 the top and bottom templates in place. Now you've got a guidance for shaping the contour as seen from above. When that's done the plug looks like this:
From now on, the real shaping begins. I started with a block plane and rounded off the corners. Just make sure you don't alter the shape of the side and top view. The centerline on top and bottom should stay visible!
When the planing is done start sanding. Always with a firm sanding block to even out high and low spots.
|Oct 30, 2011, 10:14 AM|
The boom part:
I liked the rear part of my last fuselage so I decided to make only the boom part in my old mold and attach it to the new front part. I made the boom from 3 layers of 160 gsm fiberglass. No need to waste carbon on something like that I made it of 3 heavy layers just to have something to sand away later on.
For the attachment to the MDF I drilled a hole in the end, put a wooden dowel in, smeared lots of epoxy with microballoons and foaming agent inside the boom, aligned everything on a flat table and let it cure. The epoxy grew so fast before curing that half the length of the boom is now filled with epoxy-microballoon-foam.
After sanding away the excess epoxy I soaked the MDF with regular epoxy.
Brush on lots of epoxy, heat with a heat gun until all the gloss is gone and repeat that about 3-4 times.
There was also a bit of spackling necessary to create a nice transition from boom to MDF.
|Oct 30, 2011, 11:30 AM|
Thanks Paul and Jesper!
If any of you guys have questions or anything else please chime in.
Next step is to create a wing dummy.
How wired using just the bottom part of the cutting templates. Bagged with the approximate amount of cloth the wing will have.
|Oct 30, 2011, 03:45 PM|
South Africa, GP, Centurion
Joined Dec 2008
Would my two fuselages be the old one or the new one?
Either way I'm going to order two of these again soon.
|Oct 30, 2011, 05:46 PM|
Since I will be using a hinged stab this time I will include a stab mount on the plug.
I leveled the plug on its wing saddle area so that the boom part is also perfectly horizontal:
The rear part of the boom gets a piece of waxed chipboard located at the right distance from the boom:
A generous amount of bondo is added to form the pylon:
After that has cured I sanded it round until the shape looked fine.
|Oct 30, 2011, 06:01 PM|
To create a really smooth surface on the wing dummy I painted it with gelcoat and finished it. More on surface finish later...
This piece gets a coat of wax to ensure a good release. It is then placed under the fuse and everything is set right:
To create the wing saddle I simple put a good bead of bondo on the plug and pressed the very well aligned fuse onto the wing dummy.
To prevent having trapped air between wing dummy and bondo, I put the bondo in a ridge-like shape on the plug. When the plug is pushed down the wing piece makes first contact with the bondo in the center of the fuse. Excess bondo is then squeezed out from the middle to the sides:
|Oct 30, 2011, 06:02 PM|
Jonas,dont leave the tail boom as a "straight boring stick".
On Your drawing its curved ,but not on Your plug.Correct me if I am wrong.
Looking forward to see Your next great work.
|Oct 30, 2011, 06:12 PM|
Yuri, it's the other way around. The transition from mdf plug to oval FG boom is pretty smooth. The bottom has a slight curvature, approx. 10cm in length, after that it's a straight boring stick
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