9 Development of a composite twin boom pusher airframe. Posted by Leo Hogg on September 29, 2012 at 5:11am Tags: airframe, boom, compsite, pusher, twin E-mail me when people leave their comments – Follow
From page 3 of this thread, looks like you've got a hardpoint in the foam wing for the boom. Can you share how you made those?
Anyway all a bit academic now as estranged wife has removed all UAV and tools from workshop in order to screw up any chance of me making a business.
Am starting again from scratch. Will be better next time.
What happened with this project?
I thought you were converting the side profile and using the top curvature as your base.
So this was after your wing was already lofted (I presume is the way you modeled your wing), then you sketched your mount, on the surface of the wing? Then used convert entities?
I also was considering drawing the flat profile then projecting it onto the top surface, then use sketch entities to use it as its own...
We us foam core with great results in the sailplane word... With wings being as light as 100 grams fora 1.5m wingspan... Curious as to what foam you might have used? My plan for the prototype is just simple foam cut, and vinyl wrapped. I will have small parts like the boom mounts 3D printed on shapeways. Then the production model is honey comb core fiberglass/carbon wing and fuselage.
If you have goodluck with simonk let me know, I would love to do the same reverse motor direction for a speed brake on landing.
I can't remember excatly how it was drawn in solidworks. But Convert Entities can be used in sketch mode to copy profiles. The section is an old Clark-Y, the profile is constant along the wing, this made fabrication easier. I think you could still mold wing joiners onto a swept wing profile, provided allignment is spot on. The fuselage is quite long because I wanted to avoid having to ballast the nose in a tail heavy situation. A 5 cell lipo sits in the front nicely.
If you do the foam core method, I would reccomend using carbon-fibre cloth and not fibreglass as I did because of the weight. The wing seemed to 'drink' resin during the laminating process.
I was looking at adding flaps, but undecided as its more complexity. I am aware that the SimonK firmware will allow reversing of brushless outrunner motors, but I have yet to experiment with this.
I as well have been thinking of investing in a 3d printer. It would allow for rapid prototyping and a better product in the end. It would also allow me to make a few one-off custom parts for customers.
Our aircraft dimensions are fairly similar. Your fuse is a tad longer, mine is a bit wider. Our wings have similar wing area, mine is more swept and higher aspect. This is great as it really gives me a feel for the final product. Especially seeing yours, and your set up, flight times, etc.
In my opinion I like foam core composite wings. We use this technique often in the sailplane world and it makes for light, strong and accurate wings. Weight can be saved of course, however the wing is much more precise, allowing for higher performance airfouls. (which are generally more susceptible to inconsistency)
I like the idea for reversing the motor. It would be really nice to have reverse thrust, without having to venture into variable pitch props. Airbrakes are rather difficult. I would suggest, if you are planning a next wing build it with flaps and dual aileron (two servo channels). This will allow you to use some crow. Ailerons up creates drag, and reduces tip stalls, meanwhile the flaps create more lift for a nice, slow touchdown.
Do you mind PM'ing me a bit lore in detail what you used to convert entities? Was it actually a side view of the foil, or were you able to make a sketch on the wing surface its self and convert a sketch to the relation of the wing contour?
I've also been following your work. For the wing boom mounts, I used part of the wing profile and did convert entity on the top side of the airfoil section, it can be helpful to save profiles as blocks in solidworks.
Constructing the boom joiners was a time consuming and laborious process. The joiners were laminated onto the skin of the wing with a seperating polythene sheet. A carbon tube was then laminated onto the joiners with a foam wedge to get the correct geometry.
Now that I have a 3D printer, I would print the part. I would also change the wing design. It would be built up from 3D printed ribs with carbon spars and an oracover skin. The Wing I have constructed is from a foam core laminated with fibreglass, its heavier than I would have liked.
The design is very slippery in the air and landing required a shallow angle of approach and a large field. I have been looking at speed breaks but have been investigating the possibiltiy of reversing the motor in flight.
The fuselage length is 78cm and width 12cm.
PS, congrats on 10,000 views!
Leo, love your build log! looks great!
Quick question. I am familiar with solidworks 09, and just renewed up to 2014... So many things have changed it is as if I am learning a completely new program!
Any tips or tutorials on how you did your wing to boom mounts? That is where I am having trouble the most right now...
Also mind giving me some info on your internal space/fuselage size?