|Mar 02, 2013, 07:05 AM|
Great timing Cooler,
I think you knocked the nail on the head with your comment -
This will be truly a composite aircraft. foam, fiberglass, plywood, balsa and might even have a little CF to boot!!
Getting the weight, strength and formability balance right is a real challenge, but made easier by people like yourselves happy to share their success & failures so openly.
I’m hoping to have my first play with foam this weekend. It will be interesting to see how I get on with some compound shapes, where your need to roll / stretch the foam in 2 directions – pic.
Looking forward to your next update,
|Mar 02, 2013, 01:20 PM|
For those of you, who are unfamiliar with John Morgan’s building talents with foam, check out his builds in the Pusher Prop Jets forum. In a recent PM to John, regarding his techniques, he said this:
If you are going to build in foam, there is a learning curve. This book is $20 and worth about $1,000 if you are serious about foam building. I very highly recommend it.
As meerkat13 stated,
“Getting the weight, strength and formability balance right is a real challenge, but made easier by people like yourselves happy to share their success & failures so openly."
I agree, a day doesn't go by that I don't learn something new, here on RCG. The text and photos from the build logs are invaluable.
OK, back to the thread.
Now that I'm all caffeined up it's time to get back at it. meerkat13 brough up "compound shapes, where your need to roll / stretch the foam in 2 directions". Not all are possible. I have been working on the ones around the intakes for days without success, you can stretch it some, but not compress the foam. May have to cut some out in the bend area to achive what I want. That will give a chance to try out this product, pic below, comes highly recomended by RogueAce.
" The consistency and characteristics of Foam Putty are similar to foam, making sanding, carving and painting easy. Fill cracks, sculpt or carve, sands smooth"
As a noob to foam, like me, somethings that are handy to have around. A good
selection of various dia plastic pipe, damn handy for making curves. A rolling pin is good! Be creative, look around, you just don't know what might work?
If you have something that works good for you, and you want share it, please post it here.
Just wanted to add this, back in post #58 I posted just a few of the pics I got from yakhakker, who's own the plane. I have many more, which is primarily what I am building this from. Some he had, some he took for me. What makes this even more difficult is I don't have all the angle shots I need, and GLOSS BLACK, although makes a great looking plane, is HELL to get any real perspective of what the angles and cures really are!! The glare and reflections don't help, either!
|Mar 07, 2013, 08:59 PM|
It may not look like it, but I'm getting close to starting this build. Worked out lots of details, and procedures. The pink FFF does not lend itself very well to this, the plastic backing does not allow it to lay flat, and wont hold shape well. Great for practicing on, then you don't mind screwing up so bad!
Plans (if I had any) call for a number of internal formers, 2 aft for stab mounts, and one forward for dowel pin for front of wing. Nose gear retract mount and electronic bay, will be installed after fuse is glassed. Same with structure for fan, rear wing (bolt down) and elevator/or differential stab servo mount. Still have not decided yet. Glassing will depend on how well I am satisfied with the final out come. Hope not to have to do a re-build!!
Assuming all goes well, there is a ton of measuring that will need to be done. Stabs mount at 10° anhedtral each, vert stabs cant outward at 27.5°.
Horizontal stabs need to be 0-0 with thrust tube, which makes fan height critical to mount up with thrust tube and intakes. I will need to make the intakes also, but thats a long ways off!! And vertical stabs need to be perfectly parallel with fuse center line.
When I made this:
http://static.rcgroups.net/forums/at...ture%20002.jpg Working with 5 axis to get all lined up at 0-0 took forever.
Yet another unfinished project. Change the intakes, and it will be perfect for my JF90/Het 1200Kv set-up. Actually its about the same size as the Scorpion.
Well I have my work cut out for me. More when I have it.
|Mar 13, 2013, 11:07 AM|
I figured it was time to either SH*T, or get off the pot!! So now to appease RougeAce and Stupot46, I have made this a build thread. Everyone knows how much time goes into the lead up to a build, this was no different. The exception being, that the drawings I used are for the Aviation Design turbine version of this plane. I changed what needed to be for the E version, best I could, only having photos to work from. The single biggest change was in the horizontal stab--- go with a flying stab, or stab/elevators? I really wanted to keep all the properties of the original, but simplicity won out. Stab/elevators. How ever I will put the servos in the stab to make the linkage simple and straight forward.
The E-version, did not have either flaps or rudders, this will.
I have to agree with acesimmer, as he said in his 76" Scale twin 90mm Composite Typhoon Scratch Build, this MODEL PLANE FOAM is very nice to work with!! Bends and hold shape very well. I can tell you this, marker pens don't work so well on this foam, it doesn't penetrate to good. My fingers are still purple!! This will be a bit of a different build, hardly any formers in the construction!!! Why, you ask? I spent alot of time figuring out how to do this, and the reason simply is you don't need them. With the way this foam hold shape, and the god awfull amount of curves it has, it will hold itself together, and strong enough until I glass the fuse. Then I plan on installing all the formers needed afterwards. Three main areas, nose section-- for nose gear retract, batteries, receiver, etc, mid section-- forward wing hold down and fan mounting- incorporates rear wing hold down. With no plans these have to be cut to fit--PITA! Third area-- stab and vert stab formers. These have to be hand cut and fitted before final sheeting. Stabs have 10° anhedral, and vert stabs have 25° outward cant. On the mock-up I made, I didn't do this, just a waste of good ply. So will need to do it on the fly. I can see lots of measuring in my future!!
Any way here's a few pics, updates will follow when I have made enough progress to warrent it.
|Mar 13, 2013, 01:28 PM|
I like it, your doing an excellent job.
The fact your doing it with just a set of hand made plans and pictures is an inspiration to me. I need the computer and my CNC machine and I still cant do that good.
|Mar 13, 2013, 02:29 PM|
Thanks guys, I have spent since before Christmas working out dimentions, scales, etc. Finally starting to come together. I do have to thank yakhakker (Brad) the owner of the black/yellow Scorpion, he was willing to take some more photos of his plane, and some of the angles I needed. Still could use more. Only so far you can go on imagination. It's what I have, and will do my best to get it right. I set pretty high standards for myself!!
I keep re-evaluating my weight, have to keep an eye on it, everything counts!! The re-tracts I thought I could use (older set of Rhoms) not up to task. I had looked at some here in the classified, but a no go. Thought about the E-flite .60-1.20's, but In a thread I had in the EDF Talk forum, wasn't overly impressed with performance. So currently I'm lookinig at these- http://www.espritmodel.com/robart-ai...20w1-wire.aspx I don't mind air, I had them before, and they work! A little heavier than the Rhoms, 12oz, then Robart wheels and axels add another 6.2oz-6.9oz, depending on 2 1/4" nose-2 1/2" mains, or 2 1/12" nose- 2 3/4" mains. Saw some nice ones at HK, but very heavy--3oz ea!
On grass, I think bigger is better, only .7oz difference. I can just see you guys cringing on the weight! It's not your little foamy! I had first thought 10lb migh be
possible, but that will depend on what the complete airframe weighs. I think 11lb is more realistic.
So---Back to bending foam!
AirX -- If I didn't have a printer that enlarged, and reduced, I'd be lost!
|Mar 14, 2013, 08:41 AM|
meerkat13 --Ducting? I have given it lots of throught, and as much as I wanted it, one piece and seamless, not going to happen. The intake is 2-layers, iniside piece is short- 1"-2", 1/32" x 1" ply in center, and out side skin. That makes it rigid, and ply in center will help keep radius of lip, centered. Intake length, about same as in photo. That will glue to the fuse side & top of intake. Wing fairing is in there somewhere too!
Should be some fun to maintaine symmetry from one side to the next!!
D_FAST-- Not a problem. I'm using the photos I have for visuals on which ever area I'm working on. Not ideal, but all that I have. A lot of the info on the web is more about the turbine version, its bigger, and differs slightly. It might not be an "exact" copy/replica, but damn close!!
|Mar 15, 2013, 11:09 PM|
Sometimes a little inspiration doesn't hurt!
I don't know what the set-up in the plane is, but here's what they have suggested.
*- 1 fan 90 mm, 3 kg (6.6 lbs) to 4 kg (8.8 lbs) thrust
*-RC lander, Schubeler
*-8S or 9S lipo pack, from 3400 to 4400 mah
*-Complete landing gear (Spring Air SA 202 recommended)
I can see where my extra weight comes in, 12s - 5000 mah instead of 8s or 9s, and additonal sevos to start with.
|Mar 16, 2013, 10:49 PM|
Some progress, although slow! Got a little done on the "rear end", not exactly the same, but close enough. The "ring" for thrust tube is a temp, until I hot wire a exhaust cone.
The fun part starts with photo #2. Needed to make a thrust tube to get right measurements for the (2) formers that will go approx where blue tape is. They will accept the two stabs, and twin tails. As soon as I figure out how I am going to do it! Stabs are 10° anhedral ea. and tails ea. have 25° outward cant. Then to figure out and build in the fairings for both. There is lots of "stuff" going on in the back-end.
This came up in the JetFan thread not long ago.
Originally, Rainer(JetFans) said outlet should be 75-76mm dia, he has changed his thinking.
I made it 79mm, I'm not over concered with speed, it will be more than fast enough, but this should help on verticals, and take-offs. Grass field, don't you know!
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