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BIG 1/12 scale SU-37 mid-pusher - blue foam build

Old 12-14-2007, 05:31 AM
  #1  
Larry3215
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Default BIG 1/12 scale SU-37 mid-pusher - blue foam build

This is going to be a "think-out-loud" build thread. When Im working on a new plane I get a general idea in my head then work out the problems as I go on a TLAR basis.

There will probably be a number of problems to solve this time around because Im doing several things Ive never done on a scratch build before.

Im going to have removable wings and stabs and retracts. This is going to be the largest direct drive setup Ive tried and its also my first build with the ridgid blue foam insulation board.

Good quality 6mm Depron is very scarse at the moment. Thats generally my prefered building material - even for large builds like my 85" span foamy.

Leadfeather gave me the idea of using the 1/2" thick blue foam ridgid insulation board. He is planning to use some in building one of my Capricorn flying boats. I searched all over locally and cannot find any 1/2" blue foam. 1" is the thinest thats available. It looks promising for this project tho.

I just finished my second SU-37 with a mid-pusher setup and I really like how that plan form flys. I decided to try a larger one from the thicker foam. The 1" thickness should make room for retracts too - barely.

Attached is a plan view showing where Im planning on having the wings and stabs removable.

The plane will end up about 50" span by 72" long. Thats just about exactly 1/12 scale.

I just bought a sheet of 1" x 24" x 96" blue foam for under $9.00 at my local lumber yard. It should be just about exactly enough foam to build the plane with some small pieces left over.

I have a Great Planes ElectriFly Ammo 36-50-1500kV Brushless In-Runner Electric Motor that only cost $35.00. Im going to try it direct drive on 3S2P 2100 packs turning a 10x6 APC E to start off with depending on the final weight. Should end up in the 500 watt range peak.

I have plenty of packs and servos and rx laying around. The only pricey part is going to be the esc and I have a Phoenix 80 I can use from my 85" foamy. So over all this will be a cheep build.

The full 2x8 sheet of foam weighs 35 ounces now. Im hoping for an all up weight of under 60 ounces. We will see

The reason for the removable wings and stab is to make transport easier.
Ive decided on the 1" foam because Ive nevere tried it and its cheep and I cant get good Depron.
The motor because I have it and its cheep and should work.
Retracts just because they are cool and they might fit in this size plane.

Thats enough for now I think. I'll probably start cutting foam tomorrow.

Larry
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Old 12-14-2007, 05:40 AM
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By the way - I almost got some 1" pink foam, but its made from some cyanosomething?? stuff which I know puts out very very nasty fumes when cut with a hot wire cutter.

Im thinking I may want to do some hot wire cuting to thin down/taper some areas.

This blue stuff is styrofoam, so the fumes should only be moderately nasty instead of instantly deadly

Larry
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Old 12-14-2007, 05:25 PM
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Just thought I'd share my experience with blue foam. I helped my buddy make a 54" 3D scratch build with 2" blue foam. It cuts easily with hot wires and is very rigid. It's a belly lander, and if it comes in too fast or too rough, the fuselage snaps in half. Brittle like a pringles chip. My buddy has been adding balsa reinforcing to prevent this. Just something to think about. I really like the SU-37 airframe. Will yours have working canards? Check out the one by the x-flight.hk boys if you haven't seen it. Good luck with it.
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Old 12-14-2007, 05:44 PM
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Alpea42
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Larry u could build a porta potty that would fly.Heck u probably allready have.LOL
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Old 12-14-2007, 10:27 PM
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Larry,
I have several sheets of the pink foam. Cut it with a hot wire all the time. My hot wire sets right inside of a window which gets opened up before use. I never, (cough-cough), have, (belch, hack, spit) a problem, (Choke, falling to the floor), with, (breathing hard), the fumes, (fading away), affecting me, (gasp, last breath) DOA
Rick
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Old 12-14-2007, 10:31 PM
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No really, IMHO, as long as you have some decient ventilation, you shouldn't have a problem. I do have some and wire it often under the window. I'm still kicking.
Rick
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Old 12-14-2007, 11:39 PM
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The fumes from a burning lipo are much worse.
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Old 12-15-2007, 02:20 AM
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Yeah, there are lots of toxic/risky things to deal with in this hobby. Care is always called for

I cant remember for sure what the fumes from EPS were, but they were bad. The fumes from the Polycyanostuff were way worse. Lots of air movement/exaust is good!

Just thought I'd share my experience with blue foam. I helped my buddy make a 54" 3D scratch build with 2" blue foam. It cuts easily with hot wires and is very rigid. It's a belly lander, and if it comes in too fast or too rough, the fuselage snaps in half. Brittle like a pringles chip. My buddy has been adding balsa reinforcing to prevent this. Just something to think about. I really like the SU-37 airframe. Will yours have working canards? Check out the one by the x-flight.hk boys if you haven't seen it. Good luck with it.
Thanks for the heads up. I may add functional canards later. For now just elevons, ailerons and rudder.

It looks like this stuff is stiffer than Depron but not as forgiving in bending loads.

I got lucky today in my shopping. I was out of 6mm carbon tubes to use as spars and didnt want to wait to order some on-line.

I went to Sportco to pick up some cheep carbon target arrows. They normally run about $2.80 each. The shafts are carbon fiber - if you pick the right ones. They tend to be a little heavier than the hi-end shafts from some suppliers but they are fast and easy.

While I was there I found some micer longer lighter shafts for $2.99 each that they had mis ordered. Then I happend to notice that they had some aluminum arrow shafts that looked like a slip fit over the carbon shafts - YES!

I was worried about making up the sleeve and tube araingement for the removable wings and stabs and this solves that problem nicely.

The carbon arrow shafts were only $2.99 each and the aluminum arrows were $3.5 each.

I still have to decide on which cheepo retract set Im going to order...

I'll post a pic of the arrow shafts in a bit.

Larry
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Old 12-15-2007, 02:22 AM
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Originally Posted by Alpea42 View Post
Larry u could build a porta potty that would fly.Heck u probably allready have.LOL
I had some trouble with the CG.... there was some heavy %#@*&! sloshing around that made balancing the thing dificult :p

Larry
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Old 12-15-2007, 02:33 AM
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Pics of the arrow shafts. The larger diameter ones are the aluminum.

The carbon shafts are just under 8mm OD and the larger aluminum ones are just under 9mm OD.

I hadnt really planed on a camo color scheme, but thats what they had.

Larry
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Old 12-15-2007, 11:17 PM
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Got some foam cut and the rough shape layed out to get a feel for it.

Its bigger than I had pictured in my mind to start!

The wing span now is 49". I still need to add on the outboard missles.

The main "fuse" section is 46" long now. The nose section will glue on later and add another 20" or so. The elevons will hang off the back another 6" or so probably.

Im going to have to clear off more of my work bench than I thought!

Im debating trying some A123 packs on this thing. The extra weight might actually be good....

Larry
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Old 12-26-2007, 05:14 PM
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Larry, couple a weeks no progress. Did the holiday madness put it on the shelf? I know you'll get back to it
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Old 12-27-2007, 04:35 AM
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sweet
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Old 12-27-2007, 09:33 AM
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Originally Posted by Alpea42 View Post
Larry, couple a weeks no progress. Did the holiday madness put it on the shelf? I know you'll get back to it
Yeah, the holidays and family stuff have been slowing me down

I have made some progress, but its mostly been the invisible kind - solving problems befor I glue stuff together and its tooooooo late!

Ive been having two main issues. The 1" foam is bothering me to a large degree. I sure wish I could find some 1/2" to work with. 1" is too thick for the tail surfaces but not enough for the fuse. The retracts are 1" deep so they will require cuts all the way thru the wing, weakening it a lot.

I have been debating wheather to hot wire some of the foam into 1/2" thinck pieces or carve/sand it down or what.

Shaping the foam is going to be more work than I originally pictured. Im used to doing built-up or heat formed structures on my larger foamies that dont need much sanding/carving.

The retracts are the other main issue at the moment. I havent worked with mechanical retracts in 15 years or more so I was starting from scratch basically. I finally got the mounting plate and servo setup figured out last night.

Thats the other issue. Normally with mechanical retracts you would have a single servo in the center of the wing activate both retracts with cable linkages. However, I want removable wing panels, so I have to use a seperate servo on each retract.... Im going to have 3 servos just for the retracts plus one for each elevon/aileron side. 5 large servos are going to need a seperate BEC for sure.

My BIG jet's wings are starting to look kind of small and full of holes!

Im going to have to do a double spar set up now to make up for the large retract and servo cut outs.

details details....

Pics tomorrow.

Larry
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Old 12-27-2007, 09:38 AM
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Old 12-27-2007, 02:48 PM
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Originally Posted by CHELLIE View Post
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Old 12-27-2007, 03:01 PM
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are u make in a profile or scale like the b1b it takes about a day for me to make a foam mold that i can reuse over and over my b1b mold was made out of 2" pink foam from Home depot but you'll need a hot wire i used a striker wing to get my air foil but to cut them you'll need to make a 2 pivot point hot wire cutter i made mine out of 1x2 pine finger joint and use oak for your hot wire guide pine or soft wood burns and makes the wire jump after first cuts hope i may have helped
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Old 12-28-2007, 04:19 PM
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LOL u got all that Larry
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Old 12-29-2007, 09:01 AM
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Originally Posted by b1bman View Post
are u make in a profile or scale like the b1b it takes about a day for me to make a foam mold that i can reuse over and over my b1b mold was made out of 2" pink foam from Home depot but you'll need a hot wire i used a striker wing to get my air foil but to cut them you'll need to make a 2 pivot point hot wire cutter i made mine out of 1x2 pine finger joint and use oak for your hot wire guide pine or soft wood burns and makes the wire jump after first cuts hope i may have helped
Hi b1bman,

Its going to be more profile than scale, though the fuse will be shaped to some degree. How "scale" it ends up will depend largely on how lazy I am when it comes time to do the shaping/sanding

I have a small hot wire cutting setup, but its not up to splitting large peices or doing complex shapes. Ive been debating options on how to do some simple hot wire work followed by sanding to final shape.

My initial goal on this project was to do a quick-n-dirty type build mostly to try out this foam as a building material. Its cheep enough and easy to get, so it has potential for large sized projects.

However, I dont want to sacrifice the "quick" part too much! Its turning out that the details are slowing me down more than I anticipated.

Im almost wishing I had gone for a large profile Yak or Edge 3D machine or possibly even a big bipe instead.

But Im going to see it thru

Here are some shots of the retracts on the mounting plates. I'll start cutting holes in the wings tomorrow and start doing some shaping.

Larry
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Old 12-29-2007, 02:36 PM
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Default su 37

i here ya i done like spending lots or time on a new plane that i am not sher how it wll fly spending all that time to make it sweet and then crash it right off the bat nothing herts like that thats how i did the b1b that why i dont have to many close ups the foam i used for first mold was to soft and dented in vacum bag the biggest reason i am makeing a new mold here are some pic I'll send u more via email dont reallly want to shear them with people that make fun of my sort comeings if there so smart let them figer it out LOL LOL
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Old 12-29-2007, 02:55 PM
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Default hot wire cutter

cutter
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Old 12-30-2007, 03:29 AM
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B1b nobodies making fun of you your finished product is right on. I like that wire cutter too.Are you using the green florist foam in your fuselage
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Old 12-30-2007, 03:46 AM
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AS a matter of fact the lancer is a great idea for a model.Not done by anybody but you.And you have done it the most complicated way.Swing wing ,2 motors ,tailerons and you made it fly .
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Old 12-30-2007, 05:34 AM
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I agree. B1B, I think your project is very impresive!

Alot more work than Im willing to go thru though!

Larry
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Old 12-30-2007, 08:06 AM
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I decided I needed to get the basic sanding/shaping on the wings done before I do the retract cut outs. They will be stronger without the holes cut in them.

I got my small hot wire cutter out and removed the bulk of the foam on the leading edge and tail on a small test piece.

With a little sanding it will be close enough.

I'll do the actual cutting on the wings tomnorrow - when the wife isnt home to complain about the smell of melted plastic!

Larry
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