Scratch Building, Aircraft Design, 3D/CAD If you are starting/building a project from scratch or want to discuss design, CAD or even share 3D design images this is the place. Q&A's.

Building a 108" C-130 and need some outside input

Reply
Old 09-24-2013, 09:36 PM
  #1
jordanorville
Thread Starter
 
jordanorville's Avatar
 
Join Date: Sep 2013
Posts: 16
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Question Building a 108" C-130 and need some outside input

I am building a 108" C-130 from scratch. This bird will have retracts, brakes, fowler flaps, functioning ramp/door, cargo rails, and will be used to airdrop pallets, Jeeps, ect. I am quite a ways into the build and have several questions.
1. This aircraft will have a modified flat bottom airfoil, a wingspan of 108", a chord of 12.5" and about 2.5" of camber. I don't want to overbuild this thing but am worried about the overall strength as I have never done a complete scratch build. It goes without saying but i have no intentions of pulling high g`s in this bird.

My initial thought is to make a 1 piece detachable wing using 2 parallel boxed spars, one 3" aft and one 9" aft. This is very similar to the actual aircraft except it uses I-beam spars and the outer wings detach outboard of the #2 and 3 engines. I would love to set up mine to detach the same way but don`t want to create a weak point or add the excess weigh of aluminum tubes or carbon rods. I was planning to use 3/8x1/4 or 1/2x1/4 hardwood for the upper and lower parts of the spar and 1/8 balsa for sheer web. I am hoping that someone with a little more experience could give me some insight, i would estimate that the fuselage will weigh between 8 and 10 lbs. fully sheeted with radio and servos. all of the fuel/batteries will be in the wing aft of each engine or in the aft nacelle, this should help with wing flex a bit. This brings me to my second question

2. Power plant: First of all i need to decide how much thrust i will need, I planed to use 4x .25 or .35 glow motors, however i am terrified of syncing and keeping 4 glow motors running. I also thought of using 4 electrics for reliability but have ZERO experience with them. Thoughts?

I took a picture this morning while cleaning the garage to show where i am at.
Attached Thumbnails
Click image for larger version

Name:	130.jpg
Views:	196
Size:	1.54 MB
ID:	1924646  
jordanorville is offline  
Reply With Quote
Old 09-25-2013, 05:15 AM
  #2
Edwin
 
Join Date: Feb 2002
Location: Leander, TX
Posts: 6,199
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I think for that size, I'd go electric, and I'm a wet power kind of guy. In a four engine wet power setup its not so bad losing one engine, but its catastrophic losing two on one side. I've lost one engine on a B-17 without incident. I always wondered how a dual power system in each nacelle would work out. I was thinking of an edf run at a lower rpm to provide the jet part of the turbo prop sound, along with the prop motor. Sounds over complicated but I bet it would sound cool. As far as the spar goes, a dual box spar setup should work fine. I'd use the 1/2x1/4 hardwood but I think you can get away with 1/16 sheer web. 1/8 would work, your choice. For me personally, I'd go with a one piece wing if you can travel with it. I have a trailer which wouldnt be a problem for me. For a three piece, I'd do the partition outside the engines, making the center piece hold all four engines. There is more help than you can imagine in any of the forums to help with e-power setup. But I would highly suggest you get a watt meter to tell you what you are really using versus guessing. I'd also prototype the system on a 1x8 anchored to a table to make it easier to sort out. Seen many fires driving electric too close to the limit. I design my electric power systems to have about 30% minimum over head. But then, I'm no e-power expert. My electric is mostly smaller stuff, I've never done big electric.
Sounds like a really cool project.
Edwin

What, no opening cargo door? Wouldnt it be cool to drop stuff out the back?
Edwin is offline  
Reply With Quote
Old 09-25-2013, 05:42 AM
  #3
invertmast
 
invertmast's Avatar
 
Join Date: Dec 2003
Location: North Port, Fl
Posts: 7,649
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Just use the aluminum tubes and phenolic sleeves for joining the outer wings to the nacelles. At your weight, the added weight for the piece of mind of not having to worry about the wings folding is worth it IMO

id go electric, ive seen quite a few c130's go in from an single engine failure. All of them avoidable IMO...
invertmast is offline  
Reply With Quote
Old 09-25-2013, 10:09 AM
  #4
jordanorville
Thread Starter
 
jordanorville's Avatar
 
Join Date: Sep 2013
Posts: 16
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I will have to read into the electric but am sure that is the best way to go, even though i wont get the sound and smoke. On that note Edwin, a dual power system with ducted fan running out the exhaust and electric prop would be cool but probably overly complicated to set up, once again i know little about electrics but i would think that if the prop and ducted fan could both run off of the same battery and speed control then it would be easy. I have decided on 1/2x1/4 dual hardwood spars as you were saying, i really just wanted to make sure the overall strength would be sufficient. Thank you both for the input, I think a 1 piece wing is the way to go as i can then sync all 4 flaps together and run off of a single servo. i drive a truck so i can transport the wing inside of a crate in the truck bed.

Quote:
Originally Posted by Edwin View Post
What, no opening cargo door? Wouldnt it be cool to drop stuff out the back?
this model will absolutely have an operational cargo ramp and door. It will also have retracts, brakes, and fowler flaps. i have designed a parachute extraction system and will be able to drop 3 pallets in series. this was a deciding factor when i chose an airframe, that and i am a C-130 crew chief and know the plane in and out.
jordanorville is offline  
Reply With Quote
Old 09-25-2013, 11:08 AM
  #5
Edwin
 
Join Date: Feb 2002
Location: Leander, TX
Posts: 6,199
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Well that is way cool. I have a nephew that is a C-130 crew chief in Japan right now. He's fixin to get a new assignment so no telling where he will end up.
Edwin
Edwin is offline  
Reply With Quote
Old 09-26-2013, 04:09 AM
  #6
wildwillie3
 
Join Date: Sep 2008
Location: Claysville, PA
Posts: 186
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Have you ever read through this thread?

http://www.rcuniverse.com/forum/twin...130-build.html

Awesome build thread!

Bill
wildwillie3 is offline  
Reply With Quote
Old 09-28-2013, 02:32 PM
  #7
Boomerang1
 
Boomerang1's Avatar
 
Join Date: Jun 2005
Location: Sydney, AUSTRALIA
Posts: 2,832
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

108 inch C130, wow, big project!

I have been interested in multi engine models & built 3 with IC engines which was successful
but messy & hard work.

The coming of practical electric power really was a godsend, everything instantly became easier,
cleaner, more reliable & fuss free. That was 20 years ago, electric power has become 10 times
better since then!

This is the model I would like to say I'm flying at the moment but I stuck it in a tree at an unfamiliar
field & damaged it quite a bit getting it down. Fortunately, the most complex part, the wings, escaped
relatively undamaged.

1/ It, like yours, has a modified flat bottom wing which works fine. The span is 110 inch & is in one piece,
if you can store & transport a one piece wing it will be lighter & more convenient to use. Mine also has
I beam spars with hardwood top & bottom plates & balsa webbing. The spars are tapered along their
length to reduce weight. The centre join uses plywood joiners but a triangular box is built in the middle
to allow for the wing sweep. My batteries, flight & radio, are in the fuselage, necessary because the motors
hang off the trailing edge of the wing.

2/ Power plants - For glow engines you probably need less power than you think, the amount of propeller
area is the key. To give you an idea I still have a 100 inch B-29 which used a pair of OS 40's & a pair of
OS 20's. These were basic engines (FP series) & not very powerful but heaps of power for a model weighing
15 pounds + fuel. The B-36 uses 6 geared 400 brushed motors, about the equivalent of single 25! It presently
weighs about 10 pounds with batteries, a change to lipo's saved a pound & gave more power.

Have a serious think about electric power, lighter, simpler, cleaner, more reliable, cheaper, no fuel proofer required
over paint, no mufflers to try to hide, no needle valves sticking out, no fuel filler tubes or filters, no fuel tanks, no
throttle linkages, much much less maintenance & the model will be as easy to operate as your toaster. No fuel bills
either although no one will claim the batteries last forever.

A big advantage is no vibration or stresses when using an electric starter. Everything can be lighter & simpler.

It's really a no brainer these days to use electric power for models like this. Good luck!

John.
Attached Thumbnails
Click image for larger version

Name:	B36 Blacktown2.jpg
Views:	40
Size:	87.2 KB
ID:	1925713  
Boomerang1 is offline  
Reply With Quote
Old 10-07-2013, 07:45 PM
  #8
jwrich
 
jwrich's Avatar
 
Join Date: Jul 2002
Location: Enid, OK
Posts: 744
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

A few years back,a group of club members decided to build the C-130 using Skip Mast plans. We had no instructions only the plans to guide us. Of the four who agreed to build one, only 2 were completed and was flying in our air show team. The skip mast plans called for the airplane to be constructed from foam and sheeted with balsa & fiberglass. We powered them with 4 OS La 40s which was plenty of power to fly the 24 lbs. airplanes. We didn't do a construction thread on any of the forums, but I did do construction photos on our club web site. Both airplanes flew great, not hard to fly at all. After the show team disbanded, I sold my C-130, a few years later Kenny's 130, flew through some trees. He gave it to another club member who has it about ready to fly again. Kenny enlarged the templates and has built a bigger one with 4, 20 cc gas engines, we cut out the foam parts in my garage. He maiden it this this summer. The Spads RC Club web site is http://okbarnstormers.com/, I am the web master for the site. Click on the C-130 Project page and also you may enjoy the Reconstruction of the C-130 page. I did get any pictures of the construction of Kenny's new C-130, I will post a completed picture. Also on the index page, there are links to videos of it flying. If you do build the 130, do a construction thread, I'm sure my would be interested. Here are the pictures.

Rich
.

Last edited by jwrich; 10-07-2013 at 07:49 PM.
jwrich is offline  
Reply With Quote
Old 10-15-2013, 09:17 AM
  #9
jordanorville
Thread Starter
 
jordanorville's Avatar
 
Join Date: Sep 2013
Posts: 16
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Thanks for all the help, i have gotten a lot of ideas from the links and other builds. This is my progress as of today. the flight deck has been formed and the wings are well on their way.
jordanorville is offline  
Reply With Quote
Reply


Thread Tools
Search this Thread
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -8. The time now is 04:32 PM.