BlueSky RC Mega Quad - RC Groups
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Aug 01, 2011, 02:35 PM
AMA 46133

BlueSky RC Mega Quad

BlueSky RC sells a limited line of multi rotor frames that are made out of plywood. They are not high tech materials like G10 and carbon fiber so they don't appeal to the techie crowd. However to the old modelers like myself carbon if fine, steel is real but wood is still good. I like to work with wood. I like to get saw dust in my hair and nose. I like the smell of wood when I sand. Wood is also light and very strong.

Combine that with some other material and we can have a very light and strong frame that is relatively inexpensive.

I have been collecting, building and flying those BlueSky RC frames since I found them. I am not associated with BlueSky RC except as a customer.

I started building their basic xRotor sport. That worked out so well I am using one for my default AP machine for tight or confined space.

I am flying their Spider Hex and wish Qrome will come up with the kit so I can build a larger one.

I have flown their tricopter and building the second one.

I have also build their larger quad called the Mega quad. The Mega quad is designed around the 1/2" square tube arm that the user supply their own.

I have done some search and found a couple of sources for 1/2" square tubes. First you can get 1/2" aluminum square tubes from your local hardware store. They are robust but at the same time heavy. You will have one indestructible quad if you use the 1/2" aluminum tube for arms. I have some but did not build one with the aluminum tube yet because I am always on a quest for lightness.

So I figured I will source out some composite materials. I couldn't find any 1/2" carbon square tube so far. I am all ears if some one can point me to some good ones.

So as an alternative I bought some 1/4" pultrude carbon square tubes instead. My logic is that I can put four of them together and I have a 1/2" square tube.

Unfortunately those 1/4" carbon square tubes while good and strong have a round hole in the middle. So the wall thickness is tremendous for the size. They are also heavy. With four arms made up they are only 50 grams lighter than the 1/2" aluminum square tubes in the same lengths.

Nevertheless I finished the Mega quad and it flew extremely well with four Avroto 2814/770kV motors.

Being an anal person I am still searching for a lighter alternative. So the next question to myself. When I was young the saying was something like "you can't fit a square peg in a round hole or a round peg in a square hole" to signify something that doesn't fit.

As I grow older I found that you can always fit square pegs in round holes or round pegs in square holes as long as you are willing and ready to be a little outside the box.

So I found some pultrude 1/2" round carbon tube. The wall thickness is not bad and they are fairly light and very strong. How do I fit those round tubes in the square holes?

There are many ways and the most elegant to me will be to machine some sort of light weight adapter. That will take time, effort and money. I will do that later.

In the meantime some epoxy and thick sil (or micro balloon) will have to do.

So here is just a long way to tell you I have glued four round carbon tube to four square holes.

Thanks for letting me waste your time.

In the meantime I am glad to report that the frame with the wood center piece and four arms is lighter than just the four aluminum arms by themselves.

The first picture is the first Mega quad with four 1/4" carbon square tubes. The second picture is the close up of the round tube going in the square hole.
The third picture shows how I splice the center of the tube. I use one tube full length for two arms. I ground a half round on the end of the other two tubes to match up to the side of the full length tube. So when I glue them together I have more strength.
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Nov 22, 2011, 12:04 PM
30 RC's and counting
Bmr4life's Avatar
So how much does it weigh?
Nov 22, 2011, 12:27 PM
Destroyer of G-10
askman's Avatar
if you can use 10" long tube, goodluckbuy has 1/2" square tube (13mm tube) they have 1.2mm and 0.8mm wall tubing. cheap.
Nov 22, 2011, 01:24 PM
AMA 46133
Originally Posted by askman
if you can use 10" long tube, goodluckbuy has 1/2" square tube (13mm tube) they have 1.2mm and 0.8mm wall tubing. cheap.
That's a bit short. I am keeping the motor to motor distance at around 30".

I wound up making my own wood parts for now. I will post on another thread.
Nov 22, 2011, 01:40 PM
AMA 46133
Originally Posted by Bmr4life
So how much does it weigh?
It depends on what material and length I use for the arms. The plywood part is super light.

The 1/2" aluminum with 1/16" wall thickness is the heaviest. The next alternative I did was to order four pieces of 1/4" pultrude carbon square tubes for the arm. I glue the four tubes together to make a 1/2" by 1/2" arm. At 30" motor to motor I only save 50 grams from the aluminum version.

The third alternative I did was to use 1/2" carbon pultrude ROUND tube. I had to make adapters for the round tube to fit into the square holes but this alternative is the lightest. It worked very well until I crashed it.
Nov 22, 2011, 02:33 PM
Destroyer of G-10
askman's Avatar
you could get some small triangular stock with the round tube as well to hold the tube in as the glue sets.
Nov 22, 2011, 03:41 PM
AMA 46133
Originally Posted by askman
you could get some small triangular stock with the round tube as well to hold the tube in as the glue sets.
Yes I could. I was using some engineering foam and drilling a pilot hole and gluing them inside the square hole. Then I enlarge the pilot hole to 1/2" and epoxy the arms in the 1/2" hole. Works well except I am running out of engineering foam. I think blue foam may work.

Unfortunately my next quad will use these arms:

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