czech89

My Feedback: (4)

I'm bored with all the ARF's, so decided to design my own delta that will be capable of 199.9 mph. Basic specs so far: 4" rocket tube fuse, 16.5" ogive nose cone, span 37", length 54", Dry weight 7-7.5 lbs, Spring-air retracts, Turbine 14lbs. I am curious what the correct CG is for a delta. My plan is to use a CG at 15% MAC. Any constructive comments are welcome. Terry

cobratraxxas69

My Feedback: (31)

How about these online calculators:

http://www.palosrc.com/instructors/cg.htm

http://home.comcast.net/%7Etipstrickslinks/wingarea.htm

erbroens

As usual, it´s nice to see someone´s new concept. and IMO it will fly well with the proportions and CG stated in the plans..

as a suggestion, you can use a vortex generator device to improve the handling of the plane at low speeds , as well a good amount of washout.

b.regards, Enrique

FalconWings

My Feedback: (57)

14 lbs on a 8 lb airframe? Now that's what I'm talking about. you should be able to hit around 199.9mph with that combination at .255556 throttle .

This one is going to rock.

Good luck. Looks awesome.

David

joeflyer

My Feedback: (48)

Interesting concept. Reminds me of my Enforcer. Here's a couple of thoughts:

How are you planning to get sufficient air to the turbine? You'll obviously need some inlet scoops, or perhaps cut away the tube above and before the turbine.

You may want to move the turbine back so that the tail cone extends outside of the tube, otherwise heat will be a problem.

Keep in mind that a round fuse will not generate much lift. With the fuse that long you may need canards to keep the nose up, especially in turns.

The CG looks a bit too forward, if you added canards it would be about right. I suggest that you make a scale glider to fine tune the CG location. I don't believe the online calculators are very precise. Another thought is to make a flying prototype with a pusher prop

14# is way too much thrust. If the airfoil is not too thick it should easily do 200 mph with 7-8 # thrust. Also your wing loading will be quite high with the weight of a 14# turbine and 3-4# of fuel. You might consider a MW44, Simjet 700, or a dialed down Artes Bee.

A better idea is to make your plane bigger. My Enforcer is approximately 48" ws by 60" long and you have to keep it close in. It weighs 12# dry (15.5# wet) with an 11# thrust Ram 500. It's been clocked at 160 mph and can get away from you in a hurry.

You'll need significant material upgrades, wing and turbine mount reinforcements. At the speeds you are talking I doubt that a cardboard tube with a foam wing would stay together.

What kind of fins do you have in mind? You will need a functional rudder.

Here's a picture of my highly modified Enforcer which flies very well. You are off to a good start keep us informed of your progress.

Joe

SJN

well, if this plane is intended fore some kind of speed contest........it should do nicely

czech89

My Feedback: (4)

Thanks for the ideas and comments gents! Joe, good idea to move the turbine back so exhaust temp is not a problem. I will most likely build a smaller glider to tweak the CG. As far a structure, the fuse is phenolic and is designed for model rockets traveling several hundred mph. It will be reinforced with carbon fiber at high stress locations. The wings will be sheeted, glassed and reinforced with carbon fiber as well. The wing spar will be a one piece 1/2" carbon tube. I have not got around to the fin yet, but was contemplating a single vertical mounted on top of the fuse for reduced drag. I will update as it progresses! Terry

Woketman

My Feedback: (6)

If the wing is very thin, you may have a problem creating a strong enough joint between the wing spar and the wing's foam. Might I suggest at least two or three 1/8" ply ribs on each side (like a Roo wing).

joeflyer

My Feedback: (48)

Terry,
I agree with Wocketman, and was mainly concerned about the wing to fuse joint. I was thinking about a couple of formers with extensions on each side that act as wing spars. Kind of like this: -O-.

It may be difficult to mount a single fin on top of the turbine and have room for a former and proper reinforcement. Two smaller fins mounted out on the wings would add a lot of stability, and if done right could also help strengthen the wings.

Make sure that you carve some washout into the elevons and that you have a couple degrees of reflex.

Joe

Woketman

My Feedback: (6)

Joe, that's a GREAT idea. Make two of the spar supporting ribs grow at into the verticals or at least part of the supporting structure for the two verticals!