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Thoughts how to make this kind of desigh fly

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Shouldn't center of lift be behind center of mass rather than ahead of it?

At least the guide which appeared on Reddit says so:

http://i.imgur.com/MQnxOYH.jpg

And your rear wheels seem to be way too much in the back.

Edited by Kasuha

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It looks like you're going to have problems with tail strike with the size of those engines, which might explain what you're seeing. Nose comes up, tail goes down, engines hit runway.... boom. If you can, move the wings back slightly to compensate. If that moves your centre of lift too far back, try adding canards to your nose.

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Yes, you have to push the center of lift back, as i see there is plenty of space for the wings at the back of the airplane, so it should not be a problem. You can also make it so the front landing gears are lower than the rear, so the airplane's nose would raise on the runway. Front canards can help a lot too, to make your plane turn faster around the pitch axis. With the size of this plane, i think 40-50 m/s should be enough to start to raise from the runway (you dont have to go to the end) - at this speed your plane does not have to be too stable on the ground either.

And generally - the more wings the better :)

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I will try but it does not even try lift off before 85m/s. So bigger wings? and lift back to mass?

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Yes, and front canards - those will help a lot to raise your plane. Btw, maybe you dont know: the fact that it wont raise before 85m/s does not mean that it can't fly under 85m/s. But raising from the ground can be difficult. This is why you need to help it with front canards, and by lowering the front wheels, so the angle of the plane is better on the ground. (The air can go under the wings)

Edit: front canards are not a must have, but they help a lot. With a good design, you can make it so your plane lifts up easily without the canards. But until you build such planes, i think you can allow them to be on your designs :) (some people does not like to use them, because in real life (unlike in KSP) front canards can make the plane unstable by causeing random turbulence at different angles)

Edited by Vlk

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No it barely stays together but stays! Again littbit lift at +85m/s and even slight lift off 1/10 times that I tryed. Ended up in ocean. I am starting to think these engines simply are too heavy and weight/efficiency rate too poor to planes...

First two pictures, slightly improved design:

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Now (desigh unchanged) it started to hardly drag to right. -.-

Yeah, thats a common problem if you re-design too much :) Weight and engine performance can be a problem too - i dont know the parts you use.

I just noticed that your plane has 4 wheels. Maybe you should try 3 wheels, with only one wheel in front.

And the front canals you choose are pretty weak, because only the small parts are rotating. Choose a better one, where the whole wing rotates.

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This video reveals all my problems with this plane: (now with even bigger wings!)

Edited by TUFOM

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Structural panels are a dead weight (I see at least 2 tons of it, maybe 3 tons). Drop 'em.

Move tail landing gear closer to CoM, just a tiny bit behind it. You'll have to pitch carefully after that.

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Yeah, the thrust of those engines seems to be too low for their size. I guess they are high-ISP thrusters designed for space navigation? SSTOs usually use jet engines so they can get the oxygen from the air - this makes them light and efficient, but they also give good thrust.

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Vertical and Horizontal Stabilizers mate.

Your vertical stabilizer is basically spot on your center of mass, making it useless, and the only thing counting as a horizontal stabilizer is the front wing, i foresee that if you get it airborne, it'll flip and fall tail first (or simply spin).

You may want to add a tail, add horizontal stabs on it, and move the vertical stab, this should make it stop dragging to one side and allow you to pitch off the runway :)

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I have had good success with canards at the front of the craft and ailerons at the back for pitch control. But I have crashed more planes that can fit in a 64-bit integer, so you should probably not follow my advice :P

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This is kind of challenge for me. I can make plane fly easily with air breathing engines. But these engies look cool and they work in space! I very well know that their thrust/weight ratio sucs but I think with right design it just enough. I will try to apply your suggestions. =)

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