SR71 BUILD - The Blackbird.

Hmm, those cheater holes look like they're going to pull the CoG forward as well. Any chance you can do the maiden without the inlet cones?

The cheater holes are about centre of the C/G , but the fans do suck a lot of air in, i will try it with the cones in first i think from here on in it's suck it and see
And it's bloody raining here so no flying for about a week on the salt lake takes that long to dry out enough, mind you the rain makes the surface very smooth ideal for the SR
Fitted circlip springs to retain the fins on today so its ready to fly at last

The problem with EDF is that the angle of attack of the fans is so huge they're partially stalled, once the aircraft is moving, frontal air pressure speeds up the flow through the fan, this decreases the stall and allows the fan to get 'on the step' so to speak. Those cheater holes will not allow this. Question is there any airflow going in from around the cones?

Yes the is a little air going in around the cones but the most i could get was a 1/4"gap all the way round so not much
We shall see when i get a chance with the weather its dry today up to yet but windy still it helps to dry out the salt lake fingers crossed

That may be enough to get them working. You'll at least get some axial air through.

BB
I think you are asking a lot from those fans with the cones in place.

Unlike a turbo jet an EDF produces nearly half its thrust from the inlet side so any obstructions or bends in the inlet path are almost as detrimental as they would be on the outlet.
Just imagine what the effect the cone and cheat hole would have on the thrust if they were in the down stream part of the duct.

The full size SR manages with the cones because the inlet volume is only about 1/6 that of the exhaust and even then at take off speed it has a significant number of inlet relief doors to let more in.

If you know the claimed thrust of one of your Lander fans on 6s it might be interesting to hold the SR back with a spring balance to see how much static thrust you actually have, hopefully it would be getting on for 75% of its total weight.

The static thrust on the ground when i tested it was 13.7 Kg with the cones in place and that was on 12s hooked up to my digital fishing scales

Theoretically how much thrust should you need BB

Quorneng wrote: BB
I think you are asking a lot from those fans with the cones in place.

Unlike a turbo jet an EDF produces nearly half its thrust from the inlet side so any obstructions or bends in the inlet path are almost as detrimental as they would be on the outlet.

I have had no experience with DF of any type but I always thought that with DF whatever comes out of the tailpipe must have went into the inlet first, afterall, you cant create something from nothing.

Have you tested without the cones

I have not tried it without the cones but at 25Lbs weight and 13Kg thrust in my total ignorance of these things it should work if i can get the nose up :silly: :silly:

It should in theory go vertical with that thrust!

Klipkopwildlife wrote: It should in theory go vertical with that thrust!

28.66lbs thrust on a 25lb model ..... It may not be enough to hold vertical speed due to drag losses .... but it's at least got enough thrust to prop hang ... if it had a prop. :lol:
I would imagine that going into a vertical climb at speed .... it should have enough inertia to carry itself a long way up. :woohoo:

Pol.

LETS HOPE
The SR 71 is loaded in the carrier box and sitting on top of the car ready for the morning, went this morning and it was suprisingly quite dry and very smooth. :silly:
And the Sprint is inside the car so it should be a good couple of hours, i dont stay long on Sundays as Natalia is at home.

Hope it works this time.

If it does I expect it will need an awful lot of sky!