SR71 BUILD - The Blackbird.

Hi Tony i finnished it the same as i did my B17 and i had no problems with that, the thing is i was going to do it with Poly C but it was all in the parcel i had stolen i only have a little resin left and cant get any more here, nobody will post it out here so it looks like things will be on hold until i get back to the uk, god knows when that will be, next year maybe.

Don't let this get you down BB, it's just a setback.
You've got a bit of sheeting to fix but it's not the end of the world.
What would be the best way of covering this? ... the choices you have are "Glass epoxy" .. "Glass Polyester"... "Tissue Varnish" etc.
I personally think that the structure looks pretty strong on its own and Tissue/Varnish would be good enough.
If you choose something different, then you've got a forum full of people willing to send you whatever you require ... providing the chemicals can be legally sent through the post.
If I know most of the guys on here, they won't even want paying for the stuff. ( Me included)
This is a fantastic build thread .... don't let one set back spoil it.

Pol.

The SR71 and the Lancaster posing with my thired model Natalia




Lucky me

Garry, when BB refers to soft I think he's referring to the start, not the timing. Soft start definitely eases the start up current, especially if you think your ESCs' are a bit on the light side.

Klipkopwildlife wrote: Garry, when BB refers to soft I think he's referring to the start, not the timing. Soft start definitely eases the start up current, especially if you think your ESCs' are a bit on the light side.

If that is the case , then I agree with you Kippy. I read it as referring to the timing. Maybe BB could clarify this point

Garry

Yes i did mean the start, i set the timing to high, it just seemed to my logical way of thinking a soft start is better for the esc,
I have ordered a watt meter and a 120 amp lipo from GC its 120amp 180 amp bursts
£106
Maybe we should start a thred on lipo's i am useing on the SR gens ace from GC but i find the voltage is a little high according to my lipo tester23/24v for the 6s and a they seem to always be unbalanced, any advice welcome again

Just charged the Gens ace 5500 50c 6s lipo and it's reading 24.947v, unbalanced, 3 cells 14.14
2 cells 4.15 and 1 cell 4.23
With a Fusion charger
Your thoughts

Hi BB

The Lipo question can be quite comp;icated, so to simplify it, think of each cell when fully charged to be 4.20 volts , so a 2S lipo will be 8.40 v charged, and a 4S will be 16.80, again FULLY charged.

Working on that system, you are using 6S lipos,so fully charged should read 25.20 volts ie 4.20 x 6.

As far as the cells not being balanced, it depends on what you are checking the individual cells with
My system is to put the lipo on charge, and when completed and it is reading 16.80 v I use the charger to check each cell. Most good chargers have this facility.

If any cell is vastly different I have a unit called a Battery Doctor, which will balance the lipo down to the lowest cell. When they all read the same I recharge, and this sorts the problem out

I do however ALWAYS balance charge every charge, and as some of my lipos are 3 yrs old , and still perfect, I think it pays off

Hope this helps, if not, ask more questions.

Garry

That pack needs balancing and then when all are equal, recharge. Unless the pack is balanced it will always charge up to that voltage.

The Fusion charger is a good one by the way

Garry

With my company staying i get to sleep with all three of my models for a week

THS SR71 EDF PROJECT

CANCELLED

OK
I have been told that i need 40lb of thrust for a 20lb edf model to fly, i can only get maybe 26-27lb
But i was working on 200 wat per pound for edf
The Lander fans that i bought in the first place and had stolen give 3800w each=7600w now i thought i had a chance of it flying, but no chance at 40lb of thrust
And as you have all seen i know next to nothing about edf so why waste anymore money on it

THE BLACKBIRD wrote: OK
I have been told that i need 40lb of thrust for a 20lb edf model to fly,

Something doesn't ring true here BB ... As I've said previously, I'm a bit of a scientist and I've done degree level physics.
Now I've never built an EDF model but my knowledge of physics tells me that if you have 21lbs of static thrust in a 20lb model ...... it'll go vertical !!!!
I think we need to do a bit of research here & if you want, I know just the man to confirm my beliefs .... He's a flying buddy & a mod' on another forum. He's also professor of engineering at Liverpool University .... If anyone understands the laws of physics, it'll be him.

I think I'll e-mail him.

I've e-mailed the guy & I'll let you know if he replies.
I'm fairly sure 21lbs of thrust will lift a 20lb object but the only other thing I can think of is that you may need a bit more to maintain flying speed because of the model's drag factor.
I can't see this being a problem unless you want to do vertical take offs because I assume that the model will be at flying speed before you pull back on the stick. ... its own inertia should pull it through a loop but you'll have an extra few pounds of thrust which should keep it accellerating upwards.

You've got my curiosity going now ... I can't wait for his reply.

Pol.

I think somebody has their .5 in the wrong place. Lets face it, we commonly fly prop driven models with a thrust to weight ratio of less than one! In fact it's unusual to have unlimited vertical performance, I think the SR71 will fly very, very nicely on 20lb.