DSC radio course feedback

[ChrisE]

Finally did this last night and I was generally impressed with the thought that has gone into the system. A couple of things came up that I thought were worthy of further dissemination.

1. Distance of a sighted parachute flare. I'm sure that the old salts around here know this but as I'd not heard before here it is. Max range you can see a flare (all designed to go up 1000' and burn for 45 secs) from a yot is about 26 miles and then it will appear breifly on the horizon, ie it is horizontal to you. If you set off a flare on your craft it will be stringht up from you ie at 90 degrees. From these two sides of triangle you can work out how far the flare is away from you. So if you see one at max elevation of 45 degrees it is about 10-13 miles off, 30 degrees nearer 16, etc.

2. SARTs, these seem to me be really useful things to have in the liferaft. I like the idea of a pointer on a big ships radar showing where I am. Off to buy one this weekend.

One last odd point, you can send off a DSC piracy Mayday automatically that gives your position, just what another pirate might want to join in the fun, I thought. I suppose that you could disconnect the GPS but then the rescuers wouldn't know where you were either!

 

[jonjo]

Re: Decimal point problem

Did you mean to type 4.5 and 3.0 degrees?

 

[ChrisE]

Re: Decimal point problem

Nope, 45 and 30 is what they said at the course but now I do the sums, I think that that you are nearer the mark.

By my reckoning now a flare that goes up 1000' at 20 miles would give an angle of approx. 0.5 degrees, at 10 miles about 1 degree, 5 miles 2 degrees, 2 miles 4 degrees and 1 mile 8 degrees. I took the original figures at face value from the RYA instructor, he'll be getting some feedback from me along with these sums.

Thanks for pointing this out because it could, has(!), cause confusion.

Chris

 

[Solitaire]

Re: Decimal point problem

I think you'll find that the instructor was referring to the angle at which the tube is held - i.e hold the tube at an angle of 45 or 30 degress.

 

[Spyro]

Its a while since I did geometry but if you are seeing a flare at an angle of 45 degreees then you are the same distance from it as it is high so if you were 10-13 miles away it would have to be 10-13 miles high /forums/images/graemlins/confused.gif ( I think )

 

[ChrisE]

No, it was a specific piece of 'knowledge' given as part of the course. Hurrmph!

 

[DJE]

No Spyro is definitely right. If it is 1000' feet high, and you see it at 45 degrees above the horizon, it is 1000' feet away. Have a look at a 45 degree set square, the two sides next to the right angle are the same length.

 

[ChrisE]

Sorry, the no was not to Spyro who is right, the no was to Solitaire.

Err, I wish that I'd never started this!

 

[Cornishman]

I don't think it is a good idea to let a flare off 'straight up' as when it descends there is a chance it will come 'straight down'!
One reason for firing it at an angle downwind.

 

[fireball]

For modern flares that I've come across there are 2 reasons for firing at an angle down wind ....
1) Cos when you fire anything downwind the rubbish burning off will be blown downwind - careful cos of any wind swirling around you, so standing across wind might be advisable.
2) Parachute flares track into the wind - so you fire downwind cos of point 1 and then it tracks back into the wind and should end up above you. Any wind will take the flare away from you as it decsends ...

The angle of firing is altered if there is low cloud - the flare doesn't sense when it is entering into cloud (yet) and so would end up in it - pretty .... useless!!