Velcro
- Thread starter coveman
- Start date
coveman
Well-Known Member
You need to dream of better velcro
Stuff I was given is used, amongst many applications, to secure modules inside million dollar gyro stabilised cameras on helicopters. Crazy strong and will never have a nut rattle loose
That then sounds good enough for my tiny chartplotter
!!ShinyShoe
Well-Known Member
Intresting though process , but you do know a vertical fighter plane will pull around 9 G and the normal human can handle around 5 G
I think the G force of an object placed on a bulkhead has very little G force on it , a typical jet taking of you feel around 1.5 G
And F1 pulling around maximum 4.5 G
So if your Boat sails down a large wave pulling heavy G you will not care about your Velcro more your underpants
Yes 10G sounded unlikely.
The difference with something like a boat is the force will be momentary.
RichardS
N/A
Can a boat really ever experience more than 1G? I suspect that anything more is extremely rare.
Richard
Seajet
...
I'd think it obvious a boat will sustain pretty severe momentary G shock loads when battering into waves or falling into troughs, hence why things which seem well stowed end up on the cabin sole.
Also when working on the foredeck it's not unusual to have the deck drop from under one, so negative G at the front, momentarily.
It would be interesting to fit accelerometers on a typical cruising boat in heavy weather or going through overfalls, I'm sure plenty of designers have such data to hand.
Also when working on the foredeck it's not unusual to have the deck drop from under one, so negative G at the front, momentarily.
It would be interesting to fit accelerometers on a typical cruising boat in heavy weather or going through overfalls, I'm sure plenty of designers have such data to hand.
RichardS
N/A
Falling into troughs or having the deck drop away can only be 1G by definition, as I said.
I suspect that anything more is rare, as I also said.
Richard
Seajet
...
I don't know what definition that is, but the impact of slamming into waves will ' by definition ' be more than 1G, I suspect quite a lot of G momentarily; British fast jets usually have a crash switch which turns off all the electrics on a 27G + impact, ie a hard but survivable crash landing - a lower figure would risk losing the electrics in life's jolts.
The foredeck dropping away will be briefly negative G at the bows.
The foredeck dropping away will be briefly negative G at the bows.
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RichardS
N/A
I don't know what definition that is ...QUOTE]
The definition that when one free falls under gravity one experiences negative 1G.
Richard
ShinyShoe
Well-Known Member
I don't know what definition that is ...QUOTE]
The definition that when one free falls under gravity one experiences negative 1G.
Richard
If you are falling at 1G but the hull is now rising up a wave is there not a moment when those two multiply/add/combine in some way...?
RichardS
N/A
Indeed .... but that's not the falling into the trough or the deck dropping away. That's when the falling/dropping stops. But it's not much of a fall and it's usually a reasonably watery stop so I suspect that large G's will be very rare.
Richard
Robert Wilson
Well-Known Member
Gee!
I never knew sailing was so technical
I never knew sailing was so technical
Buck Turgidson
Well-Known Member
Every time the bow raises on a wave or stops sinking off another it experiences more than 1g. Every time it stops raising and starts falling it experiences less than 1g. If you've ever been bounced on the foredeck you have experienced more than 1g and momentarily less than 1g. A falling object accelerates until it's drag equals it's mass*1g. It is then in equilibrium and no longer accelerating. The g you would "feel" starts at 0 and increases to 1.
-1g would require some other outside force to to accelerate you faster than gravity, like a wing or the rails of a rollercoaster but you cannot free fall at -1g. You free fall at 1 g and feel 0 to 1g as your acceleration rate reduces to 0. When you hit the ground you will experience considerably more as your velocity reduces to zero rather abruptly.
Baggywrinkle
Well-Known Member
If you manage to pull 10g hitting a wave, then a 70kg adult will briefly weigh 700kg .... I'd be more worried about my ankles, knees and spine than a plotter falling off a bulkhead.
RichardS
N/A
thinwater
Well-Known Member
Weightlessness is 0G. Negative Gs would be the effort required to hold yourself down (which I have experienced!), which would typically be minimal (a tenth?).
Drawing ANY corollary to the max G force of a boat slamming back down is a fool's errand; I'm quite sure it can range from a fraction with a deep keel to over 10 Gs with a flat bottomed skiff. Additionally, the location on the boat is a huge factor, as others have explained. I think Richard is close, and that anywhere near the cockpit 1.5G is probably conservative.
Drawing ANY corollary to the max G force of a boat slamming back down is a fool's errand; I'm quite sure it can range from a fraction with a deep keel to over 10 Gs with a flat bottomed skiff. Additionally, the location on the boat is a huge factor, as others have explained. I think Richard is close, and that anywhere near the cockpit 1.5G is probably conservative.
Buck Turgidson
Well-Known Member
http://finot.com/nouvelles/actucourse/0301recherche/csys4.pdfSo what do you think .... max say 1.5G or max say 10G?
Richard
5g max at the bow in this report.
RichardS
N/A
That was the maximum single recorded high on one racing boat in 5m waves out of all those tested on one occasion right at the bow.
1.5G was the usual maximum and that amongst large ocean going racing boats in severe conditions.
I refer to my original hypothesis.
Richard
Buck Turgidson
Well-Known Member
This one?That was the maximum single recorded high on one racing boat in 5m waves out of all those tested on one occasion right at the bow.
1.5G was the usual maximum and that amongst large ocean going racing boats in severe conditions.
I refer to my original hypothesis.
Richard
Which is not correct. A boat will probably experience more than 1g about 50% of the time. The other 50% being less than 1g.
Or this one?
Which is patently incorrect.
As for using velcro or similar. I'm all for it.
RichardS
N/A
Absolute tosh, I'm afraid. A sailing boat will experience about a fraction over 1G 49% of the time and a fraction under 1G the other 49% of the time. During the other 2% it will experience slight more with a typical maximum of 1.5G and, extremely occasionally, for a racing boat in storm conditions at the bow, up to 5G. However, a cruising sailor will probably never experience 5G in his or her entire life, and 10G is totally impossible.
I refer you to my original hypothesis. :encouragement:
Richard
Buck Turgidson
Well-Known Member
Take a breath and read what I wrote and then your rebuttal.
I wrote "more". You call that tosh because you describe it as "about a fraction over"!
I wrote "about 50%". You call that tosh because you describe it as "49% of the time"!
I suggest you are looking for an argument where there isn't one.
Earlier you asked if the maximum g was closer to 1.5 or 10. I found a report where the MAXIMUM value recorded was slightly over 5.
As for 10g being totally impossible, I would be rather less certain. Your caveat of "cruising sailor" makes the whole thing moot as I don't know what that means. Do cruising sailors never get storm bound? Sail the southern oceans?
As far as I can see your original hypothesis is that anything more than 1g is extreme. It is in fact common place.
Again, I'm an advocate of velcro and similar products. I don't like drilling holes where not necessary.
:encouragement:
