What is the definition of "Trim"? I hear that word bandied about. But, it seems to mean different things to different people and different groups. I see it mentioned often in diving circles with varying meanings. So, I am confused.
In my history and to me today Trim does not mean the relative postion of the body or the vessel. airplane or scooter, to the earth. An airplane, for example, can be in perfect trim while is a vertical, climbing position relative to the earth. Or, it could be in any other angular relationship to the planet.
In airplanes Being In Trim merely means maintaining the current three dimensional attitude with no, or minimum, effort on the part of the pilot. That is what trim tabs and computer augmentation are for; to take all stress off the crew so the airplane essentially is 'flying itself".
When I did my wreck diving work, from a guy who actually does the stuff, that definition was carried over. Body postion relative to the ocearn floor or the deck or whatever was not the issue. It was maintaining the appropriate body postion with no effort. If that body position was horizontal then the diver should essentially float there. If, like in my avatar, the appropriate body position is vertical then, once obtained, the body should want to stay in that position as if floating.
Lots of words that I hope have not obfuscated the question. So, what is Trim? Does it necessarily equate to a particular body position? If so why?
(Note: I have posted here because I am attempting to shed some light on the subject, not get involved in a culture war which happens all too often in the technical forums. If I ever get back in the water I will continue to learn and expand my personal ability and reject that which doesn't make any sense to where and how I dive).
Trim?
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ArcticDiver
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Trim?
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Re: Trim?
It is shorthand for horizontal trim. "Breaking trim" would be some other position dictated by the conditions/situation, staying parallel to a sloped bottom, floor, or ceiling, or dropping your feet to help get drysuit gas out of them, etc.
The body in water will have a "default" trim which is dictated by the center of bouyancy relative to the center of mass. You want these two aligned and one basically over the other to avoid tipping forward, backwards, or side to side until they are in alignment. If they aren't naturally aligned, you will expend energy proportional to their offset to maintain position. The generally ideal swimming position with the least drag is horizontal (as opposed to a seahorse) so ideally your center of mass and center of bouyancy will be aligned when you are horizontal to create a default flat horizontal trim which takes little effort to maintain. Then when you need or desire to break trim you spend a small amount of energy to do so, complete whatever needs doing, and return to your generally horizontal default to continue.
The body in water will have a "default" trim which is dictated by the center of bouyancy relative to the center of mass. You want these two aligned and one basically over the other to avoid tipping forward, backwards, or side to side until they are in alignment. If they aren't naturally aligned, you will expend energy proportional to their offset to maintain position. The generally ideal swimming position with the least drag is horizontal (as opposed to a seahorse) so ideally your center of mass and center of bouyancy will be aligned when you are horizontal to create a default flat horizontal trim which takes little effort to maintain. Then when you need or desire to break trim you spend a small amount of energy to do so, complete whatever needs doing, and return to your generally horizontal default to continue.
Sounder wrote:Under normal circumstances, I would never tell another man how to shave his balls... but this device should not be kept secret.
Re: Trim?
+1LCF wrote:That's a beautiful, succinct summary, Richard!
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"Anyone who thinks this place is over moderated is bat-crazy anarchist." -Ben, Airsix
"Warning: No dive masters are going to be there, Just a bunch of old fat guys taking pictures of fish." -Bassman
Re: Trim?
I'd add one detail, which is that horizontal trim is also ideal for deco stops in addition to swimming. It makes you hydrodynamic to be able to move horizontally when you need to (particularly against current), while presenting the most surface area to the vertical motions that you are trying to minimize. Errant fin kicks when horizontal will also tend to propel you forwards and backwards and not up and down and minimizes the effect of fin kicks on your buoyancy control. Its a lot easier to be able to get distracted and task loaded and still be able to hold buoyancy when you have horizontal trim, which is a critical part of building a stable platform.
Re: Trim?
Cool question. It is interesting the understanding we bring to this from our various backgrounds. The original question approached trim from an aeronautical point of view. When I heard the term applied to diving, I assumed it had the same origins as I had studied in ship hydrostatics. My professors defined trim as the longitudenal alignment of the ship. A ship that was "in trim" floated so that its designed waterline was parallel to the water. Since I only served on surface ships, submariners may have a different twist on the term. I'd like to hear from one of them. (Kimo?) None of the statements contradict each other, just add nuances of meaning.
Before we had BC's, this was a meaningless discussion. If I were weighted to be neutral at 50 ft, I could only be horizontal at 50 ft. Above that depth I was head down, kicking to stay down. Of course, below I was head up kicking to keep from sinking. Ah for the good old days.
-Curt
Before we had BC's, this was a meaningless discussion. If I were weighted to be neutral at 50 ft, I could only be horizontal at 50 ft. Above that depth I was head down, kicking to stay down. Of course, below I was head up kicking to keep from sinking. Ah for the good old days.
-Curt
Happy to be alive.
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ArcticDiver
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Re: Trim?
Interesting responses. In my personal case I have operated airplanes, cars, boats, etc. In all of those environments Trim referred to the person/craft being stable in the desired positional attitude relative to the planet. That attitude could be at any angle to the planet. For, example a space reentry vehicle would be in "trim" if it was in the correct attitude for successful completion of its' flight. Bring it down in other than the correct attitude and it could very well be destroyed.
This is a dictionary definition:
a.to balance (a ship) by ballasting, shifting cargo, etc.
b.to put (sails or yards) in order for sailing
7.to balance (a flying aircraft) by adjusting stabilizers, tabs, etc.
8.to modify according to expediency; adjust; adapt
I appreciate the education on the non-standard use of the word. Lots of groups use common words in specific, non-standard ways.
The issue of whether the slavish adherence to a horizontal positional attitude is another matter and one that would turn this thread into something I really don't want to get into. I'm only commenting about it here so the sensitive won't try to read something into my posts I don't intend.
This is a dictionary definition:
a.to balance (a ship) by ballasting, shifting cargo, etc.
b.to put (sails or yards) in order for sailing
7.to balance (a flying aircraft) by adjusting stabilizers, tabs, etc.
8.to modify according to expediency; adjust; adapt
I appreciate the education on the non-standard use of the word. Lots of groups use common words in specific, non-standard ways.
The issue of whether the slavish adherence to a horizontal positional attitude is another matter and one that would turn this thread into something I really don't want to get into. I'm only commenting about it here so the sensitive won't try to read something into my posts I don't intend.
The only box you have to think outside of is the one you build around yourself.
Re: Trim?
I know it wasn't the original intent of the topic, but since Richard and Lamont listed some of the benefits of horizontal trim I'll add two more which I think are important. In the horizontal position the diver's lungs and regulator are at the same pressure thus reducing work of breathing compared to upright positions that place the lungs at a higher pressure. It is my unqualified idiot lay person opinion upright scuba-breathing is a risk factor for pulmonary adema. The other thing is deco off-gassing has been proven to occur more efficiently in the horizontal position because body-wide pressure is more equal.
"The place looked like a washing machine full of Josh's carharts. I was not into it." --Sockmonkey
Re: Trim?
Me likey.airsix wrote:I know it wasn't the original intent of the topic, but since Richard and Lamont listed some of the benefits of horizontal trim I'll add two more which I think are important. In the horizontal position the diver's lungs and regulator are at the same pressure thus reducing work of breathing compared to upright positions that place the lungs at a higher pressure. It is my unqualified idiot lay person opinion upright scuba-breathing is a risk factor for pulmonary adema. The other thing is deco off-gassing has been proven to occur more efficiently in the horizontal position because body-wide pressure is more equal.
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ArcticDiver
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Re: Trim?
I wish I had made this a No Hijack Zone. But I didn't. Please return it to that status.
Summary:
In my examples I pointed out that Trim as commonly used refers to being stable in the appropriate positional attitude referenced to the planet. Since in air or water we are in a 3D world that can be in any of 360 degrees. It was pointed out that for a certain segment of the population the word Trim also includes the positional attitude and that attitude is horizontal. This is a non-standard use of the word. But, that is not an issue as there are lots of groups who use words in a non-standard way.
The result is that my question was answered. Maybe others were also educated.
This thread is not the place to argue the merits of any particular attidudinal body position. If someone would like to reopen that topic for yet another discussion of that topic please, oh please, start your own thread. I might even participate in that discussion. But, this thread is not the place.
Again please keep any posts on topic. NHZ
Summary:
In my examples I pointed out that Trim as commonly used refers to being stable in the appropriate positional attitude referenced to the planet. Since in air or water we are in a 3D world that can be in any of 360 degrees. It was pointed out that for a certain segment of the population the word Trim also includes the positional attitude and that attitude is horizontal. This is a non-standard use of the word. But, that is not an issue as there are lots of groups who use words in a non-standard way.
The result is that my question was answered. Maybe others were also educated.
This thread is not the place to argue the merits of any particular attidudinal body position. If someone would like to reopen that topic for yet another discussion of that topic please, oh please, start your own thread. I might even participate in that discussion. But, this thread is not the place.
Again please keep any posts on topic. NHZ
The only box you have to think outside of is the one you build around yourself.
Re: Trim?
Back to ships and such. The first definition alluded to the movement of ballast and cargo. My first job on a ship included maintaining ship stability. Unlike the smaller boats I owned later, my destroyer had no trib tabs. We maintained trim by moving fuel, water, and onboard stores. Not unlike adjusting weight and and air in the BC. To my captain at the time, and subsequently to me, this meant keeping the ship level.
The second meaning, the trimming of sails, relates much as you describe aircraft. Trimming sails meant optimizing speed and course in a given wind and current. Often, our efforts in trimming sails attempted to leave the boat with neutral helm. In that case, a well trimmed boat would "sail itself", maintaining course without touching the helm. Joshua Slocum sailed around the world singlehanded in the 19th century sailing that way.
It seems to me the difference in applications of the term trim deal with the differences between hydrodynamic and hydrostatic situations. With the aircraft, sailboat, and planing powerboat, trim involves the balancing of the forces involved with objects moving in relation to the fluid media. On the other hand, with my ship trim was expected to be maintained at the pier, and a diver wants to maintain position even while "hanging" in the water, we are just balancing weight and bouyancy. In either case, you are trying to maintain a desired position, horizontal or otherwise.
In either case, defining trim as the longitudenal alignment of the body works. I am sure that my dive intructors never gave it that much thought. When they said trim, they meant horizontal - right or wrong.
-Curt
p.s. This is fun!
The second meaning, the trimming of sails, relates much as you describe aircraft. Trimming sails meant optimizing speed and course in a given wind and current. Often, our efforts in trimming sails attempted to leave the boat with neutral helm. In that case, a well trimmed boat would "sail itself", maintaining course without touching the helm. Joshua Slocum sailed around the world singlehanded in the 19th century sailing that way.
It seems to me the difference in applications of the term trim deal with the differences between hydrodynamic and hydrostatic situations. With the aircraft, sailboat, and planing powerboat, trim involves the balancing of the forces involved with objects moving in relation to the fluid media. On the other hand, with my ship trim was expected to be maintained at the pier, and a diver wants to maintain position even while "hanging" in the water, we are just balancing weight and bouyancy. In either case, you are trying to maintain a desired position, horizontal or otherwise.
In either case, defining trim as the longitudenal alignment of the body works. I am sure that my dive intructors never gave it that much thought. When they said trim, they meant horizontal - right or wrong.
-Curt
p.s. This is fun!
Happy to be alive.
Re: Trim?
Your initial post included the following question:
I agree with you that part of the definition of trim includes the idea that you're balanced in a particular position and aren't having to work hard to stay there. I'll add that interestingly enough, in my lexicon, "breaking trim" means leaving horizontal, "good trim" means as close to horizontal as possible, and "bad trim" means not close enough to horizontal to achieve the various ends stated above and without a valid reason to be out of "good" trim. It also gets measured in degrees: 0 degree trim, 5 degree trim, 10 degree trim, 20 degree trim, 30 degree trim. To pass some diving classes, you have to maintain trim within certain parameters.
Like Curt and others said, sometimes you need to be completely vertical or somewhere between horizontal and vertical in order to get somewhere or do something that you can't do horizontal.
I hadn't thought about the fact that "trim", by itself, doesn't necessarily mean horizontal; I thought that it did until I read this thread. It has been cool to read about other uses of the term. Thanks!
Maggie
Others have already answered the "why".ArcticDiver wrote: Does it necessarily equate to a particular body position? If so why?
I agree with you that part of the definition of trim includes the idea that you're balanced in a particular position and aren't having to work hard to stay there. I'll add that interestingly enough, in my lexicon, "breaking trim" means leaving horizontal, "good trim" means as close to horizontal as possible, and "bad trim" means not close enough to horizontal to achieve the various ends stated above and without a valid reason to be out of "good" trim. It also gets measured in degrees: 0 degree trim, 5 degree trim, 10 degree trim, 20 degree trim, 30 degree trim. To pass some diving classes, you have to maintain trim within certain parameters.
Like Curt and others said, sometimes you need to be completely vertical or somewhere between horizontal and vertical in order to get somewhere or do something that you can't do horizontal.
I hadn't thought about the fact that "trim", by itself, doesn't necessarily mean horizontal; I thought that it did until I read this thread. It has been cool to read about other uses of the term. Thanks!
Maggie
Re: Trim?
Non-standard (incorrect) word use used to drive be mad. A perfect example is "turbo". For example, I used to see personal computers with a "turbo" button on the case. Really? Because I don't SEE an exhaust-gas-driven compressor anywhere.ArcticDiver wrote:It was pointed out that for a certain segment of the population the word Trim also includes the positional attitude and that attitude is horizontal. This is a non-standard use of the word. But, that is not an issue as there are lots of groups who use words in a non-standard way.
I got over it. Why get worked up over re-purposed words? I think you're right that we use "trim" incorrectly. But saying "horizontal attitude and in trim" would get burdensome. It's a lot easier to just say "in trim" so I'm going to play along instead of going all Sheldon Cooper about it. I'm not calling you a Shelly, I'm just saying there was a time I would have gone there myself.
You know who's really in trim? The sidemount kids, that's who. Screw gravity. They're like rock fish; statuesque upright, inverted, prone, supine, doing their fancy 4-point rolls...
"The place looked like a washing machine full of Josh's carharts. I was not into it." --Sockmonkey
Re: Trim?
Shelly hehe I think that's gonna stick. :luv:airsix wrote: You know who's really in trim? The sidemount kids, that's who. Screw gravity. They're like rock fish; statuesque upright, inverted, prone, supine, doing their fancy 4-point rolls...
SM is just as much work as backmount. Bogeart's is a strong diver and burly man, he can make it look easy to be in some wacky position, esp. with maximum 11-12lbs of gas on him in AL80s. But its not necessarily a natural "balanced" position. The Razor wing is excellent at putting the center of bouyancy very close to the center of gravity so that helps too. So there's a very short lever between the center of gravity and center of bouyancy. In an ideal diving world these would be the exact same spot. Other SM rigs and tanks are not like this at all. I can guarantee you those "ballet" moves are not gonna be so pretty and fluid with LP95s in a drysuit.
Sounder wrote:Under normal circumstances, I would never tell another man how to shave his balls... but this device should not be kept secret.
Re: Trim?
trim (trm)
v. trimmed, trim·ming, trims
v.tr.
1. To make neat or tidy by clipping, smoothing, or pruning: trimmed his moustache.
2.
a. To remove (excess) by cutting: trim a budget.
b. To remove the excess from by or as if by cutting: trimmed off the rotten wood.
3. To ornament; decorate.
4. Informal
a. To thrash; beat.
b. To defeat soundly.
c. To cheat.
d. To rebuke; scold.
5. Nautical
a. To adjust (the sails and yards) so that they receive the wind properly.
b. To balance (a ship) by shifting its cargo or contents.
6. To balance (an aircraft) in flight by regulating the control surfaces and tabs.
7. To furnish or equip.
v.intr.
1. Nautical
a. To be in or retain equilibrium.
b. To make sails and yards ready for sailing.
2.
a. To affect or maintain cautious neutrality.
b. To fashion one's views for momentary popularity or advantage.
n.
1.
a. State of order, arrangement, or appearance; condition: in good trim.
b. A condition of good health or fitness.
2.
a. Exterior ornamentation, such as moldings or framework, on a building or vehicle.
b. Decoration or ornament, as for clothing.
3. Material used in commercial window displays.
4. Dress or equipment.
5. Excised or rejected material, such as film that has been cut in editing. Often used in the plural.
6. Personal quality; character.
7. A cutting or clipping to make neat: My hair needs a trim.
8. Nautical
a. The readiness of a vessel for sailing with regard to ballast, sails, and yards.
b. The balance of a ship.
c. The difference between the draft at the bow and at the stern.
9. The position of an aircraft relative to its horizontal axis.
adj. trim·mer, trim·mest
1.
a. In good or neat order.
b. In good physical condition; fit; slim.
2. Having lines, edges, or forms of neat and pleasing simplicity. See Synonyms at neat1.
adv.
In a trim manner.
v. trimmed, trim·ming, trims
v.tr.
1. To make neat or tidy by clipping, smoothing, or pruning: trimmed his moustache.
2.
a. To remove (excess) by cutting: trim a budget.
b. To remove the excess from by or as if by cutting: trimmed off the rotten wood.
3. To ornament; decorate.
4. Informal
a. To thrash; beat.
b. To defeat soundly.
c. To cheat.
d. To rebuke; scold.
5. Nautical
a. To adjust (the sails and yards) so that they receive the wind properly.
b. To balance (a ship) by shifting its cargo or contents.
6. To balance (an aircraft) in flight by regulating the control surfaces and tabs.
7. To furnish or equip.
v.intr.
1. Nautical
a. To be in or retain equilibrium.
b. To make sails and yards ready for sailing.
2.
a. To affect or maintain cautious neutrality.
b. To fashion one's views for momentary popularity or advantage.
n.
1.
a. State of order, arrangement, or appearance; condition: in good trim.
b. A condition of good health or fitness.
2.
a. Exterior ornamentation, such as moldings or framework, on a building or vehicle.
b. Decoration or ornament, as for clothing.
3. Material used in commercial window displays.
4. Dress or equipment.
5. Excised or rejected material, such as film that has been cut in editing. Often used in the plural.
6. Personal quality; character.
7. A cutting or clipping to make neat: My hair needs a trim.
8. Nautical
a. The readiness of a vessel for sailing with regard to ballast, sails, and yards.
b. The balance of a ship.
c. The difference between the draft at the bow and at the stern.
9. The position of an aircraft relative to its horizontal axis.
adj. trim·mer, trim·mest
1.
a. In good or neat order.
b. In good physical condition; fit; slim.
2. Having lines, edges, or forms of neat and pleasing simplicity. See Synonyms at neat1.
adv.
In a trim manner.
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ArcticDiver
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Re: Trim?
Actually, I used Trim only in a moving sense. In other trades/industries the word is used quite differently. As a person who has been privileged to build his own habitation the word Trim is used for the finishing pieces around doors/windows and such to hide things and present a more pleasing appearance. It is also used to shear off unneeded or unattractive material such as cloth, wire, etc. It is also used as a reference to grooming a plant or tree.
Saying the word is used in a non-standard way does not mean it is used incorrectly for that group of people. It just means they have changed the language to suit their desires.
Only in a school of scuba diving, as far as I've been able to determine, does it also mean a particular body position. In the others often a further word or set of words is used to identify the specific item and postion. For example: Crown Moulding is trim applied to the juncture between wall and ceiling.
While all this may appear to be a bit frivolous it really has a puropose; better communication.
Yes, you are correct I did open the door to stating the "why" of horizontal. My Bad. That was opening the door to essentially theological arguementation that has no end. Sorry. Can we close the door before people's blood pressure rises to unhealthy levels.
Saying the word is used in a non-standard way does not mean it is used incorrectly for that group of people. It just means they have changed the language to suit their desires.
Only in a school of scuba diving, as far as I've been able to determine, does it also mean a particular body position. In the others often a further word or set of words is used to identify the specific item and postion. For example: Crown Moulding is trim applied to the juncture between wall and ceiling.
While all this may appear to be a bit frivolous it really has a puropose; better communication.
Yes, you are correct I did open the door to stating the "why" of horizontal. My Bad. That was opening the door to essentially theological arguementation that has no end. Sorry. Can we close the door before people's blood pressure rises to unhealthy levels.
The only box you have to think outside of is the one you build around yourself.
Re: Trim?
Not really. We just call those with danglies everywhere Xmas treesJeremy wrote:Doesn't trim in scuba refer to having all your stuff intelligently stowed away and not dangling all over the place as well?
Sounder wrote:Under normal circumstances, I would never tell another man how to shave his balls... but this device should not be kept secret.
Re: Trim?
See Jeremy's post, definition #9.ArcticDiver wrote:Only in a school of scuba diving, as far as I've been able to determine, does it also mean a particular body position.
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Joshua Smith
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Re: Trim?
Nobody has brought up the slang definition, which disappoints me a little.....
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John Rawlings
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Re: Trim?
It's a NHZ, or I'm sure that it would have been posted....Joshua Smith wrote:Nobody has brought up the slang definition, which disappoints me a little.....
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