learn to sail exam test question

calicosine

calicosine

New Member
hey all, i'm taking this class at a parks and recreation facility so i can rent their lasers so i can take a friend out on the lake. as part of the requirements i have to take a written test and this is one of the more confusing questions on it. now is it just me or does this question seem confusing? any thoughts?

WHEN THERE IS RISK OF COLLISION,THE FOLLOWING MUST KEEP CLEAR OF A SAILBOAT ON A PORT TACK.
A. a close-hauledsailboat on a starboard tack.
B. a sailboat running on a starboard tack.
C. a small power boat underway.
D. a sailboat also on a port tack and to leeward.


A SAILBOAT IS SUBJECTTO NAVIGATION RULES APPLYING TO POWERED VESSEL WHEN:

a. it is designed with a an inboard engine
b. it is under sail
c. it is in heavy marine traffic
d. it is navigating under power

A SAILBOATS CENTERBOARD, DAGGERBOARD, OR FIXED KEEL.
a.provides lift to windward
b.prevents the boat from sliding to leeward
c.prevents the boat from sliding to windward
d. a and b


its an take home open book test but the answers to these questions don't seem to be in the book( i've read it cover to cover twice). i belive it's just a poorly worded question(s) what does everybody think?........thanks terry:confused:
 
calicosine said:
hey all, i'm taking this class at a parks and recreation facility so i can rent their lasers so i can take a friend out on the lake. as part of the requirements i have to take a written test and this is one of the more confusing questions on it. now is it just me or does this question seem confusing? any thoughts?

WHEN THERE IS RISK OF COLLISION,THE FOLLOWING MUST KEEP CLEAR OF A SAILBOAT ON A PORT TACK.
A. a close-hauledsailboat on a starboard tack.
B. a sailboat running on a starboard tack.
C. a small power boat underway.
D. a sailboat also on a port tack and to leeward.


A SAILBOAT IS SUBJECTTO NAVIGATION RULES APPLYING TO POWERED VESSEL WHEN:

a. it is designed with a an inboard engine
b. it is under sail
c. it is in heavy marine traffic
d. it is navigating under power

A SAILBOATS CENTERBOARD, DAGGERBOARD, OR FIXED KEEL.
a.provides lift to windward
b.prevents the boat from sliding to leeward
c.prevents the boat from sliding to windward
d. a and b


its an take home open book test but the answers to these questions don't seem to be in the book( i've read it cover to cover twice). i belive it's just a poorly worded question(s) what does everybody think?........thanks terry:confused:
Click to expand...

Hi Terry, I think the questions are worded OK.

1. WHEN THERE IS RISK OF COLLISION,THE FOLLOWING MUST KEEP CLEAR OF A SAILBOAT ON A PORT TACK.
not A, because Starboard tack boats have right of way over port tack boats, it doesn't matter if it is closed hauled, beam reach, or running
not B, Starboard over port
C is the answer because sailboats under sail have rights over boats under motor power
not D, because of boats on the same tack, the boat to leeward has right of way

2. A SAILBOAT IS SUBJECTTO NAVIGATION RULES APPLYING TO POWERED VESSEL WHEN:
d. it is navigating under power. This means when a sailboat has both sails and a motor, if it is using the motor, it is treated as a motorboat under the rules of navigation. If the boat has both sails and a motor but is not using the motor, then it is treated as a sailboat-- with rights over powerboats. Just so you know, the exception is there are no rights over working powerboats such as fishing trawlers at work, dredgers, and tankers.

3. A SAILBOATS CENTERBOARD, DAGGERBOARD, OR FIXED KEEL.
I believe the answer is D. Both lift to windward and an anti-sliding-to-leeward device.

What say ye other sailors?
 
#1 C

#2 D (what's a motor doing on a sailboat anyway.....kidding kidding...but...)

#3 They probably want you to say D. I don't know the physics behind a symetrical daggerboard, but I never think of it as lifting me to windward, just allowing me to track the boat and fight the healing moment of the sail. again, no physics major here
 
Isn't the answer to one and three technically "All of the above"?

1) All boats have a duty to avoid a collision if possible.

3) The centerboard stops the boat from sliding to leeward and provides lift to windward, but if there were a force pushing the boat to windward then it would prevent that too.

The questions are horribly worded and appear to have been written by someone in the parks and rec. department who had read the book but who didn't understand the reality of the situations he was asking about.

The answers they probably want you to give are C, D, D.
 
Merrily is right, their is lift being created to weather. It has to do with Bernoulli's pressure drop theory and voila! lift is created!

Tim
 
thanks everyone, i was right on the answers, it just seemed to me the questions were worded by committee.but i passed the test so it's all good.....terry:D
 
TimClark said:
Merrily is right, their is lift being created to weather. It has to do with Bernoulli's pressure drop theory and voila! lift is created!

Tim
Click to expand...

Huh? I suppose the lift created by the centreboard is not offset by the opposing forces pushing to leeward because I cant imagine a boat could drift to windward
 
I always wondered how a centre board that is symmetrical could provide "lift to windward". An airplane wing has to be asymmetrical to create lift, ie longer on the top than the bottom, so there is less pressure on the top (ala bernoulli) and it provides lift.
I suppose though that as a yacht will always slip to some extent to leeward, then there will be a greater pressure on the leeward side of the centre board and this greater pressure on one side means a force (lift) in the windward direction. To me though its confusing to say its lifting to leeward, its still only limiting the slippage to leeward and saying theres a lift is just another name for the same effect.
 
abenn said:
I always wondered how a centre board that is symmetrical could provide "lift to windward". An airplane wing has to be asymmetrical to create lift, ie longer on the top than the bottom, so there is less pressure on the top (ala bernoulli) and it provides lift.
I suppose though that as a yacht will always slip to some extent to leeward, then there will be a greater pressure on the leeward side of the centre board and this greater pressure on one side means a force (lift) in the windward direction. To me though its confusing to say its lifting to leeward, its still only limiting the slippage to leeward and saying theres a lift is just another name for the same effect.
Click to expand...

I see where you are coming from. The only reason it provides lift is because there is slippage!
 
abenn said:
An airplane wing has to be asymmetrical to create lift, ie longer on the top than the bottom, so there is less pressure on the top (ala bernoulli) and it provides lift.
Click to expand...

If an airplane wing only provides lift because it's longer on the top than the bottom then how is it that stunt airplanes can fly upside down? :confused:
 
The centerboard is providing lift as a result of flow over the foil based on its angle of attack through the water. There is some interesting discussion on angles of attack etc at: Proper Course
 
Thanks for that link Sailchris - some interesting discussions from following that and I still find it interesting that after all these years of building planes, fluid dynamics, aerodynamics etc that there still doesn't seem to be a definiticve answer as to how sails work !

I see what you mean about the "angle of attack" providing lift. Its just like the example shown at http://www.phys.unsw.edu.au/~jw/sailing.html where he discusses holding his hand at an angle to the wind as he rides his bike. With a boat going upwind, it's pointing in a certain direction, say 40deg to the wind, but because its also slipping sideways its actually travelling at say 45deg to the wind direction, so the centreboard iseffectively angled at 5deg to the water as its is pushed through it and so experiences the lift force.
Again though I think its confusing to many people to call it a lift as if its an aerodynamic effect like an airplane wing. If the boat was travelling straight through the water there would be no "lift". If the centre board was just rectangular it would generate just as much "lift" although obviously go a lot slower. ie its just a reaction force to being pushed through the water at an angle rather than "lift".
In answer to the comment about stunt planes flying upside down, I don't really know ! I think when I've seen them do this the tail of the plane is very low, so maybe its doing the same thing, tilting the upside down wing at such an angle that it works using the "angle of attack" method.
 
abenn said:
Thanks for that link Sailchris - some interesting discussions from following that and I still find it interesting that after all these years of building planes, fluid dynamics, aerodynamics etc that there still doesn't seem to be a definiticve answer as to how sails work !

I see what you mean about the "angle of attack" providing lift. Its just like the example shown at http://www.phys.unsw.edu.au/%7Ejw/sailing.html where he discusses holding his hand at an angle to the wind as he rides his bike. With a boat going upwind, it's pointing in a certain direction, say 40deg to the wind, but because its also slipping sideways its actually travelling at say 45deg to the wind direction, so the centreboard iseffectively angled at 5deg to the water as its is pushed through it and so experiences the lift force.
Again though I think its confusing to many people to call it a lift as if its an aerodynamic effect like an airplane wing. If the boat was travelling straight through the water there would be no "lift". If the centre board was just rectangular it would generate just as much "lift" although obviously go a lot slower. ie its just a reaction force to being pushed through the water at an angle rather than "lift".
In answer to the comment about stunt planes flying upside down, I don't really know ! I think when I've seen them do this the tail of the plane is very low, so maybe its doing the same thing, tilting the upside down wing at such an angle that it works using the "angle of attack" method.
Click to expand...

Question: How do I use all this to stop coming last!
 
The angle of attack is small for the centerboard -- only a degree or two. Next time you're driving around at moderate to fun speeds, put your hand out and point it directly into the oncoming wind. Then let it move "outwards" a little bit. You'll feel the lift (basically). For the centerboard to create lift, the bow of the boat will not point exactly in the direction you're moving, but will point a degree or two into the wind compared to the velocity (direction of movement) of the boat.
 
abenn said:
There still doesn't seem to be a definitive answer as to how sails work !
Click to expand...

They remove money from sailor's pockets.

They do it very effectively and relentlessly

back to the ythread subject...

I say the proper answer to the third questrion is "This question cannot be answered properly by any of the selections."

You should write a note, says me, to the instructor and inform him about this discussion and tell him there are many of us who would love to help him / her to create more proper questions on the next exam. ( Maybe print out hte discussion and give him / her a copy.)

It is great to have wonderful folks who are willing to spend the time to teach introductory boating courses. The best way we can thank them is to help them in any way we can.

One possible re-write:

The usual purpose of a modern SAILBOAT'S CENTERBOARD, DAGGERBOARD, OR FIXED KEEL is to
a. provide some lift to windward
b. slow the boat's tendency to slide to leeward
c. prevent the boat from sliding to windward
d. a and b

I don't love my version of the question but at least the answer D which was obviously the intended answer on the test, is a correct answer in this version of the question.

Also, I believe a discussion in the classroom should be held about the "absolute correctness" of ALL the offered answers to the first question.

I believe the focus of that discussion should be, "No boat, car, truck, or even a person EVER has blind charge ahead without looking RIGHT OF WAY!"

As an example: On our local lake, we had a night time collision between an unlit boat and another boat. Each boat driver was cited for improper operation.

It is an obligation of all boat operators to maintain a proper lookout and do whatever is reasonable to avoid any potential collision.

What is reasonable?
That answer lies somewhere between:

I would have had to set down my beer to grab the wheel

and

I would have had to toss a match in my gas tank and blow my boat and self to smithereens

Enjoy your course and thank your instructor for spending time teaching it!!
 
Skipper Johnson said:
Question: How do I use all this to stop coming last!
Click to expand...

Take some friends out and teach them to sail!!

Sometimes the only sailors behind me are the ones I have recently introduced to the game...

very recently
 
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