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Mansfield171
4th October 2011, 08:53 AM
Sorry for the misleading title; I have a new board that fits nicely on my roof rack upside down with the fin facing the rear of the car, but have been told that it should always go fin forward. To me, this sounds illogical as the fin acts as a wind vane and would tend to keep the board centered if in the rear and might push the board to one side or other if in the front (both scenarios assuming the straps/tie downs loosen up). Also, it looks cooler fin aft.
Why fin front? Thanks
Ps I keep a safety line around the fin, tied to rear strap, to keep the board from possibly sliding aft.

nonopr
4th October 2011, 09:45 AM
The reason the fin side goes to the front of the car is because the board rocker is almost flat on the back of the board and it won't push the board down or even push to board up off the racks.
You should never leave a fin on because you can hit something and bust your box or maybe even the board. Every time I see a guy with the board like you like to do it I just laugh because we know is a beginner. New comers are always welcome. Enjoy windsurfing no matter how you put your board in the racks but not fin back and even better with no fin.

Unregistered
4th October 2011, 12:26 PM
This question of how to position a board on the car roof rack crossed my mind too. I have seen many people putting boards upside down with the front of the board pointing to the front of the car. It may look good as the board's shape follows the curve of a car's roof. But I think this will actually cause more drag hence you will get less milage per litre of gas. If we were to think of the aerodynamics of a board, then a board on the car roof would behave more like a spoiler if the board is placed with the tail of the board pointing to the front of the car and with the deck of the board facing up. Another reason why I place my board in this manner is to prevent possible damage to the bottom of the board.

One thing I don't do is to leave the fin still fixed on the board when I transport my board on a car roof rack.

Any one with a good understanding of aerodynamics care to share your thoughts on this?

Sailboarder
5th October 2011, 12:29 AM
Most of the time, I carry my board upside, front to the front, with the fin back. I even leave the mastfoot! I have to admit that I'm lazy and that I don't need to go far.

If I travel further, I will remove the fin (and mastfoot) to reduce drag. I put the board upside down, but still with the nose to the front. My board curve follows roughly the curved flow of air around the car. However, since the nose is larger than the tail, It might be better with the tail first? I'll try it next time.

Ken
6th October 2011, 11:12 PM
With the tail first and upside down, the board is more stable with less frontal drag, no downward force, plus the nose rocker at the back directs the air flow down the back window and minimizes turbulance for better gas milage.

I have a van now, but traveled extensively at one time with up to three boards stacked in one pile on top of my sedan.

nakaniko
8th October 2011, 02:08 PM
As far as I can see at least 90% of riders here in Europe travels with nose forward, boards upside down. In german highways I've travelled also for two hours at 170 kmh with Ventura 343-255 lt and over it Mistral Score 112.

joe_windsurfer
8th October 2011, 03:14 PM
fin damage is one thing
just donut overload :)
http://forums.pelicanparts.com/uploads2/356_dachlast1071432365.jpg

Unregistered
9th October 2011, 09:54 AM
As far as I can see at least 90% of riders here in Europe travels with nose forward, boards upside down.

If 90% of people are doing something wrong, does it make it right?

Ken
11th October 2011, 01:12 AM
One other tidbit for those that travel with boards on top. - ALWAYS use two straps on the front, one to secure the board(s) and the other for a back up. Generally, new straps will not fail, but as they age and get cooked by the sun, they begin to wear.

On a long trip at 70 mph with two boards on top, I left the highway on to a side street where the front strap suddenly broke, luckily while moving at only 30 mph. The boards shifted to the side, but did not fall off. From that point on, I always used a second "safety" strap on the front.

I shutter to think what may have happened if the strap broke 5 minutes earlier on a highway filled with cars.

Unregistered
11th October 2011, 03:09 PM
Here is my "analysis":

Assuming the board is not in a board bag and it is placed upside down on the car roof rack, there will be a pressure differential when air passes over and under the board, hence there will be a lift force in the direction of the hull (is it called hull?, the bottom of the board).

With the nose pointing to the front, there will be more drag than if the tail is pointing to the front.

However, if the board is placed with the deck facing up and nose pointing to the back, the pressure differential will press the board down onto the roof rack, hence less force on the straps (lesser risk of strap breaking?)

2 other disadvantages of putting the board upside down:

a. the roof strap might cause depression marks on the hard edge of the board if straps are pulled very tight. (eg, slalom board)
b. risk of flying pebbles hitting and damaging the bottom of the board which you want to keep it smooth. (Deck of a board will be easier to repair if damaged)

However, I'm not sure if this drag & lift is significant with regards to fuel efficiency and when the board is transported with a boardbag. : )

Ken
12th October 2011, 10:10 PM
To solve the strap/rail damage issue, I always slipped a small piece of carpet (8 cm square) under the straps at the corner. I would also twist the strap as it ran across the bottom of the board so it wouldn't "flutter" and mark/damage the board.

Basically any rock hit on a horizontal surface (top or bottom) should be insignificant. However, the leading edge (nose or tail) are at the greatest risk since the hit will be straight on rather than at a parallel angle.

COACHG
12th October 2011, 10:19 PM
Mercedes Benz conducted a wind tunnel test on boards carried on roof racks and the findings showed that wind noise and drag could be reduced by positioning the equipment on the car with the nose toward the front of the car, the deck facing down and the nose overhanging the roof as little as possible. This study is posted in the book “Start Windsurfing Right!”

Coachg

nakaniko
13th October 2011, 05:18 PM
Mercedes Benz conducted a wind tunnel test on boards carried on roof racks and the findings showed that wind noise and drag could be reduced by positioning the equipment on the car with the nose toward the front of the car, the deck facing down and the nose overhanging the roof as little as possible. This study is posted in the book “Start Windsurfing Right!”

Coachg

And so if a german car brand gives this test results, usually it mean that this is the better way to carry a board.
Anyway when I went to Munich to pick up the Serenity, the Starboard distributor staff suggested me to put the long serenity (460 cm) over my 430 cm car in this way. So Starboard itself does agrre with the test.

Philip
14th October 2011, 10:56 AM
And the NP board bag I have is silver side to the bottom of the board which to me says the silver goes sunny side up nose forward. Have always carried boards that way because I don't want lift at the front of the car at motorway speeds.

nakaniko
17th October 2011, 07:00 PM
And the NP board bag I have is silver side to the bottom of the board which to me says the silver goes sunny side up nose forward. Have always carried boards that way because I don't want lift at the front of the car at motorway speeds.

For sure! I was forgetting the simple and right thing you say! I know a lot of famous brands that use to do this.
I can also add that all bags are streamlined to go tip forward, having smooth edges in the bow, and instead having zipper and more free edges in the stern; so they are clarly ALL intended for a bow-forward carrying.
Therefore the main pressure imho comes not from straps, but from rack bars pressure, so it's way better to have the stronger deck in contact (even with foam spacers) with them.
No more answers from the opposite party?

Farlo
17th October 2011, 10:49 PM
I also carry my boards upside down and nose forward (now always in bags). In the past you could really damage the hull with over-tightened straps plus solar heat. I remember polyethylene and also ASA boards with very deep marks. However you don't need to tighten the straps too much, moreover with a soft tube around the bars. The only advantage I see with tail forward is that you can check the fin through you windshield so you know the board is still on the roof.

Unregistered
18th October 2011, 11:26 AM
For sure! I was forgetting the simple and right thing you say! I know a lot of famous brands that use to do this.
I can also add that all bags are streamlined to go tip forward, having smooth edges in the bow, and instead having zipper and more free edges in the stern; so they are clarly ALL intended for a bow-forward carrying.
Therefore the main pressure imho comes not from straps, but from rack bars pressure, so it's way better to have the stronger deck in contact (even with foam spacers) with them.
No more answers from the opposite party?

Wow, the way you make your conclusion is so ludicrous!
A follower. Not a thinker. :-p

Philip
18th October 2011, 03:41 PM
Nakaniko makes a good point with the roof racks. In the early days a lot of people learnt the hard way that the forces acting on the bars and their roof connectors is a lot more than imagined. So nose forward uses this downforce to an advantage provided you have quality roof racks which most people have now days. Roof outlines on some cars are a odd shape though (for roof racks anyhow) and might affect the way the board is carried. A bit like buying a car to go snow skiing only to find that chains can't be fitted.

nakaniko
18th October 2011, 08:14 PM
Unregistered, I'm not an engineer so I can find proofs for one or other opinion only with the tests made by privates and brands. But It's not me the one that have just told that Mercedes made a test and found the better way was the "classical", I'm surprised a bit you consider this not relevant, especially seeing how Mercedes and other german car brands are considered there in Usa (I'm not german, I'm italian).
So pheraphs mine are not proofs like the Mercedes one, but they are added elements to talk about the problem. But If none between NP and other brands have considered the other way of carrying the boards there should be a reason, don't you agree?
I must confess that mostly I go windsurfing alone with two boards lying inside the car beside me, so I don't carry boards outside too much, only when travelling with my girlfriend. As far as I can remember I've tried some time the not-classical way, without feeling relevant differences, and pheraphs a little loss of speed; but I'll try again, having nothing to loose as my boards (Score) are old, so not much value to risk.
The classical system anyway has big advantages for sure with a board with daggerboard, as this last can easily fall down on the car roof if board is carried stern forward and hull down, so for sure I'd avoid to suggest the other way to all beginners and raceboarders; hey, this is a Nico's original idea! So at least in this I'm a thinker not a follower!!




(BTW a 44 years male, with C6-C7 ernia but still windsurfing (33 times from 1st of April) and snowboarding in winter, with 8 various windsurf boards, who dared to go alone in Munchen and buy an out of time 460 cm board called Serenity and carry home in his town, being pheraphs the only or one of two owner of this crazy marvellous board in Italy ; windsurfing (also) in Venice watertown where he use to go out and rig over the water surface in shallow waters unloading the board from a boat; and also who madly travels in summer north to Denmark to look for real even if colder summer winds instead staying in quiet sunny beaches of Italy (being "the only italian to go windsurfing north in Denmark" as told me kidding mr. Keppler in Pforzheim); so all these things seems coming from a follower or a thinker?)
;-))

Farlo
18th October 2011, 10:27 PM
Did Mercedes make the test with or without bag? IMHO the difference is much less sensible with a bag. Moreover if you add one boom, two masts and three sails it may become unnoticeable. But as you say women and windsurf are not compatible inside the car. By the way Nakaniko, you're not the only Italian to go windsurfing in Denmark;-)