Buffeting or Turbulence from the Windscreen

[didier]

On 11/10/2020 at 6:08 AM, Canzvt said:

A bit offtopic but where did you get this nice pics with torque specifications?

[Canzvt]

2 hours ago, didier said:

A bit offtopic but where did you get this nice pics with torque specifications?

T7 Manual (European). Happy to email it to you (17Mb) if you PM me your email address. 

[Annihilator]

The reason you get such bad wind buffeting with virtually every screen setup is because of the extremely steep angle of attack.  The windscreen is virtually vertical which is absolutely the cause of the violent turbulence.  I have a giant Madstad screen on my FZ09, for which the angle of attack is fully adjustable, so I have played a lot with the angle of windscreens and can say without any doubt that the angle is the biggest factor.  And making the screen higher or wider will only make the problem worse unless the screen is absurdly large. The screen needs to sit at at least 45 degree angle to get rid of buffeting.  Ride a supersport motorcycle with a 30 degree wind screen and, despite the fact that the screen is tiny and barely covers you, there is zero wind buffeting.

[Anibal]

On 7/11/2020 at 2:52 PM, CaptainBackfire said:

@MGG Thanks for that!. That gives me hope. I am totally with you on the clean air theme. Ideally I would like to be able to remove the screen and get the airflow of a naked bike and then just be able to add the screen in cold weather or on long trips. I am a bit surprised how much noice the front generates without the screen. If I do end up keeping the bike J will see if I can remove the whole screen holder and move the speedo down or up on the handle bar. Just to verify that it is not the fairing around the forms that is the issue when it comes to the clean air alternarive .It really is a pitty that yamaha made that tall speedo...  will report back when the givi d2145st arrives.

 

It would be nice a trully naked configuration for summer or offroad riding. I been changing from winter to summer windscreen configurations in all my dual sport bikes. 

 

The best way to do it would be removing the windscreen bracket and move the speed display down but this mod seems far from easy, even more thinking about changing back to tall windscreen configuration regarding the next ride your are planning.

[Toei]

On 1/31/2021 at 5:55 AM, Annihilator said:

The reason you get such bad wind buffeting with virtually every screen setup is because of the extremely steep angle of attack.  The windscreen is virtually vertical which is absolutely the cause of the violent turbulence.  I have a giant Madstad screen on my FZ09, for which the angle of attack is fully adjustable, so I have played a lot with the angle of windscreens and can say without any doubt that the angle is the biggest factor.  And making the screen higher or wider will only make the problem worse unless the screen is absurdly large. The screen needs to sit at at least 45 degree angle to get rid of buffeting.  Ride a supersport motorcycle with a 30 degree wind screen and, despite the fact that the screen is tiny and barely covers you, there is zero wind buffeting.

I said the same thing in this thread back in October.  I wish more people were up in arms about this design flaw so that perhaps Yamaha would design different [backwards-compatible] windscreen supports that are angled to the rear more.  Of course the moto site reviewers tend to gloss over deficiencies like this so as to not upset the OEMs and jeopardize their invitations to press rides.  

 

I've got a screen adjuster on mine and it doesn't help much.  The buffeting kills my enjoyment to such a degree that I wish I hadn't purchased the T7, even though I love the engine and the handling.  But I can't afford to sell it at a loss and reinvest in a different, and likely more expensive, bike.  Hopefully Madstad will have a solution that's not too painfully ugly.  

[Aleksandar13]

26 minutes ago, Toei said:

I said the same thing in this thread back in October.  I wish more people were up in arms about this design flaw so that perhaps Yamaha would design different [backwards-compatible] windscreen supports that are angled to the rear more.  Of course the moto site reviewers tend to gloss over deficiencies like this so as to not upset the OEMs and jeopardize their invitations to press rides.  

 

I've got a screen adjuster on mine and it doesn't help much.  The buffeting kills my enjoyment to such a degree that I wish I hadn't purchased the T7, even though I love the engine and the handling.  But I can't afford to sell it at a loss and reinvest in a different, and likely more expensive, bike.  Hopefully Madstad will have a solution that's not too painfully ugly.  

Sport screen from power bronze works very well.. It is shorter than stock and you don't need to sell the bike...  

[vagrant318]

43 minutes ago, Toei said:

I said the same thing in this thread back in October.  I wish more people were up in arms about this design flaw so that perhaps Yamaha would design different [backwards-compatible] windscreen supports that are angled to the rear more.  Of course the moto site reviewers tend to gloss over deficiencies like this so as to not upset the OEMs and jeopardize their invitations to press rides.  

 

I've got a screen adjuster on mine and it doesn't help much.  The buffeting kills my enjoyment to such a degree that I wish I hadn't purchased the T7, even though I love the engine and the handling.  But I can't afford to sell it at a loss and reinvest in a different, and likely more expensive, bike.  Hopefully Madstad will have a solution that's not too painfully ugly.  

Same here. I bought mine for distance riding, I have a DRZ for trails which is  more pleasant with clean air at speed with a small parabellum rally windscreen.

16 minutes ago, Aleksandar13 said:

Sport screen from power bronze works very well.. It is shorter than stock and you don't need to sell the bike...  

I'll probably try the short screen

[Toei]

34 minutes ago, Aleksandar13 said:

Sport screen from power bronze works very well.. It is shorter than stock and you don't need to sell the bike...  

I had the equivalent on my prior XSR700 (Dart flyscreen).  The lack of wind protection was my main reason for selling the XSR!  Lot's of insects around here.  Here's my helmet halfway through one ride.  

Edited February 18, 2021 by Toei

[Hammerhead]

Is the T7 screen ideal? No, far from it. @ 180cm my bean seems to be just edging out of the bubble to where it’s louder sitting than standing.  
   Does this bother me to the point of regretting the purchase? Hell no, far from it.

   Screen does keep wind & rain off the upper body reasonably enough & I didn’t but a ADV machine to feel like I was riding in a car, entirely out of the elements.  
   First bike I’ve owned that has any type of screen, in fact.  And this one, despite it’s obvious short comings, feels FAR better to me than ripping the highway without. 
   Finding things to gripe about is way too easy. Finding ways to be content with what we’ve got & making  the adjustments to improve them when we’re not, is a path I’d much rather ride.

[Canzvt]

On 1/31/2021 at 6:55 AM, Annihilator said:

The reason you get such bad wind buffeting with virtually every screen setup is because of the extremely steep angle of attack.  

While a massive contributing factor, this is not entirely correct. The trailing edge of the screen has as much affect on the behind the screen turbulence as the angle of attack. Un-obstructed (as in not riding directly behind another vehicle) airflow coming directly at the screen (incidence angle) is stationary until you move into it. From there the air flow radiates out in a laminar fashion on the screen face until the flow separates as it leaves the screen edge. The sudden separation yields turbulence. The distance from the screen where the airflow transitions from laminar flow to turbulent flow is dependent upon the incidence angle, the rake angle (of the screen) and any lip condition of the screen edge. Increasing the length of the edge by rounding the edge to just below the point of separation will increase the transition distance from laminar to turbulent. By decreasing the rake angle, you are effectively increasing the length of the edge. You can see this is real life by looking at any cube van 18 wheeler in North American that has a fold-up tail fairing on the back of the trailer, or on any F1/IndyCar/MotoGP etc. helmet back. 

 

So, one possible solution (though not practical) is to wrap a clear plastic strip around the edge of the screen so that the flat of the strip extends back towards you, playing with the angle to the screen, increasing the laminar/turbulent transition distance further back on the bike. Another could be to rake the screen as was suggested. A third is to purchase a screen that is designed to place the transition point behind the rider. I believe MRA has something like this on the market for the T7.

 

Lastly, if you guys are interested, I believe that a screen mount design whereby the screen pivots around the GPS mount bar, and somehow adjusted from the original mount points could be designed and 3D printed to facilitate adjusting the rake angle, and hence the transition point. It would also allow air to vent under/behind the screen which will help increase the transition point further back on the bike, thus decreasing rider turbulence.

 

Sorry for the long winded scribe. Let me know if there is interest in an adjustable mount, and I'll see what I can do. 

[Toei]

6 hours ago, Canzvt said:

Lastly, if you guys are interested, I believe that a screen mount design whereby the screen pivots around the GPS mount bar, and somehow adjusted from the original mount points could be designed and 3D printed to facilitate adjusting the rake angle, and hence the transition point. It would also allow air to vent under/behind the screen which will help increase the transition point further back on the bike, thus decreasing rider turbulence.

If you just change the rake angle of the stock screen the "flip" section at the top of the screen will still be there.  Won't that tend to cause turbulence even with the screen raked back more?

[Landshark]

This might be helpful

 

https://www.laminarlip.com/

[Canzvt]

Yes. All flow off the screen will cause turbulence. By angling the screen and adjusting the screen length (with an after market taller screen)you can position the point of flow transition from one in from of the rider's helmet to one behind the rider's helmet. Without a solid model of the complete bike/rider and some CFD software, or a wind tunnel, this is going to be VERY EXPERIMENTAL, and will vary with wind (road) speed and rider height/distance from stock screen location.

 

One trick I always do when adjusting my screen on my S10 or T7 is while riding down a quiet road at desired speed, I take my left hand, holding it vertical, I move it to the lip edge of the screen to 'feel' the wind coming off the screen. Now move your hand back/up/down to 'feel' where the wind goes from laminar to turbulent. It will be noticeable. Keep playing until you figure out what you might want to change in terms of position of the screen. If you can't get anywhere near your helmet, you may need a taller/swept back screen.

[Canzvt]

3 minutes ago, Landshark said:

This might be helpful

 

https://www.laminarlip.com/

Yep. These work. I had one on my GTS before going to a sport (low) screen. They effectively lengthen the screen, and move the flow transition  back behind the rider (if correctly sized and positioned). They are also vented between the stock screen and the laminar lip allowing air to fill the backside of the screen area, further effectively lengthening the screen.

[BADDANDY]

I only have turbulence if I follow another vehicle.  Anything else is just airflow.

Edited February 19, 2021 by BADDANDY

[Toei]

I contacted Madstad to see if they are developing a kit for the T7.  The response was that they would like to but haven't been able to get their hands on a T7 to do so.  They are in central FL if any members in the area are interested in helping.  You will get a free screen/kit for doing so. 

 

Canzvt- Looks like you likely won't have any competition for a while if you want to develop your own adjustable rake kit.  I for one am interested, although I wonder about the structural strength of 3D printed brackets?  

[Canzvt]

Here's a couple link's to the MRA screen. I have yet to test it as I'm under snow and ice, but 'theoretically' it should reduce buffeting due to what I have explained above regarding the wrap around lip. Time and testing will tell the true tale!

 

https://www.mrashop.de/com/model-based-products/yamaha/tenere-700/bj-19/7259/tenere-700-touring-windshield-tm-2019?number=I4025066167401

 

https://twistedthrottle.com/shop/ergonomics/windshields-accessories/windshields/mra-motorcycle-windscreen-for-yamaha-tenere-700-21-tm-touring-screen/

 

As for the windshield adjuster, I'll have a look this weekend, take some measurements and see if something can be designed to work.

[Toei]

I tried this screen from Ermax, which is similar to the MRA.  It was worse than stock.  Under certain wind conditions the whole front end would start getting knocked around.  

 

Ermax High Protection Windshield

[mpatch]

After chasing major buffeting issues on my 950 and wee strom what I learned is it’s complicated. 
Everything from helmet shape, what jacket you’re wearing, mirrors, riding position, windshield shape angle and height, etc,  that’s why there’s no silver bullet. All you can do is experiment with different things and see what works for you. 

[RIDER GUIDER]

A lot of people suffer turbulence (not just T7) and it's down to the mirrors!!!   Experiment with the mirrors removed before blowing cash on different screens, a pair of Doubletake mirrors might make the difference as they're very adjustable. 

[vagrant318]

5 hours ago, RIDER GUIDER said:

A lot of people suffer turbulence (not just T7) and it's down to the mirrors!!!   Experiment with the mirrors removed before blowing cash on different screens, a pair of Doubletake mirrors might make the difference as they're very adjustable. 

I'll have to try this. Seems odd though as the mirrors appear very aerodynamic at least compared to my DRZ

[Canzvt]

6 hours ago, RIDER GUIDER said:

A lot of people suffer turbulence (not just T7) and it's down to the mirrors!!!   Experiment with the mirrors removed before blowing cash on different screens, a pair of Doubletake mirrors might make the difference as they're very adjustable. 

Before you spend ANY money, do the flat hand turbulence test I explained on Friday (above) to see what you are dealing with that is specific to you and your bike. Once you have learned what you are dealing with, then you can determine if spending money is warranted, and on what.

 

To recap the method, one a flat straight road, preferably without wind or traffic, get up to speed, and take your left hand and hold it upright, palm open flat, and hold it up behind the screen and then move it up/out left and right from the screen and 'feel' the wind. Then bring it back towards you and you will 'feel' the flow separation (turbulence). Ideally this turbulence should be behind your helmet/body, but with the upright windscreen of the T7, it is very likely very close to the screen lip in front of you. If you are relatively short and look through the screen, you might be fine. If you are really tall, you also might be fine. If you are like me, 6'-2", you are right in the WRONG place. Good luck.

[TimmyTheHog]

10 hours ago, RIDER GUIDER said:

A lot of people suffer turbulence (not just T7) and it's down to the mirrors!!!   Experiment with the mirrors removed before blowing cash on different screens, a pair of Doubletake mirrors might make the difference as they're very adjustable. 

oh god, I hated that on the Vstrom first gen...bought it for a week then sold it after for the same price which wasn't much to begin with.

Only to find out the stupid mirrors were the problem...

[vagrant318]

I was shocked at the difference, more experimenting necessary but promising. Will remove right side next with just the doubletake mirror on the left. My phone mount likely adding turbulence as well

[Rickster]

17 minutes ago, vagrant318 said:

I was shocked at the difference, more experimenting necessary but promising. Will remove right side next with just the doubletake mirror on the left. My phone mount likely adding turbulence as well

Please let us know your findings!