Fairing/Screen Buffeting - Solutions?

  • Thread starter Thread starter paul-haggis
  • Start date Start date
P

paul-haggis

Guest
Hi All,

Looking for your general experience to solve a problem on my winter-hack FJ1200.

The bike has a (non std) screen with a flipped up top. At any speed above 40mph the buffeting is extreme and feels like going a few rounds with Mike Tyson when he has forgotten his medication. Just before I was about to slice the flipped section off, I took the bike for a ride with a very tall tank bag - bliss - no buffeting whatsoever. Getting rid of the low pressure void between me and the screen (the bag filled it) causes the wind to flow up and over my head perfectly. So the screen is a good shape for flow, I just need to get rid of the aeroelasticity behind the screen, which is destabilising the flow and dragging it down into my face.

Ideas so far are:
* Drilling some holes in the screen to allow some air to leak in and reduce the under pressure.
* Spacing the entire screen off the fairing by a few mm with spacers, again to allow frontal air into the low pressure zone.

Any ideas.

Sorry it's not directly Lav - but answers could be useful in Lav land.

Cheers, Paul H.
 
With an unfaired Bandit there were problems with wind buffeting.

On my previous bike I had a tiny fly screen that just about covered the clocks and it was fantastic, no problems even at 140+.

On my next Bandit it has twin lights and I cant find a screen that will fit.

Conclusion............The bigger the screen with or without flip up, is maybe not as important as the possition and rake.

Andy

Drilling holes may do the job but if it doesnt it will be a bit of a mess
 
 Cut a nice NACA duct in the lower edge of the screen can help, either that or a few 1" holes. A home made laminar lip can also be fitted to the top of the screen, there is endless discussion about this over on the BMW forums.

 Or you could just get an RGS.  :D


   Keith
 
Hi Paul

Interesting question. I have some venting examples on Deauvilles.
Standard screen is low and not a  problem however the tall aftermarket screen does pretty much what you describe when there are no holes (ie pan european...old style)  The tall afternarket screen for Deauville in the picture has 2 nostrils which do as you describe.  Even the Piaggio X9 scooter has 2 screens, one layered over the other with an air gap which does the job even more effectively but is more easily achieved OEM than aftermarket, like most new bikes now inc FJR1300

Hope that helps  Rob.

I wont offend by posting pics of Hondas all over this forum but some examples as below.

http://pic100.picturetrail.com/VOL740/2931391/23445165/391108737.jpg
http://pic100.picturetrail.com/VOL740/2931391/23491566/392616268.jpg
http://pic100.picturetrail.com/VOL740/2931391/23229362/387382110.jpg
 
Grow your gut to fill the gap. I recommend lots of Beer and pies.  :D

On a more sensible note: Before hacking holes in your windscreen or fairing, it might be a good idea to do some experimenting to see if it'll work. Get some of that flexible heater ducting (like the stuff used in car heating systems) and gaffer tape it to the fairing to duct some air into the low pressure area. If that fixes the problem, then you're on the right track. If not, then maybe you need to think of another solution. You might be able to come up with a permanent ducted solution with some sexy little air scoops in the fairing.

Cheers,
Cam
 
If you take cast acrylic sheet to 170c (domestic oven) it becomes sufficiently plastic to conform to a simple mould.
It would be easy enough to try some edge vanes to break up the air flow or an internal duct from slots near the lower edge.
If you don't like the shape stick it back in the oven and it will relax back to flat.
I used little polycarbonate ears, same idea as the Monty fairing ones, on my narrow FJ1100 screen to deflect all the rain and
windblast past my hands.

Had a similar vacuum effect when teenage son decided that it wasn't cool to sit close and got a strange Thunderbird puppet
head wobble once speeds got to "don't tell your mum" levels.

No such problem with his mum after I could tell how much fun she was having by the way she was waving her feet in the air
in front of me.
 
Errr, Sonic we assume you are talking about when she was pillion...  8)
 
i get quite a bit of buffeting on my 1200 trophy at speeds over 200kph, but under that it's more or less okay. my screen is a taller aftermarket, colour coded thing which i hate so i am going to cut it down a bit to see if that improves it as i want to change it anyway, it looks a bit like that deauville thing, rob, especially at the top.
i like keith's comment about "get an rgs" - about as smooth as it's possible to get, comfortable in every sense of the word!
 
Many thanks for the replies guys. Step one will be to lift the screen off the fairing a bit - just a few spacers required, then Cam's air duct idea, then out comes the drill. I have also found a few pre-moulded NACA ducts on the web, and quite fancy introducing one. I'm quite enjoying having a shit bike again - one that can be cut/shut/bashed without destroying the value.

Keef, dearly wish it was an Argie, but the FJ cost ?300, plus about ?50 quid to get it running sweet. Not much Argie available for that price these days.  :(

Cam - good idea to grow the gut, have been working on that for many years. I have developed the belly to the stage where I can balance a pint on it, but I haven't seen my dick for about a decade, so need to loose a bit of weight to check it is still there.

Rob - interesting pics - plenty solutions there.

P.
 
Next time you are on a bus or crowded street, drop your pants, someone else will tell you if your wedding tackle is still there straight away.

I don't get buffeting on my RS screen at any speed but I can tell you the adjustable lip on the top edge makes absolutely NO difference at all, waste of money I reckon.

A higher screen might help though.
 
In my view, the tall screens are the ones that cause buffeting. It's not the wind in your face, its the turbulence behind the screen.

Out of all the bikes I've ridden. the  extended aftermarket screens are the worst or older  bikes before the manufacturers fixed it with ducting and layered screens.
 
I have an SS bevel fairing on my 3C,coming up behind a truck over 100kph the buffeting almost makes me sea sick if my head is above the screen,its so bad it comes close to generating a weave,tuck in and its nice and smooth
 
      Hi Vince,      Do you have any photo's???  That is ultimately the look I want for my Black and Gold 76.    I dream of it with pinstriping on the fairing too.

      Cheers Shorty NZ
 
Mate if you do a seach on,Vince we need an update,there is a pic there from the NSW Ducati concorse.
Ping me your email and I will send you some more.These days with the cop dramas here having a fairing is
not that usefull,handy over 130,but where can you do that for long enough to need the wind deflection.
And the amount of work to fit one is more than you might think,got mine from Ian Gowanlock,not Gowanlocks the shop but the bloke himself.Long story but they are differant supplyers now.
 
Vince said:
I have an SS bevel fairing on my 3C,coming up behind a truck over 100kph the buffeting almost makes me sea sick if my head is above the screen,its so bad it comes close to generating a weave,tuck in and its nice and smooth
Click to expand...

Vince

I'm contemplating the same fairing, there's a local bloke here who makes replica bevel fairings dirt cheap. Do you by any chance have any pictures of the mounting brackets you used on yours? The local bloke is prepared to modify his brackets within reason, but it would be nice to know what other people have done. And I'd really rather not weld any bits onto my frame unless absolutely necessary.
And I commute to work on my Jota, at 6 am the local cop is sound asleep and I sit on a steady 130-140 kph. In traffic. America's a crazy place.

Ken
 
Thats the rub Ken,for years when I had the TT Montegi fairing fitted I used the big U shaped exhaust clamp around the frame headstock trick but even then it still needed a bolt welded at the frame to stop it slipping sideways.The fairing mount was made from an SS mount with a plate welded on the end at the head stock rack angle bolted to both the exhaust clamp and the welded bolt.The welded bolt kept braking
with the fairing work hardening it.Thats even with a mount bolted through the standard lock stop with a couple of arms comming back to bolt up with the lower wings of the fairing beside the tank and a centre of the  steering head Ducati SS mount adapted and bolted up to the upper fairing wings.In the end a BMW main fairing mount  was welded on both sides of the frame,its bloody strong now.I then pissed off the Montegi fairing and adapted all the mounts to work on the much nicer,sorry Red,SS bevel fairing.I have tied into this fairing mount both instruments and the headlight,helps a lot to get this weight off the steering but fitting it in and having a comfortable bar position and not hitting any of it still make me sweat.
BTW I got the bevel fairing made with and extra layer of mat,good advise Marty Moose,its much stiffer,standard they are light but fragile.Sorry but I cannot see a way to mount them without some welding and not be riding one handed holding on the fairing with a broken mount at some stage.I probably went nuts,its held on with 8 bolts but does not ratle.



 
You must log in or register to reply here.
Back
Top