• Announcements

    • UnderDawg

      A Few Simple Rules   05/22/2017

      Sailing Anarchy is a very lightly moderated site. This is by design, to afford a more free atmosphere for discussion. There are plenty of sailing forums you can go to where swearing isn't allowed, confrontation is squelched and, and you can have a moderator finger-wag at you for your attitude. SA tries to avoid that and allow for more adult behavior without moderators editing your posts and whacking knuckles with rulers. We don't have a long list of published "thou shalt nots" either, and this is by design. Too many absolute rules paints us into too many corners. So check the Terms of Service - there IS language there about certain types of behavior that is not permitted. We interpret that lightly and permit a lot of latitude, but we DO reserve the right to take action when something is too extreme to tolerate (too racist, graphic, violent, misogynistic, etc.). Yes, that is subjective, but it allows us discretion. Avoiding a laundry list of rules allows for freedom; don't abuse it. However there ARE a few basic rules that will earn you a suspension, and apparently a brief refresher is in order. 1) Allegations of pedophilia - there is no tolerance for this. So if you make allegations, jokes, innuendo or suggestions about child molestation, child pornography, abuse or inappropriate behavior with minors etc. about someone on this board you will get a time out. This is pretty much automatic; this behavior can have real world effect and is not acceptable. Obviously the subject is not banned when discussion of it is apropos, e.g. talking about an item in the news for instance. But allegations or references directed at or about another poster is verboten. 2) Outing people - providing real world identifiable information about users on the forums who prefer to remain anonymous. Yes, some of us post with our real names - not a problem to use them. However many do NOT, and if you find out someone's name keep it to yourself, first or last. This also goes for other identifying information too - employer information etc. You don't need too many pieces of data to figure out who someone really is these days. Depending on severity you might get anything from a scolding to a suspension - so don't do it. I know it can be confusing sometimes for newcomers, as SA has been around almost twenty years and there are some people that throw their real names around and their current Display Name may not match the name they have out in the public. But if in doubt, you don't want to accidentally out some one so use caution, even if it's a personal friend of yours in real life. 3) Posting While Suspended - If you've earned a timeout (these are fairly rare and hard to get), please observe the suspension. If you create a new account (a "Sock Puppet") and return to the forums to post with it before your suspension is up you WILL get more time added to your original suspension and lose your Socks. This behavior may result a permanent ban, since it shows you have zero respect for the few rules we have and the moderating team that is tasked with supporting them. Check the Terms of Service you agreed to; they apply to the individual agreeing, not the account you created, so don't try to Sea Lawyer us if you get caught. Just don't do it. Those are the three that will almost certainly get you into some trouble. IF YOU SEE SOMEONE DO ONE OF THESE THINGS, please do the following: Refrain from quoting the offending text, it makes the thread cleanup a pain in the rear Press the Report button; it is by far the best way to notify Admins as we will get e-mails. Calling out for Admins in the middle of threads, sending us PM's, etc. - there is no guarantee we will get those in a timely fashion. There are multiple Moderators in multiple time zones around the world, and anyone one of us can handle the Report and all of us will be notified about it. But if you PM one Mod directly and he's off line, the problem will get dealt with much more slowly. Other behaviors that you might want to think twice before doing include: Intentionally disrupting threads and discussions repeatedly. Off topic/content free trolling in threads to disrupt dialog Stalking users around the forums with the intent to disrupt content and discussion Repeated posting of overly graphic or scatological porn content. There are plenty web sites for you to get your freak on, don't do it here. And a brief note to Newbies... No, we will not ban people or censor them for dropping F-bombs on you, using foul language, etc. so please don't report it when one of our members gives you a greeting you may find shocking. We do our best not to censor content here and playing swearword police is not in our job descriptions. Sailing Anarchy is more like a bar than a classroom, so handle it like you would meeting someone a little coarse - don't look for the teacher. Thanks.
    • B.J. Porter

      Moderation Team Change   06/16/2017

      After fifteen years of volunteer moderation at SA, I will no longer be part of the moderation team. The decision to step aside is mine, and has been some time in the works but we did not wish to announce it in advance for a number of reasons. It's been fun, but I need my time back for other purposes now. The Underdawg admin account will not be monitored until further notice, as I will be relinquishing control of it along with my administrative privileges. Zapata will continue on as a moderator, and any concerns or issues can be directed to that account or to the Editor until further notice. Anyone interested in helping moderate the forums should reach out to Scot by sending a PM to the Editor account. Please note that I am not leaving the community, I am merely stepping aside from Admin responsibilities and privileges on the site.

Archived

This topic is now archived and is closed to further replies.

leonsuperfly

rudder humm

56 posts in this topic

went sailing today on share kahn in 20+kts and the brand new betts rudder resonated for half of the time

I normally sail on tigger and we haven't had this issue with the new rudder, but this was bad

real bad, were talking as loud as a lawn mower and very persistant

 

hard to see why, pintles seem tight, just noisy and slowing

 

anyone else with this issue? or is it just a bad day at the mould?

 

it wasnt just a small humm that happens ocasionally we're talking about three distinct tones that were increasingly severe

the top one would rattle screws out of a rolex

and IMHO was costing the boat 10- 15% boatspeed at worst ,let alone stopping it from accelerating

Share this post


Link to post
Share on other sites

Sideshow:

I'd check that rudder for trailing edge treatment first, that's easy, then symetry. That will require templating it. A slight change to the trailing edge could fix it. I have no idea how the trailing edge was designed but I favor a chamferred trailing edge. The three different tones is worrysome. Make sure the traliong edge is a crisp cut. You can't really do that in a mold but you can fair it by hand. Maybe Jim Betts has some ideas.

If it really as violent as you say then symetry could very well be the cause. You neeed to ask Betts for some rudder templates.

Share this post


Link to post
Share on other sites

bad / disturbed flow across the rudder

 

the leading or trailing edge needs adjustment ( shaping )

 

one the OEM rudders was humming and it was eliminated by sanding ( reshaping slightly with sander ) one of the edges. The price point is relatively high for the aftermarket rudder, I would contact the mfg and ask for guidence. I wouldn't think there is much room for error. Sending it back would be expensive and time consuming to let them do the adjusting, but probably the better option. The rudder mfg is probably not interested in an exchange.

Share this post


Link to post
Share on other sites

went sailing today on share kahn in 20+kts and the brand new betts rudder resonated for half of the time

I normally sail on tigger and we haven't had this issue with the new rudder, but this was bad

real bad, were talking as loud as a lawn mower and very persistant

 

hard to see why, pintles seem tight, just noisy and slowing

 

anyone else with this issue? or is it just a bad day at the mould?

 

it wasnt just a small humm that happens ocasionally we're talking about three distinct tones that were increasingly severe

the top one would rattle screws out of a rolex

and IMHO was costing the boat 10- 15% boatspeed at worst ,let alone stopping it from accelerating

Are you sure it was not there with the old OEM rudder? On most boats, the 8 kt humm is from the keel. Humms at 8 / 16 / 24 kts....

 

Clew

Share this post


Link to post
Share on other sites

Actually, the humming is an indication that the foil is quite symmetrical, usual cause being that the flow is exiting the trailing edge to symmetrically, believe it or not.

 

Take the rudder off and square off the trailing edge with a file (just take off what you need to get 90 degree edges), then put a tiny 45 degree bevel on one side only.

 

This prevent the oscillations from starting.

Share this post


Link to post
Share on other sites

I templated & faired the rudder of my boat (not an FT10) a few months ago, and repainted it with a twin-pack polyurethane which has a high gloss finish. When I sailed the boat again the rudder was humming at 14-16kts boatspeed. I took the gloss off the paint and the hum was gone. Maybe there really is such a thing as TOO perfect?

Share this post


Link to post
Share on other sites

I templated & faired the rudder of my boat (not an FT10) a few months ago, and repainted it with a twin-pack polyurethane which has a high gloss finish. When I sailed the boat again the rudder was humming at 14-16kts boatspeed. I took the gloss off the paint and the hum was gone. Maybe there really is such a thing as TOO perfect?

 

There is such a thing as too perfect.

 

IIRC and the numbers are rough (pun) for planing dinghies/fast sprotsboats etc. the hull shouldn't be any glossier than approx 600-800 grit wet and dry. Slower lead mines need 400 grit. High speed powerboats need glossier - ie 1200-2000grit.

Share this post


Link to post
Share on other sites

Mark:

"Too symetrical" that's a new one on me but you sound like you know what your're talking about so I will consider it. I do know that with other ruder and keel vibe problems fairing them to symetry has most often helped the problem. I agree with you trailing edge treatment.

 

Boy, 65 years old (almost) and still learning.

 

Bill Garden once told me. "If the rudder flutters check the trailing edge. If it's round square it. If it's square round it."

Share this post


Link to post
Share on other sites

Mark:

"Too symetrical" that's a new one on me but you sound like you know what your're talking about so I will consider it. I do know that with other ruder and keel vibe problems fairing them to symetry has most often helped the problem. I agree with you trailing edge treatment.

 

Boy, 65 years old (almost) and still learning.

 

Bill Garden once told me. "If the rudder flutters check the trailing edge. If it's round square it. If it's square round it."

 

"Too symmetrical" is a very inexact term for it. But if the trailing edge is loaded even a bit in one direction it tends not to start oscillating, and it's all very much about the trailing edge on hum.

 

The science of it is over my head, but here's a paper on vibration problems in hydrofoils by a real Mr. Science. Hydrofoil "singing" is dealt with in chapter 4.

 

http://docs.hydrofoils.org/hiper.pdf

 

I learned how to fix it from the early days of thin daggers in cats. Everybody had the problem at one time of another.

Share this post


Link to post
Share on other sites

It is actually Von Karmann doing the singing. Watch this clip and you can see how just knocking off the square edge on one side of the trailing edge will prevent the alternating vortices by upsetting the occillations. I like a bit of foil hum as it serves as an audible knotmeter and helps me optimise boatspeed without taking my eyes off the sails much like an audible variometer in a sailplane. With time you will get the pitch calibrated to the indicated speed from the knotmeter and find the groove, especially when surfing a wave or keeping a multihull in the 'power band' on a reach. If it is too loud though, it must have an adverse effect of speed...

Share this post


Link to post
Share on other sites

This one is even better, flow starts off laminar but then after a while breaks down into the alternating Von Karmann vortices. CFD will play a huge part in the upcoming wing design for the AC 72's...

 

 

Not sure if this would work to dampen the vortices, but might be worth a try. There was a guy in the California surfing scene who came up with the idea of putting flexible chines of a sort on the bottom on his surfboards. His thinking was that in a hard bottom turn, if you could bet the sheet of water flowing diagonally across the bottom of the board, it would reduce wetted surface and reduce drag and add speed. He would mask off a tapered width of 1/2" or so across the board and then apply silicone caulk between the masking tape and then tool the silicone into a V shaped chine for the lack of a better word. Peel the tape and this little flap would offer little resistance to straight line speed as it was mostly parallel to the CL, but when the board was turned it would trip the flow! He would tryit for a day or so and then razor knife off the silicone and try a different configuration. I never got the knack of troweling the sticky crap into anything that could possibly help, but perhaps a nice clean trailing edge V added to the 1/8" flat on a well tuned foil would clean up the flow but due to the resilient nature of the silicone would damp out the vortice formation??? Worth a try?

Share this post


Link to post
Share on other sites

Rap:

Those are interesting buit is there on showing the flow around a chamferred trailing edge?

Thanks for that link.

Share this post


Link to post
Share on other sites

This one is even better, flow starts off laminar but then after a while breaks down into the alternating Von Karmann vortices. CFD will play a huge part in the upcoming wing design for the AC 72's...

 

 

Not sure if this would work to dampen the vortices, but might be worth a try. There was a guy in the California surfing scene who came up with the idea of putting flexible chines of a sort on the bottom on his surfboards. His thinking was that in a hard bottom turn, if you could bet the sheet of water flowing diagonally across the bottom of the board, it would reduce wetted surface and reduce drag and add speed. He would mask off a tapered width of 1/2" or so across the board and then apply silicone caulk between the masking tape and then tool the silicone into a V shaped chine for the lack of a better word. Peel the tape and this little flap would offer little resistance to straight line speed as it was mostly parallel to the CL, but when the board was turned it would trip the flow! He would tryit for a day or so and then razor knife off the silicone and try a different configuration. I never got the knack of troweling the sticky crap into anything that could possibly help, but perhaps a nice clean trailing edge V added to the 1/8" flat on a well tuned foil would clean up the flow but due to the resilient nature of the silicone would damp out the vortice formation??? Worth a try?

 

awesome links mate thanks heaps

this is how I had pictured it (from people describing it to me)

the answer that so many seem to disagree on though is a symmetrical or asymmetrical solution,

Betts prescribed an asymmetrical trailing edge as a solution, but it irks me somewhat to do anything asymmetrical to the underwater shape of a boat.

 

Fortunately it isn't the tiger i sail on normally so the PBO will have to make his own mind up on this one.

 

I'm still curious though if this is the only one of these rudders that has this issue

 

tiggers rudder has only a slight hum that certainly seems too small an issue for us to worry about, and the other tiger I've been on was much the same

 

could there be another factor contributing?

for example a loose pintle?

Would that allow the resonance to grow and become more established?

Share this post


Link to post
Share on other sites




thought this one shows quite well the reynolds number relationship to votrex shedding that extrad mentioned above

Share this post


Link to post
Share on other sites

 

 

thought this one shows quite well the reynolds number relationship to votrex shedding that extrad mentioned above

 

Strange how conversations in the CY on a Sunday afternoon and posts here merge into one.

 

Good job we weren't discussing Colebrook White backwater step factors - that would surely bring out guns at 12 paces amongst hydrodynamicists

 

PS I think that the 1st step in resolving Shere Kahns ghetto blaster loud rudder hum issue would be to clean the bottom of the boat. Followed by confirming that it isn't the keel. (AKA put an unsymettrical chamfer on the back edge of the keel.)

Share this post


Link to post
Share on other sites

For the record..... equipped with anew Betts rudder and having never had ahum off the keel previously, our rudder hum begins at exactly 6.9 knots downwind and never stops as the speed builds further. Me thinks that Mr. Betts should be responsible for a fix given the cost of the rudder. i surely would not want to being tweaking my trailinig edge without specific instructions from the builder; better that a technician responsible for the result does

Share this post


Link to post
Share on other sites

While my boat is not a FT but to some degree similar in setup (transom hung rudder) and high aspect foils i can tell you that I do have a very little amount of humm - it starts at about 19 knots and stops at about 19.5 knots and doesn't re-appear (at least not under 26 knots). The humm used to be a little worse but got better after we rafaired both the hull and foils a couple of years ago - I did use the recommendations from Steve thompson I posted above regarding trailing edge treatment.

Share this post


Link to post
Share on other sites

That's just wonderful Christian. But this is the FD thread and my question was addresed to Matt with an FD 10m.

Share this post


Link to post
Share on other sites

While my boat is not a FT but to some degree similar in setup (transom hung rudder) and high aspect foils i can tell you that I do have a very little amount of humm - it starts at about 19 knots and stops at about 19.5 knots and doesn't re-appear (at least not under 26 knots). The humm used to be a little worse but got better after we rafaired both the hull and foils a couple of years ago - I did use the recommendations from Steve thompson I posted above regarding trailing edge treatment.

 

Christian takie your Viper 870 and your 19.5 knots to a thread that gives a fuck! you fucktard want a be FT10 owner and don't even go into how you didn't follow threw with your order cause ??????? what ever the fuckin reason you come up with cause your boat is more of an orphan than a Tiger will ever be. Lots of luv to Perry, Scoot, and Hip for a really good boat.

 

While my boat is not a FT but to some degree similar in setup (transom hung rudder) and high aspect foils i can tell you that I do have a very little amount of humm - it starts at about 19 knots and stops at about 19.5 knots and doesn't re-appear (at least not under 26 knots). The humm used to be a little worse but got better after we rafaired both the hull and foils a couple of years ago - I did use the recommendations from Steve thompson I posted above regarding trailing edge treatment.

 

Christian takie your Viper 870 and your 19.5 knots to a thread that gives a fuck! you fucktard want a be FT10 owner and don't even go into how you didn't follow threw with your order cause ??????? what ever the fuckin reason you come up with cause your boat is more of an orphan than a Tiger will ever be. Lots of luv to Perry, Scoot, and Hip for a really good boat.

Share this post


Link to post
Share on other sites

Sideshow:

Anything to report on your rudder hum problem yet?

 

this is a rudder on a tiger that I don't normally sail on,

so I'm not sure

but I'll find out from it's owner on sunday, unless he wants to chime i here and give us an update

 

Share this post


Link to post
Share on other sites

#58 had hum on the OEM rudder, it started around 7 knts, it got very annoying and felt slow. I faired the trailing edge and added less than 1/4" of epoxy to the edge and ended with a blunt edge of about 1/16" in width. Recoated the rudder with interlux two part epoxy, wet sanded w/ 500 grit. Humm is gone, and feels like a hot knife through butter. It may not be any faster but it is definitely less distracting.

Share this post


Link to post
Share on other sites

Sideshow:

Thanks. I'd like to know how he has dealt with it.

 

Can you Fed Ex me some fish and chips?

I prefer the ones from the fish shop across the street from the Ashfield train station.

It's probably a Boutique now.

Share this post


Link to post
Share on other sites

That's just wonderful Christian. But this is the FD thread and my question was addresed to Matt with an FD 10m.

 

Bob, I understand - my point was that foil humm is not unique to FT's and is something that happens on a lot of boats with high aspect foils and I posted some recommendations how to help minimize/eliminate the problem.

Share this post


Link to post
Share on other sites

That's just wonderful Christian. But this is the FD thread and my question was addresed to Matt with an FD 10m.

 

Bob, I understand - my point was that foil humm is not unique to FT's and is something that happens on a lot of boats with high aspect foils and I posted some recommendations how to help minimize/eliminate the problem.

 

Christian - thanks for the contributions even if slightly off topic. I think a lot of people get a bit protective or defensive given the mud that has been thrown at the FT10 over the past few years. Thanks for trying to stay above it.

Share this post


Link to post
Share on other sites

 

Christian takie your Viper 870 and your 19.5 knots to a thread that gives a fuck! you fucktard want a be FT10 owner and don't even go into how you didn't follow threw with your order cause ??????? what ever the fuckin reason you come up with cause your boat is more of an orphan than a Tiger will ever be. Lots of luv to Perry, Scoot, and Hip for a really good boat.

 

EMF!

Share this post


Link to post
Share on other sites

Christian: please translate "EMF". I'm sure it's another one of your positive contributions to this forum. Care to enlighten us? Or at least me?

Share this post


Link to post
Share on other sites

Christian: please translate "EMF". I'm sure it's another one of your positive contributions to this forum. Care to enlighten us? Or at least me?

 

Coined by the Editor - Eat My Fuck

 

 

 

Only used when people call me fucktard or some other pretty lame namecalling

Share this post


Link to post
Share on other sites

Well just as I figured unfortunately. And your intellectual response to "lame name calling" is "EMF"? I'm out of my league.

 

I was more hoping for:

Everglades Marine Foundation

or

Egyptian Mummified Frogs

Share this post


Link to post
Share on other sites

So that's it?

When someone's intellectual retort is "EMF" it kinds of brings an end to any adult discussion.

 

I really don't carte if Scot said it first.

As my Dad would have said, "If Scot jumped of a bridge so you have to do it?"

Share this post


Link to post
Share on other sites

I like the frog thing....:D

Share this post


Link to post
Share on other sites

I always thought EMF stood for "Excellant My Friend" ;) . I guess you can learn something new on this internet thing daily.

Share this post


Link to post
Share on other sites

I always thought EMF stood for "Excellant My Friend" ;) . I guess you can learn something new on this internet thing daily.

Share this post


Link to post
Share on other sites

I was thinking along the lines of:

"Elect More Frontiersmen"

 

Or from a Native American perspective:

"Eviscerate More Frontiersmen"

 

At least something that made grammatical sense. Christian is speaking ESL.

 

"Well Scot said it."

 

As all of our Dads used to say, "If Scot told you to jump off a bridge would you do it?"

Jeesus, if I had a dime for everytime I heard that.

Share this post


Link to post
Share on other sites

Austin:

that was very funny and I could use some funny today.

How is my calf doing? Are you putting a blanket over it at night? Are you taking it for walks?

Can I have a new pic?

Was it scared on the 4th of July?

I hope you brought it into the house for that night.

 

I'm thinking that we skip the cutting off the balls thing and let it grow into a huge Bull.

I'd like that.

By then it would be house broken and think of the surprise on your friend's face when they see a 3,257 lb. bull sitting watching TV in your living room.

Bulls like to watch golf.

Share this post


Link to post
Share on other sites

Sideshow:

Thanks. I'd like to know how he has dealt with it.

 

Can you Fed Ex me some fish and chips?

I prefer the ones from the fish shop across the street from the Ashfield train station.

It's probably a Boutique now.

 

chish&fips Ashfield link

 

good news it's stil there , if anything all vacancies there become chinese takeaways, asian groceries or yum-cha joints ! it's full on one of sydneys 2nd tier chinatowns

 

ur making me hungry

 

 

 

Share this post


Link to post
Share on other sites

I just saw your calf today but no pics. They've been on the DL until today. I'll get a pic.

The only reason bulls like golf is it's grass pasture porn. Can you imagine a swimming pool of scotch?

 

Watch Temple Grandin. Good flick.

 

My neighbor's mom from the conservative rural south calls tattoos 'skin illustrations'. As in, "Why on Gawd's great earth would you wanna be gettin' yerself painted with no skin illustration?"

Share this post


Link to post
Share on other sites

I just saw your calf today but no pics. They've been on the DL until today. I'll get a pic.

The only reason bulls like golf is it's grass pasture porn. Can you imagine a swimming pool of scotch?

 

Watch Temple Grandin. Good flick.

 

My neighbor's mom from the conservative rural south calls tattoos 'skin illustrations'. As in, "Why on Gawd's great earth would you wanna be gettin' yerself painted with no skin illustration?"

 

just to bring it back slightly on topic, I talked to the owner on sunday and he was waiting to finish the series, (last sunday), before taking it to a man called Bruce (who most sydney types will know) to get his midas fingers involved.

It may seem like overkill to some getting a boatbuilder involved, but i think its a good call.

this way it will be put right, not made worse, no problems created, no butchering. Or at least if there is, it will be made right again by someone who knows how.

Will let you know of the "fix" and its effectiveness in due course

Share this post


Link to post
Share on other sites

That's just wonderful Christian. But this is the FD thread and my question was addresed to Matt with an FD 10m.

 

Bob, I understand - my point was that foil humm is not unique to FT's and is something that happens on a lot of boats with high aspect foils and I posted some recommendations how to help minimize/eliminate the problem.

 

Lucky you weren't as off-topic as the dude who posted a link to docs about hydrofoiling Russian ferries.

 

And here was me stumbling across this thread when searching for posts about singing rudders. I fixed it by sanding the trailing edges finer, but since I don't have an FT10 that information will be useless to anyone here.

Share this post


Link to post
Share on other sites

That's just wonderful Christian. But this is the FD thread and my question was addresed to Matt with an FD 10m.

 

Bob, I understand - my point was that foil humm is not unique to FT's and is something that happens on a lot of boats with high aspect foils and I posted some recommendations how to help minimize/eliminate the problem.

 

Lucky you weren't as off-topic as the dude who posted a link to docs about hydrofoiling Russian ferries.

 

And here was me stumbling across this thread when searching for posts about singing rudders. I fixed it by sanding the trailing edges finer, but since I don't have an FT10 that information will be useless to anyone here.

 

Yeah those FT-s are soooooo special that the tricks that fix problems on other boats simply are not good enough for the FT folks since they are very special too

Share this post


Link to post
Share on other sites

I thought (hoped) this board might have taken a more friendly route...:(

 

fukitol_job_sucks_over_worked_no_worries_tshirt-p23505217648812291735jn_400.jpg

Share this post


Link to post
Share on other sites

That's just wonderful Christian. But this is the FD thread and my question was addresed to Matt with an FD 10m.

 

Bob, I understand - my point was that foil humm is not unique to FT's and is something that happens on a lot of boats with high aspect foils and I posted some recommendations how to help minimize/eliminate the problem.

 

Lucky you weren't as off-topic as the dude who posted a link to docs about hydrofoiling Russian ferries.

 

And here was me stumbling across this thread when searching for posts about singing rudders. I fixed it by sanding the trailing edges finer, but since I don't have an FT10 that information will be useless to anyone here.

 

Yeah those FT-s are soooooo special that the tricks that fix problems on other boats simply are not good enough for the FT folks since they are very special too

 

I don't own an FT10.

Share this post


Link to post
Share on other sites

I know this is an old topic, but I too have a hum, a violent floor shaking hum that you swear will shake every screw on the boat loose! The boat is a perfectly smooth Star that I re-faired the keel on over the winter. I thought it to be the rudder until reading this forum. During a particularly violent hummer of a sail in moderate breeze, the "humm" mysteriously and suddenly abated to a quite flutter. Upon haul-out, the trailing edge of my razor sharp bulb, solid glass by the way, was shredded to bits. Maybe there is something to too symmetrical, to sharp on some boats!

Share this post


Link to post
Share on other sites

While my boat is not a FT but to some degree similar in setup (transom hung rudder) and high aspect foils i can tell you that I do have a very little amount of humm - it starts at about 19 knots and stops at about 19.5 knots and doesn't re-appear (at least not under 26 knots). The humm used to be a little worse but got better after we rafaired both the hull and foils a couple of years ago - I did use the recommendations from Steve thompson I posted above regarding trailing edge treatment.

 

Christian takie your Viper 870 and your 19.5 knots to a thread that gives a fuck! you fucktard want a be FT10 owner and don't even go into how you didn't follow threw with your order cause ??????? what ever the fuckin reason you come up with cause your boat is more of an orphan than a Tiger will ever be. Lots of luv to Perry, Scoot, and Hip for a really good boat.

 

While my boat is not a FT but to some degree similar in setup (transom hung rudder) and high aspect foils i can tell you that I do have a very little amount of humm - it starts at about 19 knots and stops at about 19.5 knots and doesn't re-appear (at least not under 26 knots). The humm used to be a little worse but got better after we rafaired both the hull and foils a couple of years ago - I did use the recommendations from Steve thompson I posted above regarding trailing edge treatment.

 

Christian takie your Viper 870 and your 19.5 knots to a thread that gives a fuck! you fucktard want a be FT10 owner and don't even go into how you didn't follow threw with your order cause ??????? what ever the fuckin reason you come up with cause your boat is more of an orphan than a Tiger will ever be. Lots of luv to Perry, Scoot, and Hip for a really good boat.

 

 

 

So what in the f is a Viper 870? Raced a bunch on the 830 and the 640 but would love to see a 870

 

 

Share this post


Link to post
Share on other sites

Con:

I don't think you want a razor sharp trailing edge on any appendage. Snaps is right, chamfer it. But it appears it has self chamfered.

Share this post


Link to post
Share on other sites

I know this is an old topic, but I too have a hum, a violent floor shaking hum that you swear will shake every screw on the boat loose! The boat is a perfectly smooth Star that I re-faired the keel on over the winter. I thought it to be the rudder until reading this forum. During a particularly violent hummer of a sail in moderate breeze, the "humm" mysteriously and suddenly abated to a quite flutter. Upon haul-out, the trailing edge of my razor sharp bulb, solid glass by the way, was shredded to bits. Maybe there is something to too symmetrical, to sharp on some boats!

 

Class rules prohibit fairing so the correct terminology is that you fixed defects.

Share this post


Link to post
Share on other sites

While my boat is not a FT but to some degree similar in setup (transom hung rudder) and high aspect foils i can tell you that I do have a very little amount of humm - it starts at about 19 knots and stops at about 19.5 knots and doesn't re-appear (at least not under 26 knots). The humm used to be a little worse but got better after we rafaired both the hull and foils a couple of years ago - I did use the recommendations from Steve thompson I posted above regarding trailing edge treatment.

 

Christian takie your Viper 870 and your 19.5 knots to a thread that gives a fuck! you fucktard want a be FT10 owner and don't even go into how you didn't follow threw with your order cause ??????? what ever the fuckin reason you come up with cause your boat is more of an orphan than a Tiger will ever be. Lots of luv to Perry, Scoot, and Hip for a really good boat.

 

While my boat is not a FT but to some degree similar in setup (transom hung rudder) and high aspect foils i can tell you that I do have a very little amount of humm - it starts at about 19 knots and stops at about 19.5 knots and doesn't re-appear (at least not under 26 knots). The humm used to be a little worse but got better after we rafaired both the hull and foils a couple of years ago - I did use the recommendations from Steve thompson I posted above regarding trailing edge treatment.

 

Christian takie your Viper 870 and your 19.5 knots to a thread that gives a fuck! you fucktard want a be FT10 owner and don't even go into how you didn't follow threw with your order cause ??????? what ever the fuckin reason you come up with cause your boat is more of an orphan than a Tiger will ever be. Lots of luv to Perry, Scoot, and Hip for a really good boat.

 

 

 

So what in the f is a Viper 870? Raced a bunch on the 830 and the 640 but would love to see a 870

 

 

 

 

Donno what a Viper 870 is. I have an 830. There is a T870 (same designer) but is is a slightly more crusier design. Obviously the poster (before you ) is a little off................................and an idiot too.

Share this post


Link to post
Share on other sites

Having the squared off back edge (3mm) on keel, bulb, and rudder help prevent the laminar flow from each side of the foil from meeting each other at the aft end causing a vortex. "Class rules prohibit fairing", I would think that class rules prohibit changing from the original foil design. If your keel or rudder foil was done improperly leaving you with a crap foil, you should be able to repair it to class specs and have it inspected with templates by the class measurer, or you are left at a disadvantage. Taking waves out of your hull, refairing, isn't considered alteration.

 

When I received our boat, not an FT10 (but alot like it), our keel had no foil at all, professionally faired from the factory my ass. We still get a little buzz at 9.5 knots, but nothing else.

Share this post


Link to post
Share on other sites

I know this is an old topic, but I too have a hum, a violent floor shaking hum that you swear will shake every screw on the boat loose! The boat is a perfectly smooth Star that I re-faired the keel on over the winter. I thought it to be the rudder until reading this forum. During a particularly violent hummer of a sail in moderate breeze, the "humm" mysteriously and suddenly abated to a quite flutter. Upon haul-out, the trailing edge of my razor sharp bulb, solid glass by the way, was shredded to bits. Maybe there is something to too symmetrical, to sharp on some boats!

 

Check that the engine box door is flush with the hull... we had a similar prob and this was the fix.

 

Doug

Share this post


Link to post
Share on other sites