A few problems with the "The Science".
http://www.boatdesign.net/forums/boat-design/bulbous-bow-design-18043.html
i dunno
..i admit it is a very complicated science
way over my head..but i love to study this stuff
awhile back, i worked with a sports medicine company, that developed
a radiofrenquency atrhoscopic debrider wand that used the venturi affect
it was called the paragon by arthocare. it works great..
however, from most of those replies in the sited article/website
you kindly footnoted for us...
i was able gather, this;
1-that too big off a bulb,
2-the bulb being out of the water most of the time,
and
3- the fact that too great of speed affects it's performance...possibly negates it.
.seems like 1&2 don't apply to this fin or surfboards....it's.not too big, and it's under water
all the time..
and 3..hmm...these "vessels"
are being propelled
by either the wind or by an engine
which i really think changes everything..
look at kite surfing, and tow-ins...
these boards don't really resemble standard surfboards..anymore
which are being propelled by the wave..right?
and wave speed is limited in regards to us on a surfboard..right?
am i close..or did i miss out totally?
heck, i really would like to fully understand this as much as the next guy..
anybody?
Like Mr Cooper said, we can armchair the thing into another epic 20-page thread and not come any closer to understanding it than we do now. The only way to know one way or another is to get out there and feel it up.
Amen..
and for me..it works...
[quote="$1"] ...we can armchair the thing into another epic 20-page thread... [/quote]
It is what we do!
It’s interesting to hear all points of view on this, especially the science. Swaylocks has always had depth in it’s membership.
I could poke holes in some of the arguments with my half baked theories but I’m no scientist and you guys would probably get a good laugh. But…basically I feel the same way as dansan about the complexities of the differences in the 1) power source 2) size 3) speed 4) lack of proximity to the waterline 5) placement at the rear of the surfboard 6) xfactors. Basically more questions than answers.
Again, I would love to see somebody get a hold of one of these fins and gather some scientific data. It would be interesting, but even if it came back negative I wouldn’t take the fin in my speedhull because it’s what works best in that board.
btw, I have no financial interest in these fins.
Hi Dan,
not saying it doesn’t feel different, I’m just not too sure about why it feels different and that the bow bulb explanaition covers it. It may for one thing affect the pitch of the board since it’s 25% lighter than a fiberglass fin (which is insidentaly one of the claims about bow bulbs too, that it changes the pitch of the boat). I can also imagine it creating a vertical force. Anyway, I’ll send Ron an email.
regards,
Håvard
yeah..contact ron...maybe he can float you a demo to try...
what the worst that can happen?
ya don't like it and ya send it back...
heck i'll buy it from you if you no like it...
i have several friends in jax beach
that want one after trying my board with it..
well hopefully
that swell will show this weekend into next week
tuesday supposed to be the clean offshore day...
and i can try this fin on alot of boards..
especially my liddle hull..
and get feedback...some pics..etc
gdaddy wrote:
...we can armchair the thing into another epic 20-page thread...It is what we do!
That was a good, classic, Sway laugh…
I too was thinking about the fact that it was under water, would make for a different effect than on the ships, but then again, those of you saying it help/improves performance… There seems to be alot to be said for the emperical side of the surf experience…
I finished reading this, and had the recollection of Dale S. telling me how Greenough found the nice broad fin fillet increased flow/speed/lack of drag… But, like the MVG’s and tubercals, it’s about turbulence reduction, decreased stalling at high angles of attack. The interference effect of the two waves seems like something else - Drag on the overall length of the hull…
i dunno...the thing works...for me
and that all that really matters ..
alot of these projects start with some science
behind them:
simmons with lindsey lords findings,
campbell bros with the venturi affect, etc....
and then take on a life of their own
based on their merits..
i dunno...as long as it
works and increases my fun factor..
i can't ask for anything else..
[quote="$1"]
anybody try this yet?
[/quote]
Concept has been around for awhile. Like this fin made in 1987 for Windsurfing. The only problem with concept ideas is they work well at a point of condition. The trade off is the sacrific sometimes made before the concept comes into play. Mother nature is not a planned condition, so when a concept is based on a planned condition then limitations apply and trade off happens. The blub on the front in this windsurf fin worked when you were powered up especially in upwind conditions. But when using the same fin and board in lighter winds it felt like you were towing something. Something to remember when people are comparing apples to oranges. Not saying the bullet fin does not work, just that a graph and chart is alot different than on a wave. This was one of the things that always drove me crazy in the windsurfing market, so many charts and tank tests with poor real mother nature results. Nice to see new ideas never the less. Mahalo,Larry
larry,,
thanks for the info..
any front on pics of that fin?
Hi Larry, is that just a tab on the front of the red fin or is there a bulb that I’m not seeing. If there’s no bulb then I’ll still have to give Ron credit for an original idea.
The closest thing I’ve seen to this is the “Koanda” by Bob Howard. It was an attachment that fit around the fin and was very large, not as steep and it’s function was to improve noseriding which it did very well.
Although I don't think this is directly analogous to a bulbous bow, I can see how it would function. There are numerous ways to ''set up'' the flow onto a wing or control surface. Many examples in aerodynamics of aircraft and racecars. The (half) bulb would operate over a wide range of AOA, also...
As you guys are saying, how it works in actual use is the most important thing.
I've had a couple courses in naval architecture and we briefly touched on the bulb now common on ships. the volume of the bulb is on the order of a few (max 5) percent of the hull volume, and overall if you look at a ship with a bulb, you see this readily. What's missing here is that the function of a bow bulb is to reduce the wave drag created by the entry of the bow into unbroken water. simply, the bow wave represents energy lost, and my minimizing the bow wave you conserve energy. NOTE! inherent and necessary in the function of a bow bulb is that there is a nearby free surface which would otherwise have an energy-absorbing wave/wake. This is not the case, specifically, in a surfboard fin. Any wake created is not reduced by a bulb at the base, tip, or anywhere else on the fin.
Ergo, if it is posited that this bulb at a fin base somehow functions like the bow bulb of a ship, I'm calling bullshit, or at best another misplaced and misunderstood misapplication of a proven effect. At worst, nothing more than another load of the bullshit marketing that is so common in the sport today. So sad.
hey charlie...don't hold back..tell us how you really feel...;-)
seriously..have you tried this fin?
and on several boards?
i switched back and forth with my favorite fins
in the same session..to compare...
so has gene
.and it works for us...
that's all we're saying..
try it...
no like
send it back
The problem I’m seeing here is that people want to shove this into the exact same box as the bulbous bow. We’re all aware that there are huge differences in the two applications but to say that an adjacent water surface is necessary for a bulb to have an effect is ridiculous. We all see a lot of bullshit out there but in my experience this bullshit works, regardless of whether you buy “The Science” or not. I’m sorry this makes you sad Honolulu, want a hanky?
dansan, Been watching this thread and laughing on the way. I have to agree with Charlie, everything he said is pretty right on. The last 10 years nothing new really but great marketing BULL by molding companies! Here's a few things to think about when riding and looking at this bull fin.
1) TEMPLATE: Similar to a Hot Curl fin which has alot of good reviews, but more like a fin Gene calls a Comet which explains why Gene likes it.
2) The Flared base or blub pretty much follows TaylorO statement about the fillet. But also in a molded fin world having the flared base takes out some of the lateral flex to the base which is part of the drive you get off your fin. The pic below will show other molding companies doing that.
It's one thing to make statements, but to use the words REVOLUTIONARY and SCIENE and use 50 years of data they has nothing to do with the fin is when I run the other way. But what do I know, I just have been making fins for almost 40 years.
You can do 20 pages on this fin, but at the end of the 20th page the fin will still be a clean template with a flared base that some guys like.
To many designers and not enough riders (-: Mahalo,larry
Hi Gene, I think the problem is that the guys who actually make it claim that it works the same way as bulbous bow (or try to explain it that way) and this raise more questions than answers. And they still havn’t answered my e-mail. So I wrote an email to a naval arcitect whose name came up in a search on bulbous bow, here is his answer:
"I am very sceptical. To have any effect on the wave train the fin would
have to be much larger in volume. Also at the speeds that they are talking,
planing speeds, the resistance is not primarily wavemaking. Also to have
any major effect the bulb needs to be at the bow.
If there is any effect it is not because of the bulb effect."
This is a surfboard design forum after all, if we do not try to figure out why and how this could possibly work yours and Dan’s review and appraisal is nothing more than advertisements.