we are seeing more four fin boards these days as well a some 5 fin setups here on Sways. What is the design difference for a board with a “other than 3 fin setup”? If I made a 6’8" x 20" X 2 1/2", for example, what would be designed differently if I made it a 4 or 5 fin? What would the fin placement be? If I wanted a quiver and the next board was a 7’2" what would be different from the 6’8"? I’d love tio hear from everyone.
good questions , and interesting you bring this up , as my next ‘thruster’ will have the 1 to 5 fin option .
And I , too , wondered if there was anything i needed to incorporate into it , to make it work better [or whatever] as a four fin / five fin , than as a thruster , for instance ?
Well, I look forward to reading more on this subject …greg griffin ? others ?
pleease ?
cheers
ben
Well I’m no heavy weight in this department but I have had a bit of an explore into it and I reckon 4 and 5 fin boards can use pretty standard rockers but work well with wider tail areas. I think this is because of the extra possible fin area present. I’m talking about smaller wave boards here, under double overhead, as thats what I’ve had to play with mostly. I found a 5 fin set up is killer on a short wide flatter board, ( a Fish you could call it).
It’s strange, don’t you think, that posts such as this, specific to making boards receive so few replies and posts on fairly unrelated subjects receive loads. Not that I think those posts are bad as such but maybe we need a, “Lets have a whine about the sorry state of the surf industry and all other unrelated to surfboard construction posts”,section or even site.
Quote:
we are seeing more four fin boards these days as well a some 5 fin setups here on Sways. What is the design difference for a board with a “other than 3 fin setup”? If I made a 6’8" x 20" X 2 1/2", for example, what would be designed differently if I made it a 4 or 5 fin? What would the fin placement be? If I wanted a quiver and the next board was a 7’2" what would be different from the 6’8"? I’d love tio hear from everyone.
Here is photo I came across. They sure look nice, don’t they ???
What about fin placement for a 4 or 5.
Do the front boxes need to be farther forward
with a quad than thruster?
I have a thruster speed egg 7’4" thruster with the
sides at 11-12" Could it be converted to a quad by
adding two rear boxes? If so about where do you put the
rear boxes?
Quote:
What about fin placement for a 4 or 5.
Do the front boxes need to be farther forward
with a quad than thruster?
I have a thruster speed egg 7’4" thruster with the
sides at 11-12" Could it be converted to a quad by
adding two rear boxes? If so about where do you put the
rear boxes?
I guess you could use these numbers as a guide, and adjust accordingly.
Stolen from Surfline article.
If you normally put your fins at 11 and 3.25, here’s how to set up the quad: keep the front ones in the same position. Half the distance to the tail is 5.5²…your rear fin on a tri is 3.25…split that distance…half way between 3.25 and 5.5…at 4.375…also move them away from the rail…about 2" seems to be a good place. All my fins point 2" off the nose so the back fins would be almost parallel to the stringer. The cant on the back fins: straight up and down for more drive…more cant for more lift and easier turn initiation. The placement isn’t set in stone…think of taking a tri fin and splitting the back fin in half. Keep the two halves back and close together for more drive…as you spread them apart and move them up the board becomes looser with more lift but drive and back foot control starts to diminish."
Read entire article here.
with a 7-4 thruster to make it a 4 fin you would set the fins as followed:
distance from back tail: 5 13/16
Front fins: 12 1/2
depending on you tail width, let’s say you have a 12 in tail then you would set the distance between the fins at 5 1/8. If you had a 14 in tail then you would set the fins at 5 9/16 apart.
front fins are set at 1 7/16 off the nose stringer. And the back fins are set at1/4 in off nose stringer.
Front stiff fins will give more drive
Symetrical fins in back will give less drive in back, but will allow a more fluid easy turn.
All this information is taken from the McKee surfboard website.
Ive been experimenting with them and I must admit Im way stoked.
If youre a progressive rail surfer, prefer wider boards and easy rail to rail action, 4 (or 5) is awesome. Almost makes 3 fins seem insignificant (at least for me).
Generally a six in spread is a good start for smaller boards, and gets progressively larger for longer boards.
Like a thruster, pay real close attention to toein.
Fin size/geometry, particularly the rears, is critical - ie, experiment!
Any board can be converted to 4 or 5…then the skys the limit.
Endless possibilities to turbocharge your favorite stick.
Bonzer afficionados have been on it for a really long time, havent they.
On the subject of the Mckee set up, I found the boards I used it on a bit stiff and tracked some what, even with small fins. On small to medium wave boards I find this set up works for me:
Rear fin 31/4"
Rear quad 51/2" @ 11/4" off rail with 1/8" of toe & 2 or 3 degrees of cant
front quad 103/4" @ 11/8" off rail with 1/4" of toe & 4 or 5 degrees of cant
I use FCS M3 in front and G1000 set in the rear three slots or GX rear if its small.
I have a feeling that that the Mckee set up would be great on quad guns but that’s just supposition.
“If it looks like it works and it feels like it works then it works”.
Well there you have it!
Good thread. I’ve been thinking about the fin layout for my board.
As a point of clarification for us rookies, and since it’s on topic, how are all these dimension referenced? I know it’s in the archives but scattered. Seems like a good time to ask.
This is what I understand. Please correct me if I’m wrong.
Placement is the distance from the tail to the trailing edge of the fin at the base. It’s measured perpendicular to the stringer, not in a straight line from the fin to the tail.
Distance from the rail is the distance from the rail to the trailing edge of the fin at the base. This also measured along a line that is perpendicular to the stringer. The rail here meaning the outermost edge, not the breakover point.
So, distance frome the tail and rail give you a spot for the trailing edge. Then you need a line to place the fin on. That’s established with toe in.
Toe in is a line drawn from the nose to the spot described above. For example, if it’s 2" off the nose, an imaginary line runs from that point to the spot that defines the location of the trailing edge of the fin. That’s the line that the fin gets placed on and it runs through the center cord of the fin.
Now to cant. I don’t know how can’t measured. I suppose it could be measured from the surface where the fin is being applied, or from a line parallel to the stringer. How is it measured?
I don’t mean to sound like I’m telling it like it is. I’m just stating what I understand it to be. Sorry if all this is obvious to some. I need the clarification.
Then there’s tail shape as related to fin set-ups. I’d love to hear something on that.
Sparksbrand, Yah, it’s kinda odd. I guess topics like this require more specifics and less emotion. I’d like to see more specifics these days.
Yeah you’ve got the right idea, but I gave toe in the form of a measurement taken 4" up from the trail end mark on the stringer, ie say 1/4" further toward the stringer at leading tip of fin. This will point your fins just past the nose of a board around 6’. Cant I often just measure straight off the bottom of the board but with large concaves or vees this can make it look wrong and I try to measure from a straight line as if the bottom was flat.
So many variables too. But yes, fin distances are measured from the trailing edge. On the 4 fins design the measurement is is from the stringer, or how far apart to put the fins. I personally measure tri fins from the rail edge, but then a persons feet size and weight, and rail design have a bit to do with this measurement also… but i digress. Usually you can set the fins toe anywhere from 1/8 in to 1/4 that will run the gauntlet of cant. But you have to take the boards overall length into consideration. ie, 1/4 cant on a 8 ft board will cross the nose…so you see it’s all subjective, too many variables, and it all depends on the shape, width, rocker. Oh yeah rocker, the more rocker the straighter you can place the fins, let the rail line do the turning. It just goes on, and on.
I understand what you mean about subjective with all the variables and opinions. That’s where the expertise comes in. I’m a long way from having that.
I wasn’t really trying to figure out what placement to use, but how to find the placement once I know what the numbers are. In other words, if I were to take sparksbrand’s example of “Front quad 10-3/4” @ 1-1/8" off rail with 1/4" of toe & 4 or 5 degrees of cant", and follow his description, I would do the following.
Using a square I’d measure from the stringer tip, or tails for a fish, 10-3/4" up. Then perpendicular to the stringer I’d measure 1-1/8" in from the rail. This is the trailing edge point. Following parallel to the stringer I’d measure up 4", then in 1/8". This is a point to draw a line through from the trailing edge. It may not be the leading edge but he’s using 4" as a standard distance to measure the toe in from the trailing edge. This is the line to place the fin on.
Kinda hard to describe but do I have the reference points right?
I don’t quite understand the cant, but I think sparksbrand touched on it when he said “…can make it look wrong…”. That’s where the eye of the shaper comes in. Kinda tough for a newbie to see that stuff so I wind up trying to be over precise.
Thanks for the help.
Quote:
Ive been experimenting with them and I must admit Im way stoked.If youre a progressive rail surfer, prefer wider boards and easy rail to rail action, 4 (or 5) is awesome. Almost makes 3 fins seem insignificant (at least for me).
Generally a six in spread is a good start for smaller boards, and gets progressively larger for longer boards.
Like a thruster, pay real close attention to toein.
Fin size/geometry, particularly the rears, is critical - ie, experiment!
Any board can be converted to 4 or 5…then the skys the limit.
Endless possibilities to turbocharge your favorite stick.
Bonzer afficionados have been on it for a really long time, havent they.
Pretty much summed up my experience, too. And I surf way different waves most of the time. Yes, the 4 fin is very versatile.
Hi Ryan ,
What you described is basicly the same way I do it. But first I bug a whole lot of people on where should I place the fins! And then I look in the archives to see what Herb does. As far as cant I’m a follower here. I measure fin cant of most of the boards I repair and 6 degrees is quite standard for Shortboards and longboard side fins. I have a tool I think it’s called a “sliding T bevel”. Bill Barnfeild has posted some really good stuff about fin placement.
Hey Surf4fins ,
Thanks for the foam!!!
Ray
Hey Ray, you’re welcome! You need to come by check out the new work bench. The casters made it all come together.