When I was young and built blasting boards ,a long long time ago the main reason for having three fins was so when you snapped the main fin landing a jump you could still get home. It was the days of plastic football fins , ( remember those ) ? I snapped a fair few of those , one on a turtle.
Select to expand quoteSparky said..
Looks like a new toy not a trifin.
Yes it is a Bombora New Toy. As ridden in the photographs shown circa 1983 it was a tri fin set up using a middle 24 cm Kanga fin with 2 x 7.5 cm side fins on a wide swallow tail with drop wing flyers and spiral vee. Price below from a 1983 issue of Freesail is fully rigged.
Select to expand quoteforceten said..duzzi said..Shifu said..
On blasting boards? I don't understand what it's supposed to do. 
It does adds weight and drag!
Umm, drag does increase, by what degree ? This poses the question What do you want the board to do ? Go fast, turn fast , catch more waves?
The weight it depends on the comparison , between what size fins
MFC SINGLE Fin G10 42cm= 558 grams
Tri Fin, 2 additional boxes weight 104 grams
2 additional 14cm side fins= 138 grams
center fin, shorter than the 42 , say 28cm = 396 grams.
additional epoxy for side boxes 70 grams, glass and carbon that quantity , not measurable .
Total for this is 656 grams
calulate weight difference between a Tuttle or powerbox in single, as 100 grams more than a long US box , used on the tri fin.
single fin = 558 grams
tri fins= 656 grams
add 100 grams for Tuttle or powerbox
single fin = 658 grams.
tri fin = 656 grams.
my Tabou Rocket 135 liter has such a tri fin setup. The weight are from all items I have weighted, I could shave a few off the tri fin, by more selective finsthe single fin this length needs to be G10.
i did not nit pick bolts found on a Tuttle vs screws.
Where are u finding side fin boxes at 104g for TWO?
I think you mean each?
Carbon slotbox aftermarket = 80g.
US box, Cobra plastic slotbox or plastic MT = 130g
each....
Select to expand quoteMark _australia said..forceten said..duzzi said..Shifu said..
On blasting boards? I don't understand what it's supposed to do.
It does adds weight and drag!
Umm, drag does increase, by what degree ? This poses the question What do you want the board to do ? Go fast, turn fast , catch more waves?
The weight it depends on the comparison , between what size fins
MFC SINGLE Fin G10 42cm= 558 grams
Tri Fin, 2 additional boxes weight 104 grams
2 additional 14cm side fins= 138 grams
center fin, shorter than the 42 , say 28cm = 396 grams.
additional epoxy for side boxes 70 grams, glass and carbon that quantity , not measurable .
Total for this is 656 grams
calulate weight difference between a Tuttle or powerbox in single, as 100 grams more than a long US box , used on the tri fin.
single fin = 558 grams
tri fins= 656 grams
add 100 grams for Tuttle or powerbox
single fin = 658 grams.
tri fin = 656 grams.
my Tabou Rocket 135 liter has such a tri fin setup. The weight are from all items I have weighted, I could shave a few off the tri fin, by more selective finsthe single fin this length needs to be G10.
i did not nit pick bolts found on a Tuttle vs screws.
Where are u finding side fin boxes at 104g for TWO?
I think you mean each?
Carbon slotbox aftermarket = 80g.
US box, Cobra plastic slotbox or plastic MT = 130g
each....
Mark, and others:
since my first conversion I have used , along with mini US , slotbox PROBOX, surf fin boxes.
www.proboxhawaii.com/
These boxes takes ProBox fins or FCS twin tabs. I have installed 12 that come to mind, removed 4 to replace, performed my own tests to determine strength, on removal they proved very strong, for the purpose intended, multi fin and 14 cm long.
The weight, again done just now to confirm was 52grams for one. My estimate on product variance weight is 2 grams.
so 104 grams for 2 is correct with a 4grams increase possible.
my installation method , tried and true, is router out hole , fill with 8oz pour foam, re- router box hole, install fin box in carbon, glass and West Systems 105 Epoxy.
I have G10 fins that are hand made from Hawaii , I use FCS , very light weight fins with a highly sophisticated foil. K4 make FCS base that get used also. It's time consuming to modify a slot box , Futures, US box fin base to fit, but easy enough.
i like slot box bases a lot, but they are expensive . I have used Flikka, Simmer and Tabou boxes. The Flikka are best using hex head internal screws set in G10. The Simmer boxes are alout half the depth of others, but not much difference in weight.
my slot box weight is only slightly different to yours it's 132 grams, Cobra built.
witchcraft.nu/
First Series of Chakra, tri fin 88 liters, wave oriented FSW, I waited a year for it to be developed, made in Southern Europe. One of the strongest boards made, considered production, with custom details .
Easy to ride, catches waves easy, planes early enough, is strong beyond words. Very well constructed using strongest materials. The ride is like a Subaru WRI STI , compared to a Suzuki Celerio.
Flikka 99liters, 5 box, quad or trifin. Tri fin mostly, a Peter Pan wonderland board.
These board compared to the offerings from Cobra, shine. Can't say I've ridden all, just many. Simmer boards being quite nice.
The fin placement and fins themselves are critical, along with toe in, which should all compliment the rocker, bottom shape and the other design features.
if speed is your thing, and earliest planing then a single fin wave board is your thing. Dialing in a fin arrangement , size shape, desired performance ...is a challenge and Like marmite is not for everyone.
I think I was the first in this thread to mention fin box weight.
This has been a change to our boards so I thought it was worth mentioning.
I have been into my local shop and found recent boards fitted with five boxes - giving a lot of options - but their weight can be quite shocking, simply when you pick them up.
I've also picked up some boards with fewer boxes that are also built to a surprisingly heavy weight, including customs often promoted on here.
And that's all we care about. A designer comes up with a nice shape and then commercial considerations can spoil the board in an attempt to make it more diverse, to supposedly appeal to a broader market. Some construction methods can also make a board heavier than originally intended.
There's also the box weight, and then there's the extras glass and resin needed to fit it.
And then if you add loads of G10 fins they are heavy too.
It's just something to be aware of, as the extra weight is something you can feel when sailing the board, especially in the air or when trying to get planing.
I like my boards to weigh in at the 6kgs region, rather than at 7kgs+
Forceten,
Didn't realise you were using surf boxes for sidies. Yes 52g makes sense now 
I won't go to a surf system as I want standard fitments, my carbon slot boxes I make are 80g for the 130mm box, same as Flikka, Severne etc that are all moulded in a PVC block.
I tested one the other day to 100kg lateral loading so it far exceeds anything we could realistically apply on-water.
Basher,
I find the commercial considerations usually go the other way- making a nice board too light as thats what they think we want. When they cost 3K I think people would rather have the extra 500g and have it last. The 5 box thing has made them skimp on material now. Saw a top brand the other day with only 2mm corecell and 2 x carbon. Everyone else uses 3mm, what does that manufacturer think they are so much more clever? No its marketing spin about weight, and consequently skimping on material. Of course it fell to bits in a season, that is not waveboard construction. Thats a slalom board.
For an average size (say 80L) waveboard to last say 3 seasons and only heel dent a bit on the jumping side, a realistic absolute min is 6.5kg (no fins/straps). Closer to 7 is going to last and not feel that bad. Over 7 does start to weigh one down....
Select to expand quoteforceten said..duzzi said..Shifu said..
On blasting boards? I don't understand what it's supposed to do.
It does adds weight and drag!
Umm, drag does increase, by what degree ? This poses the question What do you want the board to do ? Go fast, turn fast , catch more waves?
...
Quite a lot. On my RRD FSW 90 with the same sail (Point-7 ACX-5.8) the difference in top speed I measured is around 2-2.5 knots. The board is a bit of a dog anyway, it is not designed to be on a ACX, but the tri-fin really slow it down. Even when turning you can feel the drag in flat water. After two seasons on tri-fins (Starboard FSW 81 + RRD 90) I am switching back to singles unless I am in 4.3 conditions with sizable swell. I think I would go as far as saying that unless you are assisted by gravity a single fin is all you need.
Weight and strength are not the same thing. Good construction techniques and effort can make a light board and cheaper materials can often mean a heavier board.
Some production line constructions are good, whereas others are not so strong or long lasting or even light.
Some custom brands market their products as better or stronger or lighter, when in fact the are not.
It's almost too complex to discuss, and people will still choose their favourite brands - or their favourite graphics.
But the box issue is simpler than that, namely that we don't actually need five boxes in a board once we have decided what type of fin set up we prefer.
^^^ Indeed
But the vast majority of our waveboards are coming from Cobra and I fear that as soon as they did 5 boxes they took out material elsewhere.
There is a disgraceful lack of material in some boards and its not because they used better materials at all. Its skimping.
Select to expand quoteMark _australia said..
^^^ Indeed
But the vast majority of our waveboards are coming from Cobra and I fear that as soon as they did 5 boxes they took out material elsewhere.
There is a disgraceful lack of material in some boards and its not because they used better materials at all. Its skimping.
Especially with resin .
I have seen a lot of laminates that seem dry. Especially the first layer over the foam core.
Select to expand quoteduzzi said..forceten said..duzzi said..Shifu said..
On blasting boards? I don't understand what it's supposed to do.
It does adds weight and drag!
Umm, drag does increase, by what degree ? This poses the question What do you want the board to do ? Go fast, turn fast , catch more waves?
...
Quite a lot. On my RRD FSW 90 with the same sail (Point-7 ACX-5.8) the difference in top speed I measured is around 2-2.5 knots. The board is a bit of a dog anyway, it is not designed to be on a ACX, but the tri-fin really slow it down. Even when turning you can feel the drag in flat water. After two seasons on tri-fins (Starboard FSW 81 + RRD 90) I am switching back to singles unless I am in 4.3 conditions with sizable swell. I think I would go as far as saying that unless you are assisted by gravity a single fin is all you need.
The difference between a Cobra board and a board like Witchcraft is phoenomial. To have a difference of 2.5 kts, is of no concern to me.
Select to expand quoteMark _australia said..
^^^ Indeed
But the vast majority of our waveboards are coming from Cobra and I fear that as soon as they did 5 boxes they took out material elsewhere.
There is a disgraceful lack of material in some boards and its not because they used better materials at all. Its skimping.
My Flikka has 5 boxes, I will never do another with 5. Especially a larger like 100 plus.
pick quad or tri fin.
Select to expand quoteMark _australia said..
Forceten,
Didn't realise you were using surf boxes for sidies. Yes 52g makes sense now
I won't go to a surf system as I want standard fitments, my carbon slot boxes I make are 80g for the 130mm box, same as Flikka, Severne etc that are all moulded in a PVC block.
I tested one the other day to 100kg lateral loading so it far exceeds anything we could realistically apply on-water.
Basher,
I find the commercial considerations usually go the other way- making a nice board too light as thats what they think we want. When they cost 3K I think people would rather have the extra 500g and have it last. The 5 box thing has made them skimp on material now. Saw a top brand the other day with only 2mm corecell and 2 x carbon. Everyone else uses 3mm, what does that manufacturer think they are so much more clever? No its marketing spin about weight, and consequently skimping on material. Of course it fell to bits in a season, that is not waveboard construction. Thats a slalom board.
For an average size (say 80L) waveboard to last say 3 seasons and only heel dent a bit on the jumping side, a realistic absolute min is 6.5kg (no fins/straps). Closer to 7 is going to last and not feel that bad. Over 7 does start to weigh one down....
When I started tri fin conversions, slot boxes weren't invented yet by Tabou. The cost for a Pro Box is about $8.00
im still not overly keen on slot box, but it is better than a mini us box and much better than a mini Tuttle, this for home installations. FCS , has very sophisticated fins, and ProBox HAWAII made me custom G10s, for very reasonable cost. K 4 was not yet out, but their offering s of FCS base is minimal.
Basher has been bashing multi fins , before dirt was invented.
Select to expand quoteBrent in Qld said..
Marmite is not for everyone?
Some don't like 15 YO single malt Scotch.
i would gather at minimum 50% of the world doesn't know what Marmite is.
of those that do maybe 25 % like it.
i would just as soon chew on broken glass.
OTOH, my wife luvs it.
Select to expand quoteforceten said..Brent in Qld said..
Marmite is not for everyone?
Some don't like 15 YO single malt Scotch.
i would gather at minimum 50% of the world doesn't know what Marmite is.
of those that do maybe 25 % like it.
i would just as soon chew on broken glass.
OTOH, my wife luvs it.
Jeez the things you learn on a Monday morning. But come on, everyone likes a drop of 15yr old scotch. You're just messing with my head...
By the way F10, my decades of experience indicate under no circumstances should one mention the opinions of ones (or anyone elses) spouse in a public forum, ever.
I T W I L L N O T E N D W E L L
Select to expand quoteBrent in Qld said..forceten said..Brent in Qld said..
Marmite is not for everyone?
Some don't like 15 YO single malt Scotch.
i would gather at minimum 50% of the world doesn't know what Marmite is.
of those that do maybe 25 % like it.
i would just as soon chew on broken glass.
OTOH, my wife luvs it.
Jeez the things you learn on a Monday morning. But come on, everyone likes a drop of 15yr old scotch. You're just messing with my head...
By the way F10, my decades of experience indicate under no circumstances should one mention the opinions of ones (or anyone elses) spouse in a public forum, ever.
I T W I L L N O T E N D W E L L
If everything ended well, it would be sooooo boring.
much like blended scotch
Select to expand quoteamzoun9595 said..
I surf my long board with a thruster set up vs 2 + 1. I think it turns easier and not as much stomping on the tail and waiting to turn. I have a 9-4 Ben Aipa that's 3.5" thick ( I think) and the board turns pretty darn good. I think the difference between thruster and 2+1 is the thruster has 3 fins that are the same size, smaller typically. Not sure as to why - but that's what works for me. Lots of long boarders in Hawaii go the thruster route vs 2+1 or single but I have found they ride the nose much more in Ca thus using single. I noticed Hi has more performance long boarders than nose riders as well.
Yes just one of the wonderful things with 3fin boxes is you can alter the personality somewhat, not so much the character as that's also defined by bottom shape ,rocker, etc, by using 3fins of similar size. That set up to me, depending on the board , feels more like a twin, it will be skate like, and turn sharper, but lose some stability VS a 2+ 1 fin set up. Changing to larger sides and smaller center will compromise both traits.
just another plus for a tri fin set up.
I rode a Angelo Amigu 80, with conversion to 3 boxes, it was amazing with 3fins the same , or nearly so, size. Upwind like a banshee, turned like a rat with Nike's,and quick . The board shape details obviously played into this, but as a single it didn't so much shine.
Select to expand quoteforceten said..
Some don't like 15 YO single malt Scotch.
i would gather at minimum 50% of the world doesn't know what Marmite is.
Yeah, I'm one. I prefer that my spirits not taste like a peat bog. And, your Marmite stat is probably off by 45%. If you mentioned the word where I live, most would think you were describing an explosive device. 
