Monofin Bend

[Walrus]

Just one more thing I remember that is specific to the Hyper fin only that would be adding to the footpocket "bending" effect:-

I've tried out 4 hyper fins so far and I've noticed that with all of them the heel strap is very flexible and has a lot of give. I can actually feel my foot sliding in & out of the footpocket and it is definitely adding to the blade angle. I definitely don't get this with the leaderfins although it is still bending thru the footpocket itself. With the leaderfins the heel strap is probably double the thickness and has far less give, the hyper heel strap feels like a rubber band in comparison. This is something that could be fixed by gluing on and additional rubber support onto the footpocket and heel strap. So might help reduce the footpocket "bending" effect at least a bit.

The hyper style fins are mostly used for long distance in fin swimming. They always allow for a softer more comfortable footpocket for long distance, the sprint fins should have little to no give in the footpocket (and probably very little comfort). With the hyper fins I think they trade off performance for comfort with the footpockets. With the waterway fins I used to custom order the long distance blade with a stiffer middle distance footpocket, and the performance was much better. It felt like a much stiffer fin then a normal LD1, but in reality the normal soft footpockets just had too much give.


Cheers,
Wal

 

[Walrus]

Despite all the problems it's funny that the Hyper fin still seems to be the most efficient fin for dynamic (quite good for constant too). I wonder if most of it isn't just from the footpocket angle ?
For constant weight the fancy hydrodynamic footpockets really does nothing. For most of the dive the foam is compressed, past 20-30m it's really just squished flat.

When I tried a kicking/gliding style with waterway the gliding was very difficult, need a very large knee bend to avoid putting the brakes on. Even with a classic finswimming technique I think the increased footpocket angle, therefore decreased blade angle is actually decreasing drag a lot. (When it's not bending thru the footpocket :head)
I wonder how a waterway LD1 would perform if you give it a 30 degree angle ?

Might be a good DIY project. Get a LD1 fin, order the footpocket separate. Make a 30 degree wedge out of very high density foam, like from a kick board. Then glue the wedge in between the footpocket and blade. I think I might have seen an old thread where someone has actually done that.

 

[BennyB]

Might be a good DIY project...

Who wants to put a wager on that Andy is in the shed tinkering as we speak?

 

[EdHornby]

I had no idea it could be bending like that, i'm going to get some videos done.

shout me if you want me to bring my camera to the monday pool

 

[jome]

Bending at the footpockets often isn't apparent until you slow down a video. I thought my leaderfins mono was bending pretty well, but it turns out the blade itself hardly flexes and it's all coming from the footpockets. I

Now the question is - is that automatically a bad thing? I mean weren't world records broken with that fin?

Benny - personal observations about lactics (I also seem to be "resistent"):
Most important factors are:
-The amount of ventilation pre-dive
-Warmups
-Speed and kicking style.

Quite simply the biggest lactics I get with no-warmup, no breathup, fast speed. On heavy warmup, slight hyperventilation and slow speed I get nothing.

My personal feeling is also that this has to do with the magnitude of the dive response - ie. some of us simply don't get a really good one in the pool (with max packing especially). I won't get into the whole aerobic vs. anaerobic metabolism thing, but in a nut shell not getting lactics indicates you're not very well vasoconstricted and are probably burning a lot of oxygen to swim. This would make sense since I get pretty good lactics even on a pretty shallow CW dive, which I'd like to think is because the pressure magnifies my response. My personal gut feeling is that this has to do with me being in general more of the "endurance type" physiologically. Mostly just speculation, but that's how I explain my self for sucking at dynamic All the best dyn dives I've done I felt really strong lactic burn, but on average I just "don't get that". This is especially present in bouts of aerobic training, which for me is 95% of the season. When I taper down I start to get lactics and better dynamics too...

Bit of off topic, but still...

 

[Mullins]

The Leaderfins mono was pretty good, but my dynamics are a lot better now I'm using the Hyperfin. I agree with Wal, this is mainly because of the angle. So the fact that records were set with a fin certainly doesn't make it perfect....

I agree with what you say about the reasons behind lactic buildup

 

[jome]

Yeah, there's always room for improvement and in fact I dislike it when people get hung up on records - it doesn't always mean that that particular method or fin is for example perfect for them. But I think it can be accepted as an indication that the fin is "good enough" for most uses, or at least average or intermediate divers don't need to worry too much...

I still believe that in 99% of cases, simply having the right stiffness and right footpocket size are the most important characteristics of a fin - and both properties are completely individual. Well yeah, angle is important too - agreed.

 

[trux]

Now the question is - is that automatically a bad thing? I mean weren't world records broken with that fin?

Yes, as long as the bending keep the blade in the right angle, or better told as long as it keeps the blade running through the optimal curve, it is not bad, of course. You just need to find the optimal kick style for it, so that the negatives do not overweight the positives.

The V-bending is another cup of tea, though. Although it has also some positives (better directional stability), a big part of the input energy is directly lost on moving water to the wrong direction (sideways instead of backward). So here too, the kick should be adjusted to minimize the V-bend and the resulting energy loss. Strengthening the blade accros the fin under foot-pockets and/or on the trailing edge might help too avoiding the V-bend.

 

[Mullins]

Just had somebody watch me in the pool tonight. Apparently my fin is doing all sorts of funny things, like v-bending even when I'm gliding.

 

[trux]

Just had somebody watch me in the pool tonight. Apparently my fin is doing all sorts of funny things, like v-bending even when I'm gliding.

That sounds like the fin is not reinforced under the footpockets and you bend the blade with your feet. Or the reinforcement (often a metalic plate) is bent or broken, or simply too weak. However, when gliding, the V-bend is not bad at all - in fact it stabilizes you. It is only bad when the fin is in action.

 

[ADR]

Who wants to put a wager on that Andy is in the shed tinkering as we speak?

Just came in from the shed from working on the underwater scooter project with a kick arse trolling motor.


....but already on the monofin tinkering as well Benny and ordered 2 fins and a blade only from Bogdan last week and plan to cut the top out of one and build it up internally with a secret Dave Goldie mix that is both non compressive but neutrally bouyant.....as I hate how rubber sinks an neoprene compresses

 

[Mullins]

That sounds like the fin is not reinforced under the footpockets and you bend the blade with your feet. Or the reinforcement (often a metalic plate) is bent or broken, or simply too weak. However, when gliding, the V-bend is not bad at all - in fact it stabilizes you. It is only bad when the fin is in action.

Yes, I think there is something unusual going on. As you say, it's not a problem during the glide itself, but it would make the blade more predisposed to folding if it's bent even before the kick starts.

 

[Walrus]

Hi Dave,
I was thinking about the v-bend when you are gliding and I can think of one cause. I think even when the reinforcement between the footpockets are working properly these newer style fins are much more prone to movement between the footpockets at many angles, including "roll" for want of a better word.

For example you put your feet in the footpocket, then bends your knees out apart from each other, compared to bringing them in touching. That will be putting a stress on the fin and forming a v shape. Would imagine this action would be worst when the blade is flat, ie gliding. Maybe try next time at the pool get someone to watch you glide with your legs straight and roll your knees inwards, then roll them outwards and see if there is a difference. If it does make any difference and provided there was room in the footpocket you could put material in to change the angle, perhaps build up the arch ?

Perhaps the footpockets are at the wrong "roll" angle for your feet/legs hips. They could just be at the wrong angle full stop, not just for you. I think when I glide I do tense certain muscles, arch my back, no idea what I'm doing with my legs. Everyone's feet, legs hips are different, theoretically should be the same but maybe this slight difference combined with swimming/gliding style can put a bit of an V angle in the blade. Just the shape of your foot, if you have a high or low arch for example would effect the angle your feet sit in the footpocket. More and more I'm thinking they need to really beef up the fibreglass at the base of the blade, and come up with a very secure way to attach the footpockets.


Cheers,
Wal

 

[salibandy]

About the footpocket bend issue. I wanted to ask, is it possible that it was meant to be? I was told that hyperfins (i shall use giperfins so as not to confuse between brand names) were designed around their footpockets, not the blade. The footpockets are 'springs' that absorbed energy and then gave it out. This is a known fact about gipers. Or maybe the question in this thread that I'm missing, is whether the footpockets should bend that much.

 

[trux]

Not speaking about the v-bend, the bending in foot-pockets is not a problem as long as the blade maintains the optimal angle of attack, which is definitely not the case in the picture of Ben's fin, where the blade is almost at 90 degrees to the axis of motion. In contrary, the photos of your fin look just right.

Both, bending in one point (at the foot-pockets), or continuous sinusoid bending of the entire blade, have their advantages, and I think it is difficult to tell which principle is better without making very complicated measurements.

 

[stergios]

can we use the monofins for spearfishing applications?

 

[salibandy]

If you really really want to. Otherwise a pair of stereos are more maneuverable.

 

[Mullins]

I use a mono for spearfishing sometimes. Only when it's deep though.