Force Fins vs Jetfins - tek diving and all the kicks

[ams511]

Molds aren't cheap. They require a lot of time and effort to make.

Molds may not be cheap but they are a fixed cost. The mold cost is the same to make one fin or a thousand. There seems to be a huge difference in cost from one fin to another which isn't explained by the mold cost. Going from a Force Fin pro in regular material to Tan Delta is almost double the cost, $289 to $550.

 

[TN Traveler]

The "Tan Delta" material is two to four times .the cost of the material used in Originals and Pros.
it also has a much quicker set-up time and there are many more rejects because of this. Also the molds for fins made from Tan Delta are not the same as the molds used for Originals and Pros and since there are much fewer of the premium fins ordered/produced, the mold cost per fin is much higher. Every fin made from Tan Delta material is perfect, they do not sell "seconds", unless it is just a slight color blemish. As I indicated above, Bob signs (and numbers) each one of these and he expects them to be perfect.

Hence the Significantly higher price.

 

[RJP]

Molds may not be cheap but they are a fixed cost. The mold cost is the same to make one fin or a thousand...

Simple cost accounting tells a different story...

Fixed cost ÷ by unit volume = allocated fixed cost per unit.

Which would obviously be higher per unit on a lower-volume product.

If model A mold costs $5000 and they sell 500 units, allocated fixed costs = $10 per unit.
If model B mold costs $5000 and they sell 100 units, allocated fixed costs = $50 per unit.

Beyond that, a smart marketer should try to sell a "more exclusive" product for a higher margin anyway, irrespective of the magnitude of difference in actual production costs.

---------- Post added April 19th, 2015 at 05:11 PM ----------

Force Fins were designed to mimic the action of a fishes tail and and work best when they get a hard initial flick (to load up the fin) and gentle follow through (to let the rebound finish the propulsion).

Please explain what it means to "load up the fin" and "let the rebound finish the propulsion", giving due consideration to the well-understood physics behind the law of conservation of energy.

 

[TN Traveler]

And Force Fins probably sells over 100 Originals/Pros for every 1 of the high end, Tan Delta fins. Bob makes these fins to provide them for divers who need them or appreciate what they do, out of love for the sport, not to make big $$$ from them.

 

[RJP]

And Force Fins probably sells over 100 Originals/Pros for every 1 of the high end, Tan Delta fins. Bob makes these fins to provide them for divers who need them or appreciate what they do, out of love for the sport, not to make big $$$ from them.

So you're saying that he only charges his cost for them... with no mark-up whatsoever?

Seems like a lot of trouble to go to... without the benefit of making big $$$. Why fault someone for doing so?

 

[TN Traveler]

Please explain what it means to "load up the fin" and "let the rebound finish the propulsion", giving due consideration to the well-understood physics behind the law of conservation of energy.

i fully understand the concept of "conservation of energy" - I have a PhD in Engineering.

Since the Tan Delta material has a high durometer reading, the fins are initially resistant to flexing. The idea is to kick hard enough to get the fin to flex - once the flex they return a greater % of the energy on the rebound (as they straighten out) than other materials. If you don't get the flex, they behave like a pair of stiff plastic. Unlike rubber or thermoplastic material normally used in fins, they absorb less of the energy put into them and return more as they straighten back out. It is a matter of returning more of the energy input because the material itself stores/returns a greater %.

Because of the initial stiffness, they frog kick and back kick pretty much like Jets but when you need speed/power, they require less effort and allow you to maintain that effort longer (covering greater distance).

 

[RJP]

i fully understand the concept of "conservation of energy" - I have a PhD in Engineering.

Since the Tan Delta material has a high durometer reading, the fins are initially resistant to flexing. The idea is to kick hard enough to get the fin to flex - once the flex they return a greater % of the energy on the rebound (as they straighten out) than other materials. If you don't get the flex, they behave like a pair of stiff plastic. Unlike rubber or thermoplastic material normally used in fins, they absorb less of the energy put into them and return more as they straighten back out. It is a matter of returning more of the energy input because the material itself stores/returns a greater %.

Why allow the energy to be used to flex the fin, instead of pushing water, in the first place? ie - the diver's energy could have been used to push water and thus propel themselves forward, but instead that energy was applied to flexing the fin... and not to forward propulsion. As you suggest, the fin returns a percentage of that energy "on the rebound" so obviously that's less energy than the diver put into the kick. Seems inefficient.

How is the fin "loaded" for the next stroke at the same time it is "rebounding" from the previous stroke? Or is the fin only effective every other stroke? Or only on half of each stroke?

Serious questions.

 

[TN Traveler]

If you have no flex to the fin it only produces forward thrust during a short portion of the kick. During the majority of the kick the water flow would not be going backward and moving you forward. If your proposition was correct then the most efficient fin would consist of a board, having no flex, strapped to the bottom of your foot. Fin flex (for any fin) is needed to direct the flow rearward during a greater percentage of the kick.

if flex and rebound are properly matched, the rebound occurs at a time where the rebound returns the energy while providing forward thrust. The problem with too much flexibility is that any rebound energy occurs after the kick has gone so far that it does not deliver forward thrust (the normal problem with splits.

Fins only provide thrust on the downstroke. By time you return the fin back to the starting point with the upstroke, the are back to the original condition and are ready to be "reloaded" and flexed.

This is not unique to Force Fins, all Bob has done is find ways to maximize the balance (with materials available and the fin shape) to make a better performing fin. One fin does not fit all.

 

[ams511]

Simple cost accounting tells a different story...

Fixed cost ÷ by unit volume = allocated fixed cost per unit.

Which would obviously be higher per unit on a lower-volume product.

If model A mold costs $5000 and they sell 500 units, allocated fixed costs = $10 per unit.
If model B mold costs $5000 and they sell 100 units, allocated fixed costs = $50 per unit.

Beyond that, a smart marketer should try to sell a "more exclusive" product for a higher margin anyway, irrespective of the magnitude of difference in actual production costs.

As usual your analysis and your language skills are faulty. Please pay attention to what I said, "The mold cost is the same to make one fin or a thousand". This is true unless there is some degradation of the mold before then. Which you do not mention.

As to your analysis. The mold is a sunk cost meaning it was already paid for and cannot be recovered, consequently your allocations have no cash flow effect for Bob. I am not sure when (if ever) you took a managerial accounting course but the contribution margin approach has been taught since at least the early 1980s. If Bob is able to sell the fins for more than his variable costs (production costs, packaging, shipping, etc.) then he will have cash to cover his fixed costs. The objective is to maximize the total contribution margin. This assumes the rest of his costs are fixed period costs that do not vary with the number of fins sold.

As far as developing an exclusive product that depends on the margins and volume. He would be better off selling 2 fins each with a $200 contribution margin than 1 fin with a $300 contribution margin. I am not sure of what the elasticity of demand is for scuba fins, but Force Fins start in price where most other fins end. I am sure Scubapro would sell a Tactical Jet Fin for $500 if they thought they could get it.

 

[RJP]

As usual your analysis and your language skills are faulty. Please pay attention to what I said, "The mold cost is the same to make one fin or a thousand". This is true unless there is some degradation of the mold before then. Which you do not mention.

As to your analysis. The mold is a sunk cost meaning it was already paid for and cannot be recovered, consequently your allocations have no cash flow effect for Bob. I am not sure when (if ever) you took a managerial accounting course but the contribution margin approach has been taught since at least the early 1980s. If Bob is able to sell the fins for more than his variable costs (production costs, packaging, shipping, etc.) then he will have cash to cover his fixed costs. The objective is to maximize the total contribution margin. This assumes the rest of his costs are fixed period costs that do not vary with the number of fins sold.

As far as developing an exclusive product that depends on the margins and volume. He would be better off selling 2 fins each with a $200 contribution margin than 1 fin with a $300 contribution margin. I am not sure of what the elasticity of demand is for scuba fins, but Force Fins start in price where most other fins end. I am sure Scubapro would sell a Tactical Jet Fin for $500 if they thought they could get it.

Eh... nevermind. (Feel free to add me to your "ignore" list if you like.)