Basic gear from mid-twentieth-century Italy: Other manufacturers

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Back to Tigullio Manta fins. They appeared in the 1967 company catalogue:
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The feature captions are in both Italian and English.

The unique Manta fin design was patented in Austria, West Germany and the USA. The full US patent for "a spoon-shaped swim fin" is posted below:
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And now for some auction pictures of Tigullio Mantas.

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Sufficient reading matter to digest before my next posting, which will likely be my first of 2022 and be devoted to the Tigullio Giada fin. A Happy New Year, stay safe and well in the coming days.
 
I'm grateful for the likes, Anhelo, Jale amd Sam.
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Today's Tigullio fin is the Giada. "Giada" is Italian for "Jade" (above), which is a mineral much used in some cultures as jewellery and for ornaments, mostly known for its green varieties, although it appears naturally in other colours as well, notably yellow and white.

Here is the Tigullio fin named after the gemstone in 1965:
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Italian:
Giada la nuova pinna della Tigullio

  • concettualmente rivoluzionaria
  • sfruttamento del principio di reazione
  • risparmio elevatissimo di energie
Le prime GIADA, appena uscite dallo stampo non ancora completato nei suoj aspetti estetici, sono state consegnate agli istruttori delle Scuole Federali della FIPS, senza alcuna lettera di accompagnamento o di istruzioni sulle sue caratteristiche "rivoluzionarie”, e di conseguenza senza alcun consiglio sul nuovo e diverso modo di usarle. Volevamo un loro responso più schietto possibile.

La prima reazione è stata di disorientamento e di perplessità. E questo è stato il nostro primo successo. I più competenti subacquei italiani, quali sono gli istruttori della FIPS, pur non avendo avuto il tempo di appurare quali sono i principi di funzionamento della GIADA, e di conseguenza quale è il modo migliore di adoperarla, avevano avvertito che c'era qualcosa di buono. Dopo quindici giorni di uso continuo delle GIADA la maggioranza di loro si è dichiarata entusiasta.

Le costole di irrigidimento delle GIADA, di particolare profilo idrodinamico, sono state poste completamente dalla parte “positiva” della pinna: irrigidiscono la pinna nella falcata positiva, e la rendono assolutamente flessibile nella falcata negativa. La posizione e la forma delle costole di irrigidimento sono il mezzo più efficace per ottenere i due scopi che ci eravamo prefissi:

1) Durante la falcata positiva sfruttare quasi interamente l'energia impiegata. Sotto sforzo, infatti, la “pala” assume una forma tale da costituire, insieme all'onda d'urto dell'acqua, uno tubo Venturi; l'acqua scorre parallelamente alla superficie de pinna provocando una spinta di locomozione a “reazione”. Per il conseguente effetto di trascinamento dell'acqua circostante evitato, così, ogni effetto di “turbine” o “risucchio” allo stac dell'acqua dalla estremità della pinna, nonostante e in virtù d l'estrema rigidità dell'insieme.

2) Durante la falcata negativa la pinna si flette per oltre terzo della sua lunghezza; e come è noto solo la parte flessa, questa falcata, è capace di provocare spinta di locomozione, parte che resta rigida, viceversa, assorbe in attriti e in spinta "negativa" la maggior parte della energia spesa nel pinneggiamento: nelle pinne tradizionali questa dispersione di energia assomma in media all’ottanta per cento dell'energia spesa; ne GIADA, data la forma rotondeggiante e sfuggente della parte superiore, questa parte della pinna non richiede alcuno sforzo pinneggiatore. Di qui, abituati come siamo alle pinne tradizionale, il senso di squilibrio che si prova indossando per la prima vo le GIADA (per apprezzarne le indiscutibili doti occorre usa continuativamente per una quindicina di giorni, abituandosi a una falcata più lenta e più ampia).

Le GIADA sono particolarmente indicate:
  • Nelle IMMERSIONI CON AUTORESPIRATORE (se ne possono avvertire le caratteristiche fin dalla prima immersione) e nelle sommozzate in apnea.
  • Nelle GARE DI NUOTO PINNATO di gran tondo, quando oltre al rendimento della pinna, assume un peso determinante il risparmio di energia.
  • Nel NUOTO VELOCE in superficie si potranno ottenere risultati vantaggiosi (come sono stati già ottenuti) soltanto dopo aver appreso la nuova tecnica di pinneggiamento e dopo avere allenato i muscoli nelle gambe alla diversa distribuzione degli sforzi, fisiologicamente più corretti.
Rough translation:
Giada, the new fin from Tigullio:
• revolutionary design
• exploits reaction principle
• very high energy savings


The first GIADAs, just out of the mould and not yet complete in its aesthetic aspects, were delivered to the instructors of the Federal Schools of the FIPS, without any cover letter or instructions on its "revolutionary" characteristics, and consequently without any advice on the new and different way of using them. "We wanted their response to be as frank as possible.

The first reaction was one of disorientation and perplexity. And this was our first success. The most competent Italian divers, who are the FIPS instructors, despite not having had the time to ascertain what the operating principles of the GIADA are, and consequently what is the best way to use it, had warned that there was something good . After fifteen days of continuous use of GIADA, the majority of them declared themselves enthusiastic.

The stiffening ribs of the GIADA, with a particular hydrodynamic profile, have been placed completely on the "positive" part of the fin: they stiffen the fin in the positive stride, and make it absolutely flexible in the negative stride. The position and shape of the reinforcement ribs are the most effective means of achieving the two goals we had set ourselves:

1) During the positive stride, use the energy used almost entirely. Under stress, in fact, the "shovel" assumes a shape such as to constitute, together with the shock wave of the water, a Venturi tube; the water flows parallel to the surface of the fin, causing a thrust of "reaction" locomotion. Due to the consequent effect of entrainment of the surrounding water, any effect of "whirling" or "sucking" at the ? of the water from the extremity of the fin is avoided, despite and by virtue of the extreme rigidity of the whole.

2) During the negative stride the fin flexes for more than third of its length; and as is known only the flexed part, this stride, is capable of causing locomotion thrust, the part that remains rigid, vice versa, absorbs most of the energy expended in finning in friction and "negative" thrust: in traditional fins this dispersion of energy amounts to an average of eighty percent of the energy spent; ne GIADA, given the rounded and receding shape of the upper part, this part of the fin does not require any finning effort. Hence, accustomed as we are to traditional fins, the sense of imbalance that one feels when wearing the GIADA for the first time (to appreciate its indisputable qualities it is necessary to use it continuously for a fortnight, getting used to a slower and wider stride).

GIADA are particularly suitable:
• In SCUBA DIVING (you can feel its characteristics from the first dive) and in free diving.
• In FIN SWIMMING COMPETITIONS, when in addition to the performance of the fin, energy saving takes on a decisive role.
• In RAPID SWIMMING on the surface it will be possible to obtain advantageous results (as they have already been obtained) only after having learned the new technique of finning and after having trained the muscles in the legs to the different distribution of efforts, which are physiologically more correct.
 
As a bonus, here is the Ondina: one final Tigullio fin resembling the Manta and Giada models. "Ondina" is Italian for "Undine", a category of elemental beings associated with water. Like "Giada" (Jade), "Ondina" can also be a girl's name.

Just a few auction images again:
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Enough for today and for Tigullio. Next time, midweek, we shall review another Italian diving equipment manufacturer, GSD. Until then, keep safe and stay well.
 
I did not know about the "revolutionary" Giada fins, and from the pictures I cannot figure out how the propulsion mechanism is different from other short and angled fins, which were quite common at the time.
The description suggests a strongly asymmetrical behaviour between the "positive" and "negative" stroke.
I did not understand which motion is the "positive" one: downward or upward?
Please note that I am a finned swimming instructor, and we were used to teach our students that both movements are equally propulsive and efficient, if done properly.
Did you understand which is the movement considered "positive" when using the Giada fins?
 
In front crawl the upstroke aka upbeat aka recovery does not generate propulsion. I would assume that what "negative" means, but who knows...
 
The asymmetry in the positive and negative strokes sounds like one of the principles behind Force Fins.

You can generate far more force moving the leg forward than backwards (think of kicking a ball forward or backwards) so conceptually it makes sense to try to harness this.
 
The asymmetry in the positive and negative strokes sounds like one of the principles behind Force Fins.

You can generate far more force moving the leg forward than backwards (think of kicking a ball forward or backwards) so conceptually it makes sense to try to harness this.
But several years later, Cressi released a Rondine fin equipped with a moving vane. This did open during the down kick, leaving the water flowing through, and did close during the upward kick, providing a much larger active surface.
The explanation provided was that the downward kick was ineffective, whilst the upward one was more effective.
Here the link to a previous post of @David Wilson describing these Rondine S (or Super Rondine) fins:
Please note that in these figures the forward (downward) kick is called "negative" and the backward (upward) kick is called "positive".
So the opposite of what you said...
Personally I think that employing modern carbon-fiber fins, of proper length, proper stiffness and proper angle, employed by a well trained swimmed-finning or underwater-speed athlete, there is no "negative" action.
The fin is driven into a sinusoidal motion, with a rate matching the natural frequency of the blade, which is maintained "in resonance".
In these optimal conditions a large part of the work done by the muscles (both forward and backwards) translates efficiently in a thrust perfectly aligned with the main axis of the body.
My opinion is that all those early fin designs, including the Giada, were attempts to counter-effect inefficient kicking styles employed by beginners or untrained finned swimmers.
Rondine S and Jetfins were explicitly developed for divers employing the big twin tanks of the time, which, in absence of BCD and proper buoyancy and trim control, forced most of them in a trim with the head much higher of the fins, for counterfeiting the strong negative buoyancy at depth. Hence an asymmetric fin efficiency provides a thrust with a significant component towards the surface, which allows to swim almost horizontally without "falling down".
 

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