Diecipiedi (Ten footer) Class has been created by B.C.A. - Demco Kit in 1991 with the aim of giving to amateur designers and boat builders the opportunity to taste their skills in designing and building a small boat on the basis of Class rules which encourage creativity and experimentation.
The rules are extremely simple. Boats must have a maximum hull length and beam of 10’ (3.048 m) and a maximum sailing area of 8 m². The length limit is connected to the size of the plywood sheets available in Italy, which is 3.1 m. A Diecipiedi may be build with just one sheet of plywood, without the need to scarf different pieces, which makes construction very simple, quick and cheap. This is one of the reasons why the class quickly became the favorite of amateur boat builders. In any case the Diecipiedi do not have to be built compulsorily in plywood and actually in the history of Diecipiedi there has been a high variety of materials, such as aluminum, fiberglass, hi tech composites, wood. There has been also a boat completely built in Plexiglas, which allowed an excellent view to his crew over and under the water. The problem was that the boat, being transparent, risked to be hit in crowded starts by other competitors and after a short period it disappeared from the Class activity.
Apart from building materials also in other features boats are quite different. There have been in the Diecipiedi history monohulls, trimarans and catamarans, the first type prevailing at the beginning and the second now. Catamarans never got brilliant results and it is now clear that they are not the right choice for winning. The same fantasy has been shown by the competitors and designers in sailing rigs: marconi sloop or cat, sprit sail, lateen and even Polynesian rigs are some of the favorite choices. With the possibility of experimenting even the strangest solutions at a very low cost the Class is an extraordinary practical school of boat design, and new solutions may be immediately compared in races against other builders and designers. The first race, held in 1991 in Cernobbio, on the lake of Como, with the participation of 6 boats, has been won by a Granny Pram, a very nice and elegant but not particularly fast Ten footer designed by Iain Oughtred. The following year the number of competitors had doubled and it doubled again one year later. Cernobbio race was then the only Class meeting but later the class became more organized and now there is a racing season, starting in April and lasting until the end of September, with 8 or more meetings where an average of 15 boats participate regularly. They are mainly on the northern Italy lakes but sometimes also on the sea. There is a Class Secretary and a website www.diecipiedi.it where you may find all detailed information and a rich gallery on the activity of the Class. Meanwhile the performances of the boats have considerably improved and a Granny Pram today would not have any chance to be in the leading group. This does not mean that the Diecipiedi have become “monsters” such as the Moths flying on their foils controlled by young and acrobatic helmsmen. Diecipiedi’s crew are generally middle-aged gentlemen who try to avoid difficult conditions, who hate to be cold and wet and usually appreciate the joys of living, which also means eating and drinking in good company. The atmosphere is generally very friendly and relaxed, even in the climax of the competition and everybody agrees that the victory is less important than the amusement of sailing together and competing fairly and kindly. Protests and racing tricks are, until now, practically unknown. Every year there are new boats participating and it is a stimulating exercise to keep up with the improvement of performances. The fastest boats are in this moment trimarans, and particularly fast are the trimarans with amas high on the water which can be sailed in most conditions navigating on the centre hull, which allows to reduce the wetted area and the resistance. With light winds monohulls can still fight for victory. In the following pages you may find some more technical considerations on the Diecipiedi boats.
The idea of creating the Class came more than twenty years ago from an article in the magazine “Wooden Boat” on a similar Class active in the United States. We have been encouraged to create the Class from a sentence of this article stating that in the pictures of the Class races the participants showed almost always a satisfied smile on their face. We think the same can be told of the Italian Diecipiedi. We do not know if the Class is always active in the States or if there is something similar in other countries but we hope that our example shall be followed and that other class organisations shall develop also outside Italy. We also hope that one day it could be possible to organize a World Championship, meeting other Diecipiedi coming from different countries. It would be a real success, provided that the Class does not lose its initial spirit, which is based on friendship and amusement: it has always to be considered a joke, even if made seriously, or, if you prefer, a serious activity, but made as a joke.
The Class has started in 2013 its 22nd year of activity with a rich program of races and events. Luigi Chirico, brilliant winner of the championship in 2012, has been confirmed as Secretary of the Class.
The site of the class www.diecipiedi.it is constantly updated and full of photographs, information and comments, and you may refer to it for any information on the Class, the calendar, and for having a look to the gallery.
We just mention here an initiative that we launched a few years ago and that every year we propose again, even if until now it a has not raised so much interest between our friends of the Diecipiedi Class. It is the speed record for Diecipiedi boats. You may find the very simple rules of this speed record on the site of the Class.
The official record still belongs to Fulvio Cocchi that has established some years ago by recording 9.6 knots. I believe that this speed may be considerably improved and probably some boats have already exceeded this speed but without registering it.
You can find hereafter two articles, now quite dated, but still valid, which relate to the construction and design of a Diecipiedi. Nothing particularly technical or abstruse but only a few words that can be of use to those who intend to design, build or buy a Diecipiedi.
by Paolo Lodigiani
The recently concluded 2006 sailing season has been generous in satisfactions, as I won 6 of the 8 races I competed in, got 2 second places, and naturally triumphed in the class championship. Were I not innately modest, I would be getting above myself and thinking of me as a champion! But first of all, I shouldn’t be saying “I won”, instead, as Valentino Rossi always says referring to his team, “we won”. Being my own team, I could easily speak in the singular; in my case, though, “us” is my boat and I. Secondly, my pride is forcedly crushed by the recognition that my control over the championship has been far from undisputed: never as this season, races had been so uncertain up to the last track, with marginal gaps and many competitors for the final victory. Boats too were leveled out upwards, and many of them now contend on equal terms. This is why I think it is time, on my 15 years-long experience as a ten-footer racer, to try and answer to the question: which is the fastest Ten footer? The qualities of a boat cannot be estimated in absolute terms, only relatively to its use and crew. In this respect the Ten footer Class differs from other sailing classes for two relevant peculiarities. Firstly, competitiveness is tempered by a general tendency to relax: helmsmen, by age or nature, are not inclined to strain, discomfort, let alone acrobatics. The second peculiar feature, partly related to the first one, is that when it’s cold, or too windy, or, even worse, there’s a chance to get wet, racers easily agree to replace the regatta with activities more suitable to the weather… usually a lunch in good company around the table of a restaurant. It means that races can take place in very variable wind conditions, largely between 0 and 10 knots. It is sometimes inevitable that they may suddenly get worse, and one obviously has to cope with the changed situation. All this makes it for a fascinating design topic. It is relatively easy to design, for instance, a winning Moth (Moths are 11 foot-long boats, with a 8 m² sail area, and open rating rules and limitations, fundamentally not too different from a Ten footer): build a ridiculously narrow hull, fit it with two sophisticated supporting winglets, entrust a fit, entrained, young champion with it, one able to lift the hull and keep a precarious balance on the winglets, and you’ll see that, driven by the usually constant wind, your boat will glide over the water, flying towards victory. And if it doesn’t win, it will be because another, nearly identical boat, differing only in marginal details, undetectable to the human eye, has beaten it. In the Ten footer Class, the designer’s job is a much harder one: many factors need to be taken into account, and drastic decisions need to be taken. This makes it difficult to say which kind of craft can be the fastest. Some observations can still be made, though: it is possible to say which boats are slower, which ones can’t run for victory. In this reversed classification I believe the catamaran would be first. It seems established that a catamaran has only a suitable condition, strong wind, for competing with trimarans and monohulls, and even then it can’t be certain of winning. It would be if it could sail on one hull, but as far as my memory goes, this has hardly ever happened. On a light wind condition, its large wet surface irremediably handicaps the catamaran. Between trimarans and monohulls the struggle is more open: as a general rule, monohulls are predominant in light wind, while trimarans in strong wind, hardly a surprise for anyone with a knowledge of hull resistance. As it is not surprising that in very strong wind, when the monohull starts skimming, it becomes competitive again, and, if well-sailed, can overtake the trimaran. Monohulls need to be narrow to be fast: the problem is how narrow can one make it without losing its stability. Certainly a monohull as narrow as a Moth (30 cm at the waterline) would be incredibly fast, but in a ten foot racer’s hands, it wouldn’t be likely to reach the starting line. Therefore, the designer’s problem is how narrow can a ten-footer be to be sailed by a ten foot racer. Nero Cirla’s Piccolo is a good example of a not too narrow, but well-performing (regardless of the Nero’s abilities) monohull, largely thanks to an excellent finishing and efficient equipment as well as to its reliability that makes it easy to master in any circumstance. Prina’s Emc3 is another interesting example: flat-bottomed, rectangular section, narrow, though not extremely narrow, it proved itself faster than its looks suggested. Conversely the Scheggia fell short of the theoretical expectations: the designer’s aim (of which I can confidently speak, as I was him) was to build a craft narrow at the waterline, with reamed flanks above the waterline so as to ensure both performance and stability. Unfortunately keeping a boat straight is not always an easy task, and my Scheggia, though capable of good spurts, doesn’t allow the necessary continuity to win regattas. Next year, two new ten foot monohulls, narrower than any other built in the past, fitted with terraces, should appear on the regattas fields. Unless they capsize, they will be rough customers for trimarans. It is easier to design a good trimaran, although theory doesn’t always combine with practice. One would think that a round hull should work better, and that an chine hull, similar to the round one, such as Guido Ratti’s Tripessit would be the ideal solution, only slightly inferior to the round hull. Whereas the trimarans Farò and Paci, with square section hulls, built by Marco Casavecchia seem to be faster. I had epic struggles with both of them, and more than once it was them who got the victory. I doubt though one would trace the causes to the shape of the hull: suffice it to say that Ratti “drives” his boat sitting in the middle of it on a comfortable cushioned chair, with a truck-like steering-wheel and an electric pump brought into action as soon as some water enters the boat (what next, Guido? A car radio?). Winning is not really the point here. Apart from this, Casavecchia’s trimarans have hulls slightly higher on the surface, giving them an unquestionable advantage, as only two hulls are normally in contact with water. As for myself, I have chosen what I think to be the best solution (I wouldn’t have chosen it otherwise), a compromise: the monotrimaran, a craft made for navigating on a single hull, though often needing two floats for avoiding capsizing. My Gerovital proved to be very versatile, as, even with a very light wind, it can be kept on the central hull with amas touching the water all but rarely. It can still be improved, and I did improve it designing Fulvio Cocchi’s Slim: much narrower, thus more difficult to sail on a single hull. It is slightly less fast than the Gerovital on a very light wind condition, but has a considerably faster pace on stronger wind, and a better hydrodynamics in the lateral hulls prevent it from slowing down too much when they enter in contact with water. Personally, I am convinced that it is the craft most likely to win in the class, as much as I am convinced that it can still be remarkably improved, getting rid of some small practical shortcoming and mostly continuing the search for a perfect compromise between the smallest possible resistance (obtainable mainly reducing the beam at waterline) and the maximum stability (increasing the beam). I believe there is still much more to say about this topic, and the forthcoming winter will give us the chance to study and discuss solutions, waiting for the tests that will substantiate or disprove them. I have only dealt with hulls, leaving sails aside, fearing this disquisition would lengthen too much. The topic is too wide to be dealt with rapidly: I shall leave it for another occasion.
by Paolo Lodigiani
Last year, B.C.A. - Demco Kit launched the trophy “World Speed Record for Ten footers” (the rules of participation are published on this page). Unfortunately, only few ten foot racers undertook the challenge and maybe the rules need to be changed and simplified to foster a wider involvement. The ruling champion is Fulvio Cocchi who reached 9,6 knots on his Slim, on a beautiful windy day at Cernobbio, almost ideal, save for a small detail: the GPS supplied by the organisation defaulted at the crucial point, thwarting some brilliant-looking runs. I believe that this record can be beaten easily (maybe just by remembering to put batteries in the GPS). Let us not forget that a Ten footer has its critical speed at 4,15 knots, thus the recorded speed is 2.3 times the critical speed. Considering that it starts planning on average at 1.8 times the critical speed and can reach up to 3 times as much, we are still well within limits that can be broken. The problem is that a boat can’t plan without the features that allow it to do it, and needs enough power to thrust the necessary propulsion. The planing ability, given by the displacement (in kg) divided by the product between the flotation plane (in m²) and the hull length at the waterline (in m) (see page 132 of “Introduzione al capire e progettare le barche” by Paolo Lodigiani), shows that Ten footers won’t easily plan, as for an 80 kg crew index values range between 20 and 35 according to the type of boat, whereas the ideal value should be less than 15. It is indeed a crude index, as almost all indexes are, and a more accurate study would require appropriate formulas. I don’t want to specify all the passages here (it would be long and tedious and would force me to a complex explanation of the Savitski formula and other amenities), and I shall jump to the conclusion: for a full planing, meaning a hull almost totally sustained by the hydrodynamic upthrust on its bottom, a boat like the Gerovital needs to reach a speed of 11 knots (about 2.6 times its critical speed); the resistance at this speed would be slightly less than 160 N (about 16 kg). To obtain a corresponding driving force from sails, in ideal conditions (sailing at 110° from the real wind, flat boat, efficient sail), a 25-30 knots real wind would be needed. Naturally these calculations are based on unverified hypothesis. In many respects, these estimates are easier for a Ten footer hydrofoil: the boat conducts itself more or less like an airplane, and it is common knowledge that the aerodynamic calculation of airplanes are far simpler than the aero-hydrodynamic of boats. In an hydrofoil that navigates at high speed sustained by its foils, most of its hydrodynamic resistance is made up by the component of resistance of the force acting on the foils, the same force the lift coefficient of which sustains the hull. This force is proportional to the foils area, while their efficiency (the ratio between lift and resistance) is related to their shape, their aspect ratio, to the angle of incidence and the relative velocity of the fluid. At 11 knots, efficiency would be very high and resistance possibly lesser, though not much, than the resistance of the planing boat: thus, with an equal driving force, the boat would accelerate, reaching a higher speed. The problem is the take-off: in order to lift off, a boat fitted with foils must exceed a higher resistance wall than the one a planing boat encounters to exceed its critical speed. For the Gerovital, this barrier would range between 5 and 6 knots, and could be in the vicinity of 170/200 N (17/20 Kg), requiring a wind speed superior to 30 knots. Here are, in brief, the conclusions of this disquisition that, although rather complicated, is far more elementary than the calculations it required, and also tremendously oversimplified against reality:
- It is possible to reach and exceed 11 knots, though not an easy job with planing hulls, let alone hydrofoils. Probably, a very narrow multihull is still the best, or easiest, mean to break the speed record.
- Hydrofoils offer a more difficult solution compared to planning hulls, but once problems are overcome they may be potentially faster.
- In any case, an aspiring recordman must sail with strong winds: guaranteed baths (for him/her) and guaranteed fun (for observers).
- A Moth on foils reached the astonishing speed of 24.6 knots. It is clear that with the same sail area a Ten footer could also in theory reach it, but I think we’re on different planets.
- There’s plenty of food for winter thoughts and discussions of very technical contents: mine are but hypothesis and preliminary rough calculations; I’m putting forward the talk challenge, waiting for the real ones to come.