The LAB is a space where we explore ideas in construction, engineering and design technology.
• It's a space where we publish articles and ideas to deliver a better experience for those who build and sail on our boats.
• In the Partners Network we introduce people and companies contributing components, services and technologies to the boats we design.
• And please excuse me if we throw in a few random thoughts here and there.
Welcome to the LAB
LATEST ON THE LAB
Time has Come is the latest article on the pages of the LAB
It's a story in two parts about a new racing trimaran on the Australian circuit, Put together by Tony Grainger with assistance from Time Machine's owner Matt von Bibra, it refers to Time Machine's design heritage, its history, and provides some interesting details about the design.
One of the clear advantages of trimarans is that they are generally more suitable to outboard motor power than cats. Compared to inboard motors outboards are lighter and cheaper and it's easy to get the prop clear of the water when you're sailing.
On the downside they don't provide very good steering control in tight spaces, especially in reverse. Some trimaran owners get around this by creating a link between the outboard and the rudder.
That works fine if the rudder is beside the outboard on the main hull.
For trimarans with the rudders on the floats it's a bit more complicated, and more so if the design calls for the motor be able to be deployed and retracted without leaving the cockpit.
For the R42 we experimented with some geometry to see if we could effectively link the outboard and rudders using cables without inhibiting the tilt action for the outboard. The cables go slack when the outboard is raised, but can be pulled in close to the beam using bungee chords.
What goes into a set of plans? Only a small fraction of the information that gets developed in the design office gets delivered to the builder, but that information on its own is quite extensive.
Every design office has their own procedures for designing and formatting the plans. You can read about the way we do it here:
There’s a fairly strong consensus among professional sailors that C foils in trimaran floats are an advantage for trans ocean racing, especially if those races include a lot of reaching in fresh conditions. Maybe not so much as a speed boost, but to help maintain stability and keep the bow from burying in steep seas.
For smaller boats that are mostly racing inshore or doing relatively short offshore passages - say 24 hours or less - the advantages of C foils are not quite so clear cut. The fact is that a trimaran float with a beam to length ration of around 1/16 or so is fairly slick piece of equipment and if you’re going to add some devices to it you need to be sure they’re making a positive contribution in a given set of conditions.
The C foils will contribute to your drag when they’re not operating in a speed range where they can contribute significant lift. They will add cost to your project. If they are going to be efficient and reliable they need to well engineered, have the right profile, and be carefully built to meet the required specifications.
There are five boats that have been actively racing under OMR with C Foils in recent years; Bare Essentials, Carbon Credit, Crosshair, Wilparina and Sweet Charriot.
Wilparina actually has straight boards at a 45˚ angle - so they are not strictly “C” foils but they are designed to serve the same function. Wilparina’s original owner Rob Remilton says;
“we found them great for ocean sailing as they kept the boat going with an easier motion, and reduced nose diving.”
None of these boats has demonstrated convincingly and consistently that they are race winning material under OMR.
Given that lifting devices are not penalised under the OMR you would expect these boats to be taking advantage of this and piling up a nice little trophy collection.
Of course this is not clear cut evidence that C Foils don’t work. Overall performance is a complex mix of factors and there could be other forces at play. However we can say with confidence that the C Foils are not a guaranteed free lunch to racing success for smaller trimarans mostly racing inshore.
Bare Essentials has been a very strong performer on the Australian racing circuit over an extended period of time. How much the lifting foils have contributed to her successes is not clear but until now she has not claimed a significant title like the Australian Multihull Championships in spite of her foils not being rated under OMR.
I have to say though she is a very fast boat and seems to fly the main hull more easily that the other boats mentioned here. Is it the foils, the floats, or a combination of the two?
Seacart 26 Sweet Charriot with C foils. Owner Henry Kaye previously owned a Seacart 30 which he raced very successfully without C foils. After Sweet Charriot he has now moved back to a Seacart 30, once again without C foils.
Wilparina, a strong performer and by all accounts the angled boards were a significant advantage downwind in offshore conditions. Previous owner Robert Remilton now owns a Diam 24
So to answer the question that is popping up in my inbox on a regular basis these days; “Should I have C foils?” I answer it this way; Put it in the right place in your list of priorities. Here is my personal list of priories:
1. A stiff but light platform. The engineering needs to be thorough. You have to have the right materials and the right build process. You can change the rig and sails anytime. Not so easy the platform.
2. Rig and Sails. Think of them as one. Each comes from people with very different skills and working methods - but the bottom line is they are working to the same goal - to provide you with a reliable and easily controlled driving force that is efficient through a wide range of conditions. Be clear on the philosophy behind the rig and sails. Design is critical and good communication between all parties involved is important. Yes, the designer will give you a rig and sail plan - but that’s just the starting point. Get your sail maker and your preferred rigging company on board as early as possible in the project.
3. Look at other details that you can deploy to further boost your performance. In this category I put rotating wing mast (this might surprise you - more on this in a later article), C foils (or angled boards), and canting mast. For this kind of equipment you have to consider the cost, additional weight, additional engineering and build time, and the increased number of on board controls you have to contend with when you might prefer to be attending to navigation, sail shape or looking for shifts in the breeze.
Having more of this kind of equipment requires more skills and more attention to how your boat is set up and trimmed. Franck Cammas makes all this stuff work wonders. Not everyone can pull strings the way Franck Cammas pulls strings, and not everyone wants to.
Clearly the decision to fit or not fit C foils is a personal one and it needs to be considered in the context of your level of skill and how you like to sail. If you’re considering C foils then seek out evidence that they will be of benefit to the type of sailing you want to do and consider whether you have adequately covered points one and two above as a first priority.
My next boat will be a small trimaran - 30’ or less. It’s in the melting pot now. Will it have C foils? Probably not, at least not initially. But it will be engineered to be able to fit C foils or full flight foils at any time. Not because I want to be in contention for the trophies, but because I’m interested in the dynamics of the foils and want to know more about their advantages and disadvantages.
And if we can develop a practical and affordable system for full flight foiling in the type of boats I design I want to be there. It looks likes a load of fun.
Apart from that my own personal philosophy would be to keep it simple. Leave out anything that will create complication and distract me from enjoying the sailing. Your own philosophy may be quite different to mine.
I welcome your input and what I’ve discussed here and would be happy to publish your comments regardless whether they are in agreement with my own views. Email me with your thoughts; firstname.lastname@example.org
A rolled edge on the your cockpit roof allows the rainwater and the condensation to roll around the corner and drop onto your cockpit seat cushions or down the back of your neck. . It’s fairly common knowledge that a channel or a lip with a sharp edge will send the drips packing in line with the forces of gravity. But how big to make the channel and where to put it exactly?
Daniel Perlman, a biophysicist at Brandeis University apparently spent three years studying the way wine pours from the neck of the bottle to create a solution that would eliminate the drips when pouring a glass of wine. The solution he came up with is a one millimetre wide incision, one millimetre deep just below the lip of the bottle.
Was this rocket science? Is it the optimal solution and did it really take three years and a lot of slow motion video footage to figure it out? Maybe this study was simply an excuse to uncork a few tasty bottles in the research lab. We are yet to see the publication of any detailed technical papers related to this “discovery”. However it’s a good reminder to attend to the issue in your next build project if you have a hard cover over the cockpit.
The cockpit roof solution is fairly simple to implement in the build stage. While you have your roof or cabin top upside down on the workshop floor route a groove on the underside about 20mm wide x 20mm deep and fill it with thickened epoxy. Make sure you’re not cutting through any edge reinforcement required to provide stiffness to the cabin top. When the epoxy has cured cut a new groove in your epoxy channel.
How wide and how deep? Depends how technical you want to get. Water and wine share different viscosity values and the hydrophilic properties of glass are different to the hydrophilic properties of painted fibreglass or gel coat. (Hydrophilic properties determine how the liquid beads up or spreads out on the surface).
In lieu of any technical data on the topic from Mr Perlman let’s make the groove abut 10mm deep and 6mm to 10mm wide. The depth is more important than the width and the outboard edge should remain sharp to discourage the drips from going around the corner.
Want better data? Do your own testing. Use water and have a glass of wine later.
In 1990 we introduced a new float shape for our trimarans we called the V90. It was deployed on the TR series and later as the shape evolved adopted on other trimarans including Trilogy and the Essential Eight.
In 2017 we introduce a new float shape design to improve performance and possibly make for a drier ride when pushing hard in a choppy sea. Read the full article here:
For the first time in OMR racing a fully foiling cat mixed with the action at Airlie Beach Race Week and Hamilton Island race Week 2016. So how did the GC32 perform against the other boats competing and what are the implications, if any, for the OMR?
The lines the 8.5m Livewire sports cat raised a question about the kink in the rocker line. In this article I've addressed the top of rocker profile, hull fineness ratio, and importance of asymmetry in the water planes for pitch damping. See the article here
Mad Max has been dominating the inshore race results in Australia for quite some time now and is the current title holder (2015) of the Australian Multihull Championships having won the series on OMR and taking line honours in every race.
So what makes Max Fast?
We all know about the bar talk and some of the wild claims that are made about boat performance. We've put together some information about the factors that determine the performance of multihull yachts and some of the ways that performance can be measured and predicted.
And we propose a more credible method for yacht manufacturers to promote the performance potential of their products.
In the 2015 Fastnet Race high performance multihulls dominated the elapsed time results but multihulls were poorly represented in the under 60' LOA size range. Where were the multihulls in the mid size range? We take a look and make some suggestions.
Building hours can vary considerably from one yard to another, but also from one boat to another in the same yard, even when the designs are very similar.
Building hours are difficult to nail down but we provide some pointers in this article.
When composite components come unstuck the type of epoxy that was used sometimes gets held up as the bad guy. It may not always be the case. In fact in many cases its far more likely that the issue of secondary bonding is at the core of the problem.
The combined Newsletter for Grainger Designs and Rocket Factory Trimarans
Our DuFLEX kit systems streamline the construction process for amateurs and professional yards alike. More details here…