top of page

Working up the Alioth. Boat 2

First of all thank you to all those who have bought a coffee to support the web site for the long term future.  This is not a commercial site and I make no profit from it but I do need support to ensure its longevity.  People tell me that it is a great source of information and the only site of its kind, so if you do enjoy it and get value from it why not pop over to Buymeacoffee.  It takes any currency.  If you do thank you.  If 10% of the 5000 plus visitors bought 1 coffee, I could do so much more with the site


This is a story about going backwards to go forwards.  Move from a well set up boat to one that had to be developed and optimised.  I am not a designer so some of the steps could be seen as labourious but every stage was tested and each change offered improvement.  Spoiler alert, the story is still ongoing.


None of this would have been possible without the help of Paul Barton.  He is probably one of the most experienced 3d printers of the Alioth in the UK and is a brilliant ideas man.  Of course we would not be doing this had it not been for the creative thinking of Juan Egea.  Not only has he come up with a great design but opened the door for home building once again and allowed IOM’s to become freely available to new owners (for a reasonable licence fee of course).




At the MYA AGM last year, I had a chance to buy an Alioth.  It was a completely standard boat, sprayed with clearcoat but un sanded, with an old Alioth fin and bulb.  I thought what better way to rest the Britpop than to buy the Alioth and sail it over the winter with the Britpop rigs.  When I started to sail it, I was hooked on the design but my boat setup had some issues.  I sailed a bit with Craig Richards but he was months ahead of me and truth be told a better sailor.  My boat needed to sail with the rigs at zero degrees rake for balance which meant the booms pointed upward and it all looked rather ugly.  Having the boom band 150mm from the step meant the boom was too high.  I also had a poor A rig with prebend that occurred mostly around the 600mm mark, more of a kink than a bend which was created with rollers.  The end result was a poor performing boat.


The first thing to do was to rake the fin aft 2 degrees so I could put some rake on the mast.  Unfortunately this moves the bulb back over a centimetre so the transom dropped in the water.  Then I lowered the boom band to just off the foredeck above the mast ram.  I had to the rakethe fin a degree forward to get the fore and aft balance better and that resulted in weather helm which to be frank was slow.  With the Britpop it was easy to power off upwind and drive hard.  With my set up I had the opposite and every time I took my eye off the boat it slowed.  Craig had moved his fin aft so he could rake the rigs and achieved a balanced boat and was quick from the start with his V3.  Eventually after struggling at the the ranking event at Eastbourne, I bit the bullet and moved the fin leading edge rake to a full 2.5 degrees (the aft edge was dead perpendicular to the waterline and then I moved the bulb forward 1.5cm to achieve balance and keep the stern just out of the water.  I was then able to test the following week and had a balanced boat with the bow and stern just out of the water. To measure things accurately (see the instruction at the bottom of the article),  all you need is paper, pen and a right angled set square.  Once you have the dimensions, it is easy to replicate on a new boat.


The boat came with under deck sheeting which gave me some issues, tangles and restricted range of movement which took a while to sort.  Since trying it out I would prefer on deck sheeting in another boat as you can see any wear on the sheet and quickly repair any fraying cord.  Having sorted all of this I ended up with a boat on weight but a bulb 25gm lighter than my Britpop.  So after 6 months I got the boat set up that I wanted it.  Remember I am not a designer and have to work by trial and error.  I also get nervous about moving things around although my confidence is building on this as my knowledge builds.  In a way it is good to fiddle as you learn on the journey whereas sailing a setup boat with instruction is quick but ones learning is limited.


So what to do next.  We heard a rumour that Juan was going to release a file for a 2 piece boat which would make it lighter and stronger.  After some gentle persuasion we got the file and printed the boat which I could put together just before the nationals.  I wanted a Craig Smith fin which is the lightest available and a Robot bulb.  I could not fit a Smith fin to the current boat as I had glued the fin insert for the Alioth fin into the fin box but it would fit nicely in the new boat with a customised insert and this would allow us to vary the rake from zero to 2 degrees.  The only thing we lacked was time.  Putting an untested boat on the water 3 days before the Nationals was fraught with risk and so it proved.


Other things we did to the new boat were to fit on deck sheeting, put the pulley in the centre at the back of the boat to minimise drag in the water, move the shroud base in a few mm as the eyes had the potential to damage other boats when healed over and it would not hurt to bring the shroud base in a bit.  As a consequence I shortened the spreaders on the A and B rig and modified the jib tack fitting on the boom so I can get the jibs booms as close to the deck as possible.  Then it was a case of going over the boat and minimising windage as far as possible.  There was a structural change.  After Juan had cracked his boat near the shroud area having been hit by a Venti without a bow bumper at an event earlier this year, Paul changed the aluminium posts that provided triangulation strength at the mast and shroud area replacing them with wires so that if there was impact in this area, the boat could flex and not split although the Polymax is extremely robust.  I have hit a piece hard with a hammer and seen no damage or even a mark for that matter.


It was a race against time especially as we had a couple of issues with the gluing.  While Paul was sorting the boat I went through my rigs and did everything I could to and make sure the setup was good.  New Cunningham design, lower the bottle screws, get the booms as parallel to the deck as possible.  One mistake I made was to try 80lb fishing line to attach the jib luff to the mast.  Unfortunately, the bowsie kept slipping the day before the Nationals so I went back to my trusty thicker cord.  I had put the same on the backstay and had to replace that as well.


One of the challenges I had was running the sheeting system under the deck using PTFE tube bent through 180 degrees.  The winch could not handle the friction but then it was suggested I apply silicon grease to the cord and that solved the problem.


So I picked up the boat on the Saturday before the Nationals, with the biggest job, fitting the fin and bulb in the afternoon but I had my map/diagram laid out on the floor with the optimal positions from the previous boat so I could position the fin and bulb accurately knowing the boat would be balanced and with the fore and aft weight distribution correct.  What I did not realise at the time was that the bulb cant to the waterline was at 2 degrees when hand fitted but when I secured it with the nut the bulb cant increases to nearly 4 degrees.  I only realised this after the nationals.  One little check would have shown me the issue with the bulb.  One thing I was able to do was accurately measure the bottom of the bulb in relation to the waterline and calculated I would have a 2 mm gap in the tank.  The on-deck sheeting was a pleasure to set up and worked well although the way I had set the winch up meant that you had to move the stick a long way to ease the sheet making precise adjustment upwind difficult.  Also the mix for a high mode was not working properly.  I did not have time to fix that. I did drop the shroud bottle screws to the deck to get them out of the slot and that meant fitting longer shrouds

Also checked the mast was a firm fit where it entered hull at the deck and happy to say it is rock solid.


One final tweak was to the transmitter rudder control.  I have a habit of over steering just after the start so I have introduced 20% of exponential to the steering.


I had a quick test sail on Monday to check the sailing balance and that the boat sat in the water correctly.  The transom was just out of the water and the bow 25mm out.  I had 200gm of correctors to play with which I would position when the boat was measured. 


The boat was measured in Gosport on the Tuesday.   It  was exactly 1m long and the bulb 2mm above the limit and the rudder just inside the perpendicular from the transom.  I had got something right. We had time to precisely locate the corrector weights.


Wednesday was spent practice sailing at Frensham and then Thursday I raced at Gosport.  That is when I got concerned about speed.  The boat was just not powering off the start line. Yes it was shifty but I was getting rolled by boats around me.  Not much I could do but live with it and take it to the Nationals.


On the Friday at Poole there was a decent breeze and this is where I learnt that 8mm was not enough prebend in the mast.  The jib luff sagged, the leach opened too much and the result was a boat slightly off the pace.  I could have increased the prebend for the weekend but if I snapped the mast I would be off home.  Thankfully the forecast was for light winds.

The first day of the nationals was difficult (a polite way of saying bloody frustrating).  After the seeding race I was put in C heat and progressed to B the A and stayed in A for two more races.  The things unfolded.  I was demoted to B then C and took 3 attempts to get out of C and then two attempts to get from B back to A where I stayed for the rest of the regatta.


In summary, I was getting great starts but lacked pace and dropped back into the fleet but once back in A fleet after my excursions was always able to find a way to stay there.


The result from the Nationals was not what I wanted but I was going through a commissioning process, so 14th is OK.  The boat was not as quick as I would like, and I was able to nail down the reasons why and quickly fix on Tuesday. 


So, what was the list of things to do after the Nationals


On mast bend, 8mm of prebend proved to be too little to support a firm jib luff and leech when sailing upwind.  I wanted to use the same mast but with more prebend without using my rollers.  I have found with the rollers that you have to get the roller settings to a certain point before the mast bends permanently.  It is very easy to get hard spots, so I thought it time to bend the mast by hand.  Surprisingly it is not that difficult to achieve a smooth bend by bending the mast carefully around my middle.   So my 8mm turned to 15mm over 600mm and I put a gentle reverse bend into the whole mast.  Only a few mm.  The result when rerigged was stunning.  Complete control on the jib leech and the ability to set any bend I liked and no hard spots on the mast.  I will not be using rollers again.


I also discovered the bulb cant was nearly 4 degrees rather than the two I thought I had.  I took the bolt off, and the hand fitted bulb was 2 degrees but what I had not realised was there was a high spot in the slot on the bulb and when the bolt was tightened the bulb rocked and increased the cant.  I also need to increase the weight of the bulb by 15gms.  There is a hole in the slot which I can fill with lead shot so should be able to get the bulb and fin to full weight.


I fiddled and reprogrammed the winch, so I was able to have full control sheeting when sailing upwind.  That also restored the mixing which gives me high mode.  I will put a blog up on that later.


Those three things alone will surely increase the performance of the boat.


All this done, I am ready to test the improvements.


The journey continues.  5 months to the worlds.


How to measure fin and bulb position (see picture below)


After a ranking event where the weather helm caused me issues, I ended up raking the fin 2.5 degrees and moved the bulb just over a centimetre forward.  This required careful trimming of the slot in the bulb but with a Dremel you can do a neat job but how to get the bulb in the right place


Take 2 A2 sheets of drawing paper and tape them together along the shortest edge.  Lie this on a wooden floor and place the boat on it.  Use the top side as the waterline.  The bulb draft limit is 3mm below the bottom or the A2 sheet.  Using a right-angle triangle or T square, put a mark on the water line of the boat at the bow at the point where the designer says the bow should kiss the water.  Align the boats water line with the top edge of the paper marking the exact bow and stern position.  If you do this right, you will be able to move the boat and relocate with precision.   Once you have the waterline established, raise the fin so it is parallel to the floor (3 dvd boxes should do it) and recheck the boats position. Also it is worth checking at this stage that the boat is 1m long.


Once the boat is in position, you can mark the four corners of the fin, then mark the tip and back point of the bulb so you can measure the cant.  Each point is marked on the paper using the adjustable right-angled triangle which also allows me to measure precise angles.


This Alioth design requires the bottom of the leading edge to be a certain distance from the bow by drawing that line with the fin in that position and marking the front point of the bulb is, I had my starting point for the bulb position.  I then marked where the centre of gravity of the bulb should be so I can line up the C of G of my new bulb in the same place with a raked fin.  When I changed to a bulb with a different length, I was able to position its centre of gravity with ease.




bottom of page