Developing the Alioth Boat 1 | IOM Build Race Tune

Working up the Alioth. Boat 1

This journey with the Alioth is not about 3d printing but about working up a boat to make it competitive.

My objective with the Alioth project was to work the boat up in stages and see how speed developed. There was no speed edge to start with in fact the opposite was true to start with as there were some deficiencies in the set up, but confidence is building as I optimise the boat and I see it get faster.

First a caveat on the story below. If I was to do the same again, I would have bought the fins from Juan and fitted them as standard. This would give me a balanced boat. I saw the new fins fitted on a new Alioth at the end of 2024 and I have to say I was totally impressed. Save yourself a lot of trouble and go with Juan for the full boat and foil package. You won't regret it.

The kit on the boat

Alioth hull in Polymer PLA assembled by Paul Barton. The hull is so strong you can give it a good punch with a fist.

Alioth standard fins (these were early generation fins)

Winch is RMG fast 290 H1 with 45mm spiral drum

Spars are PG 11mm

Roller bearing gooseneck on A rig

Coreless 20g Digital Metal Gear Dual Bearing Mini Rudder Servo - DFMGD1

BG Sails

The Journey

Now the boat is close to full race mode. It has been an interesting journey to race a vanilla standard boat, no finishing on the hull just a clear coat or 2 and no sanding. All the rigs were set with the boom band at 150mm from the step which made for a rather ugly look with the booms high and pointing up in the air slightly. The look wasn't improved on the A rig with a prebend in the mast that was more like a kink than a smooth bend and made the boat very hard to set up and sail. It did not have an edge as you can imagine.

After the Hampton Court charity day, I trashed the A rig and converted it to a B rig. Then I carefully prebent a new A mast and set it up with 62mm spreaders. The result was an impressive looking BG mainsail which could be set twisty and deep for a chop or flat for a breeze on flat water. There were no hard spots causing any creases in the luff as the mast bend matched the luff curve. The challenge with prebending devices is that you can get an immediate bend at the 600mm point. The bend needs to be progressive and other than bending by hand I know of no device that can achieve this. If anyone knows a way, please advise me how it is done.

The A rig mast bend matches the luff curve with no hard spots. This is the limit of bend before the sail breaks down. This Mainsail was first use in 2020 and used for practice over the last year. Pretty impressive duration and still looks superb.

All three rigs had 15mm taken off the bottom of the mast to bring the boom band to the deck. It is still 70mm or so from the measuring point on the deck. I needed to shortened the gooseneck housing to lift the kicker adjuster off the deck so I could get my fingers in to adjust.

Here you can just see the rake of the fin and mast and how the boom band sits just above the deck. FIngers crossed it will be perfectly balanced

The jib attachment point was lowered so the jib boom is as close to the deck as possible. There has been quite a bit of discussion about end plate effects which I do not buy into because as soon the boat heels or gets into chop, the wind is blocked and disturbed by the hull turbulence. However with the jib boom low and the main boom low and parallel to the deck, the centre of effort of the sails is as low as possible. The look is good and a good looking boat is often fast. Time will tell.

You cannot achieve a main boom parallel to the deck on the standard Alioth settings. The mast is too upright and if you try raking the mast you just create weather helm. To achieve the mast rake the fin has to be raked back approximately 2 degrees. Using a standard Alioth fin I shaved 2 degrees off the aft edge of the fin where it enters the fin box and added a front edge fillet using Isopon car filler making for a nice secure fit. The 2 degrees was measured with a protractor acquired in my university days. Remember to adjust the bulb angle, 2 degrees up from back to front should do it.

Of course if you rake the fin 2 degrees, you move the bulb back 8mm relative to the hull which will effect the position of the correctors. When I first launched with this configuration, I removed the correctors to see how the boat would sit and was delighted to see it sat on its marks, so I added the 70gm of correctors back on the aft side of the fin box, considerably forward of their original position.

The final job was to finish the hull. I had two choices. Either sand the 2 pack clear coat on the hull which was recommended by my builder, 3D printed RC Yachts, who is a licensed builder or go the whole hog and take off the clear coat and thin the hull to reduce weight and paint again. I chose the former as it was a lot quicker. The hull finish is superb with just a hint of evidence of the the two hull joins. I filled any groves with Isopon car filler. To sand the hull I started with specialist finishing paper. It has a lubricant coating which prevents clogging and saves a lot of time over wet and dry sanding. The main advantage is you can easily see the high and low spots. I used 320 grade specialist finishing paper and then polished with 1500 grade wet and dry and T cut car polish.

The other minor job was to add an additional fairlead for the jib sheet. The boat only came with two fairleads so I reposition one for the B rig and added the 3rd for the C rig. Each jib boom now goes out 85 degrees on the run. I had to drill a new set of holes forward on the jib boom for the A rig.

The boat is now in a position for me to check the balance which I am hoping to do tomorrow if I can find an ice free lake.

What is left to do

Consider the right fin, rudder and bulb shape. My early generations Alioth blades have a reverse camber at the aft end of the chord. I believe the new clades are good. The bulb has the max chord 25% from the front. There are a few choices for the rudder, e.g. John Gill (UK) who makes a nice product as well as a rig tension meter, Robot,Yachts (UK), Dave Creed (UK), Craig Smith (Australia). Need to do some two boat testing before making any decisions on this front.

Once I have checked the balance and got the boat footing nicely and we get near some meaningful regattas , I will bend on some new sails as the final stage of optimisation.

Of course all this work is combined with as much practise as I can fit in. It is the nut on the end of the tiller that gets the boat round the race course and all the speed in the world won't make up for bad starts and poor tactics.

The sheeting set up - Feeding the main and jib sheet through the small guide hole in the upper left of the radio pot holds any loose sheets away from the winch and drum.

Here you can see the 3 sheet lead positions. The numbers on the deck were hand drawn and cut.

If I was to build another Alioth what would I do

In constructing the hull, remove as much redundant plastic as possible and sand the hull well to reduce weight as much as possible before painting. The printed hull is approx 1mm thick. There are two options for sheeting systems. On deck sheeting where the sheets enter the deck behind the foredeck bulkhead. This will keep the boat dry. The other method is under deck sheeting with the deck entry points on the centreline of the boat. They let a tiny amount of water in although nothing significant even in wild weather. The boat does need rinsing inside after salt water sailing. Personally I like the latter set up. Other than that I would do the same as above.