ISO Skiffmaran

Discussion in 'Multihulls' started by Vantage475T, Dec 23, 2016.

  1. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    Test mounting the floats

    So now the tramp is roughly in place, onto getting the floats mounted.

    Plan is to have a thick piece of ply with some bolts embedded from the underside stickup in and then going through the ally baseplate.

    The ply will be screwed and then epoxied in place once the right position is sorted.

    Initially I attached it so the floats line up with the main hull, but after dropping it in the water and just trolling it around I thought there was too much overhang at teh front and the weight distribution wasn't right. I therefore moved it forward 50cm so it is currently sticking out behind the main hull a bit now. I will take off the last 50cm section and seal the bulkhead there and make the other outrigger 4.25m.

    The slots cut in the aluminium plate now mean the frame can be put in place and the float just lifted into place even single handed. I need to keep it all collapsible for easy transporting back and forth in pieces at the moment.

    The crossbeams now have choppping board spacers underneath and on one side to make it easier to slide it in and out. As soon as I can find the right thickness chopping board i will take those off and put them all four sides.

    In the background of the float plate picture inside my office is a wooden boar - my wife wants to have pigs and goats so I sugegsted we ahve some wooden ones for the moment...

    When I am putting the next coat of epoxy on the outrigger I will get that coated as well.

    Attached Files:

  2. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    Nemesis floats

    The boat is going to be called Nemesis.

    it was a lovely day (cold but sunny) and thought we would pop it in the water as is to get an idea of the float heightand see how it goes together.

    Also wanted to test the electric trolling motor so this was perfect - no wind at all.

    So first pic gives idea of floats as originally fitted - there is too much forward of the front crossbeam and the eight distribution is a bit front heavy. The final frame will actually be bent ally tube that will stick further forward giving more support to the front of the float. I've now moved it back 50cm and is much better.

    Then we can see my wife sitting in the trampoline and the floats easily taking her very small weight. Her bottom is not as large as the picture suggests... The trampoline was held by the old gazebo bungees which are very stretchy. Since then we have lashed the trampoline on with 3mm line and it works pretty well with very little sag.

    Next there is the boat being held pretty well perfectly upright. The flaots are a few inches out of the water, so when going along on we should always have one float of out the water. I think the down tubes need slightly lengthening though, so looking at possibly adding 2-3 inches up front and 1-2 inches at the rear. Will see once we get it going.

    Finally then we have a picture of me testing the trolling motor which worked really well. Using an old motorbike battery, I pottered about quite nicely. I will probably keep a couple of these with me and wire them in parallel for emergencies. Need to look at the weight / power benefots of a car battery.

    The shaft on the trolling motor needs to be shortened hugely and then I will work out a mounting option on the rear crossbeam. The motor can be kept up front out of the way on the other side from the spinnaker shute and just brought out as needed.

    I will need to make up a waterproof box then fix the wiring along the beams so the engine can be quickly dropped into place as required.

    So everything looks good, a few updates and then next daywe get any decent weather/tides/wind we can hopefully hop out and give it a try.

    Can't wait.

    Attached Files:

  3. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    Test sail in Mudeford harbour

    So, having changed the float position, lashed on the trampoline with line weather looked great with a little bit of wind, nice and sunny - although nad chillingly cold. Scraped an inch of ice off the car, loaded up all the crap and headed off.

    Rivetted the tramp frame back together when we arrived and got putting things together. The chopping board spacers worked much better fitting the crossbeams and not having the float attached made it very light work. then attaching the float was really easy slotting it into place then just tightening up the wingnuts.

    Popped the trolling motor and 2 old motorbike batteries in got rigging the sails. Using 2 really old sails - both main jib are pretty well toast but still give decent traction.

    I intended to keep the main sail loose to keep power down but in the excitement of getting on the water hadn't either got the sail all the way up or even put on the dowhaul. I finally noticed about 5 minutes in when we had started a reach down the main channel. We simply turned into wind and with my wife sitting on the tramp the platform was totally stable.

    Sorted out the rigging and we were away.

    In low wind with occasional small gusts we really moved nicely. Sitting in the tramp showed the basic dimensions are spot on - I can sit in it and brace my foot against the inner rail nicely and my wife found it comfortable and spacious.

    The botched up tiller extension (taken off my kaymaran project and still with the rudder attachment on it is just about the right length. I will take a foot off it but need to get on with making the support cup so it can be left supported when on the other side as it managed to get caught inside the outer rail and got bent....

    Plan is to use a sort of oarlock on the rear crossbeam that it can be dropped in. I will put some velcro over the top to ensure it can't bounce out. Thinking about the best way to lock the tiller for easy "autosteering" which will probably be velcro along the bottom of the tiller extension which can then drop into a second oarlock to hold things in place nice an easily.

    For the placement of lines, the cleat for the jib sheets still works fine but when out on the tramp I cant lock off the main sheet so I will add a small cleat 1/3 of the way along the inner rail. It should be really easy to sail this single handed with some judicious placement of the cleat and with a long enough tiller extension I could actually potentially trapeze it as well single handed.

    On that front, I need to replace the trapeze bungee - this will make a brilliant platform for my wife to contnue gaining confidence and timing with her trapezing skills. We didn't have the harness with us so only did a bit of hiking. We also need ot add some foot sraps on the tramp - we will put on some ratchet straps next time to get the placement right and see how that goes.

    I think I will add a few inches to the vertical tubes on the outrigger as I think with both floats the dihedral will be a bit high.

    There were a few other hardy souls out in single handers not sure what, but my wife really feels the cold so I knew we had to be very careful and after a few runs decided we should head in.

    We had one comedy moment where I didn't ease the main sheet quickly enough when tacking but the additional righting moment of the outrigger slowed the tipping over considerably and we easily controlled it and scooted off.

    Everything felt well balanced and the tacking was very easy still, no loss in manoeuvrability at all.

    We will wait to dick about with the spinakker until it is warmer and we have the ther float on and sorted. I am considering changing the design of the float very slightly - taking the rear 50cm off and raising the rear height slightly - marginal extra weight while keeping the thin profil ebut adding a bit of extra volume. We will see once we are out in some more shop on the open water.

    Otherwise, the biggest problem was the depth of the harbour. There is a winding channel going up to Christchurch but anywhere out side this we constantly ran aground and sent most of the time with the daggerboard partly / mostly up. Coming back in was nightmare as we couldn't have the rudder down and only a few inches of daggerboard and trying to go into wind against a strong current wanting to drag us out into the channel was not great.

    I will get the motor mount sorted on the rear crossbeam so it is easy to pop it on and off if needed but mainly the plan is to get thee much earlier halfway after low tide so we can sail/troll out the entrance channel into the sea and have more room to playround while remaining close to shore. We can then come back in using the current to get back in as well as the wind (hopefully) or the trolling motor.

    We can also look to trailer it elsewhere perhaps Lymington, Beaulieu River or over to Calshott which will probably end up being the best base once the back and forth is completed as we are straight out into the Solent and there are also some ISO's over that way I think.

    I've attached a couple of photos and will gather some video clips from the footage we got so you can get an idea of the dynamics.

    All in all really enjoyable and indicates the overall project shoud be great. I'll get onshortly with the next float and other frame so we can hopefully sail it lots this summer and get on with sorting the deisgn for the new main hull - broadly similar to the ISO but with the frame and beams all smoothly built in and some simple storage. Am looking at a simple foredeck as well to keep water off and provide a small area under cover. Plan is to do coastal trips an dpossibly camp with boom tent but realistically stay in a hotel or camp on the beach.

    I will try and sort some video in the next couple of days but back now to chaos at work for the rest of this month.

    Attached Files:

  4. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    Video of us carefully testing

    Put together a few clips showing the boat moving along. We were taking it very carefully in case it exploded/fell apart/sank/whatever as it was stupidly cold and we are hopeless.

    Shallow water so we could mostly have walked back in but that made it really painful as we couldn't get the daggerboard down and coming back in we had almost no rudder and centreboard and with the strong current wanting to drag us out into the channel t was tedious in the extreme.

    We felt it went very well and it proves the basic dimensions are about right. I will make the next float slightly deeper at the back and slightly shorter I think. I will also extend the front vertical support to the float by a few inches as I think the balance isn't quite right.

    Once all sorted and able to sail for the summer I will then get on with replacing the main hull with a similar size/shape but designed to be a trimarna from the outset although it will alos be sailable as a true dinghy as well with just some extension wings for hiking/trapezing if we want to.

    I've uploaded a video to youtube, link here:

    so you can see how it goes.

    We probably won't get out for a while now, but hopefully we will take the trapeze harness and give it more of a thrashing.
  5. Doug Lord
    Joined: May 2009
    Posts: 16,654
    Likes: 326, Points: 93, Legacy Rep: 1362
    Location: Cocoa, Florida

    Doug Lord Flight Ready

    Congratulations-looking real good!
  6. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    Next test

    Had an hour after making some quick alterations:
    - added cleat on frame for mainsail
    - adjusted tramp frame to make easier getting on and but still needs some more work
    - sorted electrics for electric trolling motor test
    - looked to see how my neighbours 4 stoke 2.5hp could be fitted

    The thing with the motor stuff is just down to narrow channel getting in an out of the harbour - it is easy to get stranded out and unable to get back in against the fast tide with unhelpful wind direction which is often.

    Anyway, another freezing cold day with wind 16 knots but gusting up hugely as soon as we got out and th tide had turned so a really unpleasant chop in the tide with the wind exacerbating it.

    We thrashed off and was quite a battle so decided to head in as my wife was struggling. As the tide was heading out the water level started to fall quickly and we got caught grounding out at about 10 knots with one of the many lumpy bits in Mudeford.

    My wife got catapulted forward smacking her face on the ISO spaceframe and splitting her knee but kept going to ensure we got in and got everything away safely.

    Her chin is black and blue.

    We have clattered this daggerboard into multiple groundings and it the hull is very sturdy indeed.

    We are hoping to move to lymington town sailing club in the spring so we can get out into the Solent easily with deep water so we can more easily tool about as getting very frustrated in Mudeford, even though it is a lovely place to scoot about.

    We got no video or gps data unfortunately but we are very happy with the basic premise.

    I am now going to get on with building the other side in February with some alterations to the float shape - shortening it slightly then adding some volume and changing the transom line.

    I am also going to weld up the frame welded in its current state for ongoing testing before I commit to getting final framework made up.

    I am getting the out tramp frame tube extended and curving down front and back vertically into the float. The crossbeams and inner longitudinal beam will then all be welded up as well so they are stackable on the boat and the tramps then won't need lacing up on the inner beam when adding as they do currently.

    This will give us something we can thrash for the summer while I make the new main hull hopefully ready for next spring.
  7. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    ISO skiffmaran update - proa style

    Not had a lot of time with massive issues at work but finally welded up the frame and been out twice but not managed to get any further footage or gps.

    I need to get the float sanded and painted asap and then get on with making the other float - changing the shape a little so I can compare perfomance.

    Stability and tacking is great - we had crappy swirly winds at Lymington and needed to come back up the river head to wind and a turning tide and it coped really well. Quick tacking and stability when you are a crap sailor is a bonus....

    The new long tiller is working well - only ally so will be easily damaged but makes lying on the tramp comfy and keeps the boat very controllable.

    Looking forward to getting some good conditions and get the confidence up and start giving it some beans.

    Attached Files:

  8. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    I'm going to revisit this thread as I'm about to remake the frame and a new larger float as we destroyed this in July 2017 when we snapped the beam off in some heavy winds and chop.

    It really wasn't meant to be out in conditions like that but we had been having a great blast and gave it too many beans.

    We took off at just over 20 knots and when we landed the beams went off like a shot. Unfortunately lost the GoPro with the amusing video which was a shame.

    This thread also ties up a bit with toadboy65's thread over on Sailing Anarchy where he has putting training wheels on his I14 dinghy.
  9. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    So, I’m finally getting a bit of time free from work and health issues to get back to sorting out a new ongoing small trimaran project.

    This post will be quite lengthy and rambling so please be prepared. And patient...

    The basic premise I am after is a fast stable trimaran that is essentially a big Weta and can be sailed solo or double handed. I want to be able to do some fast single handed cruising carrying camping kit etc and am really interested in trying to get involved in some sort of raid style events which don’t really exist here in the UK as far as I can see (so I’ll look to try and start one perhaps).

    The conditions will be close to shore mainly and we’re based in the Solent which can have some significant winds and the “famous” large Solent chop. It needs to be trailerable and max 16 foot I think so it is possibly to get in and out of my narrow access drive at home relatively easily although it will mainly be stored at our local club I hope. Again though, length and width is at a premium there as well.

    I’ve sailed on a Weta two up and it was pretty slow and they are still pretty expensive 2nd hand here.

    I’d be interested in having the possibility of foil assist further down the line or possibly fully foiling.

    I’ve been looking at loads of possible options to see what might be good alternatives but I would prefer to build something as I really enjoy tooling about in the garage.

    I have a Spitfire F16 cat currently that I could use the mast and sails from initially but would want to change the main sail so it is properly reefable and preferably make the jib furling as well for safe solo sailing.

    Currently the main has a mast top cleat that is pretty painful and cannot be easily taken off and depowering is by cranking on massive outhaul and downhaul to bend the mast to release the square top and flatten the lower part of the main but would not be ideal for solo tougher conditions….

    The jib also hooks onto a mast cleat and has a lower steel frame between the hulls that goes about 3 feet up the front of the job and so cannot be furled. I could replace the forestay and add a furling jib fairly easily.

    I’m about to make up a new float and frame for the ISO test bed so I can get a view on possible float sizes – the ISO has quite a bit less sail power than the Spitfire but is close enough to take a view on where the project could end up.

    The old float sliced through the water but was too flat bottomed and not deep enough so could get overpowered although we were only sitting on the other side of the main hull so not much leverage (it was a kind of proa-maran).

    The new float will be approx 450 litres (probably double the old one) to get an idea of how that performs with another bodged up aluminium frame again. Hopefully I will be getting on with it within the next couple of weeks. The float bottom will have a more pronounced V than the previous one as with the chop there was a lot of slap and this transmits some sizeable force through the currently crappy beams which obviously helped result in carnage last time.

    It is perfectly possible I will actually make 2 float sizes – one larger set for safe single handing and 2 smaller lighter ones when double handing with my wife who likes to run around hanging off the side.

    I like the idea of the centre hull having a more skiff like bottom for easy planing and giving more load carrying capacity as I can also end up with some large clods occasionally coming out with me.

    The ISO test rig worked really rather well, getting some decent speeds up while feeling really safe. Testing the new float shape and volume will be very useful.

    There is now sufficient dihedral to ensure that only one float is in the water reducing drag – I’ll need to look more closely at whether/how the floats get caught with the chop and how that manifests itself exactly.

    For demounting / folding, currently I have simple slot in beams that are quite awkward as they are quite tight but still doable single handed by me.

    However at about 4.25m wide for the new project it will take up virtually the whole ramp so I need some mechanism for reducing the width that can be then folded out on the water and I can then probably motor away from the ramp to the jetty to actually finish rigging. For the test bed I will only go down when it is nice and quiet.

    Options here are:
    • inward folding Farrier style
      • I’ve mocked up a couple of folding mechanisms for this – a bit of farting about will get it how I want it so it gets the float close enough and vertical enough to enable easy locking and leave room to stand and steer it. Would probably drop one side before motoring anyway.
      • I need to be aware of the overall width for trailering and where the floats would be in relation to trailer wheels etc
      • Also need to ensure the tramp can be at least lowered a little to reduce side winds catching it while trailering
    • forward folding Sting 600 style
      • This could well be a good option but it lengthens the boat when trailering which may not be ideal for easy manoeuvring about - the trailer tongue needs to be longer
    • rearward folding
      • Seems a bit dim as folding forwards has a built in “lock” when on the water
    • folding over the main hull
      • obviously needs a seriously strong hinge mechanism which if they fail will collapse the float upwards and the boat over which doesn’t seem great
      • Also the weight is higher up when trailering
      • also can’t have the mast up with the floats in unless it is supported in a frame like the ISO as the shrouds would be in the way
    So either forward or Farrier – not sure yet.

    Keeping it simplest, strongest and lightest. Farrier type system doesn’t appear overly hard – I can fabricate initial under beam frames in mild steel then get some decent Stainless ones welded up from those as I don’t have that capacity at present.

    One thing further to consider is it will almost certainly have a frame similar to a Weta / Searail with verticals to help keep the beams out of the shop so that will make the Farrier folding system a bit more difficult potentially as total width with tall floats and frame could get excessive for trailering. I will tool around with it some more and see what comes of it once I’ve done this float. I could make it a bit shallower and wider to keep volume or just stick with slightly lower volume hulls so it works.

    I think having the ability to raise lower mast on the water will be critical so I will need some sort of gin pole system that can be lashed up and winched from the rear – not too difficult I think.

    For camp cruising a thought is to have the interior with vertical sides so a wood floor lattice can be installed – this can then be lifted up in2/3 parts and slotted on runners ate deck level to make a large useful area for camping etc. This would give loads of room for a 2 person tent. If just me single handed camping then I would probably sleep in the foot well with a simple boom tent.

    There will plenty of side storage in the main hull and under foredeck can be used as well.

    The spinny will be bag mounted on the deck and the sprit retractable like on the ISO with one pull to reduce windage when not in use.

    A small Mantus dinghy anchor folds flat and will be stored in a sheath on the foredeck ready for easy deployment. I’ll do more testing on this but it seems to hold incredibly well.

    For outline dimensions I am looking at 5m max then and main hull width up to approx 110cm on topsides - I should probably look at dimensions for a 49er skiff? Max beam when sailing approx 4.25m so pretty square.

    The main hull will be up to say 600mm tall so a decent amount of freeboard for the various sea states we’ll have.

    I need to think about rudder and dagger board options. As I’m going to be lashing this up I am thinking of making the dagger board position adjustable fore / aft by about 6 inches either way to ensure I can get decent windward / leeward balance and then I will lock it in place. Basically this will be a drop in case that I can change with blocks to decide where it finally goes.

    I am thinking something like a 49er board and rudder? Any other thoughts on something I could investigate and use? I have made a leeboard and rudder for my kaymaran but it is never going to be anything decent compared to something I can buy. I might also look at the board/rudder from Len Surtees for his Sting 600 especially as that would be T rudder which could be useful with regard to foil assist.

    I will have an outboard attachment for my 4 hp long shaft and I am also very interested in some pedal assist options as an alternative. I’ve been looking at h2 proped and various others – it would be useful to be able to move from boat to boat easily.

    I think that covers a decent amount of my current thinking and I will do a separate posting with various plan/buy options and my thoughts on pro’s cons for each of them as this is already very long to plough through.

    Any useful comments appreciated!
  10. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    Listed below various possibles with outline thoughts.

    Potential Home Build Boats

    Woods Designs
    I’ve swapped some emails with Richard who is a good guy.
    14 ft skiff hull – the most similar thing to get to a Weta I imagine? I like it, it is just too small for what I am after.

    Strike 15
    Bought the plans and very close to doing but still feels a bit too small.

    Strike 16

    Really do not like this shape

    Strike 18
    Too large and really do not like the shape

    Thinking long and hard about this. I think it is probably the closest thing I could find to self build.

    Sport Trimaran
    Having built a CLC Sport Tandem kayak and converted it with much modification to a sailing trimaran with jib and tramps etc I would be confident of something decent from them. However, this has never come to anything and is more like a Windrider with single forward facing seating.
    Link here.
    Junior Outrigger
    Totally left field but I find this utterly charming.
    CLC Outrigger Junior, a 15-foot Tacking Proa
    Again they have still not made final plans - I've been following it up for well over 2 years now but no progress.

    Slingshot 16
    Forward facing mainly and underpowered – would need a lot of reworking but a lot to be thought about.

    Slingshot 19
    Forward facing, too long and underpowered for what I am after but interesting.

    Seaclipper 16
    Some level of interest but the low beams will drag and also some people seem concerned about the strength of the folding mechanism. Things to ponder though.

    Cross 18
    Possibly interesting but too long and heavy

    Retail Boats for Reference


    As discussed above – too small and seems like a lot of cash for a small boat

    Windrider 16
    Forward facing – people seem to love them but not for me

    Windrider 17
    Same as Windrider 16

    Astus 16.5
    Holy crap these are expensive. I can’t even get to see one in the UK as the dealer doesn’t have one. Seems bizarre. Look like they are the closest to what I would want but not self build obviously and the dismal build quality reported by Tom Kirkman on SA is quite worrying.
    Basically this with folding (in or forward) not sliding plus raised, angled beams as it looks like they would catch a lot in our chop would be fantastic.

    Astus 18.2
    Too large but look very nice.

    Sardine Run

    Interesting but too long and heavy for easy movement on land.

    Chris White Discovery 21
    Too long and heavy

    I think that covers everything I've looked at. Now just trying to pull together all the good points from various ones to see if I can get something close enough.

  11. Vantage475T
    Joined: Aug 2016
    Posts: 88
    Likes: 24, Points: 8, Legacy Rep: 10
    Location: Lymington,UK

    Vantage475T Vantage475T

    Here is the float I'll bodge up:

    which is only 475 cm to go with the ISO dinghy length.

    Outline of main hull so far:

    Tops of beams to be flush with gunwhales then angling up a bit.

    The foredeck will extend further back to around 2.2m from the front.

    Self draining cockpit.
    Doug Lord likes this.
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.