Following on from DavidBS’ post, I thought I’d share some info. on a first time newbuild project that I started a few months back.

I designed the lines myself having observed some of the newer popular designs raced at my local club. I know the target displacement is 4kg and I deducted an allowance for the keel, bulb and rudder to create a target volume for the hull. I then drew and faired (probably not very well faired!) the lines plan using and A0 drawing board and ship’s curves. This was an iterative process because I had to check the centres and volumes of the hull (Simpson’s Rule) and adjust the lines to achieve the target volume and centre of buoyancy.

Having watched numerous videos on youtube I made a base board and cut frames/shadows for each section (having deducted and allowance for the skin thickness) and created a planked hull using balsa. My aim was to create something quick, cheap and cheerful for this first attempt. I’ll try to add some photos shortly. I constructed the foredeck using a dry joint at the deck line, so I can remove it to clear out the inside of the hull by removing the frames, before glassing and finishing.

Lots more to do and the cold weather doesn’t make me want to spend too much time in the garage at the moment!

 

The process is pretty quick because balsa is very easy to work. I know it's not as pretty as cedar, but I just wanted to build up some experience before making something a bit more serious. Here are some photos:

Nice job, looking forward to following your build.

If this is your " gaining experience" project, the next one is going to look fantastic

I am going to enjoy watching progress- whilst pretending not to being jealous of your skills!

 

I know some people like doing things the old fashioned way but either Defltship or Freeship can do a lot of the work for you.  3D tools are also good at visualising the fairness of curves. I am currently making a 10R that I drew in Delftship and all the hydrostatic calculations are done for you.  It can also plot frames, buttocks & waterlines at any chosen location very useful for making the internal structure.  A bit of a learning curve obviously but worth it in my opinion.

Delftship : https://www.delftship.net/

Freeship: https://freeship-plus.en.softonic.com/

Thank you John, that’s really interesting. In fact I was planning to ask in a future post if anyone had recommendations for a software package. So that’s really helpful. I made a little research into 3d drawing and naval architecture software a while ago, but felt that I might not be able to afford a decent package. I’ll definitely check out the links. One possible limiting factor for me is I only have a MacBook Air these days… But definitely my preference would be to use dedicated software over traditional drawing and design techniques.

Is the plan to put a protective layer around the balsa ?

I race two wooden  full size dinghies and they are both very competitive- the only downside is the effect of any collisions with my " plastic" competitors

Yes, I will definitely be putting glass and epoxy over the balsa to protect it. In its current state the balsa is very soft and doesn't have much strength in any direction other than along the length of the grain. Plus the glass layer will help seal the hull. As a long time dinghy racer I do understand your point. The laser gunwale in particular is immensely strong and can do a lot of damage. I race an Aero now which is a bit fragile compared to a laser; and the best policy is to avoid contact with anything.

A friend at our club has made several really excellent IOM hulls using the foam plug method (as per BG's video on youtube). His finished hulls in moulded glass epoxy are amazing. I really wanted to do the same, but lacked a bit of confidence and couldn't find a source of reasonably priced styrofoam sheet.

I've also been tempted to finish the balsa hull and use it to make a plug, but I'm impatient to get something on the water to see if the hull form works. So the current plan is to press on and see where the journey takes me.

Wooden boats rule!

No question at all that Ospreys rule! 

Martin, good source for XPS foam is easy composites. This stuff is so hard to find and they seem to have started stocking it recently.

I sail Merlin Rockets so totally agree with wooden boat comments. However disagree about laser not being fragile !! Have had several ( lack of crew) and they are poorly built and fragile but the strict one design, ironically, does not allow improvements. 

Simpsons rule is hard work, and like you, I have no software apart from "excel" to do the number crunching. You must post your final hull shell weight.

Richard

Hi Richard, Thanks for info on the XPS foam. I have recently bought a can of expanding PU foam, just for a few experiments; though I'm not expecting it to be easy to use. I'll let everyone know how that works when I get round to it.

I will weigh the IOM, but I need to buy a suitable set of scales first!

Simpson's rule is very useful and pretty straightforward to use in a spreadsheet. The time consuming bit is taking offsets from the lines plan; and I'm with John on this one - 3d NA software is the way forward. Sadly for me not many are compatible with Mac.

Martin, I would recommend 2 part expanding foam. Much easier to use than the instant spray can stuff. I use CFS but there are others. It expands in a truly amazing fashion and always surprises on the volume it achieves. I use it for moulded hull cradles for transporting boats.See pics: keeps them really secure and snuggly.  Never tried deep mouldings but am aware that it will produce a pressure in deep mouldings that could deform a pattern / mould.

Richard

 

 

Good for you Martin. Looks really good.

A bit time heavy for me, so I will keep looking for a used boat

 

Thanks Richard, That's another avenue that I need to investigate. BTW, I found your previous posts on your construction project especially inspirational. Thank you for the time you spent putting the words and photos together.

David, I totally get it - good luck with your search. I wouldn't attempt a new construction project without have a fully working boat to use at the club. I enjoy making/repairing things, but I would pretty much always rather go sailing (especially racing).

Two part foam… old mate of mine, to sort out his glass fibre kayak before the next disaster on an N Irish River, just dragged his kayak into his house in Omagh, stood it up in the stair well, and poured in half from each container. His house proud first wife arrived home to find him coal skuttling it out of the kayak, leaving a trail through the house and in lumps in a wet rear yard… clear grounds for divorce, not reading the instructions 

2 hours ago, Stephen B said:

Two part foam… old mate of mine, to sort out his glass fibre kayak before the next disaster on an N Irish River, just dragged his kayak into his house in Omagh, stood it up in the stair well, and poured in half from each container. His house proud first wife arrived home to find him coal skuttling it out of the kayak, leaving a trail through the house and in lumps in a wet rear yard… clear grounds for divorce, not reading the instructions 

I worked as a watersports instructor for London Borough of Redbridge in the 70s. One of the local schools borrowed one of our canoe moulds to make their own fleet.

It would have been a good plan if they had used release agent on the mould before starting the layup of the first one

A bit of an update...

Sadly, recovering from a heavy cold and suffering from an eye infection I couldn't join my mates at the club for the Saturday morning racing in IOMs today. This was a huge disappointment for me as it was really windy and I love those conditions. But, no worries, I thought I'd give a brief summary of the meagre progress I've made since last time.

The two partial bulkheads and foredeck are fitted and the aft well for the rudder post is partially fitted. Additionally I have cut openings in the hull skin for the rudder and fin. The next task is to fit and construct the fin box and surrounding structure to house the radio gear and shroud connection points. I'm feeling my way along slowly because I've not done this before and I'm aware that if I build things in the wrong order I could make difficulties. For example I think it's best to fit and glue the rudder tube inside the hull before gluing the top of the aft deck well, otherwise access for gluing will be difficult and I could risk a leaky joint.

The boat shown in the photos weighs 275g, but of course there's no glass or resin used yet and I have yet to fit the aft deck and fin box etc. I'm guessing that's not especially light and would be interested to hear others views on this given the partial state of construction.

The photo showing the hull profile has the rudder and fin loosely attached for a dry-fit/measuring session. They are "borrowed" from my old Widget and will be used in this hull. I'm slightly nervous about the bow, which I have deliberately designed with less rocker than most current designs. The aim is to achieve about a 1cm immersion of the forefoot in the final floating condition. This is to maximise hull length (the idea being to increase the maximum hull displacement speed which is roughly proportional to the square root of the hull length). I'm pretty sure it's an idea that's been tried before and probably discarded, but experimenting and finding out is part of the fun of building these things - right? Several people believe the idea is flawed because having an immersed fore-foot will work against tacking quickly. That's what we'll find out and is mainly why I'm a bit nervous! But on the other hand it also allowed me to make the bow quite full too, so I'm hoping this will help the boat resist nose diving in stronger winds... We will see.

 

Watching your progress is like cycling up a hard climb in the Peaks, feeling really strong  and then being overtaken quickly by two others- chatting and laughing!

The boat looks beautiful- and I wish I had half your skills!

 

Haha! Thanks Ian, that's a nice compliment. Actually the photos are a bit like seeing something on eBay - they make the boat look good, but once you're close up you can see the imperfections!

One of the advantages of using balsa strip is that most of the undulations in the hull can be removed by gentle sanding. The hull was quite un-fair when the planking was finished, but it surprised me how smooth it looks now. I'm pretty certain that it'll need some more filling/fairing before and after the glass cloth goes on.

Do you have a build on the go at present?

I can sail ( a bit), but replacing rigging and hull patches is my limit.

Enjoying my Df65-95 and waiting for the right used boat to come up for sale

Looking very nice Mr Brooking, cant wait to see it on the lake, 

 

PS, you were missed on Saturday (well Val was ) 

Hi Martin, congratulations on your new build. I have built a few boats of my own design and learnt some hard lessons.

I think the immersed bow is going to spoil what is otherwise a very promising design. The static waterline (floating upright with no wind) is never the same as when the boat is actually sailing. The high rig means a high centre of effort for the sails and this tends to push the bow down another cm or two upwind and even more downwind.

Although modern designs float with the bow clear of the water, when sailing with a bit of pressure the bow is ideally just kissing the surface giving you the full immersed length you are looking for. An immersed bow will also compromise the handling upwind as tacking will be sluggish.

Another effect, which could just be my imagination  is the effect on the bow wave. With the bow in the water the water climbs up the hull quite noticeably on the weather side so that you have this extra mass of water in contact with the hull, which requires energy to be pushed out the way and adds drag from the extra wetted surface area. The raised bow stops this from happening although its still noticeable with a fine rounded bow. The new broader flatter forward sections of the Venti and K2 keep this effect to a minimum.

Although buoyancy up front helps keep the bow up downwind I don't think it has as much effect as people imagine. The 'secret' of the more modern designs is to take a leaf from the Widget and move more volume behind the keel. This allows the keel to be further aft and also gives you a very 'light' bow.

If you sail the boat and find it not quite right, rather than immediately scrapping the hull, experiment first by simply cutting the front third of the hull below the waterline and replacing it with a more flat section and get the bow clear of the water surface. Something like the attached file. Then add balsa to add volume at about the 70% (of hull length) position and move as much weight in the boat further aft if possible. Brad's development process for the Britpop involved multiple iterations of earlier designs with volume being added to existing hulls to find the design he wanted.

Best of luck

Craig

 

Edited February 15, 20233 yr by Craig Richards

Hi Craig, Many thanks for your post and thoughts. I appreciate it because I'd really like to see more of this type of discussion on the forum. There's a lot of knowledge and experience out there and the forum is a great opportunity to share that.

Is the photo you showed your latest boat? It looks fantastic and the finish is excellent. If you have time it would be great to see photos of your various builds and if possible a few thoughts on how and why you modified each successive boat and whether or not you thought the modifications were successful.

There are a lot of different designs at my local club and it seems that as long as it's a metre long, pointy at both ends and displaces no less than 4kg, it gonna work ok! I've figured out that hull design, though important, is only a small part of what makes a successful IOM. The rig set-up makes a massive difference and of course a good skipper, who can adjust the boat (and himself) for the conditions of the day probably has the biggest impact on speed.

I bought a Widget (early flat-deck design) as my first boat just under a year ago. I probably didn't give it enough time, but I became frustrated at how easily it would 'go down the mine' in gusty conditions when other boats were not. I wonder now, whether this trait was due to the flat-deck design having the rig set too high in the boat relative to similar boats with a 'vang well’, but most likely it was my lack of experience in setting the boat up properly. I bought a Lintel late last summer and have been really impressed with it's heavy wind performance against some pretty decent club competiton. My wife bought an Italiko from an elderly club member who was giving up radio yachting. Like the Lintel, this boat doesn't have the up-to-date lines of a modern narrow design, but in light to moderate conditions the Italiko has a very decent performance.

I think you’re right about the risks of the bow design on my new build, but as you say the boat can easily be modified after it's built - and it's not such a big deal to make another hull if I need to! For me, this is an opportunity to indulge my interest in naval architecture and have a bit of fun. Your observations on hull design are really interesting and I'm looking forward to learning more about this in relation to IOMs as my experience progresses.

I've been away for a few weeks and have made no progress at all since posting the photos. My next step is to buy some resin and cloth to get on to the next stage of the process. I can't wait to see it on the water and continue the learning process!

I will put something together about my different boats in the near future, but even though I come from a engineering background I have abandoned the very scientific approach to boat design. The first boats I build from a new male plug are really ideas stolen from what seems to be fast. The plug is an average shape, but then gets auto filler added and sanded off until I have added a few personal touches, but really these can only be a few mm here or there different from the current top designs.

The real test is then to take it sailing and find the weak points. I feel my first boats never have enough buoyancy and I always end up adding more filler to the plug for each subsequent hull. I try to aim for a maximum waterline beam of about 150mm and a canoe rocker of about 56mm. The volume distribution curve should peak at about the 66% mark and the prismatic coefficient should be as high as possible (volume in the ends). The boats when floating with the stern and  bow just touching probably displace about 4.2 kg. I use Robot fins. The back of the mast should be about 12-14mm in front of the fin and the fin has a 5-10mm sweep back from the vertical measured at the bottom. 

I am not sure if there can be any more design breakthroughs as the Britpop has not really been improved on an is still possibly the best all round boat available after more than 10 years. That being said we thought the same in paragliders when we were gliding at a L/D of 8 and the latest are over 14!

Brad is currently sailing a TS2 and winning even in the light, so perhaps there could be a surprise with wide skiff type boats again.

If I am stupid enough to start another design process then I would probably try the very narrow route with about 135mm on the waterline and shapes tending towards the last IACC non-foiling boats. They got squarer and flatter over time -> https://www.sail-world.com/Australia/The-AC-Finalists-Arms-Race-who-has-the-edge/-34184?source=google

 

Or something really silly like this -> https://thomastison.com/scow-hulls-part-1-the-pros/

 

Edited February 15, 20233 yr by Craig Richards