Tammie Norrie by Iain Oughtred in foam?

Hi all,

I recently came across these station moulds on Craigslist for a Tammie Norrie by Iain Oughtred - designed for a wood build. I was wanting to practice my composite skills and thought I could use these stations to do a foam strip plank boat in Divinycell. Possible?

 

Those are for the glued lapstrake build, you need to buy the plans (and the licence) for the strip or cold molded version and modify the stations accordingly. Tammie Norrie https://www.woodenboat.com/boat-plans-kits/tammie-norrie
Use vertically arranged wide foam pieces and thermoform them to shape.

 

Why not horizontally arranged foam pieces like this?

 

More work, more waste.

 

Are you able to explain to me why that is? This method of foam construction is very common. Perhaps vertically planked over slats may be better (for reasons I don't yet understand), however given the above stations already exist, I'd be interested to understand why having a whole new set of stations manufactured would make a significant difference over making these existing ones work.

 

Those stations are not round, they are like a series of steps. It's made that way to accommodate the flat plywood planks for glued lapstrake. In order to make them round you either cut them down or pad them up to achieve a smooth curve. Otherwise you end up with a stepped hull (multichine).
You need the plans to establish the fair curve and for the stem and transom patterns, and you need the licence to build from the desiger, otherwise it's a pirate copy (a mindfull guy would refuse to sell the stations to somebody who does not already own a set of plans).

Horizontal strip planking with foam is wasteful, you cut the foam into strips, glue them together then you need to fair the entire surface. Fairing the foam is complicated by the many gluelines wich sand differently than the foam, plus you loose thickness. With thin foam you probably will need more stations to provide support.

Vertical stripping has less gluelines, the foam is thermoformed to shape, so less fairing (only the joints need it). The battens provide more support, and it's simpler to add more battens then to add more stations. Depending on what the plans show, battens could be inlet or raised over the existing lapstrake stations instead of completley reworking the stations.

Horizontal stripping with foam is a method from before people realized foam can be safely thermoformed in place with a heat gun. It's not less good, just more work and more waste.

 

I understand what you are saying now. In theory, given your preference for vertical strips, battens could run stem to stern and potentially smooth out the shape, I suppose. I also understand I need a license and am not attempting to create a pirate copy - I need to purchase the plans for everything else, such as the sailplan, rudder design etc. The possibility of using these existing stations is just to avoid extra work in having them re-cut.

This is very helpful, thank you. I cannot for the life of me find any up to date books on this subject. I can find plenty of books on wood boat building, and even glass building (with moulds), but virtually nothing on strip planking foam - why is that? It seems the most logical composite construction method for amateurs, yet there seem to be no books on the subject.

 

Leaving aside the matter of designer's rights,the technical challenge has been described well.I don't interpret anything posted so far as expressing a preference for vertical strips and it would be a very time consuming way to cover a male mould built for the purpose.It would't be an exaggeration to say that building a comprehensive mould is about 60% of the work required to build the wooden hull.Then you start the process of applying the foam,laminating,fairing and painting before turning over and glassing the inside.It isn't less work than building the wooden original and its hard to see the appeal of all the extra work.

There was a bit of a vogue for one-off composite boats in the late 1960's/mid 1970's and there were a few books written on the topic.Since then the range of resins and foams has increased but the human input hasn't changed in as much as it still takes a lot of work and you are likely to spend a lot of time dusty and itching.For a hull with developable outer surfaces it isn't so hard to wrap the foam and one of the best approaches seems to be sewing the foam to the stringers of the mould with fishing line.It can be laminated over and then ,by crawling underneath after the outer skins have been applied,the line can be cut to free the hull.The sheets can have darts cut in them to allow a small measure of compound curvature and if needed small infills can be applied.Strip foam is really a last resort and not a first choice because you would only do it if you really had to.You can use hot melt glue to hold the foam in place,but because of the excellent insulation properties of foam,it needs to be held in place for a very long time before the glue solidifies.

As for why there are no up to date books on the topic,just cost the materials for building a suitable mould,foam,glass and resin and it isn't hard to see why not too many people have written books on the topic.If the cost wasn't enough of a deterrent,the thought of several dozen hours of fairing and priming is probably the final straw.It would be less work to build the wooden original.

 

Wanting to make a foam composite boat from these existing stations is not out of a love of foam boat building, it is merely a small practice project to use these materials, as I am planning a significantly larger build. I saw the moulds come up and thought it might be a good opportunity to make something small using the same materials and techniques as the larger build.

I'm still intrigued by the lack of books on the subject. For anyone wanting to make a one off composite boat, this is really the only way to do it. Perhaps most amateurs interested in this kind of thing do cold moulded wood instead...

 

I suggest you seek out one or more of the older books on one off foam building.Where a boat like the Tammie Norrie may need dozens of hours of fairing,a larger boat will need hundreds of hours-possibly thousands.It isn't much fun but if a builder is determined it can be done.In the heyday of amateur building of large boats,some actually got completed and a few of them were launched without a divorce.Many,many more were abandoned in boatyards along with their similarly incomplete ferro sisters.

Currently there are thousands of used boats for sale for less than the value of the hardware they hold and indeed there are tales in this country of boats being given away while still in good order.It would be less work to find a hull that suits your purposes and refit it to match your approved layout.It would also come with a lot of the hardware that is such a large component of the total cost to launch.On the other hand,I know a man who did such a refit and he said after doing it that it would have made more sense to get a part time job,even shelf stacking,and use the income from the same number of hours of work to buy the boat he really wanted.Its your time and your money,so spend it as you wish.

 

I doubt there are many customers for a new book on fiberglass boatbuilding. There are indeed new methods now accessible for the home builder, but there are few of those to use them.
Just a quick enumeration:
Vertical thermoformed foam with infusion.
Flat panel infusion on tables, chined or combined with round sections.
CNC milled EPS and PU male plugs.
Various "one time" female molds based on CNC cut stations.

My advice, tell us what your big project is and let's discuss the best approach for your hull form and finances. Then you can choose a dinghy to experiment that exact method and materials combination.

 

For foam construction you'd need to reduce the frame size by the thickness of the foam, batten and layup otherwise the hull will not be built to the plan. You could contact the designer and ask if it would work without reducing.
I'm building vertical foam over a male mold using a thermoforming oven. What these guys have said is accurate .. you're building a male mold which must be fair. Then the foam is laid on that and faired. Lay it up and fair that. It is alot of work. I've got about 2,000 drywall screws holding the main hull to the mold no way you could tie 3/4" foam down to the mold with line even after forming.
All that said I say go for it if that's what you want to do. It doesn't matter what build method you use they all have pros and cons. Foam over male/female mold allows complex shapes not possible with other methods.

 

Rumars post sums things up fairly well.

However, if the frames were free and they could be modified easily; then you could try it. Try what?

The frame distances are too far apart for raw foam. You would need to batten the entire thing. Then the battens are running the same way as the strips; not ideal; won't work honestly. Maybe if you got really crafty and fancy and lowered the ribbands to say 1.25" and ribbands were 0.75" and then you thermoformed intermediaries, but yuk.

If you were to build lapstrake; you could glass the inside of each foam panel. Then glass the rest of the hull in situ. Piece by piece. But is the lapstrake version spec'd for foam even?

Or if the frames are close enough; after ribbands or battens are added; you could thermoform vertically.

The challenge is rather significant. It should only be done for a boat you really want.

By the way, to the OP, Rumars is not preferring vertical. You are not realizing the problems and why this mould cannot be used for horizontal strip unless perhaps preglassed insides. The stations are too far apart. Supporting the foam better can only be done with ribbands which run the same way as long strips.

 

Vertical foam strips is the way to go. Stringers run longitudinally. Running the foam the other way would be a fairing nightmare.

 

I'm not entertaining this idea purely out of an attempt to save money - I'm interested in it because I've been sailing for a long time, and I have some downtime for the next few years - so there is an opportune life moment to possibly do something like this. I'm most interested in the challenge and craft of building my own vessel. I understand all the logical arguments for not doing so, but, life is full of such conundrums. Why create art or walk in the forest. Etc.

Back to boat building. I'm interested in building a composite ~37ft boat of expedition flavour, with an exceptionally minimal race-like interior and some special features, solely designed for shorthanded sailing in adventurous places. Why not steel or aluminium? I can't bare the maintenance & weight of steel, I've been there. Why not aluminium? Cost, maintenance and my inability to weld at that level (same with steel). To pay a yard (I've looked in Europe & South Africa) to weld up a hull & deck alone in aluminium is around $140k USD in aluminium.

I delved into cold moulded building, which is still a good option I think. However, I believe there's still a high level of skill involved, it's effectively wood boat building. So then comes composite building, using CNC to create the stations, as well as CNC to cut all the bulkheads and interior furniture. From my research, this appears to be the fastest method, and possibly also the method which can be learned and understood the fastest (at least when it comes to the hull & deck), assuming the naval architect is competent in understanding the builders level of skill and ensuring their part of the job is done well and with maximum simplicity.

One final hybrid method could be having a yard weld up the hull alone, delivered to my workshop to be fitted out and a composite deck put on...

These are my thoughts thus far.