THE DIFFERENT METHODS
"Doing it right the first time is far quicker and less expensive than having to do it again"
Many different building systems have been investigated, tried, and used for Farrier designs over the past 30 years, from basic hard chine ply construction to female molded production methods. There has also been a huge amount of feedback from hundreds of builders, both amateur and professional, on what really works, and what doesn't. It is important to take advantage of this huge knowledge and experience base, so as to avoid hundreds of hours of wasted time. The main methods include:
HARD CHINE WITH COMPOSITE PANELS: Pre-made and pre-cut composite panels are now available for hard chine construction, and these are being used by some designers, while low cost and quick building are commonly claimed. However, only limited hull shapes are possible, and once experienced, it soon becomes obvious that such panels not a fast or a cheap way to build a boat. One range of such kit panel boats in Australia was even withdrawn from sale after many complaints that construction was taking much longer than the claims.
The problems include panels that are very expensive, plus many panels have pinholes requiring resin coating or filling. The extensive taping required uses up enormous amounts of time and resin, adding considerable weight compared to a clean round bilge hull. The tape also sits proud and is a lot of work to fair, particularly for inexperienced builders. The frequent claims that such hulls do not require fairing is simply untrue. If any exterior taping is required over the many join seams then one will have a lot of fairing to do - I've been there - done that. Kit panel hard chine hulls are also less attractive, with a reduced load carrying capacity, and a much lower resale value.
Building the hulls can actually be the easiest and quickest part of a boat, most time actually going into fitting internal bulkheads/panels, and then assembly and fitout. Most of the internal bulkheads are already fitted in vertical stripped hulls when removed from the form frames, whereas they have to be done later with many pre-made panel systems. This can be very awkward, and further increases building time.
The methods that years of practical experience have now shown to be the best choice are:
An F-9A float being strip planked - a much better system than sheet ply, but there are many strips to carefully fit and join
Strip planking gives a light and stiff hull with no need for complex internal stringers or framing. It is easy to fair, and strips can be from a number of different materials, western red cedar the most common, it being very light and durable.
A wood stripped F-25 main hull, still in the female form frames, with interior glassed and the bulkheads
FORE AND AFT FOAM STRIP PLANKING: The weight of wood stripped boats however can be disappointing, and to improve this, fore and aft foam stripping was tried in the early nineties. The lighter and more durable foam is not stiff enough to lay fair on its own so the strips were preglassed on one side with a fore and aft unidirectional. A vertical unidirectional was then laid across the strips, to complete the laminate. However, it was time consuming to pre-glass and cut up the strips, while the finished stripped hull was difficult to fair, and it took a lot of fairing putty or extensive sanding to blend in all the little flats and any raised 'hard' fiberglass edges. Laminating vertical unidirectional on a multi-curved hull, particularly inside, also tends to be slow and tiresome.
Fore and aft foam stripping - lighter, and a good advance over wood stripping, but there are still all those
To improve matters, frame spacing was reduced, so that the foam strips did not need to be pre-glassed. This was better, and the F-36 was designed to be built this way with unglassed fore and aft foam strips. But the basic problem of all those long narrow strips that had to be made/joined, handled and fitted, whether foam or wood, remained, plus there were many more form frames to make.
There had to be a better way.......!
FOAM VERTICAL STRIP PLANKING.... the very latest procedure, and the next major step.
It came about from using foam fore and aft strips, which gets very tiresome, there being so many strips to cut, edge glue and fit. It was suddenly realized that much wider and shorter strips could be used simply by turning them around and running them vertically. The more ductile foam core makes such a vertical orientation possible, and the strips can be held in place and very fair by temporary fore and aft battens. The vertical foam strips (or panels in some areas) are considerably easier to handle and fit, and the female form frame mold system also makes it very simple to hold them in place, as access is easy from both sides. Not only were the hulls lighter, but they were fairer, with significantly fewer joins, easier to laminate, and much quicker to build.
Fore and aft planking requires multiple glue joins,
But better still, one also does not have to buy thicker foam in order to allow for the extensive fairing required with fore and aft strips to take out all the little flats, as is recommended by some promoters of fore and aft stripping methods.
Henny van Oortmarssen's F-39 float being vertically foam stripped. The small pieces of wood are
The battens do take a little longer to setup, but no longer than say the first 10 to 15% of the numerous strips required for the more traditional fore and aft wood stripping. Fewer more widely spaced form frames can also be used. The relatively few battens are then just quickly laid in wherever they want to go, or as needed, and from then on the much fewer/wider vertical strips are considerably quicker and easier to apply.
An F-41 outer hull half being built with vertical foam strips. The large foam deck and cabin side panels are also being initially held in place by temporary screws and ply pieces from inner side until join glue sets. Quick and easy. Screws are then added from back for laminating, the original screws being removed. There are more screws this way but overall it can work out faster and easier than just using screws from behind
There is actually around 3000 less lineal feet (915m) of glue join line required with a foam vertical stripped 41 footer, and every foot of these joins has to be carefully fitted and glued. It doesn't take much math to work out the considerable extra work and weight with over 1/2 mile (1 km) more of glue line to be done.
F-9A foamed hull, with the screws on the outside to hold foam in place being visible
An F-33 main hull, fully foamed, laminated, and with bulkheads starting to be fitted.
Once all foam is in place, the inside of the hull is laminated, using either epoxy or polyester/vinylester resins as desired (epoxy only with wood). Bulkheads are then made from full size patterns and fitted, which is very easy to do at this stage, eliminating difficult fitting later. Hull is then removed for exterior glassing once resin has cured. Form frames are then simply reversed, and battens re-positioned to build the other hull half.
Completed float half, with bulkheads being fitted. Black material is peel ply - color makes
F-33 main hull with all bulkheads now fitted and just prior to removing hull from form frames.
Advantages over the old male mold method of foam core construction include all the holding screws being on the outside for access (no awkward crawling inside a mold) and stiffening bulkheads are already there when hull is removed from the form frames. This makes the partly finished hull rigid and easier to handle, a major problem with the traditional foam system being the hard to handle ‘floppy’ hulls that are produced.
A completed F-39 float hull being lifted out of form frames
The vertical foam stripping system has now been used on many F-Series designs with excellent results, and has become the recommended, and designer's preferred method.
Dean Snow's F-9R ready for final laminate and finishing. Note how wide the vertical foam strips are
The final word has to be from a builder, and probably the best qualified is Australia's Dean Snow, from Geelong, Victoria, who has built three Farrier designs (F-9A, F-82R and F-9R), and is one of the few to have practical experience with both types of stripping. He used fore and aft wood stripping for the F-9A and then vertical foam stripping for the F-82R and F-9R. Dean considers vertical foam stripping to be much faster and says "A float half in wood stripping used to take days with all the fiddly strips, lots of messy glue, and edge pins. With foam it's a fast moving, no mess, low stress job (on both form frames and builder) - a foam float half ready to glass takes less than a day."
A fore and aft cedar strip planked F-25A - still a good way to build a boat,
F-41 hull halves having been joined, with outer laminate of port hull inner side being vacuum bagged.
Infusion is now becoming more popular in general and I first used this back in 1991, with a view to replace the vacuum bagging system we were using at Corsair Marine. However the infusion process proved to be slower, compared to our bagging system, and the finished product was actually heavier, so we did not persevere with it. The heaviest F-31 ever built was resin infused in fact.
The main reason for the weight increase was the relatively open cell foams in use at that time, which is now being rectified by the foam manufacturers. There is still a weight increase, but much less significant.
The infusion time was also slower than the vacuum bagging techniques we had developed for the F-27, but the cleanliness, lower fume level, and fewer hands required to setup (can even be done single-handed) has definite advantages, particularly with items that have very little core (such as the beams) and the F-32 beams are currently being resin infused.
F-32 beam being infused
However, I still do not recommend infusion for 'one off' boats, as the learning curve is long, and one could lose a whole hull if not done right. Setting infusion up will also take much longer than just getting in there and laminating 'one off' hulls manually. Plus hulls that have been hand laminated well are likely to end up lighter.
But in series production, there can be significant time and emission advantages for a boat manufacturer, once set up. If more interested in the process, rather than getting the boat built in the quickest possible time, or the higher level of cleanliness appeals, then by all means give infusion a try - but be warned that it will take considerably longer, and there are some risks.
The only area where I would consider using infusion with a 'one off' boat would be flat panels bagged on a table, as it is a cleaner process, but this again will take longer to setup due to the learning curve.
Many however do not share by my caution on resin infusing, and some good arguments for infusing are on Henny van Oortmarssen's web site: