Construction methods for O-1

It seems to me now that we have the speed down, (literally) O-1, can be built many different ways. As Will said if O-1 has all developable surfaces sheet stock can be used. Wood or foam core GRP can both be done without the need of any special tools. With plywood stitch-an-glue you need only a minimal of fixture. But if the hull is not developable the home builder still has many ways to go. Strip plank, cold mold, or foam core GRP, or one of many combinations of the three. Also very strong light weight hulls can be built from glued lapstrake plywood planks.

I left out steel only because lightweight steel hulls take a great deal of engineering. Aluminum would be great but requires a little more skill and good welding equipment can start to add up.

Let’s toss this around some, what do you think?

Gary

 

I vote for Form Core GRP

Your reasoning appears flawless to me, but that isn't saying much.

I agree that steel would be too heavy and welding Aluminum is too challenging for the average home builder. I think Aluminum would only be an option if it was going to be a production hull that the home-builder completed.

I don't know enough about the rest of the options to comment intelligently except that plywood seams to be out of style. I think the foam core GRP sounds much more appealing.

Cheers;
Mike Schooley

 

Well...

What I had originally thought was that the hull could be built professionally using the most appropriate method and the boat would then be made available either completed or for completion by the home builder in "Kit" or "hull only" form. - The hull could also be made available to other boatyards wishing to build "on spec" or "to order", their own version of the boat.

That way if (for example) a female mould were built - that is a major capital investment that needs to be recouped asap - by ensuring that the hull mould was being used that investment can be made to work. Building a completed boat could then be almost to order - keeping the risk and outlay down for the yard. For the designer there could be a per hull built fee, and then extra plans available for the details if the yard wanted to build a completed boat or re-sell the plans to a home builder.

This would mean as designers we have to design in as much of the interior and the interior details as possible. For example if we were to use a foam cored system we would design in the solid laminate (or aluminium or plywood cored, or pads) areas required for cleats, windlasses, heavy equipment mounts etc etc. There would be CNC files available to cut the interior furniture, - that would include the mounting points and holes for the electrical and plumbing systems, ducting and pipe mounts would be built in.

There would be provisions for all the luxuries - even if not required at time of build. - This means a good sale/resale value as a potential new owner looking at buying a new or used Option-1 would know that if they wanted to put in Air-Con or a heater it would be a quick and easy job that is already provisioned for - with mounting pads, pipe routes etc already planned and provided.

For a shipyard building on spec they get paid for the finished products - not the amount of hours invested (they of course might not think so!) so the easier and faster the boat is to build the better for them. This pre-planning also brings the benefit of a more consistent quality to the boats. - and so kudos and more business to the designer.

This kind of design I would think would need the input of naval architects, sailors/owners, builders, electrical engineers, plumbers, materials specialists, mould makers, cnc experts etc... etc....
Now where on earth would we get all those people together to help design a boat ....

Paul

 

In that case

Paul;
I think this is a brilliant approach. I especially like the way that it supports the owner builder and opens up the market to small businesses yards for completion work. I have heard of owner completed hulls before, but I am not aware of any production hulls that are completed by another yard.

If the hull is professionally fabricated then that changes the options.

Since we have already made the decision that O1 will be trailerable and weight is critical to performance and trailerability. I think that the lightest available construction technique should be used provided it is affordable.

I have read that aluminum is cost competitive with solid fiberglass construction but comparable weight to cored fiberglass (GRP). If this is true, then aluminum appears to provide both low cost and light weight.

Doing a YachtWorld search for aluminum express boats in the 26' to 32' range I get 11 (all built by Marinette Marine), while fiberglass yields 4,004. Going to NMMA facts and figures for stern drives by hull construction http://www.nmma.org/facts/boatingstats/2001/files/hullmaterial.asp shows that from 1997 to 2001 fiberglass stern drive boats sales decreased from 77,100 to 70,200 while aluminum stern drive boats increases from 1,500 to 3,900. In 2001 aluminum boats were only 5.6% of the stern drive boat market. OTOH aluminum boats showed a net gain in a shrinking market.

Please correct me if I am wrong, but I believe that the main reason that buyers preferred fiberglass over aluminum in the past was for corrosion resistance. Considering the problems that fiberglass boats are having with blisters and the new protective coatings that are available for aluminum, I think this is an unfounded concern. In addition since most trailerable boats are stored on their trailer, I think corrosion is even less of a concern.

Another consideration is construction flexibility. Paul points out the need for solid laminate areas for attach points. With welded aluminum construction bosses and brackets can be welded in as required or added at a later date. I think aluminum provides greater flexibility for customization and modifications.

It may be possible to have a common hull and multiple deck house design options. If the hull and deck house are fabricated to a common interface, it would be simply a matter of aligning the top and bottom sections and welding them together.

Unless someone sees a problem that I haven't thought of yet, my recommendation is for aluminum construction.

Cheers;
Mike Schooley

 

Aluminium does represent a good oportunity for customised boats. It allows the builder to make any number of alterations to suit individual owners at a minimal cost penalty.
However, there are three drawbacks to aluminium that immediately spring to mind. One is that it is very nosiy. Chances are that O-1 will be a hard chined vessel. Anyone who has spent a night aboard a fibreglass or plywood boat with waves lapping on the chines will know that it can make for a restless night's sleep. Multiply that noise by 2 or 3 and you will have some idea of what it would be like aboard an aluminium hulled boat.
The 2nd is that aluminium is a rather poor insulator - it conducts both heat and cold quite effectively. On a hot, sunny day, an alloy deck is rather uncomfortable underfoot and on a cold one it is just as unpleasant. Inside, condensation can be a real problem.

Thirdly, aluminium welding requires some fairly specialised equipment and high levels of skill. It really depends how much owner-builder input we want O-1 to be capable of. Remeber our all up budget of US 50K. Can we get a professionally built hull and deck, engine(s), ancillary systems for that sort of money? And if the boat is customised - one of aluminium's greatest advantages - that will drive the cost up further.

 

Sound and heat transfer can both be handled with insulation. Sealed blankets of glass batting can be installed just like on large airliners. You can buy the batting in big rolls with facing on both sides, cut the shape you want, and seal edges with tape.

I’m going to try to get a price for a hull only, in aluminum. I think it will be big hit to the budget. But a factory built GRP hull would be about the same. If the cost were the same, I would go with aluminum. Also almost any hull done in aluminum I could do in GRP over plywood. Which I can easily do myself at home. So everybody could pick the flavor they wanted. And the one they could afford
Gary

 

Aluminium does represent some challenges as far as corrosion goes. Sure, there are some newer aluminium friendly antifoulings out thereb but as O-1 is to be trailerable that is probably not the issue.
The biggest problem here is the use of dissimilar metals - and unfortunately it's the aluminum which tends to be the sacrificial part. Leave a stainless fish hook in the bilge and you run the very real risk that it could eventually result in a pinhole in your boats bottom. Similarly, anchors and chain should always be kept isolated from aluminium surfaces.

I'm not against aluminium, but there are a number of things which need to be taken into account if it is chosen. Personally, I rather like the idea of making the hull shape so that it could be built out of a number of different materials (ie developable surfaces so that the home builder could use ply or glass over foam core, or a professional yard could use aluminium or GRP) It would require more work in the design phase as I imagine that the construction details would need to vary from one material to the next, but it would certainly ensure that O-1 is versatile

 

Aluminum

To protect against dissimilar metals corrosion from misplaced metal objects, the deck and bilge should be painted.

Here is a quote from http://www.yachtfinders.net/aluminum_verses_grp.htm (presumable an unbiased source), "In terms of cost, aluminum construction is about equal to solid fiberglass construction – yet stronger, and is less costly than foam or balsa cored fiberglass construction. Therefore, as a material it can outperform fiberglass on a cost basis. In terms of weight, aluminum construction is lighter than solid fiberglass when comparing the materials on strength basis, and is about equal in weight to cored fiberglass construction. Thus, it is very competitive with advanced fiberglass laminates – yet at a substantially lower cost."

Cheers;
Mike Schooley

 

I probably didn't use very good examples in my dissimilar metals post.
What concerns me most is that there may be problems for the amateur builder when it comes to fitting out an aluminium boat. All fittings must be isolated from one another where dissimilar metals would otherwise come into contact. It's true that an electrolyte must also be present, but given the propensity for salt water to work its way into every nook and cranny, no part of the boat can be considered safe from corrosion.
So, for instance, stainless or bronze bolts need a nylon washer and need to pass through a nylon grommet or similar to avoid any contact with the aluminium. These are cretainly not insurmountable problems, but must be taken into account if the boat is to be home buildable. If five years down the track Jo Blo's nice new boat turns to dust - whether it be as a result of his own doing or not - it won't bode well for the long term reputation of O-1

 

Cost of aluminum hull

Prices for an aluminum hull range from US$13/kg in South Africa to US$30/kg and up in Europe and North America. That's about $5.90 to $13.62 per pound. This is for a bare, uninsulated and unfaired hull and includes both material and labour. When calculating the cost include only the weight of the bare shell without engines, interior, etc. Designing O-1 with developable surfaces would probably reduce the cost further by reducing the amount of labour.

Transportation as deck cargo on a ship is reasonable so having the hull built in some far away place shouldn't be a barrier. Personally, I would also add the cost of having a number of the welds tested but I would do so even if the builder was just down the road from me.

 

Re: Cost of aluminum hull

Will;

You have a good point about dissimilar metals. The home builder would need to be educated to take special precautions where dissimilar metals could come into contact with each other. The design should also try and minimize dissimilar metals as much as possible, which means using aluminum or plastic as mush as possible. I saw one aluminum boat that used aluminum nails installed with a nail gun through the aluminum ribs to attach furring strips. It was very easy and quite effective. The biggest problem was disassembling it if you made a mistake.

How does this compare to solid GRP and foam cored GRP?

Cheers;
Mike Schooley

 

Re choice of building material

Duflex should be considered for the with flat panel construction.

This can now be obtained from ATL Composites with all the panels cut and tabbed. The builder assembles the full size panels, joins them with the supplied Z joints and then knocks out the panels.

The hull can then be formed over the frames made from the same material. The joints are filled and then taped.

The advantages are:

light (the composite panels are factory made with the optimum
pressure and temperature)
shipped to anywhere in the world as a flat pack
suitable for amateur builders
less filling and faster


Standard kits for sailing multihulls using this approach have been developed by the Australian designers Fred Schionning and Tony Grainger. The approach is also used for sailing and motor multihull by designer Bob Oram. This technique should be applicable to the project.

 

Do you know of a web site where this building technique is displayed step by step?

 

Check out this one-
http://www.atlcomposites.com/pdf/DuFLEX_brochure.pdf

--------------------
Brian

 

DuFLEX brochure

The DuFLEX brochure is pretty informative (PDF 639K) http://www.atlcomposites.com/pdf/DuFLEX_brochure.pdf

Cheery;
Mike Schooley