Building Methods

Gents i know this topic has come up before but i would like to know what your ideas are at present.

What build method do you prefer and why?
This is for a cruising SAIL boat approx. 8 m or 27 ft

Skin on frame OR stich and glue in a basket mould
for reference i enclose a copy of the K800 and the Bateau Vagabond 26

i personally wont build skin on frame because it is simply too much work
and i am not even sure if it is lighter, however it would be nice to hear from guys that have done it or the guys in the trade


http://www.bateau.com/studyplans/VG26_study.htm?prod=VG26#building

thanks

 

Thanks Rick

Just for everybody else

I am a Bateau supporter, and i think that their plans and designs are excellent
AND they have the BEST supporting forum of the whole lot
I have been suggesting to all manner of folks to look at buying their plans

with this question

Building Methods

i am not trying to measure one designer against the other

i am looking for your opinion and EXPERIENCE of skin over frame vs. stitch and glue

when you look at the relative ease with which Mas is building his dream cat i am trying to learn why do folks still build skin over frame
Easy cats are skin over frame as well as Didi's

WHY :?:

 

I look forward to comments as you are Manie.

I am committed to panels in a basket, so that all the internals (furniture, bulheads, bunks etc) can be done before rollover.

In previous projects, rolling over to do internals last means you have to take out all the moulds, then very carefully re-align the whole hull in a "basket" before putting in the internals.

Seems a lot of work, and back to front to me.

Also, the outside dimensions of the basket method are much closer to plan if you use a basket - which matters in some boats.

 

thanks Rwatson

and the internal "furniture" provides all the stiffening required

 

Well well

the silence is deafening - rwatson we are right

out with the old in with the new

Rick thanks for the PM




bottom line is - skin over frame sucks and is for "traditionalists"

look how "easy" mas has built his beautifull dream cat in a basket mould
Oram rulezzzz

my microcruiser basket will be up in 2 weeks

 

Manie - since we are in the righteous majority, would you like to try a little experiment for me ?

Assuming you can weld ....

Can you make your basket from welded steel section in one big solid basket, and put rollers on it so you can rotate the whole basket left and right, for laying up the glass.

I just need to see how I should do it

 

Jeez this is so coooool

i loooove it

you and i are still gonna go places

fact is i can weld, still do little odd jobs myself, and i will most definately build my own trailer for the microcruiser.
This was the trailer for the chigger, which is still going strong !

Your pics are amazing, just very very sad that many of those factories are closed NEVER to open up again. As you know i am a very optimistic person, with my feet on the ground AND an eye on reality. The world will lose boat building skills like never before. SAD

As you know i am an epoxy man who actually doesn't like steel.
I will reveal a bit more later when i have more facts and figures, but the idea at this stage is to build a composite mast for the micro. I strongly believe that a light floating mast is a huge asset to help in turning the boat upright if rolled over completely. The mast must be filled with closed cell foam.

 

I had a dinghy (5 meter, 16 ft) with a watertight mast. Indeed this is a great help righting the boat after a capsize. Actually from all the capsizes I have done (many!!!) I have only been able to turn the thing turtle once. Luckily on Lake Garda, so plenty of depth over there, not to hit something.

It is just a bit fiddly to get the mast watertight. Careful planning and careful use of sealant is needed.

 

cold molded strip ply on frames and stringers. Light and very strong and not constricted to chine hulls only as with glue and stitch method....

 

Oooh - be veeery carefull. Foam is quite heavy, and near the top of the mast can make a little boat a bit tippy. Might be better to use an air filled something - bubblewarp?

 

I have built 9 skin-on-frame boats, and also other small boats of conventional plank and GRP. I love the skin-on-frame method for these reasons: It is very light, it uses much less materials (cost much less to build), design changes are fast and easy to execute, it assembles much faster than stitch and glue, it results in a tough and durable hull, usually only simple hand tools are required. And for me, unlike GRP, there is no need to EVER handle toxic materials.

All of the boats I have built were under 20 feet LOA (kayaks and dingys, including a 14' sloop), but I know of vessels as long as 40 ft using the method.

It is a very efficient use of materials so it is both light and less costly since less materials are used, there is not as much detail fitting of panel edges, garboard, etc. so it is much faster.

For example a SOF sea kayak would cost about $100-$200 in material cost, and about 100 hours to build (including ripping your own stringers and gunewales from larger stock). finished it would weight about 25 lbs. An equivalent sized SNG sea kayak would take about $600-700 in material costs and about 300-400 or more hours to cut, assemble and finish. And it would weigh about 35 lbs. Installing bulkheads and cargo hatches is easier on SNG, but these add weight and cost and not really normal in traditional designs (but I have installed water tight bulkheads and hatches in skin-on-frame kayaks).

The disadvantage with SOF over SNG I think is that there is somewhat less interior usable space because of the frame (but no less than conversational plank-on-frame), and you are limited in hull shapes because you can not have hollow or concave surfaces.

I do not know why anyone would not consider the construction method other than ignorance. I like the construction method so much I am considering designing a 20' sloop with a small cabin for weekend sailing trips. It would be fast and inexpensive to build, and very light for trailer and launching.

There are a number of sea kayak builders' forums you should investigate before dismissing the method. Since it is not a conventional construction method for most larger boats, you will not find a lot of people on this kind of forum that are familiar with it. No matter what method you choose, do not dismiss this construction method because of ignorance. There are many ancient examples of skin-on-frame boats in many cultures, not just Eskimos. My favorite story is of St. Brendan the Navigator, an Irish monk who apparently built a 36' skin on frame sailboat and made it to North America and back to Ireland in the 6th (?) century with 6 sailing companions. This was long before Columbus and perhaps even the vikings.

 

quite the opposite actually. Expanded closed cell Polyurethane foam only weights about 38kg per cubic meter (1000 liters) and that is a lot of foam that will give positive buoyancy of about 987kg in sea water.

An average 27ft boat as Manie mentioned will have about 145lt volume in mast and the weight of that foam will only be about 5.5kg (12lbs) and that foam will be helpful providing positive righting buoyancy where needed most when knocked over.

 

To itemize the question Manie was asking.
There are three methods in question
1) Skin on frame (hull material built over moulds and /or fastened to frames)
2) Stitch and glue (developed panels tacked then taped together over minimal female moulds)
3) Female Moulds or "basket" assembly (compound curved or full developed panels or a mixture of both in a "hollow" substantial set of moulds.

That doesnt make sense to me. Stitch and glue ends up being the same skin materials, LESS the temporary moulds and framing material.

because, as you state later
"The disadvantage with SOF over SNG I think is that there is somewhat less interior usable space because of the frame "

The material list for the two types of hulls would be identical but for the retained frame.

The time taken to build in a female mould system or stitch and glue is significantly less than Skin On Frame - because you don't have to remove the internal moulds to install furniture and fittings. The furniture and fittings *are* the internal moulds.

The other big time waster in building say a canoe/kayak on skin on frame, (especially stripped plank construction), is the painfull cleaning up of the hull interior after hull turning. It is far far easier to fair and smooth a convex (outer hull surface) than a concave (inner hull surface).

Nor do you have to create a temporary suporting structure to keep the hull fair on SOG construction, (after removing internal temporary moulds), while you complete the interior.

You may be keen and experienced in SOG construction, but it doesnt sound like you have had a chance to try the alternatives. You might be surprised.

 

I think it depends in part on the actual design.




This is really derived from plywood on / stringers on / frame .

That boat could be built stitch and glue I guess , but the prefab flat panel construction used here looks faster to me.
I would pre finish the interior of those panels while flat on the bench ,
except the glue lines .



I would love to see a catamaran built that way .

I like stitch and glue guys , it gives nice clean interiors , but all that sanding in tight spots ....yuk !









Bolger box boat construction....nothing much easier ..( not all can live with the looks )



I think glued lapstrake plywood is a real alternative to strip planked construction.

Would love to see a cruising cat built that way .It could look real nice.

 

Why not foam the near the ends only so as to keep weight down?