Any information on sectional or bolt together boats

observations drawn from lightweight rowing shells:

each end has a frame/bukhead which is an inch thick piece of plywood with
stringers partly recessed into it. The frame/bulkhead is closed (like a
transom) to a little way above the waterline, and is open above that point
(weight savings).
the bolts pass through a close fitting hole and tighten up against large
washers. they do not have any obvious seals on them, but I've never had
problems of water ingress in a newer boat (some in older ones). Bolts are
M8, and there are at least 10 (I think) on a four, more on an eight (larger
boat). I would always advise greasing these bolts not only because it will
prevent sticking nuts, decrease bolt together/apart time, but also because
it will increase the longevity of the bolts.

On a recreational boat, I think the inch thick plywood ends to the halves is
a good place to start from. I might consider running a small (i.e. thin)
rubber seal around the edge of one half, such that when bolted together, it
prevents any water ingress, but this could reduce the stiffness of the hull.
I personally wouldn't bother, just make sure that the ends are solid to
above the waterline. You may like to back the washers used with rubber
which when under pressure will squeeze out slightly to form a seal around
the bolts, but as I say, on well selected washers, I have had no problems
with water ingress.

I personally think that the secret to the success of these sectional boats
is that they are bolted together *firmly* (don't get too keen, you don't
want to crush the plywood, just get it nice and firm) and thus act as one
unit, the two halves do not work relative to each other. With this in mind,
I would not want to make the two halves too smooth, a little friction
between them will help.

Many designs use hinges, I would be tempted to reinforce each hinge with a
bolt. A bolt would be in tension under most loads, while the hinge would be
in shear, I'd trust the bolt over the hinge.

Other than that, designs from a reputable designer are always a good way to
go for what you don't know. If you want to convert a design, make sure
you've seen a number of different designs and understand how they work, so
that you can see how the adaption can be made.

I hope some or all of this was helpful.

Al
 >> Stay informed about: Any information on sectional or bolt together boats 

Have you tried a google search on "nesting dinghy"? `cos I did and got
around 1500 hits- not all relevant I`m sure .
Bob
"k.t.h" skrev i en meddelelse

 > Hi, due to space and access dificulties I'm trying to find information on
 > building a sectional, bolt together, boat.
 >
 >
 >> Stay informed about: Any information on sectional or bolt together boats 

I tried a few searches but didn't try 'nested dinghy', the problem seemed to
be thinking what to search for, I'll try that thanks.

Kevin.

"Robert Larder" wrote in message

 > Have you tried a google search on "nesting dinghy"? `cos I did and got
 > around 1500 hits- not all relevant I`m sure .
 > Bob


  > > Hi, due to space and access dificulties I'm trying to find information
on
  > > building a sectional, bolt together, boat.
  > >
  > >
 >
 >


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 >> Stay informed about: Any information on sectional or bolt together boats 

I'll think my way through what you've told me and I'm sure I'll then know
much more about where I'm going with this thing.

Al many thanks.

Kevin.


"Al" wrote in message

 > observations drawn from lightweight rowing shells:
 >
 > each end has a frame/bukhead which is an inch thick piece of plywood with
 > stringers partly recessed into it. The frame/bulkhead is closed (like a
 > transom) to a little way above the waterline, and is open above that point
 > (weight savings).
 > the bolts pass through a close fitting hole and tighten up against large
 > washers. they do not have any obvious seals on them, but I've never had
 > problems of water ingress in a newer boat (some in older ones). Bolts are
 > M8, and there are at least 10 (I think) on a four, more on an eight
(larger
 > boat). I would always advise greasing these bolts not only because it
will
 > prevent sticking nuts, decrease bolt together/apart time, but also because
 > it will increase the longevity of the bolts.
 >
 > On a recreational boat, I think the inch thick plywood ends to the halves
is
 > a good place to start from. I might consider running a small (i.e. thin)
 > rubber seal around the edge of one half, such that when bolted together,
it
 > prevents any water ingress, but this could reduce the stiffness of the
hull.
 > I personally wouldn't bother, just make sure that the ends are solid to
 > above the waterline. You may like to back the washers used with rubber
 > which when under pressure will squeeze out slightly to form a seal around
 > the bolts, but as I say, on well selected washers, I have had no problems
 > with water ingress.
 >
 > I personally think that the secret to the success of these sectional boats
 > is that they are bolted together *firmly* (don't get too keen, you don't
 > want to crush the plywood, just get it nice and firm) and thus act as one
 > unit, the two halves do not work relative to each other. With this in
mind,
 > I would not want to make the two halves too smooth, a little friction
 > between them will help.
 >
 > Many designs use hinges, I would be tempted to reinforce each hinge with a
 > bolt. A bolt would be in tension under most loads, while the hinge would
be
 > in shear, I'd trust the bolt over the hinge.
 >
 > Other than that, designs from a reputable designer are always a good way
to
 > go for what you don't know. If you want to convert a design, make sure
 > you've seen a number of different designs and understand how they work, so
 > that you can see how the adaption can be made.
 >
 > I hope some or all of this was helpful.
 >
 > Al
 >
 >


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 >> Stay informed about: Any information on sectional or bolt together boats 

The reference I found was for Danny Greene's Chameleon. I remembered
Danny Greene but not the name of the boat. Good place to start might be
boating mas, looking on the plans section for Danny Greene.

Danny Greene, Offshore Design Ltd.,
PO Box GE 213,
St. George's, Bermuda, GE BX

And I'm sure that cunstruction of one of them was written up, perhaps in
Wooden Boat?, several years ago.

Dave Cannell
--
 >> Stay informed about: Any information on sectional or bolt together boats 

This concept is used by the US Army they call it a pontoon boat. It is used
to aid in the assembly of pontoon bridges. The concept is valid, but the
material is not. I would suggest that aluminum would be far better for that
application.
Steve

"k.t.h" wrote in message

 > Hi, due to space and access dificulties I'm trying to find information on
 > building a sectional, bolt together, boat.
 >
 > For a number of reasons includig cost I'm looking to draw my own plans
but
 > I think I once saw mention of some plans for a dinghy that could be stored
 > on deck, one half inside the other, though it, understandably for
comercial
 > site, didn't give information on how it was done.
 >
 > My thinking is to build the thing in two sections with watertight
bulkheads
 > at the ends to be joined, then to assemble, pass bolts through the two
 > bulkheads, with perhaps rubber washers sandwiched on the bolts between the
 > bulkheads to stem the ingress of water.
 >
 > My main worry is the stress loads and as I'm not a structural engineer I'm
 > unsure what they are likely to be.
 >
 > I'm thinking of something like a 14 foot dinghy built in two sections but
an
 > open canoe or anything is ok, I don't intend use in heavy seas but being
 > confident it will hold together in a bit of chop would be nice. Primary
use
 > is with small 2-3hp outboard but easy rowing would be nice.
 >
 > I'm a bit worried I'll go to much on the stress thing and end up with two
 > sections too heavy to manage, so as a reasonably lightweight attempt
anyone
 > able to say whether 3/4 inch plywood bulkheads with a 2x2 frame epoxied
 > round its inside edge and to the sides and bottom of boat would be
 > sufficient, then to assemble bolt through this into the same thing on the
 > other section???
 >
 > Or is the idea crap?
 >
 > Kevin.
 >
 >
 >
 >
 >
 >
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 >
 >
 >> Stay informed about: Any information on sectional or bolt together boats 

 > I'll think my way through what you've told me and I'm sure I'll then know
 > much more about where I'm going with this thing.
 >
 > Al many thanks.

sorry, my mind doesn't do straight lines. If all that lot turns up any
questions apart from ones of a "what is he on?" nature, drop me an email or
something.

Al
 >> Stay informed about: Any information on sectional or bolt together boats 

Al I think the 1 inch ply bulheads and bolts seems maybe ok but I'm worried
about the bulkhead pulling away from the 1/4 inch side/bottom planking
caused by flexing if if it's a bit choppy or hitting bow waves.

Wonder what your thoughts are on this, do you think there would be benefit
in perhaps bonding a strip of ply to the sides and bottom plywood planking
next to the bulkhead, then run a generous fillet of epoxy/bonding along the
joint or maybe bond a large radius quarter timber along the joint.

Al I'm wondering are your rowing shells used only on flat water, a rowing
club local to me train and race out in the bay, they go out when it's quite
choppy and often seeming to disappear in the swell, I don't think their
boats are bolted together, next time I get chance I'll look to check.

From what little I turned up on the internet, the few pictures I found of
nested dinghies in ply didn't, from what I could see, appear to have beefed
up the area around the bulkheads/joints very much though it was difficult to
tell.

I've not been able to turn up much on the subject, I'd be grateful if you
could add anything to that which you wrote previously, or indeed if anyone
else can.

many thanks

Kevin


"Al" wrote in message

  > > I'll think my way through what you've told me and I'm sure I'll then
know
  > > much more about where I'm going with this thing.
  > >
  > > Al many thanks.
 >
 > sorry, my mind doesn't do straight lines. If all that lot turns up any
 > questions apart from ones of a "what is he on?" nature, drop me an email
or
 > something.
 >
 > Al
 >
 >


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 >> Stay informed about: Any information on sectional or bolt together boats 

On Sun, 22 Jun 2003 07:25:33 -0400, Glenn Ashmore
wrote:

 >If you are thinking about designing your own, the best place to start is
 >Dave Gerr's "Nature of Boats". That will give you a foundation on
 >stability and the basics of how boats perform. The book also includes a
 >useable set of plans for an 11' nesting dinghy that you could use as a
 >starting point.
 >
You could also try the nesting dinghy at
<a rel="nofollow" style='text-decoration: none;' href="http://www.bateau.com/plans/small/FB11.php3." target="_blank">http://www.bateau.com/plans/small/FB11.php3.</a> I believe our own Evan
Gatehouse was the designer. (Of course, I could be wrong, too.)

- Rick Tyler
 >> Stay informed about: Any information on sectional or bolt together boats 

"Rick Tyler" wrote in message


 > You could also try the nesting dinghy at
 > <a rel="nofollow" style='text-decoration: none;' href="http://www.bateau.com/plans/small/FB11.php3." target="_blank">http://www.bateau.com/plans/small/FB11.php3.</a> I believe our own Evan
 > Gatehouse was the designer. (Of course, I could be wrong, too.)
 >
 > - Rick Tyler

Yup, that's one of mine. The bulkhead is 1/4" ply, framing is 1"x2", and 4
x 5/16" bolts are used. Rubber washers under fender washers on both sides
(inside) of the sections. The proposed section sounds plenty strong...

--
Evan Gatehouse

you'll have to rewrite my email address to get to me
ceilydh AT 3web dot net
(fools the spammers)
 >> Stay informed about: Any information on sectional or bolt together boats 

 > Al I think the 1 inch ply bulheads and bolts seems maybe ok but I'm
worried
 > about the bulkhead pulling away from the 1/4 inch side/bottom planking
 > caused by flexing if if it's a bit choppy or hitting bow waves.

bear in mind that many of the wooden shells I've smashed up (seperate job)
were skinned in 1/8" or less. As I look at them, the longitudinals are let
into the plywood partly, and the skin runs over the outiside of the
bulkhead. Now, a lot of the twisting stresses in these boats are handled by
other framing, but even with the framing removed it took more than one blow
with a hatchet to break open this bulkhead, and even then, the bulkhead
smashed but DID NOT DELAMINATE from the skin. This leads me to deduce that
it was very well bonded (epoxy/resorcinol job).

I would certainly reinforce a bulkhead in my boat with fillets, and tape
both sides. the 1/4" ply will obviously be significantly superior to the
1/8", but I would still pay attention to framing. You can dissipate a lot
of the flexing loads elsewhere if you frame carefully. In these shells,
there are a number of triagular frames for the riggers which act between a
"keel" longitudinal, and two "sheerclamp" longitudinals. I think that
something similar could be replicated by intelligent use of seating. Use
seating over these V frames so that you don't "lose" space in the boat, or
gain tripping hazards. Just a thought.

However, remember that these boats are up to 40 foot, even 50 foot in an
eight, you're maybe talking about something that will have eight to ten foot
sections? In this case, what you're asking is whether an eight foot dinghy
will resist twisting loads, if properly built with decent scantlings, of
course it will. yes, the length of two sections instead of one will lead to
a little more stress, but from what I have seen, if those two sections are
bolted together, you aren't talking about stress at the bulkhead (2 inches
of plywood mechanically fastened is not weak), and 1/4" ply over that
(suitable reinforced as previously mentioned) isn't going anywhere. I
personally feel that if you are building a sixteen footer (for example),
build the scantlings for a 16 footer, and fix the two transoms (as that is
what they are) or bulkheads that occur at the join as well is not better
than you would an ordinary transom.

I've been out in fours (around 35 to 40 foot) in up to a foot of chop, but
remember, these are extremely low freeboard, extremely lightweight shells.
I would take a shell out in more than that, were it not near impossible to
row due to the riggers constantly plowing through waves.

I think the best recommendation I can make is to find a popular split boat
similar to what you want, and look at the plans for it, this will give you a
feel for the kind of scantlings you are after.

I appreciate that the above has increased the murkiness. A well fastened 1"
bulkhead is going to take one hell of a lot of abuse. Just fix it well,
back it as you would in any other boat with knees over the main
longitudinals, use fillets and tape for strength, and remember, you're just
bolting two 8 foot dinghies together.

Al
 >> Stay informed about: Any information on sectional or bolt together boats 

 > Yup, that's one of mine. The bulkhead is 1/4" ply, framing is 1"x2", and
4
 > x 5/16" bolts are used. Rubber washers under fender washers on both sides
 > (inside) of the sections. The proposed section sounds plenty strong...

k.t.h., take this guy's advice over mine. He knows what he's talking about,
I'm just reporting observations.

Al
 >> Stay informed about: Any information on sectional or bolt together boats 

I'd like to thank everybody who's contributed replies to my questions, they
are very much appreciated.

I'll work my way through the information and if I manage to successfully
build something I'll try stick the results on a web page, or even if it's
unsuccessful!

Again many thanks

Kevin

"k.t.h" wrote in message

 > Hi, due to space and access dificulties I'm trying to find information on
 > building a sectional, bolt together, boat.
 >
 > For a number of reasons includig cost I'm looking to draw my own plans
but
 > I think I once saw mention of some plans for a dinghy that could be stored
 > on deck, one half inside the other, though it, understandably for
comercial
 > site, didn't give information on how it was done.
 >
 > My thinking is to build the thing in two sections with watertight
bulkheads
 > at the ends to be joined, then to assemble, pass bolts through the two
 > bulkheads, with perhaps rubber washers sandwiched on the bolts between the
 > bulkheads to stem the ingress of water.
 >
 > My main worry is the stress loads and as I'm not a structural engineer I'm
 > unsure what they are likely to be.
 >
 > I'm thinking of something like a 14 foot dinghy built in two sections but
an
 > open canoe or anything is ok, I don't intend use in heavy seas but being
 > confident it will hold together in a bit of chop would be nice. Primary
use
 > is with small 2-3hp outboard but easy rowing would be nice.
 >
 > I'm a bit worried I'll go to much on the stress thing and end up with two
 > sections too heavy to manage, so as a reasonably lightweight attempt
anyone
 > able to say whether 3/4 inch plywood bulkheads with a 2x2 frame epoxied
 > round its inside edge and to the sides and bottom of boat would be
 > sufficient, then to assemble bolt through this into the same thing on the
 > other section???
 >
 > Or is the idea crap?
 >
 > Kevin.
 >
 >
 >
 >
 >
 >
 > ---
 >
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 >
 >


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 >> Stay informed about: Any information on sectional or bolt together boats