Building Paterson 8 in Dubai

[Banshee Ambulance]

JimC, I'm not sure I agree with you on this one. I would say that the no foredeck option would give you a stiffer boat regardless of material, if the crew deck is joined at the gunnels. This effectively turns the whole boat into a box girder. The lower you put the false floor you are lowering the stiffness of the boat by some function of x^3 where x=the distance between load beaing pannels.
With the older boats like the dogs this was corrected by adding side tanks (effectively another box down each side) and a foredeck. Banshee Ambulance will be an interesting one as it has no foredeck and a low flase floor.
I like the idea of measuring deflection under rig load. I think Frank B did this with some of his 18 footers. I will have a look in the book and find out what the delfections were.   

[roland_trim]

Off topic, but whilst I remember:
I need to publish a book. That way after a few years people will forget I speak nonsense and believe what I wrote - "coz it's in a book"

Back on Topic:
I can see where youare comming from Jim, I wonder if the advent of the additional frame that forms the rack supports changes this slightly. These provide a very stiff compression path accross the boat at the mast? In this model the corner between deck/hull now becomes the compression path, with foredeck/crewdeck stabilising rather than actually taking the load. the shear path back to the stump is still a bit sketchy though, but that is why I'd still add a carbon  front triangle (of bulkheads).

[phil_kirk]

I believe the initial idea was to put a foredeck on a carbon boat.

RS405 you are quite right that a higher floor will increase the depth of the hull girder and restore stiffness.  Some of the 91 rules boats had quite low floors and needed the fore deck.

If you made an Elway 5 or banshee out of glass the glass boat would be less stiff than a carbon boat.  I suppose where we are going is is that stiff enough.  if not, the glass boat could be strengthened by adding a couple of layers of carbon along the hull at the gunnels and where the bulkheads sit.  This strengthens up the main load paths without adding lots of weight.  This effectively adds a stiffer composite space frame within a composite monocoque design.

if one were to try and save cost on the build of a hull, glass shells reinforced with carbon in this way and fitted with carbon bulkheads might provide a stiff and low weight boat.

[Banshee Ambulance]

I would build in glass with carbon bulkheads. I think that will be more than stiff enough. Especially as the rig loads will go through the racks which would be carbon.

[ross_burkin]

Stu and I are building in glass with carbon bulkheads. I recon it will be fine.

[roland_trim]

For my tuppence I can see what Jim is saying and yes there is a pit that you could get into, but I think the current crop of boats differ as their space frames avoid this (i.e. none of the recent boats are actually monocoque). When you have the schematic for your structure I'm sure Jim'll* be happy to give it a once over, as will all your friends on here (none of us want to see folding boat).


*Please do not take offence, I've been wanting to type that for years 

[doug1720]

Hi,
I have got back from 3 weeks travel and thanks for all the posts and ideas.

I have managed to get the hull off the mould this morning .  Not perfect but I am pleased with the result Pic attached.

I know a long way to go, but a milestone!

I am going to read up all the info on the thread and put down some thoughts.

Thanks again.

Doug
 

[john_hamilton]

looks awesome doug

[doug1720]

Planning to weigh hull in the next couple of days.  Any ideas how much she should weigh at this stage?

Thanks,

Doug

[JimC]

JimC, I'm not sure I agree with you on this one. I would say that the no foredeck option would give you a stiffer boat regardless of material, if the crew deck is joined at the gunnels.

That's a concave foredeck though isn't it [grin]. That's obviously going to work far better than a low tank and unsupported gunwhales. Probably still worth taking numbers.
Actually it might be an interesting exercise for a windless day at a Champs - find out how much the boats move under rig tension and see if it correlates to various options in internal construction.


Congrats on finishing stage 1 Doug: the next stage of internal framing and decking is probaly the easy bit, but its then followed by the really time cosuming stage of doing all the fiddly stuff!

[Banshee Ambulance]

Yes JimC, just a bit of terminology really. I think we can agree at bigger box, stiffer section.

Doug: Well done on getting this far and in such good time. Some of us sit about day dreaming and dont get on with it! Have you thought about what sort of deck you are going for? By looking at the amount of freeboard it looks like you might be going for the E5 style deck.

 My boat will be a bit like this but I'm doing things a bit differrently.

 Photo credit: NZ 12ft CA

[daryl_wilkinson]

Hey man... that's one wicked sled! Congrats!

[daryl_wilkinson]

Yes JimC, just a bit of terminology really. I think we can agree at bigger box, stiffer section.

Well done on getting this far. Have you thought about what sort of deck you are going for? My boat will be a bit like this but I'm doing things a bit differrently.

 Photo credit: NZ 12ft CA

love the Belay device trap hooks on the NZ boat . I doubt that they last long in salt water though.

[doug1720]

Hi,
In terms of deck I am also wondering about volume of air in the hull.  I think with a full gunwhale to gunwhale crew deck there will be too much bouyancy...boat will turn turtle quickly and the daggerboard will be very high out of the water.

Has any work been done or thoughts on this observation?

Because of this I am considering a crew deck that will be short of the gunwhales and so needing to step down into the boat when tacking, etc.  From what I can see in terms of photos this is more like Banshee Ambulance.

Stiffen up the gunwhales with a few layers of carbon.

Thoughts appreciated as I want to get on and shape the bulkheads and some of this will depend on decisions made

Doug

[Will_Lee]

Yes - the high floor thing is a worry. Atums was kept low (80mm at the back) for this reason.

We were a bit braver for Antidote. 170mm, which seems ok.

The Banshees (don't know about B Ambulance) have a thicker floor which may be a bit too much*, and the E6 (I think) has a flatter floor with more vertical sides to allow for the low floor and the high topsides. This is like Aqua and Ronin.

An unsupported gunwhale does need quite a lot of extra stuff on it to be strong enough, so a dished cockpit with steep edges may be something to consider. That way the deck will still support the gunwhale, you'll still have the low floor for ergonomics and statics, and topsides which are high enough.

* On the basis of one set of capsizes in Riot Van with Graham, I felt that the board was not too high out of the water, and I have no memory of the boat inverting more or less than other designs. What was apparent was the low static stability with one crewmember in the boat and the other in the water. I felt v high and unstable: on a bike but stopped! The other issue is getting aboard between the tubes and the hull.  This was possible in Aqua, impossible in Atum (due to a late drafting error by me) and was part of the design brief for Antidote. 310mm is fine for us, but you have to watch your hook as you go through the gap. I don't think this is an issue for you, looking at those topsides.