What sort of boat has chines like this and why?

The photo below is of an Australian design (or maybe ripped off US design) from the 60s possibly. I have looked through FiberGlassics a bit, (unsuccessfully so far) to try and find something similar hopefully with an explanation of the design. The chines are concave for about the aft two thirds of the boat. I have no idea what they might add to the boat's performance or if they are just there to add some stiffening as the hull is pretty flexible. Anyone have any theories or seen any similar beasts?

 

i'm sorry to say I can't see that much on the picture...

 

I've seen boats like that before. If it's the one I'm thinking of, that radius opens up and changes shape as it goes forward. Looks to direct the splash outward.

 

When the boat gets up on plane, surface area is reduced to increase speed, but you get more displacement when sitting. Helps in stability when it sits. Also adds stiffen but I don't see that being reason.

 

Yes JEM, that's right, the chines look "normal" at the bow. I found a better picture of the same breed of boat that was for sale on eBay a while ago. You can't really make out the chines from the picture, but they flatten out about half way along the side windows.

 

I'm not sure of the make and model, but the chine shapes attempts to break or shear the flow from the bottom, so it's not dragged along with the boat (which slows it down). She appears to be a round bilge or arc bottom, so some sort of device needs to separate the flow from the hull. Modern hull forms use strakes and crisp chines, this one a different approach and one that could easily be added to a mold, on a hull that was known to carry too much water up it's sides. It also adds a touch of styling to the hull.

 

Thanks PAR, that makes a lot of sense. The sole of the boat is a curve/concave also. It looks like the sole sits on the upper part of the chine "hollows" at the sides and must follow the curvature of the bottom.

As far as I can tell, the boat is a Tilli Craft or maybe a Swift Craft made in Victoria, Australia about 50 years ago. I haven't been able to find anything much to confirm or deny that. Tilli Craft apparently manufactured boats from about 1960 to 1965 and they had a very similar address to Swift Craft that were manufaturing fibreglass boats at the same time.

 

Might it help a little to prevent tripping in turns ? Probably not much, but who knows. Or as mentioned, a styling measure.

 

The early Uniflite outboards had chines of this type. As the outboard flow of the water gets to the chine it is forced to follow the small curve. This slows the outboard flow reducing the tendency of the "wake" to exit the chine laterally at high velocity causing lots of excess spray. With lots of outboard flow in turns the small curve pulls the inbd chine down increasing bank angles as is usually the case w curved chines. Lobster boats w no keel will bank excessively for this reason but while sliding down the face of a big wave sideways this feature will tend to keep the boat somewhat level and keep the lee chine up and out of the water thus minimizing the chance of chine tripping and causing a capsize. Unfortunately this type of chine will tend to pull the stern down even when the boat is loaded correctly but it should be a nice dry ride w somewhat high banked turns. Some small degree of stability will be lacking also but chine strength will not.

 

I really buy into the drier ride idea.
In a sudden turn, there is going to be a LOT of turbulant water in that U tube. Even if the boat is a outward leaner. It may actually become a beveled angle of water. That could do away with the tripping to some degree at various speeds.

 

XJ9 upload the actual image and not a thumbnail
- the system looks after that nicely and clicking on the image allows an enlarged view - use the <Go advanced> option and than click on the "paper clip" symbol to get the attachments upload facility.
- If you are not sure where the image is stored on your computer, copy the desired image to your desktop and use the browse function to find it there, and follow the options.

 

OK Masalai, I have attached some bigger pictures for you. This boat is our next restoration project, but that will be a whole other story. The boat was stored for years in the previous owners back yard where he started doing some modifications and then lost interest. We intend to put it back closer to original and reinstate the aft part of the cabin that has been cut off and used to fill in the side windows, so that it can be used as a "comfortable" river and lake cruiser.

 

Great safety design.

That OB boat HAS A REAL full depth motor well, to keep out stern waves that sink lots of sexy cut down transoms.

USCG..............MAKE THAT FULL SIZED & FULL DEPTH MOTOR WELL >>>>>>MANDATORY>>>>>>> on all outboard boats.

 

Hi,
I have just acquired the exact same boat as yours and am starting to restore it. How is yours going?

 

Hi J47

There hasn't been much progress on the Tilli Craft beyond collecting some parts (glass, epoxy etc). We are still working, slowly, on the Hobson Solocraft we are finishing off and that has been rolled over ready to proceed. The sole and stringers of the Tilli Craft have been stripped out and everything pressure cleaned, so it looks a lot better now with the slime and dust removed. Dad removed the remains of the stringers and some of the strange interior mods done by the previous owner, but didn't bother to photograph anything. If you have to do anything like that, I would love to see a photo of what the original underfloor structure looked like. Henry Hobson (designer of the Cape Cats and Solocraft that see a lot around Tasmania) was supervising and suggested a self draining, level floor instead of the original curved one, but since he passed away recently, we are on our own with that one. The next step in the plan is to look at adding some buoyancy so I'm thinking seriously about getting hold of some neolon foam to add to both boats instead of the pour-in stuff (or the water logged esky foam that we took out of the Tilli craft), but I still have to work out how much and where it will all fit.

Good luck with your project, I look forward to seeing some photos as you progress. The reputation of these boats and similar Swift Crafts, seems to be pretty good, so the result should be well worth while.

Simon