radius chine == radius bilge ?

Hey all,

I've been looking at a few different designs for many years and think it's almost time to start building.

My question is about a Ted Brewer design that I really like, the Orca 45'. The website says it's a radius bilge type hull. I've been comparing this to some Bruce Roberts designs which have radius chine hulls which are suppose to be much easier to build than a round bilge (Bruce differentiates these in his books). Yet even Ted seems to make a difference between his radius bilge and a true round bilge. Are these two processes just different names for the same construction process from each designer? Will a standard metal shop be able to provide me w/ radius bilge pieces?

Does anyone have experience building a radius bilge from Ted's designs? Is radius bilge same as radius chine? I'm wondering how much of a difference this is from the radius chines which I think I find quite easy from reading Bruces books and how much the steel process changes.

 

Yep, just two different terms describing the same thing. Both are developed, flat panel builds, but have a rounded over chine areas. This is also known as a "soft chine" type as well.

 

and in my opinion they are neither fish nor fowl, they look horrible, a serious compremise:!:

 

But besides the looks, are there any other reasons to not use this technique?

 

I beg to differ from you Jack If designed by a designer that knows his stuff, it is just as pleasing to look at as any other boat...

A little tale that happens to be true as told to me by Dudley Dix; In the early 90's, a very well known designer (now residing in NZ) and the doyen of SA designers at the time, looked at one of Dix's radius chine hulls on the dry about to be launched, and made the remark that it is one of the best round bilge steel hulls he has ever seen. Was he flabbergasted to learn that it is in fact a radius chine hull.

Yes, I had seen some less than nice radius chine hulls in my time and the Robert's version comes to mind. Some American designers also make them look sad and this is mainly due using different radius along the hull...

A round bilge is not a radius chine. Most fibreglass hulls are round bilge designs as you have ever changing curves all over the hull so to speak which makes it difficult to duplicate in steel unless you are a very skilled steel worker.
Radius chine hulls are actually a single hard chine hull with the chine "softened" as pointed out by Par. As said before, if it is properly designed, it CAN be more pleasing to look and at as a proper round bilge hull...in fact, without being biased, I think it looks better overall.
And the beauty of this type of construction is that it is well within the ability of amateur builder and actually very easy to build

Just to put your mind at ease regarding the "looks", I attach a few photos of Dix designed radius chine hulls. Three photos are of the Dix43 now under construction at my shop and as a matter of fact, one of Dix earlier - 1987 - designs and his later ones are much more pleasing if I may say so.
The other two are of a Dix65, designed in 1990/1. I had build the Dix38 (which I actually commissioned in 1991) and the Dix57 and both are just as nice.

As for the looks, study the pics and you be the judge...

 

Wynand is correct, especially in modern hull forms. Well designed soft chine designs look quite good and most amateurs would be hard pressed to tell the difference from round bilge.

 

Wynand, I am following that Dix43 project of yours with admiration.
Thanks for clarifying.

I assume that strength wise, a well designed radius chine hull is not inferior to a (multi) chine or round bilge hull?

 

Curved panels are always stronger then flat ones.

 

i am building a John G Alden tugboat Circa plans from around 1952. when i look at the hull form(i have a model) It looks like a round bilge to me- there is only on section that would be a compound curvature. the bottom appears to imitate a chine hull but there is no chine. the bottom is slighlty vee'd. and the sides plumb(for towing on the hip. would this be classifed as a round bilge?http://www.boatnerd.com/pictures/tug/images/portofindianab-th.jpg
http://www.tug44.org/tugboats.trawlers/tug-8th-sea/

 

Well designed double chine construction hulls are certainly not ugly and there might actually be a little spinoff. There is an ongoing study and debate that a properly designed chine hull in certain situations might actually be faster than her non chined sister.The theory being that the chine ridge actually creates lift resulting in less wetted surface and possibily a little gain to winward ability. Anyhow food for debate. Geo.

 

Somewhere I got the belief that radiusing the chine would take some of the snap out of the roll. Is true?

 

Like anything else, if properly done a radius bilge can look just fine.
Yes, it could take some 'snap' out of the roll but it depends upon the size of the radius (how much volume is removed), the vessel's beam, and the vessel's displacement (weight).

 

Two questions...
1. Are the radius panels wedge-shaped. square or both?
2. Dix was talking about his own personal boat and said he thought ply was cheaper than steel. Seems odd. Anyone know more about this? I found the reference on a site called small trimaran design if you want to look it up.

 

The radius panels are usually square edged, though not necessary parallel, once fitted to shape. Often the angle needs to change, particularly near the bow, so a more angular shape panel will be installed to adjust the angle and make subsequent panels "lay down" better. This is done on the "fly" as required. You'll notice, from preceding panels that they're trying to pucker, so the angle is changed to accommodate this need.

All building materials have a range of economic viability. Steel tends to favor larger yacht sizes, because of costs and weight. A smaller yacht can't afford the weight penalty and remain within the shapes desired, for its expected performance envelop. Larger yachts require significant scantling increases with wood, forcing its costs and weight issues up. At some point a threshold is reached and one overtakes the other economically.

 

Old thread, but I just happened to browse the forum out of boredom, remember I'm retired from boating and saw this post.

I knew Dudley when he was still living In South Africa and I built his designs and also commissioned him to design an in-house boat for my yard to produce, namely the Dix 38.

The boat you referred to is probably his last boat built here before moving to the USA, named "Black Cat" which he used in racing, also did the Cape to Rio race with it and it was built from cold molded plywood to radius design. I had the privilege to see the boat under construction at the time.
Due to the fact that Dix is a racer by heart, plywood would make a strong argument for weight and strength over any other material, especially in cold molded strip ply.

Dix built this boat in his backyard in Houtbay and plywood made absolutely a lot of sense for keeping good neighbors compared to let say steel fabrication. But Dix also told me plywood is the best material to build a boat, period and also his personal favorite material hence "Black cat" (and his previous boat) built of plywood.
This all happened in the early 1990's and maybe he has changed his mind about plywood but I strongly doubt it....