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You can see in pic 4 what I’m trying to do, adding curved cleats to the top of the hip and those two jacks. Well, I’m having a hard time drawing them accurately, and probably will have as hard a time cutting the actual pieces accurately too, so that everything planes in correctly.
I was wondering if anyone has used a different technique for getting the curve and flare.
I’ve researched it in quite a few books of traditional Japanese and Chinese Roof Construction and, it’s too complicated doing it that way!
Well, I'm asking mostly how to build it, the compound-curved part anyway. You see where I'm headed .. adding cletes to each hip and jacks, then bending 1x4 T&G down over it.
Actually, I'm also asking for a way to figure it out I guess, so I could cut, and lay down, tapered cletes. I could even make-up a fairing block, and fair everything in.
Or, is there some other way ?
Here is how you're supposed to buildem, but after studying Books on Chinese-Buddhist Roofs now for 2 months, I can't Even figure out how you're supposed to ! I'm looking for a Western Way, or a simplified Asian Way (preferebly) ..
my response it a bit complicated --- However turn the whole thing upside down.... as if building a groin vault ...
the hips are ellipses .... You may want to project the curves on a plan view ... Or
layout the ellipse using the run of the hip --- This is a subject that needs pictures & graphics ... I really am handicapped in that dept.
I am doing a 1 hour workshop on establishing ellipses at JLC Live in 2005 --- It's more of a hands on demo ....
I think Joe fusco could probably generate the graphics to explain this ... If he's still lurking around the forum ....
I might recommend George Collins - Curvature & Circular work - a book written in the 1800's & updated to modern english - Craftsman books might carry it -- But I'm sure it's available on Amazon
After doing much research on Curvature work of our predecessors, I realize that they plotted everything ... Math was not a major factor in their layout work. Thats why the Framing square is such a basic tool ...
The pieces you want to make can be easily plotted in plan view in 100% scale .... But for me to explain it online ??
Give me some Idea of the radius of the 'common tail' you want to cut -- If it's a regular hip - I can tell you the plot of the ellipse hip - Of course the compound flair as it approaches the hip will change the dimension.
Once you SEE the relationship it will all come together ...
Geeze Mike, I was just trying to layout a radius for you, but the problem is, each jack will have a different radius, and it's not one radius that will define each jacks' curve, but more like one gradual one and one tight one. The hip will have an even more complex curve I'd think.
You sound like you're pretty on to the concept though ! Wish I could read your mind.
I know from your previous posts that you are a bit fanatical about spacing and symetry on your hip structures. I hate to risk bringing this thread down a notch...but we would probably forget the math on the jack rafters and just establish a pleasing sweep on the hip, cut 4 scabs (for the 4 hips), tack in place and lay a straight edge on the hip and first jack (with no scab) and measure the space every 6-8" to get the "plane".
Especially with your softwoods, you can belt sand any high spots before installing the roof deck.
You are not trying to build a swiss watch. 10-12 feet off the ground and roofed with shakes, no one will know you did not figure each ellipse (smile).
Are you taking about a curve or a true elipse They create two entirely different shapes which require two different methods of working them out.
Your problem is two fold, the mathematics and the construction. You can build formers and laminate all the members. You can get exceeding deep joist material and cut the shape or you can stack splice the timber and then cut to shape.
A while back there was topic on how to calculate elipses which I contributed to.
If I were you I would seriously consider a full scale layout before you start cutting any timber. A full scale layout will also provide you with the dimensions the timber has to be to achieve the correct result. I"ve built numerous convex and concave hip ends for verandahs but never the curved jacks.
Have you ever done any geometrical stair work? If so it's a simple case of creating the curve on the edge as opposed to the face.
The roof shape you call a Dutch Hip is in fact a Gambrel roof.
The Internet, a source for Information, and misinformation
Maybe in the Land Down Under that is a Gambrel roof, but here in the USA a Gambrel roof is a roof of two or more pitches used to give more space directly under the roof, often but not exclusivly used for barns. (It makes a good hay loft.) In the picture below, taken from the Webster dictionary, we see four roofs. Here is the caption from that picture:
Also as a side note, I spent a year in Korea and enjoyed touring the Buddhist temples, but I also could not understand why they built them the way they did. They looked to be a little over engineered. But they were very beautiful examples of building/woodworking. I would never have the patience to do the painting on them. Good luck with your project, Joe.
A 17th Century French architect called Francois MANSART (not Mansard some one even corrupted the poor buggers name) designed a roof system which consisted of a modified Queen Post truss with a King Post Truss sitting on top. The reason behind this was to create liveable space from within the roof system. This in effect created a 3 storey house more accommodation on same footprint At the change of pitch a horizontal beam was used called a "curb"(curb meaning restrain or hold) beam. The curb beam sat on top of the steeper rafters and the lower pitched rafters sat on top of the curb beam. The first roofs had gable ends. This design became very popular in continental Europe especially Paris. It helped to accommodate more people in a smaller area (sound familiar) This basic design then evolved, the original design was used in the crowded street of Paris. Large houses built out in the country where there was more open land started to have the ends with a double pitch. They looked far more fancy and flash (there were posers in those days too). To differentiate between the two the word Curb roof came to mean a double pitch on all sides. The French also gave the curb roof a fancy name which escapes me at this time.
The Dutch also took up the basic design but they built masonry gable ends like a parapet wall mostly with curves which extended past the roof line. That is where the term Dutch Gable originated. That style is sometimes called Dutch Colonial or Cape Colonial because that style of roof was favoured by the Dutch colonists in South Africa, originally called Cape Colony. The Dutch also built wind mills with a mansard style roof and the Poms pick up that idea. Now when the Europeans started to migrate to America they brought their knowledge and then started to adapt European design to local conditions. Many terms then started to be labelled and attached to different nationalities. In the North East of the US many Dutch people were the first settlers (remember New York was originally called New Amsterdam). It was the Dutch that originally built the Mansart (Mansard) roof in America but they then started to build entirely in timber as opposed to masonry and clay tile as in Europe. That is where the name Dutch Barn came from which is a barn with more than one storey in the roof style of the original Mansard roof.
It wasn't until the mid 1850's that some American decided to call the Mansard roof a Gambrel Roof. Now the Poms built their roofs differently to gain liveable roof space they built a collar tie roof and single pitch on the sides. To gain more space at the roof ends that started with a masonry gable end and about two thirds up they changed the roof to a tile hip end. That design was modified to be built totally out of timber. The correct and original term is Jerkin Head. Once more it got corrupted in America to a Kentish Gable or Tudor ( because that design originated in the late Tudor era and many such house were built in the southern English county of Kent.
The roof end which starts in a hip and finish in a gable is gambrel roof. The word gambrel came about because the outline resembled the shape of a horses hind leg.The small gable end was to allow ventilation in the roof space, an idea which originated in Java and Sumatra which was then also known as the Dutch East Indies. So that design of roof came to America by the Dutch. You call the same roof as a Dutch Hip and in OZ many people quite incorrectly call it a Dutch Gable If you want to give it a more correct name I guess you should call it a Java or Javanese roof because that is where the style (originally as a thatched roof) originated.
A lean to roof is also called a pent roof.
There are many types and styles of homes which are given corrupted fancy names by real estate marketeers, purely as a marketing ploy. Misdescription is practiced in OZ just as well and often as in the US.
Some of the corrupted names that come to mind are Colonial, Tudor, Bungalow, Californian Bungalow, Spanish, Mexican, Georgian, Victorian, Regency, Gothic, Cotswold, Queenslander, Mediterranean, Cottage, Tuscan, Provincial, Chalet. Sound familiar, and if you have seen any of the real styles in their country or region of origin you would realise what a load of BS is spoken about styles and types of houses
The Internet, a source for Information, and misinformation
I think The thread to follow is understanding the Ellipse , It seems to me that it's construction is a form of the ellipse Or possibly a parabola. But understanding the principle of plotting out an ellipse from a basic radius might send you off in the right direction ... and you could probably carve out a decent represntation of it. - If it were a radiused tail that intersected a hip without the upswing- It most definately is a 1/4 ellipse. However as I think through the proccess it might be a series of ellipses that change major & minor axis as they converge in the corner.
It appears to me that the form of the roof you are trying to build is more in the Korean tradition than Japanese with the upswing of the roof hip. It is incredible carpentry & I wish I was young enough to study & master it.
I would love to follow this as you figure it out . Take a LOT of pictures.
I will be doing a short 1 hour Presentation at JLC Live this year on the relationship of ellipses to circles if you happen to be in one of the show areas ...
If the hip rafter is in fact an elipse from the ridge to the end of the rafter tail, then all rafters, commons and jacks will also have to be an elipse. The hip rafter elipse will be the reference for all the rafters. The elipse for the common rafter will be a constant but but the elipses for the jack rafters will be all be different to come into plane with the hip elipse. The other issue is whether the hips, jacks and commons are to be cut parallel or is only the top edge eliptical. The roof pitch angle and the length of the rafters will also have an effect on the size (depth) of the rafters.
The more you think about it the more things come to mind that you have to consider. I reckon you could spend more time doing the calculations and setting out than pitching it.
I don't believe it is a project for the unknowing without a great deal of on site guidance. If the roof timbers are exposed then there is no room for error.
All those Oriental roof framers are master craftsmen who have been indentured and well and truly taught and strictly supervised over many many years. How many western roof framers can say that they were taught and learnt under those conditions.
The Internet, a source for Information, and misinformation