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6th March 2014, 09:33 PM #46Senior Member
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Pam,
I often reflect on how influential our parents are on the paths our lives take. I was fortunate in that my parents were mostly supportive of anything I wanted to do - which means my failings are largely my own fault.
Regards
Derek
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6th March 2014 09:33 PM # ADSGoogle Adsense Advertisement
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6th March 2014, 10:19 PM #47Senior Member
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Next job in the sequence of things to do to get this model complete is to work on the Hip Rafter itself. The top of the hip is backed, meaning that the cross section is modified (from a square section), such that the upper surface of the hip butts accurately against the two surfaces of the roof that meet at the corner. The top of the hip therefore needs a triangular section on top, or two sloped surfaces that meet at a point in the centreline of the hip. Perhaps a picture would be easier? The cross section of the hip needs to look like this (in this image the hip has been rolled onto its left side):
Hip section.png
I have not spent much time recently, talking about the methods used here to calculate angles and dimensions for laying out. I expect that it may bore many who would rather see the pictures (I'm a picture guy myself). But it must be said that there is a good deal of work that goes on behind the scenes here, that underwrites the actual cutting of the wood so that it all fits together. As in previous models much of the calculations are made with the aid of plan and elevation drawings - in the past these would be drawn full size on large sheets of paper, or more likely, thin wood sheets. There is one member of the group who is going this route and using draftsman's ruler and pencil on door skins to draw everything full scale. Practical reasons prevent me from doing this and I have elected to do the drawing with the aid of sketch up. Determining the backing angle is one example of the purpose of this drawing effort. This angle is different to, but a derivative of the slope chosen for the common rafters. Without going in to any of the actual methods used, here is an extract of one of the drawings from this model:
planelevationview.png
With the angle determined, the processing may commence:
P1020364.jpg
More lay out and cut out to come...
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7th March 2014, 06:52 AM #48Senior Member
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7th March 2014, 07:02 AM #49Senior Member
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I'm really enjoying reading your posts, but they're also a bit off putting. It's very hard for me to visualize from line drawings, and Sketchup drives me nuts; but maybe a course like this would make me muddle through. Normally I sketch stuff mostly for proportions and angles, then for the angles draw precise, then proceed to ignore the drawings after layout is don't with wood.
Pam
Pam
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7th March 2014, 11:09 AM #50Senior Member
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I understand Pam,
And I am aware that, certainly in the era I grew up (and perhaps you did too), there were certain advantages to being a boy, and certain opportunities wouldn't have been available if I wasn't. Things have changed since then but I don't fool myself that we live in a world void of prejudice and discrimination. The web is both a blessing and a curse but one great thing it does is democratises knowledge, making it more accessible to more people.
Please don't take my earlier comment as being flippant regarding your situation - it was more of an attempt at self-deprecating humour.
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7th March 2014, 11:31 AM #51Senior Member
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Pam,
The last thing I want to do is make it seem like this sort of work is outside the reach of anyone. I try to strike a balance between giving a sense of the ground covered without going through the nitty gritty of all the processes. As a result a lot of the descriptions and sketch up graphics will be out of context to someone who isn't also studying along. The last sketch up graphic I included was simply to show that there is work going on in the background that I haven't explained in full. There is no way I would understand what was going on in that picture if I hadn't been doing the course - perhaps including it was self defeating? Remember also that this is the fifth project in this series and the concepts covered here build upon those already established in the preceding four. If one works through the material one project and one step at a time, it's very manageable.
Also, the students on the course don't create those 3D graphics you've seen - That's Chris' work which he does to help illustrate the project. I am only using Sketch Up to do the same thing you could do with a large piece of paper and drawing materials - the students only produce 2D drawings.
And you're largely correct - once the drawing is done to determine the angles and dimensions you need, it's largely put aside and the wood is worked on.
One last point regarding the mathematics - none of the mathematics used is more difficult than that covered by year 9 and 10 high school students in Australia. Admittedly many people might not have used this in some time, but there's no need for university level mathematics or membership with the Freemasons
I really hope this puts the whole thing in perspective for you, and remember there's no stupid questions. I enjoy learning this and enjoy it more if I'm learning it with others.
Regards
Derek
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7th March 2014, 12:17 PM #52Senior Member
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Never, I was feeling real bad for having wrecked a perfectly good thread. (:
As to drawings and maths, that's pretty much what I expected, I just have to decide to do the work.
Pam
PS Someone left a puppy in a basket in our front yard this morning. He's adorable and we've had quite a satisfying day. Can't keep him though, 3 dogs is too many; so maybe a friend's dog needs a pet.
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9th March 2014, 05:45 PM #53Senior Member
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20th March 2014, 10:00 PM #54Senior Member
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The three way lap joint is close to being two thirds of the way there.
In the photos of the two Keta halves seated together the higher piece is still sitting proud by about a quarter of a millimetre. I didn't take any photos of the process, but I disassembled the joint and reassembled with some carbon paper between the two mating surfaces. A few taps with the mallet to force the surfaces together, and enough of a witness mark was created on the high spots that I could pare away, and have now got the two halves sitting quite close to in plane.
The third component of this joint is of course the hip rafter, a smaller section needs to be cut away from this member where it intersects with the two Keta pieces. As the hip crosses the Keta intersection at 45 degrees the shape of the area that needs to be removed is in the form of an 'X'. The following photo shows the side view of the hip - on it is visible two hashed areas, the upper one is a 'print' where a rafter will intersect the hip, the lower one is the portion that will be cut away to form the joint:
DSCF1033.JPG
Tipping the hip over onto its side and the 'X' shaped section is more apparent:
DSCF1034.JPG
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23rd March 2014, 09:50 PM #55Senior Member
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Some sawing, chiselling and router plane work sees the waste removed from the hip. I have accurately cut the lap to depth, but am generously shy of the pencil line at the ends. This will allow for some tinkering to get the joint fitting nicely when it is offered up to the Keta pieces:
DSCF1031.JPGDSCF1030.JPG
The obligatory blood offering is visible in these photos.
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7th April 2014, 11:39 PM #56Senior Member
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My modest readership is no doubt anticipating the next and final phase in the fitting of this three way joint (four if you include the tenoned post!), namely the cutting of the trench that will house the hip rafter on its passage through the Keta lap.
I will confess that it is not only work and family matters that has delayed the procession till this point - there was a good deal of apprehension which with gentle care and feeding had grown into procrastination. It's not that this next instalment was all that more difficult, just that, in a hand tool only shop, getting this far has taken a long time and many swipes of the plane - any mistakes now would be costly (in terms of time) to rectify. But at some point one has to take the plunge, so after checking my layout lines another four or five times, I unsheathed the saw:
DSCF1606.JPGDSCF1605.JPG
No time for regrets now!
And in what was an eerily anticlimactic experience I continued a number of cuts into the waste:
DSCF1621.JPGDSCF1620.JPG
A lot of chiselling then ensued:
DSCF1619.JPGDSCF1615.JPG
I then used a shoulder plane and block plane to bring the surface down to the line:
DSCF1646.JPG
Then some trial fittings and minor adjustments till the hip cog joint fit into this trench:
DSCF1650.JPGDSCF1649.JPGDSCF1647.JPGDSCF1648.JPG
I feel the final tolerances could have been a little tighter but nevertheless I am quite happy that it has mostly worked out well. I removed the Hip and inserted the tenoned post:
DSCF1651.JPGDSCF1653.JPGDSCF1652.JPG
Well there's still more to do yet. The hip needs a mortice added (er, taken away...) to house the post tenon, and jack rafters still needed to be added, but I feel as though this project is well and truly in the home straight.
Thanks for dropping in for a look.
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10th April 2014, 03:22 PM #57Senior Member
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And a quick couple of photos to show the Keta pieces separated. They are quite unusual looking cut outs when separated from their context like this:
DSCF1669.JPGDSCF1667.jpgDSCF1665.JPGDSCF1664.JPG
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11th April 2014, 09:41 AM #58Senior Member
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Yxoc,
The apprentice is already producing masterful work!
I must come and have a look one of these days.
Regards,
Gadge
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13th April 2014, 08:55 AM #59Senior Member
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Hey Gary, great to hear from you!
Thank you for your very generous comment, and please do drop in one time.
Warm regards
Derek
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1st June 2014, 08:54 PM #60Senior Member
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Well,
When I said this project was in the home strait, I was speaking from a conceptual understanding point of view. Yes the newer concepts have been grasped well enough, but there is some work to be done that we might classify as 'administrative'. The hip or sumigi can't sit suspended in space at its normal slope. A supporting structure is needed. A brace joining the Keta with a stub post atop is the solution. The brace piece looks like this:
Brace.png
The brace is connected to the Keta via a dovetailed housing. I didn't photograph the construction of the female half but here are the left and right sides completed:
DSCF1952.JPGDSCF1955.JPG
I got a few more photos of the male half taking shape:
DSCF1958.JPGDSCF1970.JPGDSCF1971.JPG
Next - a harmonious union?
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