Catastrophe

A forum for contacting other builders of Ken Hankinson designs. These designs are now a part of the Glen-L family.

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ToddM
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Re: Catastrophe

Postby ToddM » Fri May 26, 2017 10:33 am

gap998 wrote:What Sproggy said ...alternatively you could go for a shape that looks more the Greavette Streamliners which would require a "soft sheer" & a strip planked deck.

eac7a4229431b0fb95e9e74a462fb969.jpg


Wow! So many gorgeous boats, and I can only choose one, ..., for now.

Edit: Just looked at a slew of photos of 'barrelback' type boats, and as a result of Sproggy's and other's input, I am going to make two or three drawings with the sheer "going soft" at different places and then decide what I like more. It appears that a 'hard sheer' is a definite angle point between two planes, and a 'soft sheer' is more of a curve?

ToddM
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Re: Catastrophe

Postby ToddM » Sat May 27, 2017 8:57 am

sproggy wrote:
ToddM wrote: You're just putting a radius on the sheer and that isn't now the barrel back shape is arrived at. Think about the fact that you will have a length of timber that defines the sheerline and links the top 'corners' of the frames - where will that sit in your drawings? It's the line where the sides meet the deck. Try defining that line on your drawing, but drawing cross-sectional frame shapes in isolation isn't going to allow you to arrive at a viable/buildable hull form - you need to consider the profile and plan views too.
Again, the sheerline is clearly defined and clearly visible other than right by the transom.


Now that I am drawing the sheer, what you are saying makes perfect sense. If I had drawn the sheer line first, I would not be having to change the frames as I am now having to do. My inexperienced process was to draw the frames first to transition from the frame 5 to the transom and then draw the sheer line and then modify the frames. But, if had just drawn the sheer line immediately after drawing the transom, I could have drawn the frames to match the sheer line with no future modification needed. And if I wanted, I could keep a hard sheer all the way to probably frame 2. Haven't decided yet where I want to start the transition of 'hard' sheer to 'soft', but I will draw it a couple of different ways to see what I like more.

Thanks again for your time and input.

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NAMEngJS
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Re: Catastrophe

Postby NAMEngJS » Mon May 29, 2017 7:36 am

It seems that you are on the right path but i want to re-iterate what Sprogy said before. It is not as simple as just changing the corners on the transverse frames and you achive the desired result. You should start with the major defining lines (keel, Chine, Sheer, Deck CL) and let them dictate the final achieved transverse frame shape. I have attached below some pictures of some lines fairing.

sheer plan.JPG


sheer body.JPG


sheer elevation.JPG


note you want to have the lines faired in the three major directions: Elevation, Plan and Body like I have shown above. Each photo the curves are shown as relatively fair. I say relative, as I can tweak each controling point of the curve slightly in one direction or another and still have a curve that would be fair, its when it is fair enough for me to move to the next view. The curvature shows no rapid changes in inflection from concave to convex or extreme hard points in any of the views and the relative change of curvature along the curve changes in a rate that is fairly uniform along its length. By changing the curvature in the transverse dimension only you could inadvertently create inflection points in the control curve which will be harder to achieve a good line in real life.

As a check I like to print my controlling lines in each view to a 2D CAD program and then you can scale the lines a few times in only one dimension this will create an overly exaggerated view of the lines and if you get down on eye level with the line and follow it for its length you will be able to note slight changes in inflection and extended flat spots in a line you want curvature in. IT IS VERY ITERATIVE, but it is a nice sanity check. Also I realize I have access to 3D Fairing programs to help, but this can be done in 2D CAD too.
All men dream, but not equally. Those who dream by night in the recesses of their minds, wake to find that it was vanity: but the dreamers by day are dangerous men, for they may act on their dreams with open eyes, to make them possible.

PeterG
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Re: Catastrophe

Postby PeterG » Mon May 29, 2017 8:13 am

You're on the verge of creating a new bull design... Keep on with this, fascinating work and a great exercise in how to design a boat. The CAD work alone looks like fun :D
Murphy's Law: Anything that can go wrong, will go wrong.
Griffin's Law: Murphy was an optimist.

ToddM
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Re: Catastrophe

Postby ToddM » Mon May 29, 2017 12:00 pm

NAMEngJS wrote:It seems that you are on the right path but i want to re-iterate what Sprogy said before. It is not as simple as just changing the corners on the transverse frames and you achive the desired result. You should start with the major defining lines (keel, Chine, Sheer, Deck CL) and let them dictate the final achieved transverse frame shape. I have attached below some pictures of some lines fairing.

note you want to have the lines faired in the three major directions: Elevation, Plan and Body like I have shown above. Each photo the curves are shown as relatively fair. I say relative, as I can tweak each controling point of the curve slightly in one direction or another and still have a curve that would be fair, its when it is fair enough for me to move to the next view. The curvature shows no rapid changes in inflection from concave to convex or extreme hard points in any of the views and the relative change of curvature along the curve changes in a rate that is fairly uniform along its length. By changing the curvature in the transverse dimension only you could inadvertently create inflection points in the control curve which will be harder to achieve a good line in real life.

As a check I like to print my controlling lines in each view to a 2D CAD program and then you can scale the lines a few times in only one dimension this will create an overly exaggerated view of the lines and if you get down on eye level with the line and follow it for its length you will be able to note slight changes in inflection and extended flat spots in a line you want curvature in. IT IS VERY ITERATIVE, but it is a nice sanity check. Also I realize I have access to 3D Fairing programs to help, but this can be done in 2D CAD too.


I understand. I kinda did when I started, but I did not know that I could or should work in all three planes at the same time. I was going in my usual plod along, step by step style. Now that I am drawing the sheers, it is more obvious to see that drawing all the controlling lines first will make arriving at the final surfaces much easier, and with less guesswork.

Boy, you aren't kidding about the iterative. And where do you get your radial lines? Are they created by the software you are using. So far, I have having to draw each one, which is ok, but the uniformity in your drawings leads me to think that the software is helping you create them? And I have not found a way to tweak my controlling points, vertexes, without redrawing my radials, in each dimension, and redrawing my curves. Like you said, it is iterative, (nice word for AGAIN? REALLY?).

I changed my mind and now prefer to build the Tahoe 23 instead of the Tahoe 19, and have requested an exchange from Glen-l, so with any luck, I get to start over again.

ToddM
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Re: Catastrophe

Postby ToddM » Mon May 29, 2017 12:05 pm

PeterG wrote:You're on the verge of creating a new bull design... Keep on with this, fascinating work and a great exercise in how to design a boat. The CAD work alone looks like fun :D


Thanks, but I am only changing a small portion above the waterline, and only on about the sternmost 5 to 8 feet. And with each trial drawing, I change less and less. It is fun, not as fun as cutting up a tree and gluing it back together in the form of a boat, but it is fun.
Last edited by ToddM on Mon May 29, 2017 4:24 pm, edited 1 time in total.

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NAMEngJS
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Re: Catastrophe

Postby NAMEngJS » Mon May 29, 2017 12:55 pm

ToddM wrote:Boy, you aren't kidding about the iterative. And where do you get your radial lines? Are they created by the software you are using. So far, I have having to draw each one, which is ok, but the uniformity in your drawings leads me to think that the software is helping you create them? And I have not found a way to tweak my controlling points, vertexes, without redrawing my radials, in each dimension, and redrawing my curves. Like you said, it is iterative, (nice word for AGAIN? REALLY?).

I changed my mind and now prefer to build the Tahoe 23 instead of the Tahoe 19, and have requested an exchange from Glen-l, so with any luck, I get to start over again.


Yes, fortunately for me, the 3D lines fairing program has a radio button that allows me to turn off/on the visual curvature assistance. And the benefit is that in 3D all the transformations are carried through all dimensions so all I have to do is change my view and the program updates the curve fairness lines for the view. Two of the nice aspects of this particular program is that I can bump a control point in a planar direction by a set amount so i am not randomly dragging points so i can adjust my hull/object very minutely. This program also has dependencies built into it. therefore if i have a point at 1 ft aft of the FP on CL and i build say a deck house whose points are dependent on the first point i can drag the initial point to say 5 ft aft and the house will adjust automatically and maintain the same relative size.

Also just a question, assuming that you are not doing this by hand with ducks and splines are you using B-Splines or C-Splines for your curves (C-Splines the line goes through the control points, B-spline they only go through the first and last point the line adjust based on the other intermediate points.) Because it is easier to fair B-Splines but harder to get an exact dimension with-out forcing the curves hand to an extent. C-Splines, while they will work tend to have more discontinuities. If your program has the option to change the type of curve I would say look at that as well.
All men dream, but not equally. Those who dream by night in the recesses of their minds, wake to find that it was vanity: but the dreamers by day are dangerous men, for they may act on their dreams with open eyes, to make them possible.

ToddM
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Re: Catastrophe

Postby ToddM » Mon May 29, 2017 4:23 pm

NAMEngJS wrote:
ToddM wrote:


Yes, fortunately for me, the 3D lines fairing program has a radio button that allows me to turn off/on the visual curvature assistance. And the benefit is that in 3D all the transformations are carried through all dimensions so all I have to do is change my view and the program updates the curve fairness lines for the view. Two of the nice aspects of this particular program is that I can bump a control point in a planar direction by a set amount so i am not randomly dragging points so i can adjust my hull/object very minutely. This program also has dependencies built into it. therefore if i have a point at 1 ft aft of the FP on CL and i build say a deck house whose points are dependent on the first point i can drag the initial point to say 5 ft aft and the house will adjust automatically and maintain the same relative size.

Also just a question, assuming that you are not doing this by hand with ducks and splines are you using B-Splines or C-Splines for your curves (C-Splines the line goes through the control points, B-spline they only go through the first and last point the line adjust based on the other intermediate points.) Because it is easier to fair B-Splines but harder to get an exact dimension with-out forcing the curves hand to an extent. C-Splines, while they will work tend to have more discontinuities. If your program has the option to change the type of curve I would say look at that as well.


I will have to read the first paragraph a few times to understand it, but ...

I don't know what 'ducks and splines' are, and I do know that I am using B-spline curves, because the icon tells me that is what I am using. But, I don't know what a B-spline curve is, or a C-spline curve. I doubt if the version of the software I am using, TurboCad, has C-spline curves or I probably would have found them. It appears that most of the time the B-spline curve holds my control points, and names them vertices, unless the fit is outrageous, and then it uses my control point(s) as a suggestion. That is one of the ways I know that I have made a mistake.

Unlike our CAD programs at work, my home software only allows me to use two 3D type views, isometric and trimetric. It can be tiresome, but in a way it forces me to think, rather than just see.

You made me realize something just now. The B-spline curve does move if I drag one of the vertices, I think. I think I found that out by accident and at the time it seemed irritating, but on further reflection I am guessing that instead of guessing where I want my new control point relative to one of the existing control points, I can drag a vertex, and if it looks good in all three planes, wah lah. I have my new control point/vertex. Hmmmm.

I have found a way to move, copy, mirror, etc. more that one object/element, but it entails turning off all the other layers, drawing a box around the desired objects with the selection tool. and selecting the reference point(s) per the commands.

What I find fascinating is that in drawing a boat, especially one without certain given dimensions, one can draw to make it look good, faired, without coordinates or dimensions. Since I have no artistic ability, it is gratifying to kinda draw like an artist. Kinda.

Thanks for all the help.

ToddM
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Re: Catastrophe

Postby ToddM » Sat Jun 03, 2017 5:38 pm

How little I know about boats will now become apparent. The Tahoe plans came with a lumber list and a fasteners list, but I can not find a hardware list. This is not a complaint. This is not a negative. But, how do you know what parts you will need for things like steering, propulsion, lights, electrical, and gauges, and all the other stuff? Do all of you just know what you need because of your experience with boats? Would there be a list in "The Boatbuilder's Notebook"? So far, I realize that I need an engine, a propeller, and a steering wheel; hopefully not a periscope.

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sproggy
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Re: Catastrophe

Postby sproggy » Sun Jun 04, 2017 2:09 am

There are too many options and the choice of those is down to the individual as well as affected by what's available in the country/area you live in. Steering can be hydraulic or mechanical. Things like the exhaust, shift linkages etc will depend upon your choice of engine/gearbox. Lights will depend upon local regulations and/or how you want to use the boat. Gauges will depend upon the engine package you choose and also personal choice. Electrical layout will depend upon engine, gauges, lighting, interior equipment. Part of the fun is researching all these things and deciding what you want/need! Looking at what others have done is a good starting point. I don't recall seeing a list in the Boatbuilder's Notebook - probably for the reasons I have described - too many choices to cover.

Think about the big things first (engine/gearbox, steering) and the smaller bits will fit into place as you proceed. Periscope optional :shock:

ToddM
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Re: Catastrophe

Postby ToddM » Tue Jun 20, 2017 7:24 am

Design Mods are close to being finished, so it would seem that it is close to time to cut some wood. Reading the instructions and watching a couple videos, it appears that folks use the patterns to trace and cut the starboard and port frame pieces. (Starboard is right, and port is left :D ) Is there any reason that one cannot final dimension one side and use it as a pattern with a router to final the other side?

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Jimbob
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Re: Catastrophe

Postby Jimbob » Tue Jun 20, 2017 9:18 am

Re: Frame Patterns
That's what I did. I made my patterns out of 1/2" mdf for the side shown on the plans, and then flipped it over to use as a pattern for the other side. Used a flush trim bit with the pattern after a rough cut with the band saw.
Jim
Jim Neeley
Building a Barrelback in Sacramento, CA
viewtopic.php?f=15&t=28089#p172969

ToddM
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Re: Catastrophe

Postby ToddM » Thu Jul 06, 2017 8:39 pm

Latest on modifications to Tahoe 23:
aft top.jpg
Aft right side.jpg
aft rear.jpg


Thanks for the advice on the sheer clamps, and on modifying in all three dimensions at the same time.
Last edited by ToddM on Thu Jul 06, 2017 8:42 pm, edited 1 time in total.

ToddM
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Re: Catastrophe

Postby ToddM » Thu Jul 06, 2017 8:41 pm

Decided to modify the bow(?) to look more like a Riva, but as of yet, have not been able to dray the stem accurately.
front.jpg
aft trimetric.jpg


Oh yeah, still have to draw up the curves on the back of the transom.

trice001
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Re: Catastrophe

Postby trice001 » Wed Aug 23, 2017 12:53 am

thanks


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