Kokanee 20.5

Steel and aluminum boatbuilding. See: "Boatbuilding Methods", in left-hand column of the Home page, for information about alloys.

Moderator: billy c

scotts
Posts: 3
Joined: Tue Feb 02, 2016 6:53 am
Location: Baton Rouge, LA.

Kokanee 20.5

Postby scotts » Mon Feb 08, 2016 10:49 am

Just started this project a couple weeks ago, i have set up the frames, transum & stem. started installing flat bar 1 1/2 x 1/4 stiffeners thru notched frames and am finding it difficult to get stiffeners to cooperate once they run to the last couple frames toward & into the stem. I have tried a couple things to allow stiffeners to bend but would really like to know the correct process for this.

Kevin Morin
Posts: 580
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Kokanee 20.5

Postby Kevin Morin » Mon Feb 08, 2016 3:15 pm

scotts, longitudinal bars may need to be bent/rolled or even, in some designs, cut as curves' radii in the forefoot section vary with design.

To bend; it would be common to set up a hydraulic jack on frame where the jack could 'kink' bend the curves. Depending on the transportation (truck overhead rack) having the bars rolled the 'hard way' is another choice,this would be done in a shop with pyramid rolls. In this method, like the kink bending method, you'd need to take off a curved template so that either method of forming could be compared to a ply template pattern while the forming is done.

Last, cutting forward sections of longs will also work where the other two forming methods aren't used. To cut the shape you'd have to pattern the curves off the frames, probably from the outside, to create the outline shape of the long's inside and outside edges to be cut of plate.

Depending on the frames' sections, their stiffness, some builders will weld the longs to the stem and pull them down and aft, if the frames won't be distorted acting as an 'anvil' of sorts for this cold bending by hand. Using the long end (aft) as handles and good grip on the bow stem, the bars may be pulled down into shape? This does put a lot of tension on the longs, so when you weld on them later.... there can be some sheet distortion if the weld relieves too much of that built in tension, but it does work in some bows.

I'd use a bent piece personally, there's more control to the shaping of those tightening curves. Another method used- could be to move from just bar, which is hard(er) to keep fair in a cold formed tightening curve; to an angle extrusion for the forward parts of the hull longs. The advantage is the other leg tends to keep the long from wavering/warping/wandering but the disadvantage is welding under the leg parallel to the hull panel with most MIG torches.

Hope this helps you explore some means of shaping those longs?

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

scotts
Posts: 3
Joined: Tue Feb 02, 2016 6:53 am
Location: Baton Rouge, LA.

Re: Kokanee 20.5

Postby scotts » Tue Feb 09, 2016 7:06 am

Kevin, thank you for your insight. I am not happy with my craftsmanship on the first couple of stiffeners that I installed in place so I going to redo them.
As you suggested I going to layout the stem, front frames on plywood and press them to achieve the desired radius. Hopefully pre-bending the stiffeners will save me some anguish and provide a more uniform transition to the stem.

Prior to asking for some assistance on this I looked at hundreds of photos of builds of boats in every stage of construction and from about every angle and stem tie-in on V-hulls where always conspicuously missing...., when I'm done and satisfied with my craftsmanship I'll post a pic.

thank you again for your help.

Kevin Morin
Posts: 580
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Kokanee 20.5

Postby Kevin Morin » Tue Feb 09, 2016 11:05 am

scotts,
some builders plank the area with hull plating then go back and install longs as cut pieces between the frames, this means what was designed as a longitudinal is now 'blocking' between frames but in a welded boat, once welded that is, the entire area is just as stiff as if the longs are continuous.

Also to consider, since the hull sheet in the forefoot of most V bottom shapes is under lots of tension when its pulled up to the keel seam and chine seams; the bow is often fair without needing any initial framing in the way of longs. Aft, in the more flat area, hull plating might be unfair without the longs, but where its in good tension if becomes fair. That is why builders will 'block' in the longs - by fitting to a faired surface they avoid the work of fitting fair longs to the frames in the forward two or three (sometimes four) frames, but don't give up a fair hull surface doing the work in that order.

Progress photos are always welcome among builders, and here there's a whole site filled with boat builders. No need to delay any posts, but if you're not pleased with the work, and I recall boats I'd prefer not to post until I'd had time to improve, then we'll just look forward to seeing your boat when its 'farther along'.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
Posts: 580
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Kokanee 20.5

Postby Kevin Morin » Tue Feb 09, 2016 6:11 pm

scotts, this post is about your subject in an overall sense. IT is, however, involved with my other threads on work methods and lines of hull.

I won't say that everyone will 'see' what I'm discussing without some study, and I'm not saying this is the 'end all' solution to framing bow or forefoot hull plate areas in the class of V bottom, developed surface plated boats. I'm taking advantage of an opportunity in the overall metal boat building and shape discussions to explore a framing method of this class of hulls.

If I leave you behind, if you don't 'see' what I'm explaining; then no worries we'll get more involved in shapes are the Building Method Thread evolves. For now, there may be those who can understand this set of photos without further explanation? so this post could help their considerations in framing their own boats?

The forefoot of the bow of a planing boat, usually V bottom is a conic section. Somewhere in space, there is a conic center, radius and surface that describes the bow's forefoot area, and I've listed some books and reference in the Work Methods threads where references can be read and researched. I won't go deep here, I'm just showing photos to prove a point, and that point is: bow framing a cone can be done with straight line flat bars.

Notice that the longitudinal framing elements of Scotts' post and questions require BENDING, forming, shaping a flat bar extrusion to conform to the bow's shape? THAT IS ONLY TRUE if the framing is oriented on certain "lines" with respect to the shape's surfaces.

I frame the bow in flat bars, I use straight edge pieces of metal to frame the bows of most of these boats.

Image
If you will take time to look up the Kokanee 20.5 study plan's image you can see that this photo, above, has a similar set of lines. I've already mentioned the idea of building to the deck line; air testing and building the rest of the boat, so the image will not be so strange? I hope.
I call the readers attention to the basic V bottom forefoot area and suggest this is a segment of a cone even if that is not intuitively obvious at first glance?

IF you intersect a cone, symmetrically, through its center line, radially, the intersections On The CONE's surface are straight lines. (may need to reread that line a few times?) Cones contain straight lines on their surfaces IF (this is a very important point) the sections of the cone that reveal the intersections with the cone's walls/surfaces pass through the cones' central axis as radial to that axis. You may have to sketch a bit to agree? You may not 'see' what's being argued and some may already be at "the end of this post's hallway?"

You can use flat bars to frame a cone. If the bow of your skiffs' shape is made of metal, and is not distorted by forming equipment (English Wheels) then you MAY frame the bow with un-curved flat bars. Flat metal can only be cold formed into three basic geometric shapes: flats, cylinders and cones- compound or complex curvature requires stretching the metal for other geometric shapes including bending to form other shapes.

Cones' surfaces can be described by straight lines if you align the bars on the 'radians' or planes passed through the conic center so these lines lay on the surface of the cone!

Image
The same hull as in the previous picture, here shown in the chine down or vertical orientation has flat bars of different depth welded to the surfaces of the bow cone(s, one conic section per side).

Image
This photo, above, shows the three bars used to frame the entire bow section of this skiff's forefoot. The longest 'bar' is a sheet edge cut off from the bottom (1/4" 5085-H116) used as a 6' long 'bar' but fit to both ends only. The hull edge fit because it laid true to the bow (cone's) surface. The three bars all end in the transverse bulkhead as butt's and the both the bulkhead and each 'long' are all limbered so any ambient condenstation can run aft and be drained from the bilge.

Image
This photo, above of the hull in tack up and forming offers a look at what I'm calling a conic section but I've not edited in any lines to explain that fact of geometry. The shape is however conic OR.. I couldn't have used straight line flat bars to frame inside! Proof is in the geometry.

It should be noted that the flat bars are not equal depths, I just used whatever segments of off cuts at hand, didn't trim the tops, just the ends, and the image seems to show curvature!!! but then grey on grey photography seems to show plenty that is just lack of contrast remnant.

Image
Last photo for the post, above, is not intended to argue or contest the designs where frames carry longs to the bow. I'm simply showing a method of taking advantage of the "conic facts of geometry" and achieving the same or stiffer hull pane reinforcements in bow/forefoot curved area of the V bottom planing hull's narrowing shape.

It may not be obvious butt.... is true that the hull's flats or cylindrical sections covert to conic sections AND that cones can be framed with flat bar sections. Just another idea that could be used to simplify aluminum boat construction?

If this post leaves more questions than it answers, I will be covering the relative geometry of these hulls in future Building Methods posts on that thread.

Am I advocating that scotts, cuts out his lower frame sections in his hull and uses this method? NO, I'm using a discussion of one building method to explore for the reader and future builder, the options that exist in building the same hull lines and combined shapes using different methods of construction.

There are several other framing methods, as simple as this one, that could be used to substitute for diagonal, buttline oriented longitudinals and I'll try to explore those in the next post with images.

If you would like to post questions, always welcomed of course, I'd ask you to focus on those images or text that caused the questions so I can try to focus on that aspect of the post in any reply.

Scotts, I'm not trying to ask you to reconsider your plans drawings, just offering some alternatives that you may wish to consider in your hull's framing. Changing horses midstream isn't good boatbuilding practice, so these references are as much for our Work Methods thread as reference for you.

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Kevin Morin
Posts: 580
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Kokanee 20.5

Postby Kevin Morin » Tue Feb 09, 2016 7:58 pm

scotts, I'm kind of hijacking your thread, all in the name of exploring HULL LONGitudtinals ( focused at the bow of these hulls' shapes) so you'll have to bear with me OR we can ask our moderator to move these last few posts over to the Building Methods thread?

Framing the bow, that is putting supporting metal shapes behind and inside the forefoot area of a metal boat can be done all sorts of different ways. Your plans package implies the longs will be buttocks OR diagonals OR sheet normals, lots of methods. Just above, in my previous reply post I tried to show that the conic bow section is in fact subject to framing with flat bars' on edge and radial to the bow cone. I didn't explore that cone much, I just showed pictures as my 'evidence' to support the assertion.

Here I will try another approach, some graphic evidence before showing what I think is another viable solution to this building question. I'm not trying to move you from what your plans call for in construction and especially if you've already cut notches, frame allowances and provisions based upon the plans; I'm offering theory of metal boats' building for wider consideration and using your introductory question as my spring board. (hope this is not an intrusion, but if so? let us know and I'll ask our mod. to move this out of your way.)

If anyone reading has taken time to read one of the companion posts about Hull Lines, then what I'm about to post will not seem far fetched. If on the other hand time has not provided for your review of that topic; some of these images will be a little more complex to follow.

OK, hull intersections are planes passed through the hull's surface at fixed relationships to the Keel Plane. Where Stations are at 90deg to both the Keel and the Waterplane; Buttock Lines are hull intersections on (imaginary) planes 90 deg vertical to the Waterplane and the parallel to the Keel Plane and Waterplanes or waterlines are on planes that (both design waterline and all other waterlines) are at right angles to the Keel plane and ...(longitudinally) parallel to the Keel plane as well! or at right angles to the Station and Buttock Planes in the horizontal axis.

IF that is confusing, all I can suggest is a bit of review of the Hull Lines thread?

Below, this first image is in the Plan View. Therefore the Keel is a line (top of a plane on edge) the Stations are all lines (again tops of planes on edge looking down), the Buttocks lines are all top edge lines too...... and finally the stack of waterlines is shown in true size curves as the horizontal planes intersect the bottom of the hull, like the Kokanee 20.5 in nature, so we see the top view of a 'stack of glass panes' with hull intersections outlined on them. Each (waterline) outline is referenced to the Station along the Keel from bow to stern and each outline of a waterline is offset from the Keel plane a given distance at each station.

Hope this correlation is starting to make sense to anyone reading the Building Methods thread near by?

Image
Not the most well planned image, above in what looks like grey scale but is just a faint output from a hull modeling software. Lets look closely; the outer two most lines are the plan view of the outer and inner chine. The next most outer line is a water line that is high enough on the hull (model) to intersect the chine flat- so about amidships that waterline turns out and exists the lines plan.

All the rest of the waterlines begin at the forefoot along the keel and run to the stern. All the rest of the waterline are under the hull's 'at rest' waterline shown. This is NOT, repeat that for anyone not focusing on why we're looking here- NOT the running waterline. That is not considered in this discussion.

Image
this sketch, above, shows the same hull bottom from the Profile View so now.. the Waterplanes ( waterlines) are on edge to the viewer so.. they're lines of the edges of those planes, and we can't see them as stacked intersections. Instead this view provides the chine and keel as curves because we're looking their set of planes of intersection. This view shown to illustrate the waterplanes/waterline planes on 'edge'.

Image
In this Body Plan or Section View of the bottom of this V hulled, reverse chine hull, similar in nature to the Kokanee 20.5- we see the Station (Sections) Plan or Body Plan view and this 'stack' of hull intersections shows the cross section of the hull at any point along the Keel plane. Notice the Waterplanes are all on edge, and so is the Keel, but instead of on edge from the top, the Keel plane is on edge from the forward end.

Image
Moving, here above, to the 3D perspective view of the Body Plan or Section View, the lines are now in 3D so the relative positions of the Body Sections are clear in relation to the hull's lines drawing.

Image
Now, finally I'm getting to my point in this post. ( I'm not long winded intentionally, there is a pony buried in this pile somewhere?) This image is why I began this post, but the information needs to be pointed out. This image shows the Waterlines/waterplanes' edges as they intersect the hull bottom's surface.

ALL THE curved (apparent view) waterlines in this image are straight in PROFILE VIEW. IF they are straight in Profile; the hull intersections of the waterlines/waterplanes can be made of flat bar/sheared sheet/saw cut sheet/straight edged extrusions and the time to fit them is extremely short. If they are spaced (vertically) as tight as hull longs; this method of framing can radically reduce hull V bottom, bow forefoot framing time without any sacrifice in final hull strength. The lower edge of each waterline is a straight line and only curves in the Plan View.

Image
Tiny 14 hull in the photo, above with the after hull Longs fitted and deck transverses installed but no bow (cone) framing. The keel is doubled with a plate over the 'V' of the two bottom plate, resulting is decent impact and collision stiffness. This hull is 0.100" 5052 and not recommended for first time builders working in thinned material is actually more difficult than working in thicker sheet and plate. Provided here as reference to a framing method ONly.

Image
Not the best sequential photo I've every offered!!! this pic above shows the bow as framed. There are two sets of curved flat bars VERTICAL to the waterlines, NOT 90 to the hull panels. These two bar sets describe a set of waterlines onto the inner conic hull section of this tiny skiff.

There are transverse elements and legs down to connect the 'waterlines' to the 'stations' and this method of framing allows very fast and easy fits. Once welded, water plane flat bars are every bit as stiff as any other design arrangement but they do need to be planned early enough in the build to be a sequential stiffening of the hull.

I rolled the two 'chine' or outside edge angles in a pyramid rolls to get their shape to follow the chines' taper at this section of the bow. This allowed the short legs to sit on the chine flat but all the pieces are chop sawed, not fitted or beveled. This entire framing took two men two hours, and was welded out. Yes, it is overbuilt, yes you do not need to follow my ideals of "tougher than train wheels" as a design criteria; the images shown are to illustrate a point of design and construction geometry, they are not shown to suggest your framing plan for other boats.

Again, for those who may not be tracking all the metal Building Methods posts? The framing of any metal boat can be oriented differently and achieve the same/equal hull stiffness, safety, longevity, integrity, rigidity as long as the panels of unsupported hull material is not allowed to become large enough to fail in flexure. (oil canning) There are different orientations available in framing metal boats and using bar stock or sheet sheared materials can become a labor savings if those methods are understood and employed with forethought and wise planning.

There are more orientations to this discussion, but I don't have them drawn so I'll skip them for now, not sure they'd add any clarity and we'll be covering them in the Building Methods thread before its done.

If any images, text or combination are confusing and you'd take time to show where and what caused the confusion I'd surely give it my best effort to address that confusion if anyone would please point to the image and text where I can help?

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

scotts
Posts: 3
Joined: Tue Feb 02, 2016 6:53 am
Location: Baton Rouge, LA.

Re: Kokanee 20.5

Postby scotts » Thu Nov 17, 2016 4:37 pm

image.png
Almost done
image.png
Almost done

User avatar
Gayle Brantuk
Posts: 1512
Joined: Tue Nov 11, 2003 1:02 pm
Location: Bellflower, CA
Contact:

Re: Kokanee 20.5

Postby Gayle Brantuk » Fri Nov 18, 2016 8:41 am

Scotts,

WOW! Congratulations to you on your Kokanee. Very nice looking boat! Thank you for posting the photos and I hope you'll post more of the construction too.
Gayle Brantuk
Vice President
Glen-L Marine
Visit our Blog & Create Your Own!

User avatar
Dave Grason
Posts: 3761
Joined: Wed Dec 24, 2003 5:19 am
Location: Nashville, Tn.

Re: Kokanee 20.5

Postby Dave Grason » Fri Nov 18, 2016 9:59 am

Now THAT is AWESOME!!
Isn't it amazing!! The person that never has the fortitude to pursue his own dreams, will be the first to try and discourage you from pursuing yours.

Kevin Morin
Posts: 580
Joined: Thu Jan 24, 2008 11:36 am
Location: Kenai, Alaska

Re: Kokanee 20.5

Postby Kevin Morin » Wed Nov 30, 2016 4:24 pm

Scotts, I'd say we're all waiting for some build sequence images and you can consider them you "Christmas Present" to the Glen-L Forum!

Looking forward to seeing how you did the longs, especially what method you used in the bow area as that was partly discussed above? What paint method, brands and technique? and LOTS of detail photos, in any time you care to spare to help others realize that they do can build their own welded aluminum boat.

I think in your first posted questions you asked about the "correct method" for fitting hull longs (?) and I wondered if you'd share what you learned to be correct, useful, workable or how ever you'd care to describe what you concluded? Nice looking hull, hope to learn more about her and especially her builder's conclusions about the process. Thanks for posting.

Cheers,
Kevin Morin
Kenai, Ak
Kevin Morin


Return to “Metal”

Who is online

Users browsing this forum: No registered users and 2 guests