Catastrophe

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

Moderators: Bill Edmundson, billy c

TomB
Posts: 144
Joined: Wed Jan 18, 2017 4:07 pm
Location: Holland, MI

Re: Catastrophe

Postby TomB » Tue May 23, 2017 2:43 pm

As we build wooden boats we leave the orthogonal world behind…nothing square …nothing plumb…nothing to clamp to…isn’t it grand! :D :D :D

If your Tahoe 19 plans are similar to my Tahoe 23 plans...

With respect to transom design, have a look at the pattern drawing for the profile of the plywood transom (the REAL transom). The transom profile is set at 30* on the aft edge of the plywood. (Cutting to the profile will leave you a piece too small on the top and sides as noted on the drawing.) The suggested camber for the false transom (transom veneer) is shown on the same drawing. For a suggestion for reinforcement between plywood transom and veneer see instructions page 11. Be sure to leave space around the edges of the reinforcements for the corner caps (#7 called out on instruction page 4)

There aren't many dimensions and there is a lot of information. KH made it like a treasure hunt. :wink:

ToddM
Posts: 88
Joined: Mon May 08, 2017 5:51 pm

Re: Catastrophe

Postby ToddM » Tue May 23, 2017 4:07 pm

TomB wrote:With respect to transom design, have a look at the pattern drawing for the profile of the plywood transom (the REAL transom). The transom profile is set at 30* on the aft edge of the plywood. (Cutting to the profile will leave you a piece too small on the top and sides as noted on the drawing.) The suggested camber for the false transom (transom veneer) is shown on the same drawing. For a suggestion for reinforcement between plywood transom and veneer see instructions page 11. Be sure to leave space around the edges of the reinforcements for the corner caps (#7 called out on instruction page 4)

There aren't many dimensions and there is a lot of information. KH made it like a treasure hunt. :wink:


Yes, that is the way I see it. I was questioning the other poster on the plan pages, because it sounded like he had a page with dimensions on the frames, which I do not have. I am not complaining, and I don't see any problem, especially because the other posters warned me not to expect dimensioned plans. I am glad they did, because their experience told me not to panic. Coming from a background where I read dimensioned plans all day, it is nice to see other ways to do things.

The lack of a pattern on the transom seemed worrisome at first, but then i saw the called out angles and what will be will be. Rough cut it a bit large, and make it look pretty.

I don't know if I can deal with nothing square, level, or plumb though. That may be a bit frustrating. Maybe that is why I don't like drywall.

Speaking of making it look pretty, I need some advice. Per Roberta's directions, rather than order the barrelback and try to rotate the transom, I ordered the Tahoe and am drawing a barrelbacked form of it, and I need advice and opinions on pitfalls, mistakes, no-no's, oopsies, and anything that looks a bit hincky. I will try and attach a couple of pdfs. If the attachment is successful, the red are the frames as they exist on the plans, and the green are the frames modified.

Never mind. I have to go back and give more weight to the lines, and make the files smaller.

ToddM
Posts: 88
Joined: Mon May 08, 2017 5:51 pm

Re: Catastrophe

Postby ToddM » Tue May 23, 2017 4:31 pm

Speaking of making it look pretty, I need some advice. Per Roberta's directions, rather than order the barrelback and try to rotate the transom, I ordered the Tahoe and am drawing a barrelbacked form of it, and I need advice and opinions on pitfalls, mistakes, no-no's, oopsies, and anything that looks a bit hincky. The red are the frames as they exist on the plans, and the black are the frames modified. Nothing has been changed below the set-up line
Trimetric.jpg
Stern-View.jpg


I figure next is to draw some longitudinal lines and see where the humps and dips occur?
Last edited by ToddM on Wed May 24, 2017 6:54 am, edited 1 time in total.

User avatar
sproggy
Posts: 148
Joined: Sun Jan 01, 2017 12:04 pm
Location: Welwyn Garden City, UK

Re: Catastrophe

Postby sproggy » Wed May 24, 2017 12:51 am

ToddM wrote:I was questioning the other poster on the plan pages, because it sounded like he had a page with dimensions on the frames, which I do not have.


The plans I have aren't Hankinson designs so I guess he does things rather differently from the Glen-L designs. I have full dimensions and construction details for each frame.

Regarding your proposed changes you have too sudden a transition from the curved profile at the sheer on frame 4 to the original profile at frame 5 (numbers assume your first frame on the left is the transom). With the barrelback design the sheer is effectively pulled in towards the centreline at the transom, not rounded off as you have done. It changes as you move forward from giving a smooth transition into the deck at the transom to having an 'edge' further forward.

So try moving the sheer in towards the centre rather than rounding it off - that will give you the transom profile you want while allowing for fair curves at the sheer. You can see the principle in this picture of a simple barrelback model:

Image

It's crude compared to full size but you can see clearly that the sheer is pulled in at the transom. There is still a recognisable sheer and the profile of the side transitions from the barrel back into straighter sections forward. So rather than putting a radius on the sheer only you need to work on the side frames from the chine up. You'll probably need to work below the setup line to get the curves right. It's not easy to get good lines so proceed carefully. The sheer must be perfectly fair in both plan and profile otherwise the boat will never look right. I did the same with the Overniter design - see viewtopic.php?f=2&t=30753&p=188218&. All changes were aft and above the chine and transitioned into the original design from frame 3 forward.

Keep posting on here as you progress as people may point out issues with your design revisions that you might miss - there's loads of experience on here with both the Tahoe and the Barrelback. For example if you're planning a rear cockpit as in the standard Tahoe design it'll probably have to be narrower because of the barrel back pulling the sheer in.

ToddM
Posts: 88
Joined: Mon May 08, 2017 5:51 pm

Re: Catastrophe

Postby ToddM » Wed May 24, 2017 7:15 am

sproggy wrote:

Regarding your proposed changes you have too sudden a transition from the curved profile at the sheer on frame 4 to the original profile at frame 5 (numbers assume your first frame on the left is the transom).


Totally agree.

ToddM
Posts: 88
Joined: Mon May 08, 2017 5:51 pm

Re: Catastrophe

Postby ToddM » Wed May 24, 2017 7:19 am

Oops. After reading Sproggy's response, I realized that I had not explained what the goal of the stern and transom modification is. Here it is.
Riva Ariston.jpg


Just the stern and transom treatment, not the seating arrangement or the engine location.

User avatar
gap998
Posts: 375
Joined: Wed May 20, 2015 5:40 pm
Location: Wales, UK

Re: Catastrophe

Postby gap998 » Wed May 24, 2017 2:56 pm

Regarding castor loading, materials handling standard for four castors: -

weight of transport equipment (build frame) + load (Hull weight)
three

For three castors, divide by two.

This has an allowance for safety & durability in industrial applications so is probably OTT for a one off build but will give you confidence it wont fail.

Sproggy is right about the sheer line - That's exactly what I did with my Barrel back mods; Start with your desired transom profile and curve the sheer in to meet - this should give a gradual transition to your original sheer line toward the bows.

Also you Transom bottom is flat on your wireframe - I'm sure the Tahoe has a moderate deadrise?
Gary

Planning a whole fleet, but starting with a Zip...I think.

"Just when you think you've made something idiot-proof, someone builds a better idiot!"

ToddM
Posts: 88
Joined: Mon May 08, 2017 5:51 pm

Re: Catastrophe

Postby ToddM » Wed May 24, 2017 5:30 pm

gap998 wrote:Regarding castor loading, materials handling standard for four castors: -

weight of transport equipment (build frame) + load (Hull weight)
three

For three castors, divide by two.

This has an allowance for safety & durability in industrial applications so is probably OTT for a one off build but will give you confidence it wont fail.

Sproggy is right about the sheer line - That's exactly what I did with my Barrel back mods; Start with your desired transom profile and curve the sheer in to meet - this should give a gradual transition to your original sheer line toward the bows.

Also you Transom bottom is flat on your wireframe - I'm sure the Tahoe has a moderate deadrise?


Thanks. Good catch. The cuts below the setup line will still be made straight from the transom pattern, but it's nice to have it right. And I got to learn a new word, 'dead rise'. The context was explanatory, but I looked it up anyways.

ToddM
Posts: 88
Joined: Mon May 08, 2017 5:51 pm

Re: Catastrophe

Postby ToddM » Thu May 25, 2017 10:17 am

Here is the 2nd try.
Back.jpg


The green are the original transom plywood and frame 5.
The red are the modified portions of the transom through frame 4.

Please feel free to critique and especially any aspects that will cause problems.

TomB
Posts: 144
Joined: Wed Jan 18, 2017 4:07 pm
Location: Holland, MI

Re: Catastrophe

Postby TomB » Thu May 25, 2017 12:55 pm

If I understand the look you are going for: Tahoe below the waterline; Tahoe stem; Barrelback deck; and Barrelback transom tipped forward 30*. Or to put it another way, something like a 1969 Riva Aquarama
1969 Riva Aquarama.jpg

or a 1960 Riva Aristian.
1960 Riva Aristian.jpg

The Glen L boats and the two Rivas all used covering boards and rub rails on the deck at the sheer, twisting from horizontal on the foredeck to following the curve at the transom. They all have some sort of edge between deck and hull from the first frame forward. The Glen L barrelback uses the combination of twist and covering board thickness to smooth out the corner as much as possible. Some older boats used really thick covering boards and then carved away to get more curve. On the other hand you don’t have to have a covering board at all. This is a VanDam take on a vintage race boat, all curve.

If you are thinking of using covering boards, you might want to lay them into the sections to let them help define the shape.

On my build, I followed the Tahoe frame lines from keel to sheer, and made the frames a little wider so that I would have room to do some shaping between chine and sheer. Then I moved the sheer notches a little closer to the centerline while fitting the sheer clamps to create a little more tumblehome aft (0” at frame 5 up to 1 ¼” at the transom). I am holding off on the deck beams for now, in anticipation of maybe increasing the camber of the deck an inch or two, which would further soften the break between deck and hull.

User avatar
sproggy
Posts: 148
Joined: Sun Jan 01, 2017 12:04 pm
Location: Welwyn Garden City, UK

Re: Catastrophe

Postby sproggy » Fri May 26, 2017 12:51 am

ToddM wrote:Please feel free to critique and especially any aspects that will cause problems.


The comments I made before still apply. 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. I would suggest that you study the many photos on the forum and build blogs of Barrelbacks in-build and look at the frame shapes, then try to come up with something that more closely matches them and will also merge better with the Tahoe form forward. It'll look more 'resolved' and likely be easier to build too.

Check out also the Belle Isle body plan:

Image

It's a barrel back design but every frame, transom excluded, has a clear point at which the side transitions into the deck.

The Clarion 23 is similar but this bodyplan shows more sections:

Image

Again, the sheerline is clearly defined and clearly visible other than right by the transom.

You could go ahead and build the frames as you have drawn them and you will end up with an interestingly-shaped boat but it won't look like a Barrelback, if that is your primary goal. Or a Riva. Check out the photos that TomB has posted - you can see the sheerline where the sides meet the deck over the entire length other than, perhaps, the last foot or 18" where they blend together.

Having said that, it's your boat and you can make it look however you want, whether you want a Barrelback/Riva shape or the unique one that you have drawn. There's nobody (me or anyone else) telling you that you have to design or build it a certain way but it seems to me you're wanting a particular design that you've not yet arrived at with your drawings, hence my comments.

ToddM
Posts: 88
Joined: Mon May 08, 2017 5:51 pm

Re: Catastrophe

Postby ToddM » Fri May 26, 2017 6:48 am

I am not disregarding the sheer line. I just had not gotten that far. I am drawing the sheers now, along the lines of the Ariston, which start to round off at the 4th frame. As it turns out, after drawing the sheer through frames 6,5,4, and 3, I had to redraw frame 4 because it had too much curve, too soon, just like you said. I may have to redraw 1 through 3 also? Thanks for taking the time look at my drawings and critique them. It is very helpful, even if just for confirmation.

User avatar
gap998
Posts: 375
Joined: Wed May 20, 2015 5:40 pm
Location: Wales, UK

Re: Catastrophe

Postby gap998 » Fri May 26, 2017 7:02 am

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


Even so, this would probably be easier to achieve as a modification with a lower twisted sheer as described previously and curving the deck from the sheer upwards.

Good luck!
Gary

Planning a whole fleet, but starting with a Zip...I think.

"Just when you think you've made something idiot-proof, someone builds a better idiot!"

User avatar
sproggy
Posts: 148
Joined: Sun Jan 01, 2017 12:04 pm
Location: Welwyn Garden City, UK

Re: Catastrophe

Postby sproggy » Fri May 26, 2017 9:54 am

ToddM wrote:I may have to redraw 1 through 3 also?


How many frames does the Tahoe have - 6 plus the transom? 6 including? Either way, I would say you should have blended your revised aft section into the original design by that point so they would be unchanged. Otherwise you'll interfere with the lovely concave shape of the forward section.

ToddM
Posts: 88
Joined: Mon May 08, 2017 5:51 pm

Re: Catastrophe

Postby ToddM » Fri May 26, 2017 10:29 am

sproggy wrote:
ToddM wrote:I may have to redraw 1 through 3 also?


How many frames does the Tahoe have - 6 plus the transom? 6 including? Either way, I would say you should have blended your revised aft section into the original design by that point so they would be unchanged. Otherwise you'll interfere with the lovely concave shape of the forward section.


10 plus transom


Return to “Hankinson designs”

Who is online

Users browsing this forum: No registered users and 3 guests