Need recommendations -- measurement & design tools

M

Matthew R. Snyder

Active member
Is there freeware available that makes it possible for the non-engineer to mess around with lofting a hull? I don't need results that can be plugged into a CNC machine as I am not seeking to design all the elements of the hull myself. Rather, I need to make some scale drawings of what I have in mind, and possibly a model, so that I can discuss different ideas with a prospective designer/builder.

Also, can someone point me to best practices for accurately measuring key hull dimensions and angles on an existing boat? I'm going to take my current boat and four or five other factory and custom aluminum v-hulls I am familiar with, to measure and compare dimensions like
-- deadrise astern
-- deadrise at stem
-- chine width at various parts of the boat
-- transom width
-- transom angle
-- bow depth

In other words, I'm sort of trying to "splash" a hull so I can modify the design a little and have someone build it for me. Most of these measurements I can figure out how to take with eyeballs and a measuring tape. But a few, especially some of the angles, I am not sure of the "official" tool or technique that'll let me express my findings in terms that a builder can understand. Guidance is welcome and if I actually go through with it i'll be sure to updpate the board on lessons learned.
 
Thank you! with what do I measure what I have? I went out and tried to hold my grade-school protractor under the keel and lost it in a snowdrift... Surely there's an easier way?
 
Wish I could help but I don't know what you're trying to measure. Adding some photos of your current project will help.
 
HI Mathew. Over the years, WoodenBoat magazine has run articles about varios ways of measuring boat hulls with the intention of accuratly duplicating that hull shape in new construction. As I recall there was an article in one of the last couple of issues. Some of the highlites of the process as I recall it , is that the hull must be firmly blocked up with the waterline level in both planes, fore and aft and side to side. It helps if the boat is up high enough that the person doing the measuing isisn't crawling around on the ground. One of the articles detailed using a laser level, like you use in home construction and a plumb bob to measure depth and width at evenly spaced distances from the waterline down to the keel. Then you record all these X-Y coordinates and theoretically, you have a numerical record of the hull shape. Mind you that is the barebones description of the process, and reading the article(s) would provide much more detail on the method. Oh yeah, you only measure the side of the boat that looks fairest to your eye. Then you use those measurements on both sides so that your boat is symmetrical.

John Bourbon
 
My points of departure (possibly from sanity):

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18' Lund Alaskan

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20' Lund Alaskan

The Alaskan hull (the hard-chined model years in the 18 and 20 class) gets a lot right for how we hunt. A grow'd up 18 would be neat ... call it about 19, maybe 19'6" with a 90 hp on it, 90" beam max, and max out cockpit space by minimizing the "three F's" (foam, foredecks and fruity lockers) that so limit the factory boats' utility.

There's a gap there in Lund's, and everyone else's, model lineup ... At the risk of over generalizing, I've never personally driven one of the west-coast sleds but on paper they are all heavier, and rated to carry less weight than my little boat; most of the other "name" builders either build goofy looking boats, or they are suckling at the teat of government contracts and New England wealth. In short they want to sell more aluminum than I want to buy, and they don't have any incentive to diverge too much from their general program especially for a smaller, spartan project like i'm considering.

Worst case, I'll go buy another Lund when it's time to replace mine, but recently I am finding out about a few smaller commercial-boat builders who seem hungry for my kind of business. If I can freeload off of Lund's (and a little bit of Jack Winninghoff's) hull design expertise in the process, I'd like to at least know that I'm holding the ruler by the right end.
 
Hi Mathew. I know what you mean by the mfg'ers having a hole in their line ups.....That spot you show, launching through the ice. Would that by any chance be Dillinback Bay on Champlain?

John
 
Matthew, best hull shape for breaking Ice is a v-bottom scow or garvey I worked winters in the ice, with outboard powered boats. Anything with a point tends to wedge into the ice,, a flar bottom scow or garvey usually tries to ride up on one chine, the other breaks the ice and you have trouble controling it. The v-bottom garvey will ride level on the ice until the only thing in the water is the lower unit. It will remain totally manageable while only leaving a foot wide track thru the ice. There are a lot of builders making some pretty rugged boats like this in lousiana/ Mississippi area. Check out Boats and Harbours a monthly commercial boat magazine. Rich
 
Ever consider taking the Alaskan you like and having some re-do the interior? I know a few folks around here who have done this and have been very pleased with the results. We happen to have a couple of fabirications shops that do this sort of work right here in the Twin Cities. It isn't cheap but it is nowhere as expensive as it will be to design and have your own hull built from scratch.

Just my opinion.

Mark W
 
That's Oneida Lake ... which drives a LOT about how we rig boats to hunt, fish, haul, and play on the water. We also hunt throughout NYS, much of the mid-Atlantic and lakes Erie and Ontario.

Oneida's a shoaly lake prone to high winds and high-frequency, steep-trough wavesets, no rollers. Long runs of 15+ miles aren't unusual, especially when we're fishing. The scow design is not real popular around here; most boaters prefer a sheer cutwater to make the repetitive wave impacts more of a slice than a crunch. There are a couple guys with big jon boats, but they all have good chiropractic help, too.

The Alaskan's sheer bow gets the job done. The Alaskan's deadrise astern is marginal compared to most deep-V boats here, but that has benefits such shallow draft, capacity for massive amounts of weight, and stability. Much like a scow design, the small deadrise makes it easier to run in the ice, especially with as much weight as I usually carry hunting. Not as easy to run as the scow, but easy enough (we run with jack plates too which helps a lot).

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I love this picture. It was a real good day... no waves that day either. That little island two miles off in the background is where we hunted. 2" ice both ways; at the launch it was about 8" thick when we started. My Alsakan's been used like that for 13 years and this is about all the wear-and-tear I've experienced on the hull:

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No leaks and no rivets are loose, but if I ever need to replace that keel piece it's about a $4K job because no welder that knows Lunds wants to touch that part of it ... the substrate is .100 aluminum with rivets and sealant everywhere. To change it out requires ripping the floor out, drilling out all the rivets and re-assembling, basically from scratch. I don't honestly think that the Alaskan gives up anything to most welded boats in the toughness contest, but at least when a welded boat breaks (which everything does eventually, given how we use it), I can get it re-welded locally. I've seen and hunted out of some re-furbed Alaskans and they're super-nice but if I'm going to go that route I'll prolly just buy a new 18 and start over.

And yes, Jack, we get those tangles too. Somewhere there's another photo I took just after this, not family-friendly enough for this forum, but imagine the same action with a lot more digits pointed at the cameraman...
 
Matthew, as to angles of deadrise and hullside flare, the electronic levels they sell in homedepot/Lowes work great. Look at a set of hull lines and I bet you can figure out how to take the lines off your boat and get them down on paper. You need a solid reference to work from. A boat your size should call for stations every foot. A level line under the keel down the center and perpendicular lines out from the center line should be enough to get you your half breadths which overlaid over one another gives you your body plan [front view]. once you have the body plan and the spacing of the stations, you can plot the profile and plan or top view. On a boat like yours you dont need to go into a lot of detail, keep it simple. There are a lot of books on lofting, woodenboat book section probably has what you need. A warning most books I have seen overcomplicate it. In my buisness we let the computers loft, fair and cut our construction jigs. What used to take us a month on our knees now takes a week or so for an outside contractor, and the jigs are incredibly fair. Rich
 
Ahhhhh .... ha! I hadn't thought of that (been trying to figure out how to do the same thing with a bob and a measuring tape and a flat piece of ground) but your way makes a hell of a lot of sense.

Any reason I can't measure over the strakes? They're the same height throughout (e.g. a level laid over any two parallel strakes will give the same reading as if I could lay it right up against the hull).

And does that workboat magazine you mentioned have a Web site?
 
Matthew, glad that made some sense. Find a real flat floor, a wood one is easier Either lay down two and a half sheets of cheap plywood , one edge should be your centerline.Align your boat over your lofting floor, keel aligned with one edge. Of course level your boat as to how it sits in the water fore and aft get a big drywall square and lay out your grid which will be your reference the grid ahould look like a ladder on the plywood. The distances from center line will give you your plan view.With a plumb bob measure distance from the keel to the chine and sheer at one foot stations or stations,plot these on your grid. When all references are plotted on your lofting floor use a skinny fairing batten and some finishing nails and draw out your chine and sheer. Now with a level or plum bob, you can plot your profile view off your baseline or wl.#1 record these on paper to transfer to your lofting floor when you draw your profile. Both are usually drawn over one another. Now that you have both the plan view and profile on the lofting floor you can use one of the middle stations and plot out your body plan. Sounds easy doesnt it? When I draw a boat from scratch I use a fishing rod blank for my curved lines, works better than ship splines.Hope this helps Rich
 
I haven't read through this entire thread, but I have to ask this. With all the hundreds of thousands of boat plans out there, is there is nothing close to what you want? Would it not be easier to to take proven plans and make any modifications you see fit?

I mention this because that is what I have done twice. I took a planing hull scull boat design and made it a displacement. Then I took a displacement hull sneakboat design and made it a planing hull. There were other changes as well including width and height.
 
That might be where this path eventually leads, and I'm trying to start with the Alaskan as my basis of comparison b/c it's a pretty unique hull that I am very familiar with. There are some boats that look very much like an Alaskan that handle nothing like it (like most of the big Starcrafts I've been around); and boats that look nothing at all like an Alaskan but handle similarly (like Winninghoff's duck boat). I have access to take measurements of several such hulls, to do some comparing. Not sure where I would look for V-hull aluminum boat plans, but if you know of a place, I'm all ears.
 
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