View Full Version : Lobster Boat Model
02-06-2005, 08:28 PM
I'm building a Lobster Boat model and am having some trouble bending the ribs. I'm building the model based on the methods described in the book "Model Boat Building - The Lobster Boat" by Steve Rogers.
The system used is the reduced buttock lift method... where a solid model master is built and frames are bent over it. The author suggests 1/8" x 3/16" ribs made of poplar with face grain on the wide face. He says to soak these in amonia for 48 hours to soften 'em up, then to bend 'em around the mold and nail 'em in place.
I've followed his instructions to the letter and the ribs crack when they are bent. Anybody out there familiar with A)using poplar for ribs and B)soaking them in amonia to make them pliable.
At this point, I'm thinking that steaming them as with full size building might be my best bet.
Any thoughts? :confused:
I am surprised that poplar was specified.It is not considered to be a good bending wood. Here is a list of bending woods with 100% being the best.
white oak 91%
red oak 86%
black walnut 78%
Or so say the U.S. department of forestry.
You can soak the strips in soapy water to help allow the grain to slip.You also need flat grain without grain runout to avoid breakage now and later.
- Checked the chart and poplar is 58%..
[ 02-06-2005, 10:40 PM: Message edited by: RonW ]
02-06-2005, 10:06 PM
A little heat wouldn't hurt. No need for a steam box unless you want to do completely scale construction. I did the ribs for the cat's paw model in a cookie pan (too long for the only other cookware she would let me use).
A metal strap, just like the big times, would probably help.
What's the bend radius ?
02-07-2005, 11:14 AM
Make sure you've got pieces with nice straight grain and little or no grain runout.
With pieces that size you might try boiling them. That should soften them up nicely.
My recollection is that while highly concentrated and pressurized amonia will soften wood to an amazing degree, household amonia is not supposed to do much of anything.
02-07-2005, 11:23 AM
I have the same book, but have not yet attempted to build the model yet. From the photos, the wood looks kinda dark to be poplar, but that might be one of the effects of the ammonia. I'll be interested to know what wood you find that actually works for this as I've been wanting to build this model for a couple years.
02-07-2005, 12:56 PM
Thanks for the input! I'm thinking part of the problem is grain runout which is going to be hard to alleviate at such a small scale. I'm not sure why the author specified poplar??? The instructions given were hard to follow in other areas, so who knows.
I'm thinking I'll try another wood type next and boil the stuff. I'm just glad I won't be re-milling all those ribs at full scale! ;)
Also, Skiff Junkie, the polar started out light in color and the amonia turns the wood that color after soaking for several days. Though mine didn't get quite as dark as the stuff pictured.
02-07-2005, 02:40 PM
I'd bet that grain runnout is going to be just as important as it is on full size frames. One technique for establishing the grain direction that might work especially well for something this size is to take the block of wood from which you are planning to cut the frames and split it in half both ways. Then cut your frames parallel to the two split lines. If the block is too thin to split both ways then just make sure you bend the frames so that the face that is parellel to the split line is on the inside or the outside rather than fore or aft.
I will add that besides grain runout, the obvious answer in bending wood is the bendability of various species.Poplar is not considered a wood to be used for bending stock, so change to a wood that is considered a good bending wood.Instead of trying to soak it for days in ammonia. They make mast hoops as small as 6inches out of white oak, bends in a complete circle.
I will get a little harder too on the designer. I would be willing to bet that he has never seen or even knew that such a thing as charts showing the bendability of wood even exists. If he did he would not have specified poplar.
The internet is bringing out the wanna be designers. They want to design and sell plans on the internet and sit at home and get rich. Thats cool. BUT it might be wise to say the least, to buy full size boat plans from a honest to god licensed marine architect. It sure isn't necessary to be a marine architect to sell plans for model making.But they should at least do their homework for proper plans that work.
But it is unfair to you, the consumer to buy plans and then find out they are a little sketchy here and there, don't show or exsplain this or that. And then the materials specified don't work, and are about the poorest choice possible.
I am sorry but I have no sympathy for these guys selling plans, taking your money, and calling themselves designers.And then it doesn't work.
Good luck with your lobster boat, they are neat.
02-07-2005, 04:21 PM
I do think it's worth noting that the author of the book presumably built the model in order to document the process and so at least in that case poplar worked well enough. Also, many of the woods that bend well have a fairly course texture that may be problematic (visually) on the scale of a model. Given the dimensions of the pieces in question, I suspect that poplar with less grain runout might well bend just fine. Remember, stiffness varies as the cube of the thickness so very small pieces of wood will bend better than their scaled up counterparts on a real boat.
02-07-2005, 04:59 PM
Try using green (undried) wood, chuck it into a pot of boiling water. Lowell P. Thomas, Naples, FL
02-07-2005, 06:32 PM
The lobster boat in question was designed by Alvin Beal and is a Beals Island Lobster Boat from 1935-40. I suspect that Bruce is right about poplar being used because it is fine grained.
Beals Island lobster boats are first class.
But you are working from the Book Model Boatbuilding lobster Boats by- Steve Rogers.
So I take it for granted that Steve Rogers specified poplar for ribs not Alvin Beal.
I don't agree with the opinion of fine grain, in looking at the list above, off the top of my head I know walnut, beech and birch are finer grained then poplar.
Now I am not being rude or trying to run the thread into the ground.But people selling plans, or books need to be accountable for their recommendations.Rather then trying to figure out how to make it work, or justify the writer's recommendation. It may just come down to the simple fact that the author has not done their homework which results in poor recommendations and trouble for you. I know it is just a model.
Sorry for the rant.
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