I thought I would kick things off in our new area with a couple of shots of the new footy I am building for myself.
The displacment of this design is just 270grams.
I want to see what happens with a very light displacment design.
I intend to install a 30g total radio package including batteries.So the ballast ratio will actually be better than my previous designs.
I will build a nice rig for this boat with 3mm carbon tubes for spars.
This hull will also be a platform for testing a swinging keel(swings aft when sailing downwind)
I think the swinging keel may just make sailing a footy downwind a whole lot easier and faster.
The plug is made in 2 halves and the deck edge will be rolled. A 3rd mould will be made for the deck.I have built a vacum forming machine and I am going to attempt to mould this hull in thin plastic sheet,We will see how it goes!!
Not related to the Footy topic, but how did yu get your plugs so symetrical? Was it done by hand? Ive tried out of foam and its tough. You think you have them good until one day you see from a certain angle and they arent anything like eachother. Thanks for the info.
Andrew Miller
miller,
I hope that brett responds as well, but here is the method I “came up with.” Im sure someone used this method before me, but I came to this building method on my own. Thus far, has resulted in very symmetric, quite accurate plugs that I think you can build faster than plank on frame. . . that and they are strong and robust to work with as a plug. Hope it helps!
My method is almost identical to Todds,
I design the hull in CAD software then slice it up into 1/4inch buttocks.
Cut them from MDF and glue them togther in the manner that Todd has discribed
It is the best way I have found to build accurate strong plugs as well…even for a one off hull i find this method is fast and provides a more accurate result.
The accuracy is close to CNC in my opinion.
Brett
thanks alot to both of you. Great site by the way ~tb. Hopefully I will have a symmetrical plug in a shape that I want in the near Future. Thanks again.
Andrew Miller
I agree with brett, that on a footy, I would have used 1/8th. On a one meter 1/4 is about right.
I also share the same method as brett for generating my lines. The hull is designed in a 3D cad package, and put through a quick CFD analysis in the computer. After that, the shape is sectioned every 1/4" along the buttock lines and printed out on a full size plotter.
I am in the middle of two new plugs with the help of a friend (and competitor grrrrrrrrr).
The US one meter, has the right thickness and right number of sections for accuracy and speed. The IOM though. . . was a pain due to its beam. using 1/4" thick mdf on a 6" wide boat is no problem (24 sections of mdf). Using 1/4" wide mdf on a 10" wide IOM took forever (40 sections of mdf)! This being said, I would not use 1/2" thick on an IOM as it would be highly inaccurate. Also, the 1/4" thick mdf has a more consistent density through the thickness of a sheet, the 1/2" thick can be firm on the outside and then soft in the middle. This will make fairing the plug accurately a pain in the butt.
I am considering building an AC plug that would be about 76" in length and 16" wide. I think I will use half inch on that. I personally believe the transition point between using 1/4 and 1/2 inch lies in this formula:
(Length in inches) * (beam in inches) = N
If N is less than or equal to 175, use 1/8th
If N is greater than 175 and less than or equal to 450, use 1/4 inch.
If N is greater than 450, use 1/2 inch.
~tb,
That IOM looks like the same idea I am going for with my boat, although it wasnt nec. going to conform to any class. Is this a hull that you sell or purely for personal fun/use? Im going for a maxiZ86/turbo sled idea. Thanks again for the help.
Andrew Miller
I have been living under the dillusion for some time now that once I get a design I like, I will build some and sell them. The truth of the matter has become the fact that I HATE laying up hulls! I love designing, and building the plugs, and building the first boat and getting it on the water and winning races. . . but then the thought of working on another hull comes along, and it almost makes me feel ill!!! who knows though. only time will tell, but in the mean time, no, I do not sell them, they are just for my pleasure, and possibly the pleasure of other members of the Minuteman Model Yacht Club.
~tb,
Might you be interested in selling a plug? Ive been trying to design my own boat, but keep running into snags on every aspect from the computer software to making accurate plugs and so on and so forth. Would love to build a design using a plug I know will at least sail somewhat decent without. I have planked hulls for static models, but never for real sailing and it sounds like I feel the same way about planking as you do about laying up hulls. Email me if you are interested and maybe we can talk details. Millrtme@cablespeed.com hope to hear from you soon.
Andrew Miller
Two cents worth-
(Hi ~tb!) I’ve made lots of hulls for years using nothing but good old 3/4 inch pine glued in layers and have found that the accuracy of the shapes of the layers is usually only a starting point leading to further refinement. I love to carve pine hulls becaues the shavings smell nice, especially when I use a good sharp block plane, and if you have it well secured to a good bench, you can use a draw-knife to rough it out in like two minutes, before using the block plane.
Happy sailing!
nother two cents-
(Perhaps this should be another thread.)
as long as its fair (no bumps), smoothe, and symetrical, it doesn’t matter if you take off too much beyond the shapes of the buttocks, or waterlines. You can always do your hydrostatics(Displacement, center of boyancy,etc) the low tech trial and error way in the bath-tub. I find it is amazing what the human eye can see (lumps on a hull). I’d almost rather trust my eye than what a computer tells me. Though I have seen a lot of darned good curves drawn on a computer. Its like sculpture. I love to get into the “Zone” of just me and my hull shape. Its very pleasurable. If you can hold the hull itself in your hands, and turn it around and look at it, why would you need to see your hull on a computer screen? nothing against computers I hasten to add.
I suppose you can make accurate comparisons between two different hulls in terms of performance by racing them.
You can keep it symetrical by tracing a frame pattern with dividers on one side, and checking the other side with the pattern. Or something like that. A symetrical Deck shape is a good place to start.
Thats all well and good John,I have made a few hulls the way you discribe as well.It is satisfying…but not accurate enough for championship winning models.Often there is only a few mm here and there between design evolutions in the IOM class for example.Builders of these boats have to make sure the hull is built to the EXACT shape the designer intended otherwise the process is pretty much a waste of time.I know…Ive wasted time with inaccurate plugs and models.
No more…I do it better now…comparing the hull shapes minutely in CAD.making the hull plugs as accurate as possible by methods shown above.The odds of taking some 3/4pine and carving it into a race winning IOM are about nill.
Todd, I have done a few plugs by having the MDF buttocks milled by CNC machine.Not as expensive as you might think. 2 sheets of 1/4 mdf will make most IOMs
Saves the tedium of cutting them all out by manual methods…just assemble the jigsaw when you get it from the machine shop.
I don’t know what I’m talking about but shouldn’t it be the end result that matters in a design, not the means to the result? Certainly a few milimeters difference can make a small difference, but isn’t that difference a small variable in a list of a bunch of other variables that vary a lot like changes in wind and sea conditions for a given sail area displacement ration, or skippers dumb thumbs? Ultimately we scratch builders have to rely on our eyes anyway to see if our hulls are lumpy or not no matter how we build them.
Having said that, theres a site called emachinechop.com where you can send CAD files that they sculpt out of specified materials. If you’re into precision it might help.
Hey Brett, any progress on this intriguing design?
I know you’ve been a bit busy lately [:-spin] but don’t forget to keep us informed as you build this one. I’ve got Hullform fired up and ready to go on a light-weight, but I’d rather have you test the concept first!
Between a couple of Footys, TequilaSheila US1m, and a new Soling 1m, I’ve got a couple pojects going, too. I need to retire to have time for it all, but then I couldn’t afford it!
The plug is ready to go…but time is short to produce the model from it just yet.
I have tested progressivly lighter displacments,my current “best design” is at 380g all up.
Its a hard chine design. Hard chine hulls work very well for footys.
The orginal “BobAbout” when well contructed is still one of the best.
The design shown in the pics at 270g will be intersting for sure.
Brett
Brett, any progress with the design mentioned in this thread?
I can not get the photos to open so maybe they have been shifted?
Can you post them here for all to see?
Best wishes, Ian.
Hi Ian,
Not much point finnishing that particular hull now as the new rules have made it a no go. The requirement to use 4 x AA batteries will undermine the ballast ratio to much for my liking.
Now busy trying to find the ideal dimensions/displacment etc under the new Box rule.
I understand mate.
Keep us informed on your progress, there is much interest amongst the lurkers here I am sure.
Any news on your IOM design?
Ian. :tapedshut
