About a year ago, I attempted to build a Razor 3 from sheets of 0.010" polystyrene. THe objective was to reduce weight without going to foam.
The method worked, and the hull is reasonably strong despite the wobbly material, except that the glue joints (epoxy and CA) adhered poorly, so the work was abandoned, and the hull is being used as a towing dummy. However, I have since received some helpful hints from various Footy sources regarding the glue (Testors plastic cement was recommened; I tested it on sample pieces, and it works very well), and decided to resume this effort.
Needing a new set of panels, and being a lazy person, I decided to try running the plastic sheet directly through my printer, instead of messing with paper templates. SURPRISE! It worked. The plastic sheet is sufficiently supple to go through the bends in the printer without destroying anything. Next we will start building the hull.
A friend has a vacuum-forming business and showed me how he glues parts together. He has a special solvent that he puts slivers of the plastic in to melt, and uses a small glue bottle to dispense the glue. It’s like using liquid plastic to glue the parts together. You had to be careful to use it sparingly or it’ll melt its way through and show on the other side like a spot-weld in metal.
Hey Walt - I have used both styrene and vinyl at work. I wouldn’t bother with glues, the seams will work loose over time and stress. I would use a solvent as mentioned above but I haven’t any experience with thickening a solvent to form a viscose solution.
I apply solvent directly to the joint with a brush, the brush loads up just enough solvent so that the joint bonds but not so much to melt through. At work we use a product called Resin-Bond from Schwartz Chemical. They are an industrial supplier so they will probably not have small quantities to sell but they may be able to point you towards a company that does.
If you want to come into NYC and rendezvous at my work place and I could give you enough to play with. I’ll send you a personal message with my info.
Thank you all for your suggetions for glue. They all have the common objective of containing a solvent for the plastic. The Testor’s cement, which had been recommended by several Footy skipper in the Footy USA newsgroup, also falls into that category.
Progress
The panels have been cut out, taped together, and glued. Before adding the transom, the aft end of the sides were cut at a slight angle to permit a reverse-sloped transom (about ½” was trimmed from the top). This has the objective of allowing increased water line length, because the stern fits further into the corner of the measurement box… The designed transom was discarded, and a new plastic transom was cut to fit the new dimensions. It was then taped in place and glued.
Checked hull in rule box. There is at least ¼ inch of extra length available, which will later be put into a more pointed prow. Weight = 0.7 oz.
Leak test – found one pin-hole leak on port side at seam (gap in glue). Fixed it, and repeated test for 10 minutes with no leaks.
Walt, when moving the hull farther into the corner, remember that the rudder needs to have the full travel used in racing. If you put the rudder all the way to the edge of the transom, it might get jammed by the corner of the box.
Bill, I think Walt mentioned that the extra length would go to making the bow pointier. If the stern remains unaltered it should fit into the same location as the original design and not inhibit rudder throw. If the stern should move aft in some way it should be incremental and probably not change stuff much. Since it uncertain how altering your original design will affect box placement Walt can always use the rudder location as relates to the keel fin location from your original design to peg where the rudder tube should be on the new boat.
Bill and Neill have brought up an interesting point, which I had not considered. The intent of the angled transom was to take advantage of the hull shape, in which the bottom of the transom is narrower than the top. The angled transom allows the hull to be pushed further into the corner of the rule box. The intent was to keep the hull level, in which case it does indeed limit the rudder travel. Neill is probably thinking in terms of dipping the stern, which can also be done, and would allow more travel if shaped properly. My intent is still to keep it level, and perhaps move the rudder pivot a little further forward (maybe 1/4").
Interestingly, a little more angle on the transom would allow even more length, but I didn’t have a good way of taking advantage of it. I had thought about just extending the stern (too late now). Stretching the entire hull is probably the right way to maximize the advantage of the tilted transom, but I have not yet mastered the hull design software.
With regard to Tomohawk’s comment, using the material in a molding process is probably the right thing to do, but beyond my present capabilities.
The glue has some very desirable properties. It is fairly viscous, so you don’t need to tape all the gaps; it doesn’t leak through. It also appears to have a litle elasticity after curing.
It has taken a while to get back to this project, but a new problem has been encountered. Over time, the glue has aparently attacked a little more of the plastic, causing a little distortion. Now there is a series of ripples along the bottom. The plastic is probably too thin to avoid this problem. So the project will be abandoned for now.
Hi Walt, I have been using a styrene glue for a few years now made by Plastruct. it is simular to Tenax but is not quite as corrosive, there are two types, a general purpose cement and a styrene and ABS plastic cement, the later seems to bond well and remains bonded even under hard use. my other hobby is building scale off road trucks and subjecting them to fairly hard use. the styrene/ABS cement will even bond lexan to styrene and lexan is quite hard to get to stick to anything. just my two cents, regards.
Hi Walt . you got me thinking about building a plastic/styrene hull for the footy class. some time ago I picked up a heli canopy for a wind turbine I was making for home use ,it’s one of those things that sit on your work bench in the corner and some day you will do something with it. by cutting the canopy down to stay within box measurements , and adding styrene decking it could be a possible hull. the bow is a little blunt, but not enough to slow her down to much. the canopy is made of lexan and styrene bonds well using the glue I mentioned in last post, she even floats with no leaks.
she is 11.75" long, 5.625" wide , 3.5 " deep and is 23 grams as you see her with rear deck installed. she would be lighter if I had not cut and repaired bow section. the rear deck is .010" styrene over.040" styrene stringers. canopy is for a .60 sized thunder tiger heli.
