Building & Design Tips

Building & Design Tips:

 

1. Stability is the key. Metal keels and plastic rudders are provided with the kit to help stabilize boats. Other ideas to help in this area:

(a) Build boat and test it over and over in bathtub to check for stability. After testing weights can be added to level the boat as it goes in the water, however, REMEMBER THE MORE WEIGHT THE SLOWER THE BOAT. It's best to design the boat so it's stable without having to add weight.

(b) Catarmaran design. This is the most stable sailboat there is. One can be made easily from the BSA kit by cutting the hull in half (down the middle from front to back), and then turning the two halves with the curved side down. Then it just takes the addition of a little lightweight wood, such as balsa, to connect the halves and make a mast holder. The catamaran design doesn't need to utilize the metal keels provided in the BSA kit, and thus the boat is lighter. It is advisable to use two(2) plastic keels however to help the boat run straight and true.

(c) Keep hull flat. Do not round the hull into a V as with a normal boat. The flatter and wider the hull the more stable the boat will be.

Safety First! Catamaran Idea

Unlike the standard design, building this boat requires making cuts through the kit's balsa hull block, and more extensive gluing.  Scouts must not attempt this project unsupervised!  This document is intended only to outline the work required to build the boat, not to teach safe workshop practice. Power tools aren't necessary for this project, and I recommend that they NOT be used because of the small size of these parts. Handle and use sharp hand tools carefully, and be careful to avoid burns from hot glue and glue guns, if used.  It's your (Akela's) responsibility to know how to use your tools safely, and to ensure safety throughout construction!  If, for any reason, you're not completely confident that you and your scout can safely complete this project, please don't try! Building a toy boat is far less important than your safety!  

 

Hull

  1. Make the ponoons.  Before making any cuts, lay all of them out and mark the hull.  The first cut is made down the center of the hull, and makes the two pontoons.  Use a small handsaw (hacksaw, coping saw, hand miter saw, etc.) for these, and be careful to hold the block securely.  The rounded "sides" of the original block become the bottom of the pontoons (facing down into the water) and the centerline cut (that you're now making) forms the top of the pontoons.   My Wolf scout was able to do this himself with a saw with some supervision; my Webelos did it with minimal supervision. Here's a sketch of the three hull cuts: sketch of raingutter regatta hull cut layout
  2. Make the spars.  Use the saw to trim off the rounded "sides" of the original hull (bottom of the pontoons, cuts #2 and #3 above) so that they become flat.  The pieces removed should have a maximum thickness of about 0.1-0.15", making them suitable for "spars" to tie the two pontoons together.  Do this carefully to make the two pontoons nearly equal in size/shape.  Scouts can do the cutting, but will probably need help in laying out the cut lines and starting the cut.  Any inconsistencies between the pontoons can be cleaned up by sanding later.  If you want to use material other than the hull block for spars, this step can be skipped, but the flat-bottomed pontoons made by these cuts run faster.
  3. Sand the pontoons.  Have the scout sand the two pontoons to make them equal height and straight and smooth on the "top" (centerline cut) surfaces.  Holding the pontoons together while sanding with a foam sanding block works well.  Wetted edges of the pontoons can be rounded slightly, but the bottoms should remain flat.  (I firmly believe that sanding is a character-building task which all scouts should master. ;-)
  4. Assemble the hull.  The "slivers" cut off the pontoon bottoms, pieces of mast, or other material are used as spars to tie the pontoons together.  Lay this out and glue the pontoons and spars together, being careful to keep everything square. We use hotmelt glue, but any waterproof wood glue should work as well.  If your pack or district restricts the boat's width (beam), be careful to satisfy this requirement.   (Sand the sides of the pontoons, if necessary, and make an allowance for paint thickness.)   If beam is not restricted, I recommend making the outside edges of the pontoons about 2-1/8" apart.  This is wide enough for very good stability, but not so wide that the boat will bump the sides of the gutter excessively.  Note that the mastless sail design described below won't work if the pontoons are too far apart!  I also recommend using the hull "slivers" as the spars, with the forward edge of one spar at the mast hole cutout, and the aft edge of the other spar at the stern of the boat.  These two locations provide good mounting points for the sail and rudder, respectively.
  5. Sand the assembled hull.  Trim overhanging ends of the spars even with the edges of the hull, and sand the assembled hull for painting (being careful to keep the pontoon bottoms flat).  For the wetted parts of the hull, smoother is faster.
  6. Add mast(s), if desired or required.  The mast isn't necessary, though, and a mastless design with the sail described below will perform better.
  7. Decorate before painting.  Add decking, decals, or other decorations as desired and allowed by local rules.
  8. Seal and paint the hull.  We used sanding sealer/model paint.  Good waterproofing is important to keep the boat from getting heavier during the races from water absorption.  

 

2. Make the boat as light as possible. Drill out the hull, or remove wood from the "deck" of the hull.

 

3. Put sail as low on mast as possible, this promotes stability.

 

4. Tie back sail by tying thread to each of the lower corners of the sail and then securing the "lines" to each side of the boat (tying to a straight pin and then pushing the pins into the hulls is an easy way to do this). This will keep the sail from twisting when being blown on. The sail will stay at a 90 degree angle to the hull and allow it to "catch" the most air possible thereby promoting speed.

 

5. Channeling bottom of boat. Cut channels under the hull of the boat. Some straight back, some in a V with the point towards the front of the hull. This will seem to add somestability and promote speed of the boat. It also lightens the boat which contributes to speed.

6. The bottom edge of the sail needed to be about 1/2 inch above the deck of the boat. If the sail was too low the corners rubbed against the gutter or dipped in the water. If the sail was too high the boat was top heavy and tended to tip over.

7. The boats sailed best if they were balanced with more weight to the rear. This elevated the bow of the boat, and when they were blown, they ran almost even. * The keels needed to be placed about 3/4 of an inch behind the mast. Don't follow the instructions in the kit.

8. The rudder should be placed touching the keel.

9. Blow evenly with the straw at a point about 1 inch from the bottom of the sail. Blowing the boat down one edge of the gutter rather than letting it "tack" back and forth seemed to be the fastest.

10. Use "Krylon" spray paint -- it dries in about one minute on the balsa wood hulls.

11. Wax the hull

12. Add bumpers

13. Practice how to steer your boat in the bathtub before the race.


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