EeZeBILT 50+ RAF Fire Tender
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Well, now that the Crash Tender is pretty well finished, it seems like a good time to consider if it has served its purpose of demonstrating a simple, cheap boat build suitable for kids....

Plan issues.

Accuracy

The plan was drawn up by eye, from a profile drawing on the web, and a number of inaccuracies became apparent as the build progressed. Major ones are:

  • The bow plan shape is too pointy
  • For the front superstructure, the front roof is too small and the rear roof is too large
  • The front chine former (F1) is 1/4 too small
  • Former F2 is 1/8 out of position


  • These are corrected on an error page.

    Practicality

  • You can't quite fit a small 6v gel cell across the battery compartment
  • The hook mount inside the rear cockpit was a bit of an afterthought, and the former could have been moved back an inch here.
  • Access to the motor area is limited
  • The front superstructure is fiddly, complex and tricky to glaze
  • There is a lot of complex sanding and finishing


  • I would like to address some of these on a new plan, but the latter three issues are likely to remain. In practice, once a motor is installed in a small boat it is rarely removed, but it is poor practice to make this difficult! I really need to rethink the front...

    Complexity

    Though the hull is simple, there is rather more work than I hoped, particularly in finishing. There are 17 windows, and, apart from the deck, 7 separate horizontal levels. A lot of sanding!
    The boat looks good, and has many opportunities for adding fittings, but it needs a medium level of skill to complete. I think that this should be a second or third boat rather than a first one, so we still need a very easy introduction model...

    Cost issues

    The basic hull achieved the aim of being low-cost around 3.50 in balsa. However, there were considerable extra costs which need to be pushed down.

    Fittings.
    Shafts, rudders and props are expensive, about 5 upwards for each. The Hobbies prop shaft at 2.60 would be ideal (with propeller!) were it not for the poor shaft quality. I replaced it with 2mm piano wire, which required a 2mm thread cutting. Die cost - 2. However, the problem of a coupling cost of 5.50 still remains. We must see if we can address this. SHG do a plastic coupling range for 2.50, but postage costs....

    Motor and batteries.

  • A cheap brushed motor and NiMh batteries cost 5 and gives reasonable performance
  • A Graupner Speed + NiMh batteries cost 12 and gives good performance
  • A brushless motor +Lipos + charger cost 15 (22 with the ESC) and gives excellent performance (but only for 15 mins!)


  • I think these are reasonable costs (particularly if the motor could be upgraded later).

    It's not really part of the boat build, but a modern radio can be obtained from around 30, and the brushed speed controllers I use come at 2 each from Hong Kong. A brushless motor must have a speed controller, so that puts the price up for the motor, but down for the radio....

    Glues and Paints

    This is the big one.

  • A tube of balsa glue cost 5
  • Five Halfords spray cans (four colours and a clear lacquer) and a tin of sanding sealer cost 39!


  • Of course, I did not use all the paint in these cans. Still, that's a huge cost. I suspect that using thinned polyurethane varnish for initial surface preparation might keep the price down, and with access to a spray gun cheaper paint can be bought. But I need to pay more attention to this aspect. Cutting down on the number of colours would be a start....

    Build time

    Working in balsa, total build time can be very short for an experienced builder. There is time to make a few of these for Christmas!

    Conclusion

    This is probably a bit complex for a small start model. We need a simpler hull. With only one roof...but still exciting... We will have a few more boats coming which should match this specification. Watch this space...
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