Hi Ianh, I cannot be entirely sure but I recall having seen them on other plans. They appear in a random fashion and I believe they are simply the way the draughtsman has chosen to rendered the drawing to indicate plywood. I'd be surprised if they were for any other reason. 🤞

Why not use the altogether more robust and cost effective Lithium/Iron Phosphate (LiFe) cells. They are the type of cells offered as an upgrade over NiMH by some power tool manufacturers, such as DeWalt. Theses packs often appear for sale new and secondhand on ebay. The method of harvesting them for our purposes is not difficult and can be found on a number of RC forums, or buy them new from HobbyKing and simply solder your own configuration, you will need to incorporate a balance plug in the same manner as a Lipo. Advantages include: a robust metal outer case similar to that of NiMH, they will not Ignite if punctured, they can withstand very high fast charge rates and even recover well from inadvertent over discharging, they have high thermal stability and are capable of sustained high current drain equaling that of Lipos and have a useful 3.3 volts per cell. Any sight increase in weight over Lithium Polymer in a boat is negligible and possibly at times desirable. You will find practically all modern chargers capable of charging Lipos will have a setting to accommodate Lithium Iron cells as well. The accompanying pic shows a pack I safely and simply re-constructed from a spare DeWalt power pack following the forum instructions. Fully charged the pack registers 20.3 volts and has maintained the same voltage after one year. A downside to some users could be that the max capacity of each cell is only 1.6Ahr however by doubling up the series pack and wiring in parallel a quite useful 3.2Ah will be attainted. Typical life expectancy of a new pack is in the region of 2000 cycles, I wonder how many Lipo owners could claim that.

Look for something like Kaowool, its a manmade fibre. I'm using two layers of teh 1/16" thick with a sheet of baking foil between on my Fowler (5" boiler, 1/8" gap) you can get it in thicker sheets or just double up. Not expensive you should be able to do it for under a tenner.
If you can't find it then M J Engineering stock it.
http://www.mjeng.co.uk
Blackgates Model Engineering Supplies also do Kaowool in 1mm, 2mm and 1/4" http://www.blackgates.co.uk

Hope this helps.

http://www.mjeng.co.uk

http://www.blackgates.co.uk

If I may suggest, a 21 size engine will be far too small and you'll be disappointed if you want it to plane, you would need something more like a 52 or even a 61 for a 46" hull. Moreover with the monotonous high pitch whine they'd also sound and therefore look pretty un-realistic. With an abundance of highly efficient brushed or brushless electric motors now on the market, electric is really now the way to go. Although initially electric propulsion is a bit more expensive to set up than I.C. electric motors are now equally as powerful as I.C.,if not more so, and there is a size to suit practically any model. They are also extremely reliable and convenient and due to environmental issues you are going to have a far greater choice of sailing locations to choose from and with the bonus that your model will always stay clean!

Mmmm.... turn fins? Perhaps he means a 'dagger plate' a vertical fin that should help prevent the boat from rolling and filpping on turns. Just theorizing I'm not sure though if two would be the answer, I wonder if they might actually hinder. With a single plate of the right size placed centrally the boat would be still be restrained from too much sideways roll yet not lose any directional control being able to pivot on the single plate, where as two plates would tend to act like two fixed rudders and be hinder to turning. I also fly planes and I agree with Dave M about fine control, if using a computerized radio dialing in both rates and expotential helps compensate for over enthusiastic waggling of the sticks and is nearly always required for fast craft particularly first time out. Anyway that sure looks like fun, that's a serious handful and on just 7 volts, well done!

HI Dbninja, weight makes a measurable difference to how any given model performs, could you give us an idea of the overall weight, thanks. Colin.

Any chance of details on the power set up?

Nice scale-like performance could you tell us the total weight of the model?

Unless you are contemplating fitting a gearbox to the 850 I would in terms of motor efficiency really be looking at a twin brushless setup, particularly for a craft of this size. Brushless motors are now in very wide use in model aircraft where they really do excel,from the very smallest to the extremely large models and are equally suitable for marine use. Unlike a brushed motor they are particularly efficient, they do not require a gearboxes to Improve their output so they are well suited for direct drive. Brushless motors also offer the best power to weight ratio when compared with a standard bushed motor and produce fantastic torque equaling and in many cases exceeding that of many I.C.engines. Also Important with the Fire Tender try to keep the overall build as light as possible, the original Fire Tender built entirely from birch ply and with all of its solid metal fittings was needlessly quite a heavy lump and thus often resulted in disappointing performances. it is as well to remember that heavy aircraft don't fly well and similarly heavy boats will take disproportionately more power to get up on plane,and will be more prone to dig in on turns, a light build will always outperform a heavier one, with the exception of displacement hulls of course. in terms of guidance I have an EMAX BL4030/10 which can easily turn a 15 x 7 aero prop, it is extremely powerful and runs on between 18 - 30 volts, the mounting is easily adaptable for a marine installation, one or two of theses would give you an powerful and efficient setup for a scale performance with power to spare, you will of course need the appropriate speed controllers preferably water-cooled. Finally always set up using a Power Analyser so you know exactly what current the motor drawing and can observe that your speed controllers/batteries are not over stressed. Good luck with you