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[ChrisR]

Hi everyone.

My Dad is making me a 7/100 scale Fairline Targa 38. He's done four or five excellent warships, all from blueprints and photos, but this is his first motor yacht. We'd be grateful for some thoughts/advice on the following please:

1. Will an all-wood hull do the job? I want to achieve realistic planing speeds so presumably it will need spray rails. Could they be glued on once the hull shape is finished? Are there other factors to consider?

2. What sort of propulsion and steering would be best? The real thing has twin outdrives, but I can't find any at the right scale (1:15 would be close enough). I've seen a kit boat (Robbe Najade) that just has a single prop and twin rudders, so maybe that would do? It will be invisble most of the time anyway.

3. On the actual boat, the transom is flat and the sides of the hull extend (a bit like vertical wings) under the edge of the bathing platform. Is that necessary for stability or would a simple flat transom be OK. Does that depend on the answer to question 2?

Many thanks for any help.

[pompebled]

Hi Chris (and Dad),

1) Yes, all wood is fine, if you take the trouble to build as light as possible.
If I looked at the right boat, it's going to be about 80 cm long, right?
Take a look here for materials used: http://www.modelboatmayhem.co.uk/forum/index.php?topic=34033.0

This one comes rather close, just a bit larger:
http://www.hobbyking.com/hobbyking/store/__16521__Princess_V_Hull_Boat_1000mm_Fiberglass_Hull_Only.html

At 'only' 80 cm length, you need to build very light, to be able to maintain a realistic waterline at rest, bigger would be better, as you'll have more buoyancy.

The under water hull will look something like this:
http://www.r2hobbies.com/eng/proddetail.php?prod=rcbt0028_code
Notice the spray rails and strakes.

I have two of these hulls and each one weighs about 2650 grams, ready for the water, the topspeed with the stock motor (3650 1880KV on 4S lipo) is about 65 km/h (40+ mph), runtime 6-7 minutes full throttle.
Just to give you an indication of the weight/speed relation.
For a yacht I would not want it to be much heavier than 3-3,5 kg when 80 cm long.

2) If you want long runtimes and performance, a single motor would be the most efficient solution, as one big motor can turn a bigger prop, which in turn are more efficient than smaller ones.

Motorwise you have the choice between brushed and brushless (inrunner and outrunner).
In general the brushless motors are lighter and provide considerably more power with the same motor size.
Of the brushless motors, the outrunners provide the highest torque compared to similar sized inrunners.

There are steering outdrives available, like on the Fairline Targa 38, but these are limited on the power that can be applied, most likely the wrong scale and horribly expensive

3) The extensions are support for the swimplatform, so a flat transom is no problem.

Let us know if you have more questions

[ChrisR]

Thanks for the reply, yes you're right on length. From pulpit to aft end of the platform will be 85cm.

We hadn't anticpated using glass, just sealed and painted wood - do we need to rethink that? Would the spray rails go on before or after the glass?

Thanks
Chris

[ACTion]

Chris
Have a good look at this build of my little Fairey Swordman (which is about 600mm long). You may get a few ideas about construction and materials - and you can glue on the spray rails afterwards (John and I both did!). There is a complementary article on finishing the model somewhere else on the Forum (use the Search facility). It doesn't use glass.
Dave M

http://www.modelboatmayhem.co.uk/forum/index.php?topic=7668.0

[pompebled]

We hadn't anticpated using glass, just sealed and painted wood - do we need to rethink that? Would the spray rails go on before or after the glass? Chris

Hi Chris,

I used glass for two reasons, the main reason is the material I used to sheet the hull with; it's 3 mm poplar ply, which is not only cheap, but also has a very soft surface.
A simple coat of paint would be insufficient protection against bumps and bruises during the running sessions of the boat.

The second reason is the fact that I take my boats for long walks and I troll along on the shore of the canals around our city, which are not always the cleanest of waterways.
I like my models to be able to run into debris without taking (too much) damage, specially as the model sometimes is pretty far away from the transmitter and will be rather quick, like your yacht.

Glassing the hull will keep it fit for years (decades).

The tissue & dope method gives similar results to epoxy resin and glasscloth, the latter adds more structural strength though (depending on how many layers of glasscloth are laminated on).

Sprayrails are glued on after glassing the hull, much easier.

Regards, Jan.

[ChrisR]

Thanks Dave and Jan for taking the time to reply.

It seems there is more than one way to skin a boat (sorry) so we'll probably stick with what's easiest for now. Hopefully we won't come to regret it later. I'll put some pics up when it's underway.

Best wishes
Chris