wood thickness for 24″ scratch built speed boat

[Michael BordParticipant @michaelbord10152]

I'm starting to build a 50s style speed boat . About 24" by 8" something like a semi scale Riva or Chris craft, construction from ply (so I can try and get a good varnished wood look). 24"x8" is similar to Sea Hornet and other models so ought to sail ok.

I've got as far as cutting card templates for bulkheads (4 plus transom) and I have some 3mm (1/8th inch) liteply to use. I was also thinking of using this for the keel and the deck (then building the bulkheads up from the deck). I was thinking of skinning the basic structure with 1.5mm (1/16th) ordinary ply which I have some of.

However, I've just read an article in December 2010 Model Boats about building an 18" Sea Nymph, where it is suggested using 1/32" ply for sides and bottom of the boat. It's also suggested using that thickness for boats up to 24". (simple construction, like mine).

Do people here think that would be too thin, or would it be useful in keeping weight down?

[Michael BordParticipant @michaelbord10152]

[Dodgy Geezer 1Participant @dodgygeezer1]

To some extent it depends on how roughly you expect the boat to be handled – 1/32 is very vulnerable to puncture-type damage. And it will tend to ripple between the bulkheads unless well supported. I would go for 1/16.

But some 1/32 would be very useful for fittings – panels and the like…

[Michael BordParticipant @michaelbord10152]

Thanks for that, having read the article 1/32 did sound a bit thin. I'll stick to 1/16 for the hull sides.

Edited By Michael Bord on 25/01/2017 22:08:56

[Dave MilbournParticipant @davemilbourn48782]

My experience is that 1/16" birch ply is a bit excessive on a small hull like this one, so I use 2mm liteply for skinning. It's much easier to bend and cut and a lot lighter. It's not as easy to obtain a good finish but with a bit of fine-surface Polyfilla for grain-filling and some glass-cloth and resin you'd never know it wasn't plastic (sorry, Bob!). 1/32" will sag between the frames.

Dave M

[Michael BordParticipant @michaelbord10152]

Thanks both, I'll avoid 1/32. I'll see what I've got in the garage wood pile and give it a try.

[harry smith 1Participant @harrysmith1]

Hi Michael

**LINK**

This is my Sea hornet build from last year.

It may give you a few ideas.

Harry

[Ray Wood 3Participant @raywood3]

Hi Micheal

I'd agree with DG on the 1/16" ply sides if you want it bullet proof, the bottom panels and deck only need to be 1/32" ply. The sides need tacking in place to make the ply go round the curve with brass tacks as were always supplied with the original Aerokits I drill a pilot hole for the tacks it saves a lot of cursing when they don't go in straight. I've just finished the original Aerokits version been in the build process 20 years ! but I built a smaller version above in balsa and learned that chine spray rails make the boat plane easier and stays dryer, I've used 1/8" X 1/4" obechi strips for the spray rails as the attached. Hope this helps in some way. Some more Sea Hornet build photos in my album.

Regards Ray

[Michael BordParticipant @michaelbord10152]

Thanks Harry and Ray, very nice looking models there, particularly with the varnished wood. I'm encouraged to go on with this now.

Harry's build thread is very interesting, read it right through. The running gear references were useful (your one seems to have a lot of power).

More when my garage is warm enough to spend some time in…

One thing, Harry, you mentioned a Hobby King outboard motor that you use on another boat. Coincidently I've recently been looking at these on their web site, thinking about another project. .There are 2 at the moment, "650 EP" with a 2630 kv motor and "Spirit F3" with 3000 kv motor, do you have one of these and are they recommended? Thanks.

[Michael BordParticipant @michaelbord10152]

Just been looking at Ray's photo album and found some useful pics showing Sea Hornet structure, so just the job.

Thanks.

[harry smith 1Participant @harrysmith1]

Hi Michael

My running gear is a bit over powered.

Speed around 45kph!!!

A B28-57-17L 1700kv 630 watts is what my mate has in his Sea Hornet and has a speed around 35 kph.

Prop, ESC and battery all the same.

The Spirit F3 is great, but, no spare flex drives available.

I bought a few from a local hobby shop, but, they double the price from $10 to $20 AU.

The flex drive do not last very long and do not use reverse!!!!

The 650 EP has spare flex drives available, but, again as these both are only 3mm will not last long.

The F3 on my balsa 24 inch vee is a little rocket, but, the outboard is going and it's getting the same motor( inboard) 4mm flex drive and re skinned with 2mm plywood.

The extra weight will not slow the boat as the power is more than required.

I have the upgrade motor in any case, 2836-3700kv 700 watts runs on 3 and 4S Lipo batteries.

[Ray Wood 3Participant @raywood3]

Hi Micheal

You will notice I have drilled out holes in the keel and the breast hook under the foredeck which as supplied in the Sea Hornet are 1/4" ply and makes the bow rather heavy. The deck is 1/32 ply ruled with a black pen to represent the planks and stained & varnished. The transom, rubbing strakes and windscreen support are 1mm Mahogany sheet from Mantua Models and looks good with a few coats of varnish.

Regards Ray

[Michael BordParticipant @michaelbord10152]

Thanks very much for the motor info, Harry. I'd only just come across the Hobby King outboards on their web site and I hadn't considered the flexible drive shafts having a short life (or the consequences of running a spring drive in reverse!). I guess that for faster boats a conventional set up would be better, prop shafts don't break….

My boats so far haven't been fast and have brushed motors (last project is a Revell Corvette, before that a cabin cruiser from plasticard ) so I'd like to try something different and with a higher performance. Your outboard boat does look interesting…

I read the articles by Dave Milbourn in jan and Feb 2016 Model Boats on building a Fairey Huntsman, about 24" long. He used Turnigy 2822/17 and Leopard 2826/17 motors with 30a escs in his 2 boats, with 3s lipo cells, so I though that could be a good spec to try in a similar length speed boat.

H'mm…

[Michael BordParticipant @michaelbord10152]

Thanks for the hull pic, Ray, that mahogany sheet on the transom looks good. I'd originally thought of having a flat full length deck on my model but seeing the sea hornet arrangement, the curved deck looks good so think I'll go that way. Looks like there are separate curved formers on top of the bulkheads.

This is a model for the varnished wood look…

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