Spray rails needed for Amatic Riva Aquarama?

[JeremyParticipant @jeremy15845]

[JeremyParticipant @jeremy15845]

I have seen videos of model Amati Riva Aquaramas ploughing through the water, almost submerged in their bow waves. The prototype Riva has spray rails along the chine and I wonder whether the model should also have them (although they are not included in the Amati kit). If they should be fitted, I would appreciate advice on how far forward they should go and on the ideal cross-sectional dimensions and profile. The hull is 1/10th scale and 876mm long.

Jeremy

[Paul TParticipant @pault84577]

Jeremy

I don't think that the boat had spray rails, at least I haven't come across them on any Riva boats that I have ever seen.

Your model is looking very good and should look superb when varnished, your woodwork is tremendous.

Paul

[JeremyParticipant @jeremy15845]

Paul

I may be wrong about spray rails but, as you will see from the shadows in the image below, there does appear to be some shaping of the hull to create a planing surface near the prow. This is absent in the model (or at least in the way I have built it!).

http://newimages.yachtworld.com/resize/1/9/40/4720940_20140527073856278_5_XLARGE.jpg?f=/1/9/40/4720940_20140527073856278_5_XLARGE.jpg&w=924&h=693&t=1401205136000

The Jet-Riva version built by Brian Johnson (Model Boats September 2011) didn't have spray rails and a picture taken with it not going particularly fast showed it throwing up quite a bow wave. A comparison of his model and a standard Aquarama was due to appear in the magazine in due course but not so far.

Jeremy

[Paul TParticipant @pault84577]

Jeremy

I always thought that the hull was so well designed and produced such a lovely crisp bow wave that spray rails would somehow detract from the entire spectacle.

Paul

[Dave MilbournParticipant @davemilbourn48782]

Jeremy

From my experiences with Fairey power boats and similar I'd say that spray rails at chine level are pretty much mandatory. I would suggest a square section with the lower outer edge left sharp and the upper one rounded; size maybe 4mm x 4mm. Leave the bottom face unshaped so that the water is deflected downwards as well as outwards.
This should give you a good idea of the efficiency of spray rails in keeping the boat dry.

For material I use bass stripwood which is quite soft, fine-grained and easily bent with application of steam.

Dave M

 

Edited By Dave Milbourn on 27/12/2015 09:33:17

[JeremyParticipant @jeremy15845]

Dave

Thanks for your advice. I will have to use Mahogany strip because the spray rail will end well above the lower painted part of the hull. I have some 3mm square strip in my odds& ends box, so I hope this will be OK. If you think I really need to go up to 4mm, I can always buy some. 3mm would be a bit less intrusive than 4mm and also easier to bend. I assume that the spray rail will fade out about in line (vertically) with the headlights.

Jeremy

[Dave MilbournParticipant @davemilbourn48782]

I think that 3mm square would probably do; the size I quoted is pro-rata with the smaller Huntsman in the picture (which uses 3mm sq). Quite where you end them at the bow depends on you – under the headlights looks like a suitable sort of area.

DM

[JeremyParticipant @jeremy15845]

Spray rails added. I will have to wait and see if they do the job. As they will be on the painted part of the hull, they could be modified if necessary. Thanks for the advice

Jeremy

[Tony HadleyParticipant @tonyhadley]

Jeremy,

Thought you might find this of interest, in the Build Features section of this website. The item by Steve Day (currently the top item), Taming A Pirana has an interesting note on the effectiveness of spray rails when fitted to this model. The paragraph of interest is titled – Several years later –

**LINK**

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