What thickness of ply for Herreshoff Nereia Tender

joliette

joliette

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I'm currently in the process of building the Herreshoff's tender for Nereia, as illustrated in Sensible Cruising Designs. The design shows a 5/16" top strake, a 3/8" bottom strake and 3/4" bottom planking. Heavy for an 8' tender!

The design recognises that the builder may want to use 'thinner planks' or 'laminated wood' i.e. ply, but does not suggest a thickness. I'm thinking of using 9mm all round but have also considered going down to 6mm - to get the weight down further - as the dinghy will be stowed on deck.

Any advice would be very much appreciated.
 
I know nothing of the design you mention but it does sound heavy. This little thing is in 5 mm Elite from Robbins Timber; Tippy the Tender. It is quite narrow and does have a slight compond curve so the ply is very stiff. A larger or load carrying boat would want a little thicker. Plus of course it would give better ding resistance if it is to be a workhorse. I remember considering 6 mm but was glad I went for 5.
 
IT does sound a tad heavy!

My deck was 3/8ths and is now 9mm Robbins Elite, the biggest unsupported span is about 12 inches by 18, to be honest it flexes a little more than I'd like.

I'd have thought a 12mm bottom would be fine, sides could be either 9mm lower and 6mm upper or consider 8 for upper and lower?

Cant be hard to work out the weight to give you an idea of how tough to store on deck.
 
I used 6mm for my replacement bottom panel on the Heron I restored. That was 1mm too thick to match the original and I thought it a tad heavy.
It depends on the support and any framing that the hull has. I used 3mm for the floats for my trimaran and they are light and rigid, but of course without any significant unsupported areas.

The original skiff the trimaran was based on is 9mm and bloody heavy and far too tough for the project really.

If you drift around this site http://home.clara.net/gmatkin/freedes.htm you'll find 6mm seems common.
 
This is an excellent little design. While the curvature of the two side planks would be gentle enough to be executed with 9mm ply, the curvature of the bottom suggests to me that it was intended for the planks to be steamed, as it is the only way that 3/4" timber could be persuaded to take that degree of curvature. If I were building it, I'd go for 8mm ply all round, using a double thickness on the bottom. The seam shown down the centre of the bottom would be to accommodate planks of solid pine, which could not be expected to be available in the full width of the bottom. It would not be necessary when using plywood.
A nice solid bottom is nice to stand on, more durable when beaching, and gives some added stability to the boat ( a good thing in tenders). A friend of mine had a lovely, light, clinker dinghy which he used as a tender until someone thought that they needed it more than he did. One which is less portable is more likely to stay where you left it.
Peter.
 
I hadn't considered weight being a deterent against theft, but it is a good point. A previous tender of mine was GRP. The local youth decided to jump up and down on top of that one until they destroyed it! Maybe there is some merit in sticking to the original design ... a deterent against both theft and vandalism!?

A couple of sheets of 8mm from Robbins will cost in excess of £130 + delivery. I think I'll check out the reclamation trade before I decide which way to go. With £15 worth of reclaimed oak I already have enough wood for all of the frames. I don't suppose I'll find any marine ply at the reclamation yard but there maybe some suitable board costing less than new ply. Cost will have to be the deciding factor.
 
Update on Herreshoff Nereia Tender

In the end I used materials that were available locally, at a reasonable price. I built her out of 6mm marine ply and left overs from my carpentry work ... the frames are teak, transom mahogany and thwarts iroko.

This is a first complete build for me. I wanted to work right through the process, from lofting, applying knowledge I've accumulated on a real project. And after about 200 hours of my self-imposed training and development I have a complete boat.

I learnt a hell of lot and I'm pleased with the result!
 
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There's a sheet and half of 6mm ply and the floor boards are 1/2 inch cedar. My old Plastimo P240 inflatable seems to be about the same weight, but this'll be much more enjoyable to use!
 
If you could find out the weight it woukd be interesting. She is well framed and I think 6mm is plenty. What is the LOA?
I ask as I recently had a go in Nick Skeats' Dory, a two part Gloucester Gull, designed by Bolger. It was soooooo nice to row, I want one!
This tender does look more sensible, and I may be able to stow it across the coachroof.......
 
Seanick said:
I ask as I recently had a go in Nick Skeats' Dory, a two part Gloucester Gull, designed by Bolger. It was soooooo nice to row, I want one!
This tender does look more sensible, and I may be able to stow it across the coachroof.......
Click to expand...

Small world, I also had a go at rowing Nick's Gloucester Gull when he was here in Barbados about 12 - 13 years ago - there were two pairs of oars in action, and that dory was really shifting, without a lot of effort by the rowers. And although it is 16', the two halves stow in 8' on his cabin top.

The Nereia tender above does look very nice, pretty stable, a good load carrier and should be reasonably easy to row as well (although not a patch on a dory!).

A variation on the theme is Danny Greene's Chameleon - it is sort of in between the Gull and Nereia - here are a few links to it.
http://www.duckworksmagazine.com/04/s/designs/greene/cham/index.cfm
http://www.sailorgirl.com/s/v303_robbie.htm
http://www.yachtvalhalla.net/gecko/gecko.html
 
The weight of the tender is 48kg and the LOA is 8ft. I've attached a copy of the lines drawing that I worked from. Further details can be found in Herreshoff's book Sensible Cruising Designs. I wanted the experience of building something with frames, and I was attracted to the elegance and strength of this design. Also, I wanted something around 8ft LOA, that was a good load carrier, to sit up-side-down on Joliette's coachroof, aft of the mast. I hope to arrange a tackle on the boom to launch and recover the tender.
 
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Thanks both Banjan and joliette. I shall have a good look.
FYI, Nick Skeats as just gone around Cape St Vincent and is heading for the Algarve. Nine days out of Studland ...."under full sail with a gentle breeze, surrounded by dolphins, one is a baby...." (today).
I sometimes think he has got life completley sussed!

My current aluminium RIB (yes I know!) is 31 kgs and I can whip it up on deck without a halyard-the joys of a working boat finish. It does everything apart from row and look good!


Had a good look. The Chamealeon looks a bit like a Mirror Dinghy. I like th fact that it can be assembled afloat. I wonder what the weight is??
 
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