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Plank on frame - Sparrow

First attempt at a plank on frame

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Brian Dickinson 119/12/2019 20:36:26
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183 forum posts
124 photos

Sparrow, 750.

At our Wednesday club - ROFWACS, we race four types of boats or should i say there are four categories which we hope the wind will show up and push our boats along in it.

One of the categories is for a boat up 31" long and to any design you may choose and sail plan to match.

I have a couple of boats for sailing and of course the Panache - which is very much still on my best building board, Note to self (get on with it).

back bone bowed and clamped down.jpg

Brian

Brian Dickinson 119/12/2019 20:36:52
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183 forum posts
124 photos

Intro 2

The category is filled by many different models and some of them are very experimental - the skippers who take it seriously have some very sleek vessels with innovative design and parts. I sometimes look at them and wonder who will turn up with a torpedo with a fin and sail to match the speed of the Whitehead device one day?.

A couple of chaps have a sparrow and I like the look of them with their large sail area. I have a 5 minute handicap which suits my sailing skills (always at the back)! The Sparrows soon catch up and pass me like they are J class vessels passing a sailing dinghy. I have to practice more.

Searching the internet a couple of years ago i turned up the plan and saved it for future plans in modelling. My steam engines do not get to run as much as i would like and all the hassle that goes with them teased me into looking for a more suitable and equally entertaining hobby. So i looked around a found the ROFWACS on a Wednesday and that got me interested.

I believe that if someone puts the effort into designing, testing and finally getting the result they wanted then they should have some reward. Fortunately the chap who designed the Sparrow wrote a hand book to go with it and at a few quid is well worth it. For me anyway as i dont have much vision with looking at plans and interpreting them, the detail sometimes eludes me. So the hand book for me is well written and has daily work listed and is easy to follow. Its also loaded with pictures. Nice BIG pictures.

I don't think i will deviate from the original build unless i cannot find a product in the boat in the UK.

So, i have made a start, i marked out my building board with a different coloured fine point marker to the colour i had used on the JIF build. First mistake. The boat is made- assembled on a back bone made from 5mm x 25mm balsa. All the bulkheads are glued to this and then some of the detail parts added in between them.a balsa stripper which is very basic, but it functions well with a good blade in it.

Brian Dickinson 119/12/2019 20:37:06
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183 forum posts
124 photos

Intro 3

When this has been done, the back bone is clamped to the building board and a 5mm thick packing piece put under the back bone at the centre point. The other end of the back bone is then clamped down to the building board. This puts a negative curve in the deck, aesthetic appearance, special requirement, key design? Who knows but its in the manual so i have it in my build. The chaps at the lake have not done this, but their boats sail ok so i can not see it making any difference?

I have put pictures in my Sparrow picture folder rather than put them all here, i will probably add one or two as i progress.

I forgot to mention, i have never made a plank on hull boat before. Always sticking to chine hulls with ply skinning.

That's the introduction, now to go to the model shop and get some 1/16" balsa sheet to cut up into strips. In my youth i made

Brian Dickinson 119/12/2019 20:39:43
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183 forum posts
124 photos

My simple stripper, 38 odd years old and getting a new lease of life. we did not have a milling machine so it was all free hand cut on a drill press YIKES.

 

img_4246.jpg

Edited By Brian Dickinson 1 on 19/12/2019 20:40:33

Brian Dickinson 119/12/2019 21:46:56
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183 forum posts
124 photos

PANK ON FRAME -/ really ??? 🤔

harry smith 120/12/2019 04:06:56
930 forum posts
1198 photos

Hi Brian

I've had a go at planking, but with 3mm Ikea wooden blind strips cut down to 4 and 6mm strips.

The wood bends and steams very well, also like a strong balsa.

One tip is start from the keel and work up to the deck because you can use small clamps between the frame for a better shape.

Second tip, before planking sit the deck on and mark out all frame on the under side.

Mask tape all these up and seal the deck underside.

It's one off my bucket list, a long with double diagonal veneer planking !!!

Harry Smith

Ray Wood 220/12/2019 08:28:39
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1461 forum posts
552 photos

Hi Brian,

1/16" panking sounds awfully thin to me? If that's what the drawing shows it must be ok!

Not wanting to contradict Harry from down under, I'd also start from the deck level aswell and work towards the keel if you want pretty topsides.

Happy Christmas

Raysilvermist rbirthd aug 15 004.jpg

Tim Rowe20/12/2019 09:34:16
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304 forum posts
359 photos

Brian

Great to see you up and running and good advice from Ray.

I have built this hull but with some modifications so I feel justified in making it first as a plug to make a mould from. I want three identical hulls.

Bryn is not very accurate with his metric / imperial conversions and he says 1mm or 1/16" for the planking. 1/16" is actually 1.5 mm but either way it is very hard indeed to plank a single layer at 1/16. Edge alignment is very hit and miss plus you get no sanding allowance. Very thin planking also tends to go flat between the frames as I does not wrap very well. The frame spacing on Swallow is very wide so be careful.

I would never consider balsa planking in anything less than 2mm and would use 2.5 and 3mm where there is lots of shape. After sanding and fairing up you will lose a lot of this extra thickness and anyway in the case of boats, the weight is not relevant. Some of his other conversions are a bit open but not so critical on the larger dimensions.

You will probably find than the hollows in bulkhead B give you a very hollow waterline with the bow quite pinched in. It was in this area that I made most of my design changes to increase the buoyancy in the bow. Swallow has a big rig and this is likely to cause behavior akin to a submarine at times.!

Tim R

Eddie Lancaster20/12/2019 12:13:54
508 forum posts
368 photos

Hi. Tim,you are right about the pinched bows of the Sparrow and it does want to behave like a submarine running before a strong wind.

I built mine as per the plan and used a fairly hard balsa and got a well shapeed hull, it was the second boat that I built, the first was Varmint a DF65.

Regards.

Eddie.

Brian Dickinson 120/12/2019 14:57:50
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183 forum posts
124 photos

Right so all sound advice so far. I did wonder about the plank thickness. I think I will increase to 2mm and see how it goes. The instruction says plank from the deck up

Varmint was a fellow club members design.

Only contradiction is the comment about weight in a boat. All the chaps bang on about getting the hulls to be a light as possible with out compromising the strength. I am only a beginner but I would have thought the lighter the better, which I can contradict as they have to sit correctly in the water which is all about weight ?

I also thought that the wettted surface was best kept to a minimum? Large ships have the bulb on the lower bow each designed to keep the flow of water down the ship uniform and as low as possible to reduce drag?

Works do today so no playing in the workshop.

Brian

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