Beginners design and build

[outboard]

Hi Guys, here I am sitting with three seagulls and nothing solid to put them on, other than an inflatable. Some of you guys are well experienced in design and building your own little gems so I've decided to do likewise. Only thing is I don't know how to design.
I've got a workshop (garage) about 18' long, as for tools they're in abundance, table saw, jig saw, router, planes (electric and hand), clamps, handtools, etc. My main item I have is patience, I can wait, listen and learn and hopefully it might become a winter project if needs be, so what I ask you experienced guys, would any of you like to walk myself and any other new designers through the process of designing and building techniques? Remembering this is a forum for Seagull engines whatever the outcome they're designed for these engines.

My first thoughts are of something to fit on a car top (this could change), as for weight I'd like it to be manageable by one man with a bad heart. Size would be a factor, maybe 10ft or so. At this point I'll stop and hopefully the experts will give me some guidance. The main thing is, it must be suitable for my seagulls.

Gerard

[woodbutchergraham]

Don’t wait until winter you will have missed the best boating weather, Try a simple design first and adventure into more complex designs as your knowledge expands. There are loads of free designs on the net for pram or john type boats have a look, decide what to build and get stuck in. Nothing like the satisfaction of taking to the water in something they have built themselves.
If you don’t like what’s turned out E-bay it and start again.
http://www.jemwatercraft.com/
Try this site for some good tips on glue and stitch

[Horsley-Anarak]

I would spend a bit of time reading some of the information on the web, search for stitch and glue.
There are some good boats here.

http://www.selway-fisher.com/index.htm

I would also get stuck in, Jigsaw and battery drill, beil sander if you have one.

A 10' boat would be a good starting place. Stitch and glue is very quick a good weekends work will have you testing on the water.

I find summer building is much quicker as the resin goes off much faster.

H-A

[Charles uk]

Gerard before you start with the jigsaw, can you tell us how mant people you plan on carrying, i.e. maximum load & where you plan on boating & which model Seagull your going to use.

[outboard]

Hi Lads

Thanks for the advice so far, I'm taking it all on board before I lift a jigsaw or whatever.
Manifold, your help is appreciated and if needs be I'll be in touch.

My initial spec is, within the region of 10ft, to suit one and adult and one child. My engines are 40+s, one with clutch. I would think it will be mostly used around the Ayrshire seaside, but not venturing too far into the sea. I would expect my first attempt to be a learning process so I won't hasten for anything beyond my capabilities. I would expect, by my nature, there will be more than one build to better the last one so we'll see what goes.

I see there are those who say go for it and others who say read the manual first, without upsetting anyone I prefer to try and get the geist of it before I go head first and end up putting myself off the whole idea.

I've downloaded the software from the epoxy site so I'll play around with it and probably fire some questions to you guys. Probably stupid questions, but at this point in time I know absolutely nothing about boat design so I'll appologise in advance.

Would anyone (i.e. Manifold) like to explain what the numbers being asked for in Carene relate too. I tried punching in various sizes to see what the end result would be and I got some weird shaped drawings. Understanding the program would be advantages I think!!!

Gerard

[outboard]

Superb Manifold, that was quite a lesson in a few written lines. I'll play around with this and get comfortable with my newly found knowledge. Don't go too far, yourself, Charles, Woodbutcher and HA will be sick of hearing my questions, hope I don't go too far with your patience.

[woodbutchergraham]

Good thread this one, I think we are all learning somthing new ! post some pickies of your attempts. May be we could reserect the Seagull boat of the 50s in Poole harbour (But improve on the design?)

[outboard]

These two pieces of software which Manifold suggested are good, with the little explanation from Manifold I have seen it working and I'm impressed. Is there any tool where you could get a solid image of the finished item, or am I being a bit unrealistic?

[outboard]

This is becoming clear now, the instructions from our expert (Manifold) are great. With a little trial and error this guy who makes dentures is starting to understand the art of boat design software, thanks.
A couple of questions, do I assume right that these programs do not guarantee a 100% stable boat? On one of my trial drawings I see when I went to freeship, obviously by my sizes, there will be joints on the plywood, are these best done aft, and will they compromise the bending whilst stitching? Are there any rules of thumb when it comes to scaling, i.e. transom width, max beam, in relation to the LWL?

Last but not least (for the moment), model making, I see Manifold prefers card as Charles Uk uses balsa wood, how easy is it to scale down these drawings to get an accurate lofting for the model?


Gerard

[Charles uk]

Gerard
All boat hulls are designed for purpose, you don't buy a Porshe 911 if you want a taxi.

Without the where, what for, maximum load & which Seagull, questions answered, no one has a clue which sort of hull will suit your application best.

[outboard]

Hi Charles, at this precise moment I'm just trying to get the basics of these programs so that when I take the plunge on my first build, I'll have a good understanding of where I'm heading, and hopefully not design Titanic/Posiedon MkII.
As for spec, I have already indicated further up the thread my initial thoughts of where, when and for who? I'm thinking it will be for myself and possibly my granddaughter, for having fun in the sea, using an FPC. Probably about 10/12ft.

What I'm doing right now is learning the theory/software to design and build, I don't intend building until I know what I'm doing. I want my first build to be right, and exactly what I want.
I will, before building, after annoying you more with questions, show you experts my drawings to scrutinise and correct me where there's faults.

In freeship I notice there's a pulldown showing possible leaks, do I take it that this is an indication as to where you should pay close attention, or is this advising of faults?

Gerard

[outboard]

Thanks again. I tried your link the boatpoint.net but it doesn't register as a website.
Gerard

[Charles uk]

Sorry Manifold but I'm going to have to qualify your statements.

long and thin goes faster (for the same power on displacement hulls)

wide is more stable at rest low speed (with high centers of gravity)

(deep) V bottom is better for rough water but is tippy at rest (with high centers of gravity)

when you get up on the plane ( joke seagull ??) you get dynamic stability ...( or dynamic instability with my "joke Seagull" in flat waters)

10ft 2 people 12 ft 3 people 14 ft 4 people but how rough is the water and how heavy the people .
For sea going vessel choose a side height of 20 inches 15 ok for lakes/canal etc

The faster you go the stronger you need the bottom ..on the plane you may have 60 psi on the bottom ( 0nly on a planeing hull in poor conditions are you likley to exceed 2 psi with a Seagull, the chances are that you will exert much higher loads with your feet when walking around the boat whilst afloat)

In sheltered costal waters (swells less than 3 feet) 10 to 12 foot hull length should be ok, with a width to length ratio of around 3 1/2 : 1, hull weight around 120lbs.
The transom will have to have sufficient width to give enough buoyancy foy you to safely fix any motor problems that occur, with only you in the boat.
You will need to steer from between 40 to 50% of the boat length from the transom when alone, so plan on a tiller extension with a extra long throttle cable.

With a model 55 you should be capable of 6 to 7 mph at best.

[outboard]

Cheers

Now we're getting personal, do I eat lots of pies, "No", I'm around 10st, so there's no great weight, the place I'm talking of is more like inland water, pretty well shelterd with swells of maybe 0.5mtr at worst. Any bigger and I'd be watching from the shore.
Just a wee detour, have you looked on HAs thread, there's a post showing a boat done with mahogany veneer, a beauty, how would this have been done? Would a veneer be laid on after it had been sealed with epoxy? Just asking, it's a big boys job that one, stunning to see.

Gerard

[trw999]

Gerard

Cold molding. Have you seen any of the Fairey Marine dinghies? Firefly, Albacore, Atalanta etc. They were hot molded, which included being baked in a large oven. Here is an explanation of the process from the Atalanta owners site:

During World War II Fairey acquired great expertise in hot moulding for aircraft manufacture and in the post war era adapted these techniques to boat building. Initially surplus stocks of ⅛ inch spruce or birch veneers were used but as stocks of these dwindled a switch was made to Agba - a lightweight African hardwood available in 2.5mm sheets (the only metric dimension on the drawings) - which proved to be both very durable and easily worked. The hot moulding process permitted high-volume, low cost production of resin impregnated hulls with an extraordinarily high strength to weight ratio, significantly exceeding the GRP laminates of the day.

The Atalanta hull consists of four laminate layers profiled and coated with a thermosetting resin. The laminates were laid-up diagonally over a mould and fixed with temporary staples at the keel, bilge and sheerline. With all veneers in place the hull was then vacuum-sealed in a rubber bag and wheeled into a giant autoclave, to which steam was introduced at about 50psi. “Cooking” took about an hour at 100°C after which the hull was left to cool slowly, usually overnight, while ambient pressure was maintained. Curing at elevated temperatures under vacuum not only ensured that all the veneers were firmly consolidated - conventional cold-moulding required thousands of staples - but it allowed the use of a truly waterproof, high temperature curing adhesive to impregnate the wood, creating a virtually rot-proof and very strong monocoque hull.

You can still find cold molded boats being built, but they are rare. When I win the lottery, I shall upgrade my fibregalss Dragon to a cold moulded version: http://www.petticrows.co.uk/dragons/cold-moulded.shtml

Tim