Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[MartinH-K]

This is almost certainly re-inventing the wheel...
I was stuck with trying to work out hull shape for my rather large HMS Hood. What I did was buy a 1/400 scale Airfix kit. Assemble the hull. Squirt it full of cavity wall foam and wait for it to finish expanding. I then dis-assembled the hull and was left with the shape of the model from the inside. By measuring where I wanted to put bulkheads, I was able to disect the foam and plot the cross sections. Multiply by 400 and divide by 35 gives the manned model scale and, Bob's yer uncle! Well... not quite but well on the way.
Sorry if this has allready been spoken of hundreds of times before but I AM a noob here.
Martin

[RickF]

An interesting approach Martin, but surely, with the number of plans available for "Hood", in a variety of scales, it would have been simpler (and more accurate) just to buy the cheapest and scale from that? Or am I missing the point?

Look forward to seeing the model, though.

Rick

[MartinH-K]

The ones I found didn't show the entire hull profile in the places where I needed to place the bulkheads- manned model. I would have loved to have simply scaled up but (unless you have a suggestion- which I would most assuredly welcome) this was the only way I could think of to resolve the unusual bulkhead placement and keep the general shape of the hull.

[tigertiger]

A quick and simple approach. :)

When you are palnning it might be worth contacting those who have done it before. About other factors.
If I was building a project like this my considerations would include
- ballasting - as a dead weight I will be quite high up in the vessel,
- escape - how would I get out quickly if it did roll over.



If you did want to draw it.

It should have been possbilbe to draw your bulkhesads on a drawing board if you had desired. For those who might wish to try.
If you did technical drawing in School to O'Level you have all the knowledge you need.

Most plans will have the plan view (top elevation) usually one side but you can mirror. And you have the shadows (end elevation with sections). If you have waterlines on the plan this will give you additional reference lines.
Through orthographic projection you should be able to create the side elevation (which may not be necessary).

Decide where the bulheads you want will be. Draw these onto the 'plan view'. You should then be able to do a 'section' and by using construction lines draw the new section. You will need to be careful when you raw the curve between the intersection of the constructin lines. And you may have to estimate the curve a little, but it should be close enough to scale. Although you need to consider where curves are convex and where concave.

You will need access to a drawing board and someone who can draw, if you cannot DIY.

Alternatively three is hull modeling software, some free on the internet (cannot think of where off hand but someone here should know). You can put in the measurements you have and it will construct the whole hull in 3D. Then you can get sections where you want.

Sorry if this is a bit vague.

[boatmadman]

Here is the site for free hull deign software. http://www.delftship.net/

I have played around with it, takes a bit of getting used to, but it gives good results.

Good luck

Ian

[MartinH-K]

Thanks Ian...
I was using a generic CAD program, this looks like it might be of more use.
Martin

[MartinH-K]

Thanks Tiger for your points. I have been in planning for over 6 months on this project... researching for plans, photos, you know the usual stuff. This included dealing with thorny issues such as, "Just how accurate did I want to be... immiediately?" to "How the hell do I get out if things go disasterously wrong?"I have seen other manned models and for all practical purposes, we are NOT looking at Museum grade display here. To all intents and purposes, this is a horse of an entirely different colour. Your points are valid though and, while I must make the final decisions about what I do, I would be a fool to not listen to others.

[RickF]

Martin, this is an interesting thread and I look forward to seeing the model and hearing how you overcome the problems that you are certainly going to encounter.

Tiger is right. Given a decent set of lines - sheer plan and half-breadth - it is possible to plot a bulkhead at any point in the hull - certainly as accurately as a 1:350 Airfix kit.

As regards stability, I think I would go for a hull form that was accurate in plan and sheer above the waterline, but parallel-sided and flat bottomed below. Provision for a bolt-on external keel or ballast might be a good idea - but what do I know, I've never built anything bigger than a 1:48 pre-Dreadnought!

How do you go about insurance etc? Over here on the Norfolk Broads they are introducing quite stringent inspections before insuring or licensing cruisers, which I guess is what yours will theoretically be. How about towing or launching, or do you intend to keep it afloat at moorings?

Rick

[MartinH-K]

Im delighted with the interest that's being generated by my small endevour. It may be germaine to point out a couple of things... firstly, this is not my first build though its the first after a rather long absence. I used to sail at Black Park near Slough (in Burnham Beeches). The main thing for me is that there is so much experience here that I would be foolish not to listen to what's being suggested and I can say with certainty that I am not foolish. One part of me wants to pursue this course to SEE IF IT CAN BE DONE...I've not tried building this way before though friends have with varying degrees of success. How did we do it before we had access to CAD? We did it anyway we could, is how. The plans I have and the model indicate a flat bottom anyway which is good for stability and I will be incorporating a drop centre board through the botom of the hull to cope with anything 'sudden'. Displacement is actually the key issue and I plan to tackle that in two ways. Using a kayak type cockpit hidden under the deck superstructure will effectively raise the protected crew area and prevent the ingress of splash water which would compromise both stabilty and the comfort of me. Also a low center of gravity profile will put the crew effectively 70% below the waterline. This should, according to my displacement calculations increase stability by up to 40% on an allready stable platform.
The build will incorporate all available, and size appropriate safety features- I'm NOT going down with the bloody thing if something happens! I have allready spoken to the harbour master's department in Bristol and they do not see a problem (in principal) to what I'm doing. As far as they are concerned, its JUST another boat. To be fair, they said they wouldn't licence it if the guns utilised ANY sort of pyrotechnic device but they didn't turn a hair at my alternative! Finally (for now), I have designed a launching platform that will deliver the ship either stern first or winch/slid laterally into the water... of course, I've got to build that or adapt and existing trailer yet. I figure, lets lay the egg before we build the carton...
Thank you all and PLEASE keep the comments, concerns and advice coming. Its continues to stimulate and helps me to refine the plans.

[MartinH-K]

I got the Delft Hull drawing CAD program but can see no way of importing (from Excel) the hull measurements I have so laboriously taken. I have taken measurements every 2cm laterally and every 1cm vertically with a spring calliper and a micrometer. I don't know that I can get any more accurater without resorting to laser measuring devises and scanning. Suggestions?... Anyone...?

[RickF]

Hi Martin,

Not familiar with Delft, but if it were me I would:

1. Throw away the Airfix kit and scrap all the work you've done there - I know it's hard, but imagine the inaccuracies you are building in - starting with Mr Airfix's compromises then scaling them up from 1:400 to 1:35.

2. Get a set of Hood lines and sections. Even something from a book would do. Scan the sections, convert them to whatever Delft will accept and import them.

3. Scale them up, space them as per the lines, and create a solid hull.

4. Generate sections at the points where your bulkheads are going to be.

5. Print out new sections.

Good luck

Rick

[Colin Bishop]

Get the book Anatomy of the Ship HMS Hood:

http://books.google.co.uk/books?id=JU2PbKK_x7UC&dq=anatomy+of+the+ship+hood&pg=PT2&ots=lw2Qfj__P4&sig=zQhv1x1nOO4AYgkd8052CwmNiAY&prev=http://www.google.co.uk/search%3Fhl%3Den%26q%3Danatomy%2Bof%2Bthe%2Bship%2Bhood%26meta%3D&sa=X&oi=print&ct=result&cd=1&cad=legacy#PPT19,M1

[MartinH-K]

Thanks guys... (Rick and Colin)
Firstly, I'm using more than one source for my measurements... Airfix is only one of them DeAgostini is another plus a MAJOR load of pictures etc. I am awaiting the delivery of the Anatomy of a Ship with baited breath... allready paid for and dispatched to me. Duncan and I are in close conversation about the build and he has given me an amazing amount of advice and support. I cannot 'scrap' what I've already done for several reasons but chief amongst them are;
a) I've allready spent too much to simply start again,
b) its not necessary as (with some very minor modifications) I can adapt what I've got to make it work and then engage in some extensive but cosmetic additions to produce what I need.
The simple fact here is that we are dealing with a boat, not a model- exact replica or otherwise.
1mm ply which works so well on a 3ft model simply won't work on this scale when it must also hold two people. The design implications to ensure the structural integrity of this vessel are many and, of necessity I will have to make some hard decisions about, at what point I move (temporarily) away from the exact lines and at what point (and in what manner) I can move back to them. Some hull shaping may have to be added at a later stage essentially being 'fixed' to the allready completed hull. I have taken some seriously precise measurements that I'd like to input into CAD but, until someone can educate me, I will have to soldier (or sailor in this case) on.

[dougal99]

In what format does your CAD system import data? Exel can produce a CSV (comma separated value) file which is generally the most common format for transferring data between different programs. A little checking of the manual might save you a lot of time in the long run.

Cheers

Doug

[MartinH-K]

Now that's the kind of help I really need. Thanks pal!

[Stavros]

Right what intrigues me is what type of motors are you going to run and what size of props as well

Stavros

[MartinH-K]

Two options, both with good and bad points. 1) same as Duncan and HMS Invincible - one 'drop down' motor. 2) 4 x motors to scaled props. Motors would be heavy duty truck windscreen wiper motors, each with its own 24v battery (doubles as ballast). I KNOW that's going to bridle some people but no decisions made yet anyway.

[MartinH-K]

The book's arrived!,The book's arrived! (Anatomy of a Ship) And the drawings are in 1/400! Yippee!!!

[cos918]

hi martin been reading this thread with a lot of intrest . At Beale park show they some times have a big bismark big enough for some to sit in not sure if it is a maned model. But some one from the mid Thames model boat club most know as it is there home waters. They might have some answers for you as there may have been the same problems as you are facing it the build of your boat. Hope this is of some use good luck john

[MartinH-K]

Thanks John! I'll check that out. 

[Arrow5]

Been a while Martin, any updates on your Hood ?

[MartinH-K]

Things have moved on a bit... the winter effectively halted the build but you can't keep a good man down! If you want to take a trip over to 'Manned Model Mayhem', I've got a couple of albums up with piccies but the long and short of it is;
Bow section is done and I've started 'dressing' it- two 15in turrets in place- interesting bit I was having problems with turret mounts and was about to make them from scratch when I was in 'buggeralls' and happened to look at the 15lt plastic paint drums... I measured them AND they were the right size to within a 2mm tolerance!
Midships section is constructed and awaiting having the seams fibreglassed and controls installed.
Stern section is constructed and ready to receive engines- going for twin outboards that will be hidden beneath the decks and will vent through the aft stack. Also needs seams 'galssing'.
In the evenings I am working on ships boats and her secondary armament.
Once the hull is complete, I shall install the lever and bolt system that will connect the three sections together. I also plan to install two drop boards to increase stability but these will be invisible when she's on the water.
I have thought seriously about safety for this build. The upper works are being built of 2mm ply with 'easy break' sections. In other words, I am incorporating 'weak' points so that a firm shove from inside will cause the structure to collapse completely. I have no desire to recreate her sad end.

[MartinH-K]

Thought I could add some piccies here but they're too big... ah well.

[Bunkerbarge]

Hi Martin, Do you not have any picture editing software that allows you to resize them?

What is the file size of the pictures at the moment?  I'm sure we can help you do something with them and get them posted.

[MartinH-K]

I resaved them as bmp which brought them down to only 9mb... still won't upload. Help!!!