Author Topic: Maintaining Hull Alignment  (Read 11362 times)

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Offline spaniel14

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Maintaining Hull Alignment
« on: 23 October 2014, 16:22:34 »
I'm building HMS Cossack and, having installed the bulkheads, deck templates and stringers I have found the hull has twisted. I guess I will need to build some sort of jig to hold it true, mainly because it is long and narrow. Does anyone have any tips, guidance or help in this regard?

Offline radio joe

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Re: Maintaining Hull Alignment
« Reply #1 on: 23 October 2014, 18:35:06 »
Hull distortion is a problem, unsupported hulls can be in the packaging for some time, the very first job should be to make a decent cradle that can hold the hull snugly and level this way you can easily see any twists or distortions, these need to be built out, the best way to do this is mark a centre line along the inside of the hull and make frames equal each side, sight along the hull while it's in the cradle and using weights or some other method make Shaw the hull is true, and do this each time you fit a frame, it's best to bond them in one at a time, when you have all the frames fitted the hull should be true, check again when you fit the deck, if you have already bonded the frames in I doubt you will get the twist out without releasing them. I hope this helps  :)
Joe.
« Last Edit: 23 October 2014, 18:37:26 by radio joe »

Offline colin

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Re: Maintaining Hull Alignment
« Reply #2 on: 23 October 2014, 18:36:14 »
normally by building a sturdy working stand / Cradle for the Hull to sit in, the Hull will stay in form...

if the Hull has been twisted in a bad way, one can pour boiling water into the Hull, this makes the Hull plyable to be able to reshape the Hull..

be carefull of the boiling water...!!

Offline mikearace

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Re: Maintaining Hull Alignment
« Reply #3 on: 23 October 2014, 21:37:53 »
Another way is with the help of someone heat the hull around where the twist is, gently with a hair dryer, and gently, gently as the FG softens work the twist out.  Then keep it firm still in its cradle as a jig holding it until it slowly cools down and it will remove the twist. It does work I have done it myself on a Deans V Class destroyer.  Took 2 attempts mind you but do it easily.

Offline spaniel14

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Re: Maintaining Hull Alignment
« Reply #4 on: 24 October 2014, 17:46:45 »
Thanks for your advice. I've stripped everything out and will start again once I have built a jig. I'm a bit disappointed that there is no reference in Deans instructions to the need for a jig but perhaps I have been a bit naive! I have found most of the marked plasticard profiles to be wrong so perhaps I am wrong in assuming that the word kit is relevent.

Offline radio joe

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Re: Maintaining Hull Alignment
« Reply #5 on: 24 October 2014, 18:23:57 »
I would be surprised if the was no reference to building the cradle in the guide sheets there are normally paper templates for the cradle ends that fit the hull, I say guide sheets rather than instructions, because you have to use a bit of intuition when building a Deans kit, this ultimately helps you improve your building skills, when it comes to the printed sheets don't cut out any piece until you measure the plan and the structure you are working on, then alter the piece accordingly, why not do a build log with some photos so we can see your progress and give any help if you require it.  ^^^
Joe.

Offline spaniel14

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Re: Maintaining Hull Alignment
« Reply #6 on: 24 October 2014, 18:57:51 »
Thanks Radio Joe,
No, no guidance, no paper profiles, nothing!
I will keep a log as you suggest for the benefit of others. To date I have to say I'm not impressed

Offline mikearace

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Re: Maintaining Hull Alignment
« Reply #7 on: 24 October 2014, 19:33:44 »
The stand (Jig for cradle) profile is usually on the second or third page in the instructions.  If it isn't there give deans a quick call and they will I am sure post you this out.  They are pretty good like this.  As to the sizing of the plastic sheet parts I have built kits from all the main manufacturers and without exception all had some parts that needed some degree of fettling - some more than others.

Offline paul swainson

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Re: Maintaining Hull Alignment
« Reply #8 on: 25 October 2014, 12:14:43 »
I have to agree with all of the above advise.  In my build of HMS Solebay (which was my first kit from Deans Marine) I had to think twice and measure twice and dry fit all items before I bonded then in, and like you I found the front and rear deck support templates was wrong and had to do them again.  As with all long slim hulls always make the hull cradle first and sit the hull in this and keep it there all the time until you have bonded in the bulkheads and deck supports.  Once in the hull should remain ridged. 
A trick that Joe mentioned in his build block which I used was to mark your plans from the bow to the stern with straight lines 100mm (10cm) apart along the ships plans.  This will help in marking the hull and the decks so that you can confirm positions and size of superstructure's lengths.  Hope this helps. Paul  ^^^

Offline Troy Tempest

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Re: Maintaining Hull Alignment
« Reply #9 on: 25 October 2014, 17:45:51 »
I wish I had this advice back when i discovered the nasty twist in my HMS Zulu hull.
I suspect it had ben caused by years of being stored unsupported in the loft - in its original cardboard box but with objects in turn resting inside the hull.
Unfortunately I didn't notice until after I and started to fit the Fo'c'sle deck and then had to build up one side to get things level, which has still left me with a non-perpendicular stem
This forum is hugely important to novices as it contains such valuable advice from experienced modellers, one thing this thread highlights is that if no one asks the question that advice can remain unwittingly hidden!

Offline spaniel14

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Re: Maintaining Hull Alignment
« Reply #10 on: 25 October 2014, 18:43:21 »
Thanks again all. There is a guide to making a cradle in the instructions but it wouldn't have helped - the hull sags outwards on one side and inwards on the other. The centre line (which I have set up by running a thread from bow to centre of stern) shows that the sag is upwards of 10mm in each direction. I have constructed a base board with a centre 25mmx12mm batten to correspond with the keel line and upon which I have screwed down the hull. I am in the process of forming hardboard outer profiles at intervals to push/pull the hull back into alignment. The deck profiles etc can then be measured accurately and installed, hopefully with more luck than last time!
After this I think I will be able to manage full size ship construction!

Offline colin

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Re: Maintaining Hull Alignment
« Reply #11 on: 26 October 2014, 10:19:26 »
one of the easyest ways.... would be to put the Hull in the original moulding form... at Deansmarine, then add boiling water... in a matter of seconds the Hull would be back to shape...

from your Location you seem to be at the other end of the Country... it might still be better to contact the Workshops for a helpfull Hand..!  they might suggest sending you a new Hull, and you send yours back..!!

Offline spaniel14

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Re: Maintaining Hull Alignment
« Reply #12 on: 26 October 2014, 18:09:13 »
Colin,
Thanks for that but I am well on the way to correcting the problem (as best I can), as I have described above.
Now that I have set up an accurate jig, I can see that the original hull moulding is unlikely to have been symmetrical - perhaps Deans should look to their QA

Offline radio joe

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Re: Maintaining Hull Alignment
« Reply #13 on: 26 October 2014, 19:19:31 »
It's not just Deans hulls, plastic hulls while not as strong hold there shape better than GRP hulls when in the packaging for long periods, I am working on my fifth GRP hulled boat now and they have all had issues with hull distortion, only three were Deans, my present type 42 hull (not a Deans) had a slight twist and had spread 20 mm. This is par for the course with GRP hulls but despite the extra work I still prefer GRP to plastic.  :)
Joe.
« Last Edit: 26 October 2014, 19:24:59 by radio joe »