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Twisted Keel? Options
Dinadan
#1 Posted : 25 April 2018 19:46:51

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I am starting building SoS and have got as far as just before attaching the sterncastle (but without completing the boat, cannons etc.). I turned the model upside down to check how square it was and found it rocked on the fo'c'sl and the last of the ribs. I measured the difference in height above the datum I was using of the port and starboard ribs and found the problem appeared to lie between ribs 15 and 16. For 15 and forward, I was getting an error of approximately 0mm and for 16 and rearward, the error was approximately 1mm. There is no obvious twist in the keel, but that is the only cause I can think of.

Do you think that this is too small to worry about?

If not any does anyone have any suggestions? I don't think I can dismantle it to correct the problem (I have gone as far as gluing the first two decks in place). I could reduce the height of the ribs on the high side along with the steps for the decks so that they lie parallel to the fo'c'sle and then glue the sterncastle with its top parallel to the fo'c'sle. Any advice would be welcome

Thanks,

Chris
Martyn Ingram
#2 Posted : 25 April 2018 19:50:35

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If you could take a picture of the problem we should be able to help
Martyn
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Gandale
#3 Posted : 25 April 2018 20:09:39

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Hi Chris,

Can you confirm the issue number you are working on and provide a couple of pics looking straight down the centre from the bow to the stern. Once we see these then we should be able to advise further.

Have you set the keel into a build jig/dry dock? If not, with this build I'd strongly recommend you set the keel into a jig, this will allow you to square everything up. Once set in the jig leave it there until you have at least the first three rows of planks fitted on both sides. The SOTS is a large build and it is very easy to induce a twist into the frame during the planking phase, hence the need for the jig....

I would also recommend you produce a build diary on the forum, that way we can see how you are progressing and that would make things a lot easier for us to render advice and assistance when required...

Hope this helps..

Regards

Alan


Dinadan
#4 Posted : 26 April 2018 22:23:57

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Dear Martyn and Alan,

Thank you very much for your quick reply. Sorry for not getting back sooner but I needed to charge the camera up.

Please find an image of straight down the ship from the bow.

I am up to approximately magazine 16, pane 11 or so. I've also added the next set of stringers as I thought they might help strengthen the ribs.

I took a load of photographs to start a build diary and then my mobile crashed and I lost them all.

Chris

P.S. if you need anything else, please let me know
Dinadan attached the following image(s):
SoS bow.jpg
Gandale
#5 Posted : 27 April 2018 11:00:34

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Hi Chris, thanks for putting the picture up it does help. Looking at it then I'd say it doesn't look too bad however, the fact that the pic as been taken at a slight angle and not at deck level makes it difficult to be certain.

You say in measuring you are only 1mm out and there is no obvious twist in the keel. The 1mm difference can also be caused by ribs not being set perfectly horizontal to the keel, ie there is has been a little lateral movement when gluing the ribs in place or when fitting the deck, making one side a little higher than the other. The tops of the ribs where the deck sits, needs to be perfectly level in relation to the keel so I would suggest you double check here. If your checks show everying set correctly then there must be a slight twist on the keel itself.

Let me know what you find after your checks.

Cheers

Alan




Dinadan
#6 Posted : 27 April 2018 18:13:51

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Dear Alan,

Thank you for getting back to me.

I wasn't 100% certain what you meant, but I tried a set square between the keel and the lowest deck and that mostly seemed to be at right angles (the one or two places it wasn't, typically it was on one side but not the other, I guess I hadn't hammered the deck down properly).

I also tried clamping a couple of steel rules to ribs at opposite ends of the ship and butted up against the keel. I seemed to be able to see signs of a twist i.e. they weren't in line. I also tried clamping the rulers directly to the keel with the same results.

I guess as you say it doesn't look to bad, so at this stage I am going to have to live with it. I should have checked earlier.

Chris
Gandale
#7 Posted : 28 April 2018 10:03:46

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Hi Chris,

The build jig you have created is fine for holding the keel in position but in order to remove the slight twist you could try building a frame at the bow and stern to hold the keel perfectly upright. Then set the ship into the jig, ensure everything is perfectly aligned and leave it there until you have at least the first four rows of planking on both sides fitted, this should correct the 1mm variance you have. Take a look at post four of this link, the pics show how the bow and stern are held in place.

https://forum.model-spac...spx?g=posts&t=20425

Hope this helps.

Regards

Alan
Dinadan
#8 Posted : 02 May 2018 20:03:56

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Dear Andy,

Thanks for the suggestion. I would agree with you if the twist was continuous throughout the hull. However my measurements suggest that it appears to be between ribs 15 and 16. I was wondering about tackling it like this (after finishing the fairing):

Take a piece of 'good wood', say 2x2". Mark out on it where the ribs are and where I can get at the keel (i.e. there are no reinforcements etc). Screw (or nail?) every location where I can get at the keel to my piece of plywood with two screws. I should then (hopefully) have a piece of straight wood, making a right angle with the plywood base. I then saw the areas without the screws. Now I should have a series of blocks that I can slide the model onto so that the keel is against them. I then plan to drill 1 or 2 holes through the keel into each of the blocks and screw the keel onto the blocks using large washers or similar to spread the pressure. Hopefully this should straighten the keel?

Chris
Gandale
#9 Posted : 03 May 2018 09:12:40

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Dinadan wrote:
Dear Andy,

Thanks for the suggestion. I would agree with you if the twist was continuous throughout the hull. However my measurements suggest that it appears to be between ribs 15 and 16. I was wondering about tackling it like this (after finishing the fairing):

Take a piece of 'good wood', say 2x2". Mark out on it where the ribs are and where I can get at the keel (i.e. there are no reinforcements etc). Screw (or nail?) every location where I can get at the keel to my piece of plywood with two screws. I should then (hopefully) have a piece of straight wood, making a right angle with the plywood base. I then saw the areas without the screws. Now I should have a series of blocks that I can slide the model onto so that the keel is against them. I then plan to drill 1 or 2 holes through the keel into each of the blocks and screw the keel onto the blocks using large washers or similar to spread the pressure. Hopefully this should straighten the keel?

Chris


Hi Chris,

Had to look at this a few times to follow your process through. Are the blocks going to be a permanent fixture to the keel between the ribs or do you intend to also screw the blocks to the jig and unscrewing when the first few rows of planks are fitted?

You may also consider disassembly which is not as difficult as it sounds if you have used PVA adhesive. Simply take a small brush, some hot water and brush the hot water onto the glued joints. After a few minutes the glue joints will soften allowing you to separate. You could then set the keel perfectly, clean up the joints and glue everything back together. This may be a less drastic option....

Regards

Alan
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