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Author Topic: The continuing saga of two halves  (Read 1798 times)

polycell

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The continuing saga of two halves
« on: October 21, 2010, 06:29:37 PM »




The problem is the gap!!
How in hells creation do I rid myself of this gap am I being overly fastidous.  Its not one of the two halves being pulled together its just a case of it only fits were it touchs.



I have spend too many hours nay days pharting around trying to rid myself of these gaps to no avail I'm getting to the stage whereby its going in the bin if I don't sort it!!!
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Bunkerbarge

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Re: The continuing saga of two halves
« Reply #1 on: October 21, 2010, 06:43:25 PM »

Put clingfilm over the lower joint.  Spread epoxy over the upper joint and put the two halves together.

When the epoxy has set remove the top half, peel away the clingfilm and dress up the edges of the epoxy.  You should get a significantly reduced gap from what you have now.
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polycell

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Re: The continuing saga of two halves
« Reply #2 on: October 21, 2010, 06:57:25 PM »

Tried that but in a different way.
I put cellotape over the top join Put the two halves together then pushed filler in the gap.
I may try your way.  Thanks
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RonP

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Re: The continuing saga of two halves
« Reply #3 on: October 22, 2010, 10:48:21 AM »

Joining together the top and bottom of a sub has never been easy, but with a little patience it can be done,here is an idea.
First thing to do is get the mouldings in line, dont worry about the gaps at this stage, you can get them in line by use of part bulheads and careful use of a hot air gun or even boiling water in smaller places. Once you are satisfied with the alignment then next tackle the gaps. Careful use of sandpaper and file to get deckline right, once thats done all should be well apart from those gaps.
      Grease over the joint on the lower half of the hull and then tape the top and bottom into position with a few well placed lenghs of tape at the points where the two halves touch.
Carfully spread filler over the joint , do not worry if it spreads over onto the lower half as it wont stick due to the grease, once it has set then carfully sand down until you reach the fibre glass being careful not to sand off any details. Oce the lower hull is clear of filler and there is non left to keep the two halves joined you can take off the tape and release the two halves.
The top half will now have a bead of filler attached but it will look a bit shabby so clean it up carefully so it looks presentable. Now it will not stick too well to that fine edge on the glass so it will need reinforcing on the inside with either grp resin/matt ot I use Devcon Plastic Welder, this is aa epoxy glue that hold plastic permantly---Job done!
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polycell

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Re: The continuing saga of two halves
« Reply #4 on: October 22, 2010, 02:51:53 PM »

Sorry RonP at the risk of sounding ungrateful for your idea.  I did that but in a different way.  I have made alignment edges on the inside of the boat so when the boat is together (two halves) the edges line up.  I then bought exceptionally strong bar magnets, they will find nails at 400 yards.  I put these magnets at four points along the inner edge with a 'device' in the fore ends (can explain it if interested) and a hidden 4mm bolt and fastener at the after ends.  Put the two halves together ensuring no movement.
I then sanded down the boat geting rid of all proud edges between top and bottom halves.  
I then had a perfectly aligned boat with no proud edges.
I shouuld say at this point I stiffened the bottom half of the boat as it was very flexible, with fibre glass mat and resin.
I then cellotape the joining edge of the top halve and rejoined the boat ensuring the halves were together as securily as possible.
I then squeezed filler in the dreaded gaps and left to harden.  I parted the two halves of the boat and removed the cellotape and put the boat back together.
Still gaps.  Re done the cellotape joining and filler trick again. still gaps, and again, still gaps.  It seems that when you have cellotaped and filled you get rid of the gaps as soon as you part the boat (split the two halves) remove the tape clean of access filler and rejoin you get gaps.  Am I getting wee'd off?  Yes.  I now know why the Sheerline Mk VII U boat was not a success.  Sorry am I being to critical?
I think I wouldn't have been as hacked off if I hadn't paid 250 for a pair of hull halves that needed such a lot of work doing to them!!
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Subculture

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Re: The continuing saga of two halves
« Reply #5 on: October 23, 2010, 12:56:15 PM »

Polyester resins and fillers shrink quite a bit as they cure. Epoxies shrink hardly at all, which is just one their advantages, but they come at a large premium in price.

Personally I think you're being very fussy indeed. It sounds like you are trying to get machined engineering tolerance quality from a hand made item. This is a working model , and no one will notice the tiny gap you have there once the model is painted up and weathered.

IF you want an invisible line, the only way to get it in my experience is to avoid splitting the hull in half in that way, and split it radially e.g. like the Engle Type VII or the Robbe U47.

Then you can use metal or composite bulkheads to ensure a hairlines width between the two halves. You could do this with your boat, but it will mean a lot of extra work. Only you can decide whether it is worth the pain.

polycell

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Re: The continuing saga of two halves
« Reply #6 on: October 23, 2010, 06:13:18 PM »

Yer right subculture it ain't worth the heart ache and grief!!
I have been working on the gaps today and what I got is what I am going with end off.
Lets concentrate on getting the beast in the water at least under the waves you won't see the gaps!!!
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