Model Boat Mayhem

The Shipyard ( Dry Dock ): Builds & Questions => Submarines => Topic started by: polycell on May 23, 2010, 12:41:03 pm

Title: Sheerline type VII a tale of two halves
Post by: polycell on May 23, 2010, 12:41:03 pm
My Sheerline type VII has just come to the top of my 'get opn and do 'list. It got shelved cos I was having troubles minimising the gap, when joined, of the two halves of the hull.
So come on someone how the hell do | fill the gap?
I have tried all sorts. I tried cellotape on one half of the joint joining the two halves making secure and then putting filler in the gap. It worked!!! but taking the two halves apart and taking the tape of the gap magically reappears. Grrrr
Now I am beginning to wonder if its something to do with the fact that the two halves are flexible ie easily flexed when squeezed.
So my next plan is to reinforce the the two haves by building frames from fibre glass matt.
Question anyone got any good ideas. Please.
Thanks Fred
Title: Re: Sheerline type VII a tale of two halves
Post by: 6705russell on May 23, 2010, 01:00:59 pm
Hi Fred

The best way i found was to heat the two halves up until flexible and attach the two halves together and tie-wrap them until they have cooled right down, take off the ties and they will have formed into that position, i used a heat gun/paint stripper....

Title: Re: Sheerline type VII a tale of two halves
Post by: dan on May 23, 2010, 04:44:19 pm
I've got the same problem. I'm going to try putting bars insde the bottom half of the hull to get it the same diameter of the top part of the hull, then I'll try using filler to minimise the gap
Title: Re: Sheerline type VII a tale of two halves
Post by: polycell on May 23, 2010, 05:29:20 pm
Sounds like a good idea Ross.  Was your 'two halves' a Sheerline?  As I was wondering, as the Sheerline is GRP/fibreglass construction, that heat may do something nasty!!
Title: Re: Sheerline type VII a tale of two halves
Post by: Sub driver on May 23, 2010, 06:30:45 pm
Am I correct in thinking that the two halves are the top and bottom of the hull ?

Why not just place some locating lugs in the two hulls adjacent to each other ie top then bottom then top them bottom etc then when you put the two halves together they will line up.

Its probably caused by the two hulls "springing" being made out of polyester resin. No big deal to " fix "
Regards Sub.
Title: Re: Sheerline type VII a tale of two halves
Post by: sheerline on May 24, 2010, 03:43:21 pm
Hi fellas, this is a problem with grp hulls moulded in this fashion the type 7 was partucularly prone to it. This was exacerbated by the acual shape of the hull design.
This takes longer to write than actually do but here goes with a lengthy description of how best to deal with the problems.

 I always recommend that hulls be taped down together especially initially when the boat remains unbuilt and just sitting around. The grp is perfectly straight and matching when it comes out of the mould and this 'bowing' takes place slowly and steadily thereafter as grp will go on curing even after the boat has been purchased. This continued curing process is a nutural effect of polyester resin.
 There are various ways of dealing with bowing hulls.
One way is the heat treatment, this will allow the grp to become maleable as it will give up it's rigidity fairly easily. Use your heat gun but heat it gently and steadily, you can actually get the stuff so hot you can't touch it but take care not to get too close with the gun or you may cook a local area. heat it enough to make it plyable. If the upper half has spead outwards and upwards as can be found by placing it on a flat surface, try this:
Place a wooden block under the nose and tail of the moulding . Take the top off and slowly and gently heat the whole thing up till it gets really quite hot, stick it back onto the blocks and place a weight in the centre eg: big books or whatever, until it bows downwards. Allow it to cool likethis and offer it up again, you will find the fit is much better and if not correct, repeat the process and adjust the weight till you get it where you want it. I have found a degree of hysteresis in the material and it may need to be bowed a little futher than you actually need as it will spring back somewhat. You may now find that the sides of the hull have narrowed and the lower half is wider than the top half, thats because the lower hul has spread outwards and this can be cured by fixing some cross members in the hull just fore and aft of the dive unit location so they will hold the hull shape. That may also require a bit of the same heat treatment if it is really bad.

Once you are happy with the general alignment of the hull you may find it still has a tendancy to want to bow again over time and I recommend the folowing modification:
Ditch the idea of the front hull locating plates and the aft vertical post with the attaching nut. Fill in a small area in the upper and lower stern halves with resin, tape the hull halves together and drill a 4mm hole through the bottom half and up into your resin filled area in the top half. Get a piece of 4mm brass rod, cut it to suitable lenght and taper it at one end. When inserted into the lower hull it should protrude upwards into the hole in the upper hull and form a locating pin.

For all the bonding methods in the following, do not use epoxy resin, use only polyester resin and glassfibre mixture. Get hold of some Isopon P40 from the local car parts shop. Don't get P38 as that is simply bodyfiller and has no real strength.

At the front of the hull, fix two perspex plates in the hull one above the other in the upper and lower hull halves, begin by placing the lower one across the lower hull, bonding it in with resin and repeat the same for the upper hull half with this plate sighted immediately above the lower one. The same idea applies here, ie to form a locating pin but of course now they are internal, you cant drill through these as in the stern to ensure correct alignment so here's another idea for you: Drill a 4mm hole in the lower late. Find a short lenght of 4mm brass rod, stick it in your electric drill and whilst spinning, file it to a sharp point then insert it in the hole in the plate, if you used the correct sized drill it should be a nice tight fit. Gently lower the top half onto the boat, aligning the hulls as you go and finally gently press the top hull down onto the sharp pin as this will mark your upper plate. Whip the top off and drill the 4mm hole through the marking. When these pins are glued into their respective positions, the top will simple drop on and stay there.
Ok, that doesn't cure your bowing problem so here's the next move which should solve it permanently for you:
Amidships, and each side of the boat, we want to attach a strip of half inch wide brass, one sixteenth thickness material will do it. Cut a couple of bits around two inches (50mm) long and drill some small holes in the strips for the first inch, leaving one end blank. Bond these strips into the inside of the lower hull each side so leaving a short length of around 12-15mm sticking up. The holes you just drilled in the plates will aid the fixing process and help to lock the stips into your resin. When fully hardened, lower the upper hull half in place over your two  locating pins and mark of the area where the new brass plates are. Tape the hull top down firmly to the lower half so there are no gaps and using a pilot drill, drill through the upper hull and through the bras plates (now they are fully cured of course).
If you are fortunate enough to own a tap and die set, the holes in the plates can be tapped M3 and countersunk screws used throuth the hull to engage with the threads in the pates. If unable to do this, solder a couple of nuts to inside of the brass plates and apply the screws in the same way.
Theoretically you should have cracked the problem by now but if the are any further issues with various areas of misalignment, deft and careful use of the heat gun should help to solve the problems there .

If I can be of any further assistance just ask chaps. I have been very busy and don't get on here as much as I used to but will keep a weather eye open.
If you want to discuss it directly, give me a call (01493 754007) during work hours.
Title: Re: Sheerline type VII a tale of two halves
Post by: polycell on May 24, 2010, 03:57:15 pm
Struth!!!  Thanks Sheerline.
I'll print off what you say and read it a few times so it sticks!
One of the problems I have, unfortunately is I have strong magnets fitted along the sides a device up forward to pull the front end down and a 4mm bolt arrangement in the backend and........a gap down the sides.  I also have locators down the sides to ensure the two halves are flush down the sides and ...still a gap.
Do you recommend I take all my magnets and side locators off?
Title: Re: Sheerline type VII a tale of two halves
Post by: sheerline on May 24, 2010, 06:42:09 pm
Hi Fred, I would simply recommend the aforementioned proceedure, you wouldn't need anything else to keep the hull on station but if you already have the pegs or strips set along the sides they will help keep the shape and you should only need one each side with the screw holes to hold the top down. I hope the description I gave is clear enough but let me know if you need any additional info and I'll try to help if I can.
Title: Re: Sheerline type VII a tale of two halves
Post by: dan on May 24, 2010, 09:05:51 pm
thanks for the extreamly helpful tips sheerline  :-))
Title: Re: Sheerline type VII a tale of two halves
Post by: sheerline on May 25, 2010, 12:20:42 am
No problem  Dan, I hope it works for you , heat is certainly the answer to manipulating this stuff. Good luck with it.
Title: Re: Sheerline type VII a tale of two halves
Post by: polycell on May 25, 2010, 12:28:53 pm
Received, just a couple of things, doesn't screwing the top done maske it a bit of a "xxxxx" to take the unit apart to sort problems out?
Perhaps not.  The other is the bolt/screw would have to be disguised for us "xxxxx" builders!
Title: Re: Sheerline type VII a tale of two halves
Post by: sheerline on May 25, 2010, 04:07:03 pm
There would only actually be two small screws, I would use countersunk m3 types so they didn't protrude and to be honest you should simply be able to put the top on, screw both  in and go sailing. If the boat is built properly there should be little or nothing to do once the top is on and the next time it comes off is when you disconnect before going home. It only takes moments to do up a couple of screws so it's not much of a chore and they would be below the waterline too so would remain unseen when the boat is in the water.
The only other method of securing the top would be to arrange for a strap to go over the dive unit which would be fixed to the inside of the lower hull each side of the boat. You could fix a threaded recepticle to the top of the strap and drive a screw down through the deck and into the recepticle, thus pulling the top down level with the lower half.
 Worth thinking about.
Title: Re: Sheerline type VII a tale of two halves
Post by: Del-boy1958 on August 17, 2010, 08:29:23 am
Hi Guys
I had the same problem on my type 7c u boat and I used thin fiber glass tape and resin
and made an inner flange extention round the top hull that located inside the bottom hull.
I also made up a couple long round spacers that went across the front of the upper hull and the rear of
the upper hull to hold things to width with screws through the upper hull sides these were close to the
front and rear faces of the dive unit.

I think if you just heat and pull the mouldings in after a while they will spread again if no mechanical constraint is provided.

I hope this helps

Title: Re: Sheerline type VII a tale of two halves
Post by: RonP on August 24, 2010, 10:39:12 am
I can fully sympathise with this one, in 1980 I bought one of the first 32nd parallel type VIIs and it was moulded in one piece up to the deck line, the deck was a seperate piece.
For what I intended to do this was no good at all so I cut the hull along the water line, up over the fuel tanks and then back to the water line at the stern and then PERTWANG the whole bloody thing went banana shaped. It took me ages to get the thing right again and for a while I thought I had just scrapped a hull that at that time (30 years ago)cost over 600 pounds (without fittings)
All I can say is follow sheerline's instructions and take your time and all should be well at the end. As a matter of interest the kit you have was originally made by one Martin Hartshorne from a 32nd parallel hull as a base and then modified to correct the stern, it was then plated with litho plate and rivet detail added. The etched and lost wax fittings had the masters made by Ian Lawrence of Peterborough. Ian is probably this countries leading authority on U-boat construction and his knowledge is encyclopedic, his workmanship is unbelievable and his own type IX has to be seen to be believed.
Title: Re: Sheerline type VII a tale of two halves
Post by: Subculture on August 24, 2010, 01:15:03 pm
The boat you're describing sounds more like the OTW 1/32nd scale Type VII, Ron. They took on Martyn's masters, reworked the tools and put it back into production.

The Sheerline boat is closer to the Darnell Type VII, IMO.

Title: Re: Sheerline type VII a tale of two halves
Post by: RonP on September 01, 2010, 09:19:22 am
Now you see I have learned something, I thought that the OTW boat and the sheerline were one and the same. I did know that the OTW is Hartshorns and it has a number of faults carried over from the 32nd parallel original. The problem was that the frame lines were taken from Rossler however at the time you could not get an english translation so the text was not read.
The lines they used are from a type VIIc42A and this was a project that was never constructed. sad that.
Title: Re: Sheerline type VII a tale of two halves
Post by: sheerline on September 01, 2010, 10:54:18 pm
All the boats I produce, with the exception of the Type2d were the sole creation of Dennis Cater of Eden Models and I own the masters.
There was never any collusion by him with any other manufacturer in the production of his boats.
The Eden/Sheerline type7 master was produced by him and differs from the Darnell boat in a number of ways, one notable being that none of the dive units will even fit into a Darnell boat. I have modified Darnell boats to accept a smaller version of the dive unit, a hateful task and not one I would wish to repeat' At 1:40 scale they are similar at first glance but there it ends.
I no longer produce this Type7 boat just in case anyone asks but am happy to make components for it where possible.