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Author Topic: First build using GRP hull  (Read 2128 times)

jax

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First build using GRP hull
« on: December 13, 2016, 12:15:09 PM »

As I said in my greetings messageI have built 3 boats but still consider myself low down on learning curve. I am about to start on a Bristol Channel Pilot Cutter using a GRP hull which will be first for me, having only worked with wood and plastic up to now.


There are various brass pieces to be fitted (rudder pintles, chainplates for deadeyes etc) is there any risk of problems with stress fractures with these fittings? Any tips on best way to fit these? For cutting openings such as for scuttles is simply drilling and filing the best way?


The model has internal ballast. I am using plans for a 1/12 scale model reduced to suit a smaller hull as suggested on the TrapletShop site where I made the purchase.  How do I calculate the new weight required. With external ballast calculations can be made in the bath once build is complete and all R/C equipment is fitted but once I reach that stage with this build I assume it will be difficult to fit ballast. Also what is the best material to use. I found a description of someone pouring molten lead into his hull, I've poured lead, but into moulds miles from the model, the thought of doing it direct into a hull is rather scary!


I'm assuming the rather sketchy lines on the plan indicate the tiller. Actual steering seems to be via linkage from servo under the deck and out through star to fittings on the rudder. Is there a risk of water entering the hull at these points?


Hopefully you don't find my questions too stupid.


Thanks in anticipation.


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misog

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Re: First build using GRP hull
« Reply #1 on: December 13, 2016, 12:45:43 PM »

See attached photo.


Never had water ingress in this boat, driest boat I have.


Misog
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SailorGreg

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Re: First build using GRP hull
« Reply #2 on: December 13, 2016, 04:07:43 PM »

As I said in my greetings messageI have built 3 boats but still consider myself low down on learning curve. I am about to start on a Bristol Channel Pilot Cutter using a GRP hull which will be first for me, having only worked with wood and plastic up to now.


There are various brass pieces to be fitted (rudder pintles, chainplates for deadeyes etc) is there any risk of problems with stress fractures with these fittings? Any tips on best way to fit these? For cutting openings such as for scuttles is simply drilling and filing the best way?

It is very unlikely that you will get stress cracking from fittings unless your hull is incredibly lightly built.  GRP is tough stuff and a model hull is usually way stronger than it actually needs to be.  Cutting scuttles is just as you say - drill around the edge of the hole, cut out the waste then tidy up and square the corners with a small file.  It helps to put some tape over the outside of the hull to discourage the gel coat from chipping as you drill and file (and you can mark the hole on the tape without worrying about cleaning off the marks later).


The model has internal ballast. I am using plans for a 1/12 scale model reduced to suit a smaller hull as suggested on the TrapletShop site where I made the purchase.  How do I calculate the new weight required. With external ballast calculations can be made in the bath once build is complete and all R/C equipment is fitted but once I reach that stage with this build I assume it will be difficult to fit ballast. Also what is the best material to use. I found a description of someone pouring molten lead into his hull, I've poured lead, but into moulds miles from the model, the thought of doing it direct into a hull is rather scary!

Firstly, mark the waterline on your hull (again, tape helps if you are worried about making a mess).  Put the hull in the bath (after you've filled it of course  %) ).  Put weights into the hull until the marked waterline just about gets wet then weigh what you have put into the hull.  That is the amount of weight your hull needs to sit properly in the water.  Of course that is not all ballast - decks, rig, internal structure, electronics, battery all weigh something, but at least you know the total you are aiming for.  If you can estimate the total weight of the boat without ballast you know how much to put in the keel (although there is always some fine tuning to be done once the boat is completed).

Regarding pouring molten lead into the hull - sounds scary but I know it is done at full scale - although the keel is immersed in water when the lead is poured to act as a heat sink.  I guess the same applies for a model.  But I wouldn't do it in the bathroom.  {-)



I'm assuming the rather sketchy lines on the plan indicate the tiller. Actual steering seems to be via linkage from servo under the deck and out through star to fittings on the rudder. Is there a risk of water entering the hull at these points?

Yes, those lines are the tiller, although it looks a pretty weedy tiller - pilot cutters had big, strong tillers and I suggest you look at some images online to see the sort of proportions that were used.  As misog said, it is unlikely that you will get any significant amount of water through the holes in your transom.


Hopefully you don't find my questions too stupid.

The only stupid question is the one you didn't ask.


Thanks in anticipation.

SailorGreg

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Re: First build using GRP hull
« Reply #3 on: December 13, 2016, 04:50:30 PM »

Further to my comments about the tiller, here are a couple of shots of a boat that lives near me.  The rudder is keel-hung rather than transom-hung but the size of the tiller is what matters!  :-))





I do have a few more photos of this particualr boat if you are interested, and as I said it's quite close to me.  I know the owner so getting a few more snaps shouldn't be a problem.

Happy modelling!

Greg

jax

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Re: First build using GRP hull
« Reply #4 on: December 14, 2016, 12:21:55 AM »

Thanks misog that's reassuring. Is that something like dacron that you used?


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jax

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Re: First build using GRP hull
« Reply #5 on: December 14, 2016, 12:47:19 AM »

Sailorgreg thank you. The hull certainly is much more solid than I expected, as I said new to working with this so just making sure I didn't have potential problems.


The pic of the tiller confirms what I thought the tiller should look like. Not sure why plan indicates it that way. I should be OK for reference material but I'll give you a shout if I need more.


This business of the ballast looks like its going to be rather exciting. molten lead near water - an interesting mix (maybe mix not the right word to use!).


As an aside I discovered Amazon sell a book "The Sailing Pilots of the Bristol Channel" For a mere 98.44 hardcover or paper back for 999.11. Don't think there is any point leaving hints for 'Santa'



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misog

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Re: First build using GRP hull
« Reply #6 on: December 14, 2016, 08:59:31 AM »

Jax


If memory serves me right it is builders line, got it from the guy who sold me the hull.


With regard to pouring molten lead, having done this in the past but not with model boats. I used lead shot held in place with resin, the smaller the better to get a greater density in the tighter areas.


Other good reference books are "Inshore craft" and "The gaff rig handbook"


Good luck with the build.


Misog
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hammer

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Re: First build using GRP hull
« Reply #7 on: December 14, 2016, 10:09:35 AM »

The tiller shown on the plan could have been metal not wood. like so.
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Geoff

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Re: First build using GRP hull
« Reply #8 on: December 14, 2016, 06:23:33 PM »

As a suggestion if you are using internal ballast I have used lead flashing as its easily cut to size and fixed into place with silicon so it can be removed for adjustment if needed. In my experience with internal ballast you are very likely to have a limited sailing envelop, which may be fine.                                                                                                                                                                                            Lots of scale models use a detachable fin which is invisible once afloat. The benefits are the sailing envelope is significantly increased so the whole experience is much more enjoyable.                                                                                                                                         As regards casting lead directly into the hull I have heard of this but never had the courage to do it. Possibly a better way would be to line the hull with plastic film and pour some plaster in of the requited size - a bit of a guess but you can then remove this and make a plaster mould. Once very dry (cook in the oven at a low temperature after a week of drying) you can pour the lead in safety and know that it will be a perfect fit in the hull. Enjoy the modelling .                                                                                                                           cheers   Geoff
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reg

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Re: First build using GRP hull
« Reply #9 on: December 14, 2016, 07:30:06 PM »

This AVATAR is owned by Jaydee.  Please remove and change it to one of your choice.

ken






Hi Jax
A very good book to ask Santa for is SCALE SAILING MODELS by Phillip Vaughan Williams published by Traplet
  Isbn 1 900371 20 0  a lot of the book is about how he built a GRP Pilot Cutter.
Also on Mayhem some place is a build thread with lots of photos on building a pilot cutter by 'Popeye '
well worth hunting for.
Looking forward to following your building thread
Regards   Reg         
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hammer

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Re: First build using GRP hull
« Reply #10 on: December 15, 2016, 10:10:16 AM »

 In my experience pilot cutters do not require external ballast. Small bits of lead mixed with sand & cement my method.  Having sailed in an official force 8, true couldn't tack just jibe. 
I also use builders line for rigging, different thicknesses are available measured by numbers. The problem is finding the natural type, the nylon is no good.
You have a way to go before finishing the deck but now is the time to consider access to the works, no hatches on a pilot cutter.
Some picture I hope will help. Hammer 
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jax

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Re: First build using GRP hull
« Reply #11 on: December 15, 2016, 11:33:42 AM »

As I said in a previous post I am really impressed with the help given on this site.


Looks like it will be after christmas before I can make a real serious start. (Maybe not a bad thing, I'll need to get some stuff by mail order and I've seen inside Royal Mail centres at this time of year.) In the meantime all your advice is being taken on board.


Thanks everyone for your very helpful advice.Now off to that major distraction from model making work!

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