1:28 J Class Enterprise - build log

Other Scale Sailing
61

Alan - is your fairing compound an epoxy or polyester based compound? (or something different again?)
From your description it certainly sounds similar to the polyester filler I used for fairing the plug - ready for sanding in 20mins which means if things don’t go quite according to plan the whole process can be repeated until either your arm aches or boredom sets in! I suppose I went for the epoxy fairing compound purely to keep shrinkage rates the same and also to ensure a good bond as it’ll be forming the base for primer coats etc.

Good to hear Blackmagic is meeting expectations - I read your build log on the rcgroups forum, impressive stuff. Seem to recall you had an initial issue with the rudder push rods - resolved now?

Anyway, things are nice and quiet at the moment so I’m off to do a bit of sanding.

Regards,

Row

62

Hull filling and fairing continues, but I’m thinking a little further ahead to the hull fit out and in particular the ballasting.

Some time ago I came across a German website detailing the build of a scale ‘Endeavour’ J class. The attention to detail was truly phenomenal. Unfortunately, I didn’t save it to favourites and can now no longer find it. However, I do recall their method for producing the internal ballast for the hull which I’ll outline here.

They started with two identical hulls, one for construction and a second for creating ballast. The ballast forming hull was set with its stern raised to the point where the top surface of the finished ballast would be level. The hull was then set into a container of water, maintaining the angle and immersed until the section of the hull/keel containing ballast was fully submerged. Molten lead was then poured into the hull and allowed to solidify. The finished ballast was then removed from the hull, finished and then bonded into the ‘proper’ hull for construction to continue. While I can’t dispute that this was what they actually did I do have some concerns. Would the cold water on the outside of the hull really be sufficient to prevent the resin from melting? Surely the lead, when cooled, would have bonded itself to the hull (some of the resin must surely melt). What if there were any voids in the lamination - would they explode with the sudden rise in temperature or does the softening of the resin allow them to gently vent without the horrific idea of molten lead being thrown around?

I really can’t decide how viable this method would be and was wondering if anyone had either tried/seen it being done and what the results were like.

More later,

Regards,

Row

63

In theory if they used a a “second” hull or a second keel section for pouring the lead it was surely sacrificial. I’ve poured lead and if the surface is not perfectly smooth the lead does “bond” to the surface. plus I would also imagine that some exterior reinforcement would be needed to prevent any bulging or separation if the epoxy does give way. liquid lead is just as heavy as solid and until it gets cool enough it will exert pressure.

another way to reduce the heat load and cooling time is to pour it in several pours. maybe an inch or two deep each pour. this would lessen the pressure on the hull. plus you could then make the lead into manageable sizes for easy removal

Another option would be to to use slow set epoxy and lead shot. line the inside of the hull (with this method you could use your build hull and no need for a sacrificial hull) with plastic wrap and then add your shot/epoxy slury until you are at the desired weight. Again you could pour it in manageable sizes for removal. but its not as dense as poured lead and I imagine it would not hold up very well to transportation…

Yet another option, and maybe the easiest and least dangerous. line the inside of the hull with plastic wrap. mix up some plaster of paris pour POP into hull cavity and let dry.

once dry remove POP wich is now a male mold of the shape you need. borrow your kid sandbox and use the POP mold to make a female sand mold. and pour your lead…

64

Row
I wouldn’t pour lead anywhere near water! One slip, which would be easy with ten lbs of lead, and you would have a disaster. If you must have a one piece ballast then make a plaster mold. And let it dry for a month or so. Not kidding. I have the scars.
Don

65

don,

I made a plaster mold for some footy bulbs. I dried it in the oven a week after teh most had set, and I still had steam “explosion” from the hot lead…as it found the moisture…

gotta be careful with the molten lead…

66

Marc,

Many thanks for your reply and suggestions. Not being particularly switched on at the moment, but do I assume correctly that you’ve not tried the molten lead into fibreglass/resin before? Either way, I certainly appreciate your comments. My own thoughts were to take a second molding off the plug for the keel area only, laminating very heavy, probably using 300gsm CSM & building up the weight to achieve a thickness of 3 - 4 mm, thus being more than capable of supporting the 4 Kg of lead.

I’d also considered the lead shot/epoxy route but decided against it because of the density issues and of course trying to get the weight as low as possible for the best righting moment.

Which brings me to the sand casting. In my workshop I have a bag of silica sand which I understand can be used for casting lead but the problem I have is not knowing what to mix it with to give the properties required for casting. I’ve checked out various websites which all give plenty of info but also leave me somewhat lost in terms of where to source the required additional materials (binders, clays etc etc)

One piece of info that seemed promising was on a specialist hobby site that talked of creating the sand molds from silica sand and using engine oil as a binder - is it really that simple or are there other ‘ingredients’ required for a successful outcome? I guess what I’m asking in a round-about sort of way is what did you use for your casting ?

In the meantime I think I’ll make the additional keel molding because it’ll enable me to mold various shaped male ballast plugs to see which is likely to give the best results.

Regards,

Row

67

Hi Don,

Comments duly noted and definately taken onboard!!

I’ve seen a few films of lead casting going horribly wrong when water was quite near… Needless to say, if I did go down that particular route, no water whatsoever would be ‘visible’ - I’d create a ply shroud around the mold. At the moment it looks as though sand casting is the favoured method once I’ve established what to mix with the sand to give it the required properties.

Regards,

Row

68

ROW

correct, I have not done a lead pour into an epoxy and wood mold. Although it would not be hard to make a square box plank it and epoxy it and see how it does…I guess another thing you could add to the inside of the mold would be some aluminum foil to help keep the lead from adhering to the wood mold and act as a “buffer”

* silica sand (SiO2), or chromite sand (FeCr2O), or zircon sand (ZrSiO4), 75 to 85%
* bentonite (clay), 5 to 11%
* water, 2 to 4%
* inert sludge 3 to 5%
* anthracite (0 to 1%)

http://www.eugenesargent.com/casting.htm
The Sand: Here, I am using Petrobond brand sand. It is a mixture of fine white silica sand, 30 weight motor oil (without detergents), the Petrobond powder (a specially modified clay), and a splash of liquid catalyst. The mix is prepared in a machine called a muller, which stirs and mashes the sand.

If I had my druthers. I’d make a plug out of POP find a nice spot in the yard. jam the plug intop the soil to make the female mold and the pour the lead. just to see what woudl happen…

yeah you’d get some sputtering and popping from the moisture in the soil. But it would be neat to see if it would work. also being the lead isn’t going through the water you don’t need to worry about having a nice smooth casting…IE not much finish work is needed.

what about flour…it packs down pretty good…

just thinking out loud and throwing ideas at the wall and see what sticks…

69

Wow buddy ! be bloody careful with molten lead and ANY moisture !!

Lead melts at around 360 C. and there are no any epoxies that I know of, that can handle those temperatures.

I’ve used epoxy to bond golf club heads to shafts (both carbon & metal) when I change heads I just use quick gas touch to melt the epoxy which only takes few seconds before it puffs the epoxy into crystal for easy removal, can’t imagine it was normal epoxy the used in the execise you saw :confused:

We have a foundry and when I’m back in the office Monday I will ask what formula they use for their sand molds.

btw. You’re right the filler I’m using is polyester and does have slight shrinkage & resolved steering linkage issue using smaller diameter shafts.

Cheers Alan

70

I’ve seen crazy moulds for lead, but doing an all nighter at 3 am and the yacht has to be in the water by 7:30 anything goes…

Whatever the mould was created from, the use of tin foil as a heat barrier was the first choice… Shiny side towards the lead.
It works very well, and even plywood moulds just smoulder for a short while.

Jim.

71

Amazing what solutions you can come with under time pressure Jim … brilliant !!! got me to thinking of mixing epoxy in a sand mix to make mould, then a layer of tin foil inside the mould for heat & moisture protection…I’ll give that one a try :slight_smile:

Cheers Alan

72

My 2 cents !

A very good product is the RTV 139 High temperature molding silicone.
Any forms can be made with this method. After squeezing, the form is brushed with some vaseline to favourise the release. The wooden form is also covered with vaseline
See the main sequence process and the attached PDF file :

Once the mould is ready in 24 hours, the fused lead can be filled in.

Cheers
ClaudioD

73

Brief update…

Pics to follow, but I’ve now taken a molding of the keel area of the plug with a view to casting various mortar/glassfibre male ballast plugs to establish best shape/distribution of lead so that the hull will float accurately to its waterline. The plan, once the shapes have been cast, is to establish the CoG of each piece and compare this with the CoG of the hull. The most acurate shape will then be used as a male plug to produce a female mold for the lead to be cast in. Hope that sort of makes sense - I think the photos will explain things a little more clearly.

Production of the keel molding involved covering the area to be glassed etc in parcel tape, coated with PVA release liquid and then laminated using CSM and polyester resin. Choice of materials was purely cost driven - I wanted to produce a relatively thick molding that wasn’t going to deform when the mortar/fibreglass mix was tightly packed into the ‘void’. In total I used approx 200g of 300gsm CSM & 500g resin which has resulted in an immensely stiff molding approx 4mm thick.

When it comes to casting the lead ballast, I still can’t decide how best to go about it. From the various suggestions that you guys have made I don’t really fancy the idea of pouring molten lead straight into fibreglass being cooled by water on the outside. Essentially this means sand casting or using Claudio’s suggestion of the 139 RTV Silicon. Certainly like the idea of the silicon (no moisture present) but I think the final choice will come down to price & availability of materials. Bit more research required…

Regards,

Row

74

Must have been having a ‘senior moment’ with that last post. I re-read it a few days ago and could’nt understand my thinking behind producing several mortar plugs for the lead to establish CofG. It occured to me that there really was no need - all that was required (& subsequently done) was to fill the keel molding with 400 ml of sand (hull ballast is approx 4Kg), experiment with distribution to achieve desired CofG and then cast accordingly.

To establish the required CofG, I initially marked the inside of the hull with its position from Claudio’s drawings. The hull was then floated with the ballast (3.9kg) added at required position. A further 1.4kg was added to get the hull to float on her waterline, the fore & aft position of the ballast adjusted to get the hull floating level. This position was then marked in the hull and compared with the designed position. The mark was then transferred to the separate keel molding which was then packed with sand in various ways until the desired outcome was achieved.

To test the suitability of mortar for the plug, I used an extremely fast setting type for the trial. Only a couple of problems came to light, namely, the fast setting mortar set too quickly to achieve a complete shape - once fully set and then removed from mold there were rather alot of hollows where I hadn’t been able to pack it in quickly enough. The second issue was the brittle nature of the mix (couldn’t use glass fibres as they hindered the packing process) so I’ll be casting a second plug using normal mortar mix with either glass fibres added or a mesh reinforcement.

Pictures of float test and comparison of ‘numbers’ will be in a future post.

Regards

Row

75

Very good idea ! I will copied next time

Only one recall, the Ballast CG shall stay vertically as close as possible to the CB .

Cheers
ClaudioD

76

claudio

could you make a 2 part mold using the method you mention above? you have to cut in a pour hole, but I figure it would be possible…

77

Yes of course !
The method described with the Silicon RTV is supposed to make 2 half bulb bonded later with epoxy and glass.
In your case you may try use only one box and inserting the full bulb master, or use two separate parts left and right with two different molds.
Cheers

ClaudioD

78

Ballasting etc.

Been giving much thought to this recently, and while I could afford to get some high temp rtv silicone or have a 25Kg sack of casting sand delivered I was determined to find a cheaper alternative.

I’d done a fair bit of reading around and the one theme that kept coming up was how imperative it was to ensure that the mold had as low a moisture content as possible - the idea of molten lead being thrown around like a projectile keeps the mind working keenly.

Anyway, I resolved to use a mortar mix to create the mold. Firstly it’s incredibly cheap. It also has a nice long ‘pot life’ so experience of using it wasn’t a necessity. Thirdly, having spoken to a friend who used to be a potter, I ascertained that it could be more than sufficiently dried to remove excessivemoisture.

So, from my earlier trials with a fibreglass mold of the keel, dry sand and plasticene, I was able to come up with a ballast shape with the right vertical centre of gravity and which also kept the weight as low as possible in the hull. Unfortunately this shaped posed problems with my simple casting process, namely that it wouldn’t be possible to create a one piece mold with the required cut-away at the aft end. Bearing this in mind, I recast the plug (cement, reinforced with galvanised mesh) but this time as a simplershape, the idea being that the required shape could be achieved by cutting the casting.

Initially, I made a box of four sides and a base from 100mm x 18mm timber to a size 30mm larger than the ballast plug size. This was then lined with a piece of food wrap, and approx 40mm of sloppy mortar was added. The advice from my ex potter friend was to then place the box, with contents, on to an upturned random orbit sander, which was then switched on and run for a few minutes to bring any air bubbles to the surface. Needless to say it worked a treat, so onto step two.

This invloved taking the plug (wrapped in parcel tape and then food wrap) and pushing it carefully into the mortar mix approx 10 - 15mm and then supporting it in this position while more even sloppier mortar was ‘poured’ in around it. At various stages, the box was placed back onto the upturned sander for some de-airbubbling. This process was repeated until the mortar level reached the top of the plug. The whole lot was allowed to set for 48 hours and the plug was then removed. Internal finish wasn’t great (folds showed where the food wrap followed the contours of the plug) but I reckoned it would be good enough for an internal ballast.

Now for the drying. It went into an electric fan oven set at 70 C (160 F) for 2 hours. Temp was then increased by 20 C every hour until oven was at 210 C (410 F). Temp was maintained for 1 Hour and then temp was reduced by 20 C every 20 mins until oven was switched off. I’m not sure if there was any science behind the temp increase/decrease timings, other than the fact it needed to be slow & steady. Earlier experiments with mortar & oven had always resulted in cracked molds until the sander was used.

Casting.

In the garage, amongst all the junk, we have an old ‘baby belling’. It’s a bit bigger than a microwave oven and is essentially a small convector oven/grill with a pair of electric hot plates on the top. This was set up outside with a cheap aluminium saucepan on a hob with a few pieces of 4lb/sq ft lead sheeting (approx 50x50mm) in the bottom. A combination of hob a gas torch quickly melted the pieces of sheet to leave a molten layer in the bottom of the pan (approx 5mm deep) To this was added lumps of lead (approx 20 - 30mm cubes) which had been preheated in the oven to ensure as little moisture as possible. After approx 1/2 hour I had a pan of 4.5 Kg of molten lead. A layer of scum was spooned from the top. In the meantime the mold was preheated to 200 C which was then lined with 2 - 3 layers of aluminium foil just incase any moisture remained and to ensure an effective release without having to break the mold. Molten lead was very slowly poured into the mold. Not a pop or hiss could be heard - everything was more than dry enough!

After 10 mins, the mold was rolled over onto some pieces of softwood and the casting ‘dropped’ out. This was allowed to cool for a few more minutes and was then plunged into a bucket of cold water. It’s fit was checked in the hull and the initial trimming was done to start getting it to the required final shape & weight.

That’s it for now, more over the next few days,

Regards,

Row

79

Great !
finally you got the ballast, some filler and will berfect !
Cheers
ClaudioD

80

Well done ROW !!! looking really great :slight_smile: that’s decent weight off your shoulders :rolleyes: