building materials

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28 April 2019 at 21:08 #82077
chris fenerty
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@chrisfenerty25956
hello everyone,

my question today is construction materials. normal construction ply or marine ply. in nz construction ply is similar to marine ply except for laminate thickness, unlike the ply you see on tv overseas where it is slivers of wood laid down in all directions

so can i use construction ply for my model ship the bismark

feedback would be most welcome
Advert

28 April 2019 at 21:08 #7151
chris fenerty
Participant
@chrisfenerty25956
large boats/ships
28 April 2019 at 21:37 #82078
Ray Wood 3
Participant
@raywood3
Hi Chris,

As your building a large model, I think the lower grade plywood with less laminations will be fine for keel & bukheads, in my view.

Regards Ray
29 April 2019 at 15:13 #82082
Paul T
Participant
@pault84577
Chris

Check that the glue used to stick the plywood together is waterproof as you don't want the wood to de-laminate if it gets wet.

Paul
29 April 2019 at 16:06 #82083
Ray Wood 3
Participant
@raywood3
Hi Chris,

Yes as Paul says, you would need to seal the ply with a good couple of coats of varnish or epoxy resin, full blown marine ply for models is slight overkill for a the amount of time it will be in the water, compared to a full-size boat being afloat for years.

Regards Ray
29 April 2019 at 19:26 #82085
Paul T
Participant
@pault84577
Hi Ray

Its not just the de-lamination, there is a bigger problem as the cheaper plys will also twist and warp under changes in temperature and humidity which, as we all know happens most whilst the models are in storage.

Sometimes choosing a cheaper material ends up being the more expensive option.

Paul
29 April 2019 at 19:52 #82086
Ray Wood 3
Participant
@raywood3
Hi Paul,,

Can't disagree with your ideas, but it doesn't sound like Chris has access to birch ply in nz, obviously all my models are stored in temperature and humidity controlled conditions so not an issue 😀 all the 1/4" ply I use is from China as my son in law has a van ply lining business, loads of off-cuts 😄 ,

Regards Ray
29 April 2019 at 19:58 #82087
Colin Bishop
Moderator
@colinbishop34627
'Construction' ply can vary enormously in quality, even the so called 'exterior' varieties. Some of them warp or delaminate horribly!

Over in the UK we tend to use birch play from suppliers such as SLEC

**LINK**

I don't know if this is readily available in NZ.

If you can buy small quantities at reasonable cost then marine ply will give you peace of mind. Suppliers do often have offcuts available.

Colin
29 April 2019 at 20:59 #82089
chris fenerty
Participant
@chrisfenerty25956
hi everyone, the construction ply was going to be my keel and ribs. the ribs i was going to use 18mm ply, so with a hole cut into it should not warp. the keel i was going to laminate as i want to cut the centre piece for my prop shaft, and i was going to cut the laminated keel where the the rib positions are and slide the rib into place and glue. i was going to spray the inside of the keel and ribs with polyurethane and coat the out side with epoxy resin, not sure about the top though. to line the sides i was going to use 2mm okoume plysheets most probably double skinned, and for the outside super structure a mix of 4mm and 2mm

feedback most welcome
29 April 2019 at 22:12 #82092
chris fenerty
Participant
@chrisfenerty25956
hi everyone, i forgot to ask another question, stern and bow building materials, i want something to fill the void as i do not think i can get the ply to mold to the shape. balsa wood is available in big pieces, i am not sure about bamboo, i was going to laminate and then shape

your thoughts please
29 April 2019 at 22:42 #82093
Ray Wood 3
Participant
@raywood3
Hi Chris,

Blue Styrofoam is easily carved and sanded to shape, if your going to glass cloth and epoxy the hull it works well 😊

Regards Ray
29 April 2019 at 23:03 #82094
chris fenerty
Participant
@chrisfenerty25956
hi, is that the real dense foam 12mm thick laminated to larger sizes
30 April 2019 at 06:23 #82095
Ray Wood 3
Participant
@raywood3
It comes in 50mm sheets here as insulation,, either known as Roof Mate, or Floor Mate, it's light weight, used in RC aeroplane building, I'm building a cat with it at the moment.

Regards Ray
15 May 2019 at 20:19 #82326
chris fenerty
Participant
@chrisfenerty25956
hello everyone,

my topic today is about making or buying,

as i live in nz, and billings and other suppliers are in europe, it is hard or costly to get parts in, so you are faced with making your own, now i am not very good at casting and 3d printing sometimes is not strong enough based on the size of the item.

now i need 3 propellors, 2 right hand and 1 left hand, so i had an idea about making my own, if i get some brass plate and get it watercut into the basic blade shape with a pilot hole for a spigot, i could turn down some brass rod and thread it, then comes my in decision do i solder or silfoss, silfoss is hard for cleaning up and the heat might make the blades droop even though the diameter is 50 mm. so once the is secured i could twist the blades into shape or try and make a former. i forgot to mention i have my own lathe and milling machine, which is a bonus unfortunately not all of us have this equiptment or access to it.

so back to topic, with my blade secured to a spigot i thought i could use a live center in my chuck and tailstock and try and roughly balance it. wich brigs me to my question about billings brass propellors are they balanced, or would it not matter

your thoughts please
15 May 2019 at 21:26 #82329
Ray Wood 3
Participant
@raywood3
Hi Chris,

You can turn and tap the boss 5mm and cut the slots for the blades and silver solder them and bend the blades to shape, or cheat like I did buying this one !!!

Regards Ray
15 May 2019 at 23:30 #82330
chris fenerty
Participant
@chrisfenerty25956
hello and thank you for your reply,

i forgot about the blades being mounted on a incline, and silver solder is softer and a lower melt point than silfoss. designing a three point blade is more difficult than designing a single blade and i can get more cuts than a triple blade leading to more experimentation in case of failures.

any feedback is much appreciated.
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