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Balsa Shortage

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redpmg29/09/2020 17:24:30
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Hi Dave

Been used to bend modelling ply - birch etc by soaking - with the very thin stuff you can bend it around a thin tube easily - made it very flexible .

When you steam Liteply do you get it wet ?

Presume its waterproof - so will try a scrap piece of 2mm with the soaking method - be interesting to see if it works

Dave Milbourn29/09/2020 18:29:34
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Peter

No, it's not waterproof without further treatment but it's not birch ply.

Soak it and it will delaminate, because it's not birch ply.

Try and bend a thin section of it sharply across the direction of the surface grain and it will likely snap because it's not birch ply.

You don't need much steam to bend it because the adhesive between the laminations is not a hard resin type. It quickly softens and allows the layers to slip over each other, whereas the resin in birch ply needs a lot more application of steam or heat to soften it.

Is the message becoming clearer? Frankly if you just forget the word "ply" then you'll get on much better with the stuff. Regard it more as being similar to three layers of hard balsa glued together with PVA. I do use resin-bonded ply for some parts e.g. motor mounts which need to accept screws or thin sheets which have to form sharp curves (funnels, Perkasa cabin sides). It's a question of using the appropriate material for the job in hand.

Dave M

Edited By Dave Milbourn on 29/09/2020 18:30:12

Chris E30/09/2020 08:53:20
226 forum posts

Dave M

That is a useful summary.

The thing that I note most strongly is the need to have a very durable and totally waterproof finish inside & out as the liteply isn't waterproof and compared to birch ply is impact damage prone.

Charles Oates30/09/2020 09:36:15
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Chris, wood isn't waterproof, birch ply isn't waterproof, balsa isn't waterproof, that's why we put a durable finish on it. Did you see my note about applying finishing epoxy? As for impact resistance, can you imagine a balsa model being described as impact resistant? Yet there are hundreds of models decades old, made of balsa and still going just fine.

As for finishing, I can't imagine anyone with enough brain power to breath in and out making a working model boat without waterproofing the interior in some way, even if it's just sloshing some old paint around the inside.

Presumably you are already a modeller, so surely you already know all that?

At the risk of repeating myself, may I respectfully suggest you just get some and try it.

Chas

Dave Milbourn30/09/2020 09:38:06
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Chris

Much like hard balsa, although not liable to splitting because of its laminated construction.

DM

redpmg30/09/2020 10:10:21
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125 forum posts
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Hi Dave,

thanks for the info on Liteply - understood you loud & clear ! .

Have a few strange pieces of ply here - not quite the same as Liteply - but definitely lighter than chippies or Birch ply of the same thickness - probably about half the weight . Cutting a decorative piece for a client from one of the boards as she cant wait for the proper Liteply delivery - so will have a few unusable bits left over - will see what happens to those when soaked......... no loss if it does not work. Cant quite make out what type of glue has been used on it. and steam is a problem with our glass kettle - small clothes steamer went wheels up some time ago - would have been ideal !

Usually use a white wood primer inside a hull - waterproofs to some extent - but seems to let wood dry out provided you leave the superstructure off for a few days............ Outside of Balsa hulls coated with 25% thinned Polyester Resin which soaks in and leaves a very much tougher surface - easy to get smooth too.

Water based finishing Epoxy like you use is available here - but a small bottle costs around a 1/4 of our monthly food budget.- definitely envious of whats available in the UK - and the prices !

Chris E30/09/2020 10:20:55
226 forum posts

Dave

This discussion has somehow gone wrong.

Yes I am a modeller but I have not used knowingly used LitPly. I have read some very dismissive reports on Litply and I was just trying to full understand its characteristics and how you use it with success whereas as others fail miserably.

I realise that no wood is waterproof but some are more resilient to water damage than others. I am now seeing Liteply as more like balsa than birch ply (in need of a high level of protection).

I have read what you have written about fibreglass covering & that is the way to go as well as what I do. I am, however also aware of various finishing methods suggested by others and I have known of modellers who don't do anything to the inside of their hulls to let the wood "breath". They seem to get away with this but they would not do so with LitePly. They seemed to manage to breath without great difficulty.

 

 

Edited By Chris E on 30/09/2020 10:38:58

Charles Oates30/09/2020 10:55:40
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Chris, my comment, re breathing, was out of order, I'm sorry. The point was that if you waterproof the inside of a model, it will help prevent de lamination with lite ply, and as balsa is prone to swelling when wet, it will help the model be stable for a long time. I'm certain that there are un sealed models out there that are also decades old, that's probably due to good maintainence, storage and infrequent use.

Chas

Chris E30/09/2020 11:35:53
226 forum posts
Posted by Charles Oates on 30/09/2020 10:55:40:

Chris, my comment, re breathing, was out of order, I'm sorry. The point was that if you waterproof the inside of a model, it will help prevent de lamination with lite ply, and as balsa is prone to swelling when wet, it will help the model be stable for a long time. I'm certain that there are un sealed models out there that are also decades old, that's probably due to good maintainence, storage and infrequent use.

Chas

Agreed. I think that Cascamite & real wood bread & butter construction helped as well.

Paul T30/09/2020 13:24:39
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Dear All

This discussion is going around in circles and is beset with half truths, rumour and speculation so it might be a good idea to go back to basics and examine the basic structure and uses of these materials.

Balsa Wood:

As most of us know Balsa comes in two types, these being hard and soft.

Balsa is easily worked but prone to splitting along the grain if not cut correctly.

Balsa can be curved in line with the grain but will fracture if too much pressure is applied.

Because of its open cellular construction Balsa is very light which is why it has been the model builders 'go to' material for many years. This and its compressive strength is the reason why it is used in the core of wind farm blades instead of polyurethane.

Balsa is not waterproof and its open cellular construction soaks moisture like a sponge so, after cutting / assembly its surfaces must be sealed, this applies to ALL AREAS even those parts that are enclosed within a structure. The sealing product must be able to slightly soak into the surface of the Balsa so that it can adhere to the timber, a dilute PVA is ideal for this purpose.

Common Plywood:

Most plywood is only fit for construction sites where it is used as a fast and economical substrate for other products.

All plywood will delaminate when it gets wet, the cheaper plywoods will warp and delaminate as soon as the moisture dissolves the bonding glue. Even Marine Ply will warp and delaminate if it is not fully sealed.

Common Plywood will only bend / curve over a short radius before it fails due to internal pressure and splits. The more expensive plywoods can be bent / curved by applying steam but the curved section might fail and fracture after cooling.

LitePly:

Litply is no exception as it is still a plywood however and as its name suggests it is lighter and just as strong as comparable plywood which makes it ideal for the internal structures of models, more so as it has greater structural strength than Balsa.

LitePly will bend / curve better than common plywood but will still fracture if forced too far.

Some plywoods can be bent using steam to soften its structure, the application of steam will allow a greater / tighter curve to be achieved but there is still a chance that the plywood will split as it cools.

Birch Plywood:

The best plywood for structural strength, lightness and the ability to bend / curve without splitting is Aircraft grade Finnish Birch Plywood which, as its name suggests is used in the manufacture of wooden framed aircraft. It is also used in the manufacture of Boats, Furniture, Musical Instruments and Cigar Cases.

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