Balsa wood Vs Ply

[Andy CParticipant @andyc56856]

Hi All

 

I have just bought a magazine which has plans available for the complete beginner (ME). The plans call for the use of balsa a the wood for the hulls etc.  Is this the best option or wood it be better to use ply?

 

regards

Andy

[Andy CParticipant @andyc56856]

[Colin BishopModerator @colinbishop34627]

Balsa is a perfectly good building material provided that the finished surfaces are properly sealed against moisture. If the magazine article specifies balsa then it should be fine to use it as instructed.

 

Colin

[Andy CParticipant @andyc56856]

Hi Colin

 

Thanks for the eply, I will  have a look aorund the forum, I am sure there are some posts about sealing balsa.  Seems from what I read breifly, that it is a lot of work.

 

Regards

Andy

[Colin BishopModerator @colinbishop34627]

Not really, if you use ply you would still have to seal that before you can paint it.

 

Two or three coats of sanding sealer rubbed down between coats should give you a good base for painting. Glynn Guest, who is a big advocate of balsa construction prefers to use cellulose dope. If he wants a bit of extra strength and ‘knock’ resistance he applies aeromodelling tissue over the surface for the final coat.

 

Colin

[ashley needhamParticipant @ashleyneedham69188]

Oddly enough my current project is balsa and I had forgotten just how soft it is, all my other boats have ply sides, although some of them have balsa botties.

 

I tried the tissue and dope method and was pleasantly suprised as to how much stronger it made the hull. Mind you it is all relative, as every time I move the thing around I bash it into something and put another dent into it.

 

For yet another project thats on the stocks i tried the very thin resin sold to harden up dried rotten wood in window sills etc, prior to filling and painting. This actually works quite well, the balsa and ply going quite hard. BUT it doesnt assist in a smooth finish, like wot tissue/dope does.

 

Personally, for a simple “glynn” type hull with single sheet type sides, i would use ply, personal choice.

I have not had a problem with water in any of my models affecting ply or balsa as I give all parts a good coating of firstly thinned sanding sealer, then sanding sealer then undercoat then topcoat then….    theory being if balsa is so porous, then fill up the pores with sealer and then theres no room for the water!!  The lads aircraft carrier gets a good bashing on whatever there is to bash against in the pond, and despite having a balsa  base has never had a problem (I let it dry out well before storing, though).

Ashley

Kon-tiki   wasnt that ALL balsa,,,and it wasnt painted I believe….

[Eric Moffat 1Participant @ericmoffat1]

G’day Andy;

I built a yacht out of strips from breakfast cereal boxes & stiffened it up with light fibre glass cloth & a coat or 2 of resin. A bit of tint in the resin will colour your hull whatever colour you like, and being the thickness of the hull, you will never need to paint it again!!

regards

Eric

[Andy CParticipant @andyc56856]

Thanks for all the tips.  I guess I will stick with the balsa and see how it goes.  I am sure it will need a lot of work whatever I use.

regards

Andy

 

[Andy CParticipant @andyc56856]

Hi All

Back on the Balsa vs Ply argument again. I know I can use Balsa, a very good material and relatively cheap to buy, but what if I was to use ply (as that is what I also have in stock? If the plan calls for 10mm Balsa sheets would I really want to use 10mm ply? Seems to me that it would be a lot heavier and kinda overkill.

Any ideas? I have lots of 3 & 6 mm ply sheet I could use.

Andy

[Charles OatesParticipant @charlesoates31738]

Hi Andy, what is the model you’re building?

[Andy CParticipant @andyc56856]

Hi Charles

It is one of many plans I have of models. This one is a Vosper Corvette, from another magazine. I have looked at the build story in the magazine and I am not happy with the way the thing fits together. Thinking it might be better if using ply.

Andy

[Charles OatesParticipant @charlesoates31738]

Hi andy, whatever the pros and cons of balsa/ply, it seems to me you won’t be comfortable with the model unless you use ply. You don’t mention the size of the boat, so check you will have enough displacement for the extra weight.
I’ve always believed that this hobby should be fun so if you’re not happy with balsa, don’t use it.

[Malcolm FraryParticipant @malcolmfrary95515]

Since ply is usually made from more naturally durable wood than balsa, thinner should be just fine, possibly down to the point where there is little weight difference. If ply is easier to come by than balsa, it becomes a natural choice. Back when we had model shops, balsa sheet was very easily come by, now we have hardware superstores who don't sell balsa sheet but do sell ply. Many plans still available were drawn up in the days of model shops and easily available balsa.

For finer, lighter details, sheet styrene and/or treated card will probably still be the main choice.

Weight is still important – there was a construction article many years ago by a guy who wanted a fishing boat and, being pessimistic about the strength of balsa and totally unaware of the procedures for giving it extra strength, built it from oak. Strongly. He wound up with a beautiful model that couldn't float with radio gear.

[Andy CParticipant @andyc56856]

Thanks all for your insight. the boat (ship), ends up with a length of about 25". I think I will try it out of ply and see how I get on. I have a model shop close by, so can always run off and get some balsa as he is primarily a plane flyer anyway

Cheers Andy.

[Colin BishopModerator @colinbishop34627]

I agree with Malcom's point about weight. It's easy to add ballast. less easy to add lightness! Many builders have come unstuck through underestimating stability problems.

Colin

[Dave MilbournParticipant @davemilbourn48782]

The problem with balsa is always its softness and tendency to "ding". I've just finished a kit with a balsa hull and the instructions were to cover it with TWO layers of 0.6oz glass cloth, which I did. The result is much better than the old dope-and-tissue method. The latest kit I've bought (also American) has balsa planking and is covered with one layer of 2.3oz glass cloth. If you use Z-Poxy finishing resin and allow it to harden overnight then this is almost as easy as sanding down cellulose – but I've ordered some bass sheet to substitute for the balsa this time. The stuff supplied was just a touch too soft for any modelling application I can think of. If I were to bring the Permagrit sanding block within a foot of it it would probably disappear in a cloud of dust.
25" is borderline for an all-ply boat, I'd have thought. Liteply might be a good alternative to balsa (see SLEC website).
Dave M

[Andy CParticipant @andyc56856]

Hi Dave

Liteply is what I meant when talking about ply, should probably have got my materials right. I guess liteply is lighter than normal ply given the name but is slightly more durable than balsa. Looking at the pics in the magazine she sits about an inch or so in the water so not a massive draft I am guessing. Looks like a big SLA battery too, which I don't have. I will give it a go and see what I get.

Cheers

Andy

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