Woodn't you like to know

[neil martin 1]

Does anybody have a link to the "woodn't you like to know" information in the subscriber forum or any similar resource for advice? This is in reference to the choice of wood and appropriate grades when plans do not detail what is required for each part of the aircraft. This request comes from a total build newbie that does not have this info in the plan. I have balsa and ply parts in the kit but would like advice regarding wing spars, braces and engine bearers. Thanks

[FlyinBrian]

I don't know of the "Woodn't you..." link but as a rule of thumb -

Buy from Balsa Cabin or Slec or similar suppliers and they will supply what you request.

Sheet Fuz sides - medium - In some instances you might use say 1/8 hard balsa instead of 3/16 medium etc

Sheet fuz top - med/light

Sheet fuz bottom - medium except for hard points for u/c etc.- use ply

Sheet fin and tail med/light

Wing ribs - light/med cross grain

Wing sheeting + LE and TE- l medium/ light

 

Depending on the model type you can use harder or softer (lighter) wood in various places to produce the desired effect eg light wood for cowlings and fairings.

In general keep the back end light you can always put a servo at the back if you come out nose heavy

 

Hope that helps

 

 

 

 

 

Edited By FlyinBrian on 12/05/2020 20:45:57

[Peter Miller]

If you are a subscriber this is the link

**LINK**

If not PM me your email address and I will send you the article

[Martin Dilly 1]

FlyinBrian, I think for ribs you mean quarter grain, don't you, rather than cross grain? I've no idea what 'cross grain' is when referring to balsa. Might sound worryingly like grain across the rib, rather than along it, to a newcomer.

Edited By Martin Dilly 1 on 12/05/2020 21:13:30

[neil martin 1]

Thank you...all advice welcome. Peter I have sent you a PM

[FlyinBrian]

Posted by Martin Dilly 1 on 12/05/2020 21:12:55:

FlyinBrian, I think for ribs you mean quarter grain, don't you, rather than cross grain? I've no idea what 'cross grain' is when referring to balsa. Might sound worryingly like grain across the rib, rather than along it, to a newcomer.

Edited By Martin Dilly 1 on 12/05/2020 21:13:30

Yes Martin, you are quite right, I had a brain F...t!

Having had a quick read of Peters article I note he specifies hard wood for fuz sides but I usually prefer to use medium and go up a thickness eg from 1/8 to 3/16. Also I rarely use ply doublers preferring 1/16 hard balsa.

I find this aids in the final shaping giving a bit more to material to plane/sand - obviously at the expense of more work -  but it works for me.

 

Edited By FlyinBrian on 13/05/2020 09:19:47

[Peter Miller]

Posted by FlyinBrian on 13/05/2020 09:10:19:

Posted by Martin Dilly 1 on 12/05/2020 21:12:55:

Having had a quick read of Peters article I note he specifies hard wood for fuz sides but I usually prefer to use medium and go up a thickness eg from 1/8 to 3/16. Also I rarely use ply doublers preferring 1/16 hard balsa.

I find this aids in the final shaping giving a bit more to material to plane/sand - obviously at the expense of more work - but it works for me.

Edited By FlyinBrian on 13/05/2020 09:19:47

3/16th sides are just too much, I usually specify medium to hard 3/32 for models up to .52 FS and .40 two strokes.

1/16th balsa doublers would need to be rock hard and with grain across the grain of the sides. 1/32" ply is still stronger and almost certainly lighter.

But then I prefer lighter wing loading as models fly better that way.

My wing loadings tend to be under 20 oz per sq in. Alot of people seem to agree with that.

[Nigel R]

"wing spars, braces and engine bearers"

Spars, hardest of rock hard balsa, or just use spruce.

Braces (dihedral?) normally ply, thickness depends on size of model

Engine bearers, if wood, usually maple or similar (very) hard wood. But glass/plastic engine mounts are an easier, if you can.

Otherwise, I agree with FlyinBrian's list, one minor exception, wing sheeting always light grade, sheeting is the biggest single weight contribution for a wing.

And medium is enough for me for fuselage sides, I've never used hard - ply doublers sort out any strength needed up front - 3/32 thick up to 40 size, 1/8 thick for 60

Really light wood is often enough for airbourne load but can be fragile. I like to join wings with a fairly wide bit of the thinnest of glass cloth which has a handy benefit of reinforcing the sheet near the root where you pick it up and manhandle it. For similar reasons, I often make fuselage top front decks from soft thick sheet sanded to shape - provides a good place for holding on to your creation. Rear decks, sheet - thin (3/32) and light.

Edited By Nigel R on 13/05/2020 11:52:56

[kc]

Nobody has answered the question on spars, braces and engine bearers.

For spars I prefer to use spruce rather than hard balsa - it must be really hard balsa to be any use for spars on most RC models so spruce is the substitute I use. Also possible to use softwood like pine as sold by B&Q etc in 6mm sq section etc in about 8ft lengths but watch out for the 'finger joints' which are used in this timber and dont use that section near the root only at the tip. ( finger joiniing is almost invisible in the wood until you look closely and you will see it) Make sure the length is straight. Spruce from SLEC or Balsa Cabin is available in 48 inch lengths as well as 36 which is handy for some designs.

Wing braces should be a good type of ply such as birch ply not the cheap DIY ply which is weaker due to thicker centre section of poor timber between nice looking outer layers. Lite ply ( from SLEC or Balsa cabin etc ) is probably not suitable unless actually specified by the designer.

Engine bearers are normally beech. Could be any good hardwood like mahogany if that is all that is available. Beech is easily obtainable in engine bearer sizes from balsa suppliers, but a good source of free beech is scrapped chair or table legs if you care to saw it down yourself - just utilise the flat surfaces and saw away the usually tapered bit. A bit of effort but free and the best seasoned timber you can find after it's been indoors in a centrally heated house for decades. Depends on the design but most people now use plastic or alloy engine mounts for glow. But a beech engine bearer might be part of the fundamental design on older designs.

It's a mystery why such basic things as the Woodnt you article is available to subscribers only long after it was published. Should be availble free to help newcomers etc.

[Peter Miller]

There will be an article in RCM&E on the subject soon.

[Nigel R]

"Wing braces should be a good type of ply such as birch ply"

That's a good point, the DIY shop ply is a bit naff.

Works for stuff like U/C mounts and formers.

[kc]

Neil, if you specify which model you are building and the plan or kit then probably you will get more advice and hints.

[neil martin 1]

The model is the 68" Miles Magister by Dennis Bryant (Sarik Hobbies)

[Nigel R]

**LINK**

Build log on this site, made with depron though.

[kc]

A Miles Magister as a first build? I think most people would advise against such a model. That's not to say it's impossible, just it would be easier to get a few simple models built first and gain experience. Much better to put aside and build something simpler first that could be built in much less time.  Scale models have so many fiddly bits that need to be correct.   Sports models don't need to have the fancy parts - they just need to fly well so construction is quicker and easier. 

 

Edited By kc on 13/05/2020 13:56:25