CO2 Bleriot - Rebuild

Out of curiosity and just for reference, I weighed a 1m strip of 3x0,35mm carbon at 1,7g. I calculate a 3'x1/4" x1/8" triangle of balsa at 8 lb/cu.ft would weigh 2.3g. I don't know what density hard balsa would be but I believe strength is not necessarily determined by weight. Thin cyano will stick the roughened carbon for little extra weight. Andy's point about causing a stress raiser by strength and stiffness discontinuities needs careful design however, and on something like his incredible peanut Lacey, it is probably impossible to gain advantage - I'll never know, it is beyond my capabilities!
Hope that adds, certainly not trying to detract. ☺

You make a very valid point there Nigel, thanks for posting.

It's worthwhile making a comment here on the use of cyano in lightweight FF models. Cyano is heavier than balsa cement. It wicks into the wood and doesn't evaporate, most of the 'carrier' in balsa cement evaporates as the cement is drying. Further, because the cyano wicks into the wood, it creates a hard point, which, when using very light balsa, becomes a weak-point where the balsa will break rather than flex. Finally, balsa cement can be melted with thinners and the joint re-cemented. The latter has many uses, not least being to change flying surface position for trim. Joints made using cyano are normally permanent.

I'm not knocking cyano as an adhesive, as in certain cases such as field repairs, it's an essential part of the modellers repertoire. It does, however, have limitations when applied to lightweight FF models.

And there was I thinking that I was the only one on the planet still using balsa cement. Went into a model shop(to be fair, the main thrust was to cars, but there were a/c there as well) a couple or three years back and asked for balsa cement to met with a blank stare -guy had never hear of it!
Mike (thank God for the Internet!)

I'm dragging us off topic but I can't find the PM button, so apologies for this: I hadn't worked those points out so thanks but how do you limit the amount of balsa glue that goes on a joint on something like the peanut Lacey. With thin cyano being liquid, I can use a capillary or really thin tube to deliver as little as a 1mm slug right to the corner of the joint - wait! Do I remember something about a pistachio shell and toothpick on your build thread? I'll go and re-read it, things sink in slowly these days...
Cheers

Nigel - as I think you are probably recalling - delivering a very small amount of balsa cement is dead easy, if potentially a bit messy and wasteful if you are cursed with my degree of clumsiness - you just squeeze some cement onto the end of a toothpick and use that as an applicator. For further lightening balsa cement , you can even squeeze a bit onto a bit of plastic such as an old credit card or, better, the likes of a plastic bottle top from a milk bottle or the like, add a dash of thinners, and give a quick stir - be warned, it will dry much more quickly than usual, limiting the time you have to apply it.
HTH
Mikel.

Nigel - Good thoughts with the CF strip. The fuselage has some 3mm x .35 laminated into the nose section , just back to the cockpit area. I did though if I remember right use a thin layer of epoxy resin ( the laminating resin not 5 min ) to do this which probably heavier still but I thought it would make a more flexible joint. When I returned to the hobby after many years away I built a FF Tomboy using thin Cyno -It went together so fast ! but in a hard landing things like wing ribs and fuselage uprights would break off inside the undamaged covering the structure was so brittle. After that I used Aliphatic resign and epoxy for the strong bits pretty much through out with Cyno just to tack things and as Andy says field repairs.

Andy I have been using superphatic but I notice from your build pics you use the basic aliphatic to build even small stuff like your Lacey. Do you thin it down at all or just use it neat ?

I think my plan is to rebuild using a Balsa TE making sure nothing is under tension ,better covering technique and NO shrinking dope

Chris

Another very interesting topic re, adhesives, I for one did not realise how complex and varied they are, and the different applications, thanks for the extra information, could be the start of a new thread if it has not been covered already.

If you put some cement into a small screw capped pill tub/ jar and add the thinners. And. give it a shake. (Shaken not stirred ) Oh ok stir it as well This will last a while before going off and save mixing little bits and thus save time.Even if it does go off it can be softened again for reuse. Can be taken to the field too

That works as well, although it never did for me, the mix always went solid before I could use it a second time, hence my bits and pieces approach - again, I only very rarely used thinned cement anyway. hadn't thought of trying to resurrect it.
Mike

boz wrote: Another very interesting topic re, adhesives, I for one did not realise how complex and varied they are, and the different applications, thanks for the extra information, could be the start of a new thread if it has not been covered already.

Here's a thread I started some time ago Boz: www.aeromodellers.co.uk/forum/free-fligh...l-balsa-models#48132

I'll make one amendment in that Superphatic doesn't sand well, whereas Aliphatic does.

For small models I use balsa cement diluted with cellulose thinners, for medium models (around 20" span) I use full-strength balsa cement, for 30" span and larger, I use Aliphatic resin, which I sometimes dilute with water.

I get my adhesives from SAMS Models (they are only 5 miles north of where I live, so very handy). Their current stock includes UHU Hart, Humbrol Balsa Cement, Cellulose shrinking and non-shrinking dope and thinners, and Deluxe Materials Superphatic and Aliphatic resins. Most cannot be sent through the post, but SAMS will be at Crawley Leisure Centre on Sunday 5th Feb if you're interested.

Humbrol? I didn't realise that it was still made! Used to be by far my favourite. UHU Hart is the nearest I have found for years - can't do a comparative strength test, but it's a bit runny and less stringy than Humbrol of old - just thought - we are talking Britfix, aren't we?
Mike

I have had Balsa Cement and UHU Hart Depron glue and Methanol from post/courier services in the last 12 months. I am now looking for a courier to deliver 2 Lt of Ether I've been offered . Any ideas ?
]

Nigel wrote: I weighed a 1m strip of 3x0,35mm carbon at 1,7g. I calculate a 3'x1/4" x1/8" triangle of balsa at 8 lb/cu.ft would weigh 2.3g. ☺

Sigh... knew I should have waited until the morning to calculate that one - the balsa weight would be 1,17g... my apologies for any confusion caused.

I'll make one amendment in that Superphatic doesn't sand well, whereas Aliphatic does.

Yes its only disadvantage . I end up cutting any excess away with scapel

One Tenor - I've just ordered some Non shrinking Dope from Balsa cabin and they send chemicals by My Hermes you could check them out to see if they would courier

the balsa weight would be 1,17g

Nigel thanks for calculations, you maths is way above mine. I struggle to work out wing area ! I usually end up squaring it off and lobbing a bit off the numbers for the curved bit.