Large Model Association Forum

I have some 6.5mmx 2.5 mm spruce to splice into a few main spars in a duncan hutson 1/4 SE5 i have come buy, one wing panel is shattered, to save the structure, i intend to splice the spars, i used to use white glue, but these days, there must be something better, anyone any ideas? the gluing area will be slim, but with the scarfe joints,, it will be long, and very strong, ta much

Alan,

I've always used epoxy for gluing Spruce.

It has to be Aliphatic Resin. It seeps into the grain before it completely sets. Why Spruce ? it's too brittle, try Cyparis instead as it will absorb shocks without cracking :-)

Spruce would not have been my first choice, but i am scarfing into existing structure, so, spruce it is,

i thought of aliphatic, but Phil Clarkes recent comment about a wing he stripped off that came apart ever so easy, due to the glue not penetrating caused me concern, being a set of repaired main spars, it has to be good first time, may have to be epoxy, loath working with that stuff, but, at least i wont need a lot, orrid smell,

any more ideas?

Hi Al, you could try using medium cyno, especially that "Liquid Weld" you told me to get a couple of shows ago. That really is strong stuff and soaks into the wood. Once it goes off you could then brace the scarf on both sides with some 1/32" ply, I would have thought that should be strong enough, especially if the ply braces extend across a full bay between ribs. Jonesey.

Hi Dave, i have considered the liquid weld, but i dont know if it gets brittle with age as of yet, jurys out, early doors and all that, as for bracing the joint either side, this would create 2 shear points, at the end of the brace, so i prefer to stand by a good long scarf joint , staggering the joints will be done, so that all the stress on the wing repair is spread over several joints, reallly looking forward to resurecting this model, be good to glue something together again,

I use Aliphatic resin in my job as a cabinetmaker. Two pieces of Oak glued together for 30 minutes and the Oak will fracture before the glue joint. Go figure :-)

Sounds good to me Stuart, clarky must have had some dodgy glue on his model, i will go for it, thanks, also thanks for all the help, its much apreciated,

No idea what glue was used on a '2nd hand' model I picked up a couple of years ago, but what residue there was was yellow so I'd assumed Aliphatic of some kind.

As Alan has mentioned, some rework was required and I was able to remove the sheeting from the underside of the wing in 4" wide sheets root to tip with no damage to the ribs what so ever.....the sheeting just pulled away (if I'd have wanted to, I could have re-used the sheeting as well as that was also pretty much undamaged!!!!!). Whatever glue had been used had not wicked into the balsa, it'd just bonded to the surface fibres with no penetration what so ever. If I'd have built the wing 'my way' in the 1st place with proper glue (ZAP Cyano), the sheeting would have had to be cut away bit by bit between ribs & spare before the materials left on spars & ribs was sanded down to the glue level.......

Never liked Aliphatic & it has no place in aeromodelling as far as I'm concerned...............

Phil

Bit of a sweeping statement Phil, just because someone doesn't like a particular item, doesn't mean it's no good. Better tell John Townsend to dismantle his 14 year old Magister and use a different glue then, as well as all the other modellers that use Aliphatic :-)

Alan - I have just had a look at the British Gliding Association guidance for repairs online. They say a 15:1 scarf and they use Aerolite 300 which seems to be Aerolite 306 powder mixed with water plus a matching hardener. As you are associated with the aircraft industry you may be able to source a small amount of this; alternatively a Gliding club or light aircraft/homebuilt strut could help.

The Dave Womersley 1/4 scale Chipmunk plan and laser cut parts I bought from you are coming together in slow time - regards Chris

NOW NOW BOYS, no fighting, the last post intrigues, me, i wonder if good old caskamite powder/water mix glue would suffice? it certainly kept the boats togther i used to build, spruce stringers, plank on frame types, interesting,

Stuart Solomon wrote:Bit of a sweeping statement Phil, just because someone doesn't like a particular item, doesn't mean it's no good. Better tell John Townsend to dismantle his 14 year old Magister and use a different glue then, as well as all the other modellers that use Aliphatic :-)

Each to their own Stuart.......your beautifully made furniture I'd guess has pretty large contact areas and very well fitted joints. The wing that I dismantled with ease had soft 1/8" balsa skins over 2 and 3mm ribs = tiny contact areas. It also showed no sign of any penetration at all.......I don't think aliphatic has a use in this application. John's Maggie has proved it can work......perhaps there is aliphatic & there is aliphatic just as there is cyano & cyano......some brands are better than others.

Alan Cantwell 1131 wrote:NOW NOW BOYS, no fighting, the last post intrigues, me, i wonder if good old caskamite powder/water mix glue would suffice? it certainly kept the boats togther i used to build, spruce stringers, plank on frame types, interesting,

Alan, Extramite is the replacement for Cascamite, but like the Aerolite Chris mentioned, they're all Urea Formaldehide glues, one of the strongest wood glues you'll find.

Hello Alan, I have a box of Aerolite 306 at work, It has been in the cupboard for years. If you would like to give it a try you are very welcome.

Evostik exterior pva is my main glue with extramite in some situations. only sometimes I us aliphatic. never use a non branded glue.'Good thread' .

I also use Cascamite for things like veneering or Inlay work. I buy it in a 3kg tub and it lasts a while. Mix to the consistency of single cream, the only downside is the setting time which is not a problem if it can be left clamped/weighted overnight. The 'Mossie' was built using Aerolite 306 and Cascamite as it was basically all wood, thin ply etc, which brings up another issue. If you use any Birch ply thinner than 4mm, be sure to sand the surface to get rid of any release agent that is used in the presses. I have always found the winter growth in Spruce ( I hate that word ) to be oily and needs to be abraded well to allow the penetration of whichever adhesive is used. As for Epoxy, the longer the setting time, the deeper it will penetrate and the stronger the joint, don't use 5min on spars or firewalls. Bye.

Some GREAT info here, many many thanks to you all for your contributions, i am sure that many have seen benefit
PAUL, i would love to try the 306 you have, see you at cosford? doubt i will be needing it before then, it will be nice to get this beutifull SE5 in the air, still cannot understand why the previous owner did not repair it,

For Aerolite 306 , try Axminster power tools. http://www.axminster.co.uk They do a 375g pack inc hardener for £15.60

Please note there are storage life warnings on Aerolite and they are quite short! - Chris