Joining balsa sheets

[Simon Clark]

I apologise if this has been covered before or is too basic a question but:

 

What is the best way to glue balsa sheets together for wing skinning etc.? I usually start by taping the sheets together on a flat surface then open up the join, add some aliphatic and put back down on the flat surface with a few weights. It works OK but I always end up with a very slight mismatch in angles, a glue line that is difficult to sand out etc. Does anyone have a fool proof method that gets good consistent results?

 

Thanks

Simon

[Outrunner]

I do exactly the as you and it works ok.

Maybe try a little less glue and wipe with a damp cloth before weighing down.

[Ernie]

That's the usual way. Use aliphatic glue, because it sands better, and gives you some sliding time. Also, a long flat weight to give an even pressure

ernie

[John Stainforth]

2 hours ago, Simon Clark said:

I apologise if this has been covered before or is too basic a question but:

 

What is the best way to glue balsa sheets together for wing skinning etc.? I usually start by taping the sheets together on a flat surface then open up the join, add some aliphatic and put back down on the flat surface with a few weights. It works OK but I always end up with a very slight mismatch in angles, a glue line that is difficult to sand out etc. Does anyone have a fool proof method that gets good consistent results?

 

Thanks

Simon

I do the same, but with CA. (Actually, one doesn't really have to open up the join with CA, because it wicks into the joint.) I generally use far more aliphatic glue on models than CA, but this is a near-perfect application for the latter.

[Don Fry]

Butt the sheets together, and tape, all along the butt. Then open the joint, like a hinge and glue. Close the hinge, and weight it to dry.

I keep some iron t-section fence posts for these sort of jobs. Heavy, and absolutely flat. 

Edited September 30, 2023 by Don Fry
Spellcheckeritis

[PatMc]

Similar to Don except I weigh them down on an old wardrobe mirror. The weights are old batteries & lead battery connector straps spread evenly along the length. I have also used books &/or magazines as weights with solarfilm backing plastic to protect them from the glue.    

[John Rickett 102]

A variation on the previous posts is - tape together on one side, turn the sheets over and lay flat on a board, sand the faces lightly along the join line to fill any small gaps with the balsa dust, run thin cyano quickly along the line. After a few seconds turn the sheets over, remove the tape and run a do a second run. Sand both sides again to remove any ridges and you'll have two perfectly joined sheets in less than 2 minutes! This method is good for up to 1/8" balsa sheets.

Its remarkable that two sheets placed side by side can show how curved they can be, trimming them using a 3ft straight-edge is better than trying to make the tape hold them together.       

[kevin b]

4 hours ago, Ernie said:

That's the usual way. Use aliphatic glue, because it sands better, and gives you some sliding time. Also, a long flat weight to give an even pressure

ernie

We used to send the apprentice down to the strores to fetch a long weight.

The storemen usually obliged by telling the youth to "just stand there".

🤣

[Simon Clark]

Thanks for all the replies - it sounds like I have got the right method but I need to be a bit more careful / skilled!

 

Simon

[Engine Doctor]

Just to add, always use the sandpaper with a flat  sanding block and not your fingers. 

[toto]

I have seen Don's method on a couple of Utube videos and it seems to work well. 

 

I've bought clear packaging tape just lately and will be using this method with CA on my next build ... the Sky 40.

 

Cheers

 

Toto

[Christopher Wolfe]

I am surprised that nobody has mentioned traditional balsa cement.

 

After straightening the edges and taping them together then a bead of acetate based balsa cement into the seam is excellent for joining balsa sheets.

 

It shrinks as it dries (pulling the joint closed), much of it evaporates with the solvents and it sands beautifully.

 

The resultant joint is stronger than the wood and may be re-glued if a whoopsie occurs.

 

For comparison, cyano does not evaporate, soaks into and locally hardens the area making for a inflexible and heavy joint.

Also, a cyano joint is almost impossible to re-glue as it is not solvent based whereas a balsa cement (and also aliphatic) joint may be actually stronger if it requires re-gluing.

 

Maybe balsa cement is not as readily available in the U.K. as it was in the past but it's still readily available here in Australia C23 balsa cement

 

Ask any builder of indoor competition Free Flight models what works for them - some people even apply it (thinned) with a syringe as weight is critical when building a 1.4 gram F1D model designed to fly for tens of minutes indoors using rubber power.

 

* Chris *

[Andy Stephenson]

UHU Hart is easily available and makes good balsa cement.

[leccyflyer]

Balsa cement is readily available in the UK through the usual online retailers.

[Paul De Tourtoulon]

On 30/09/2023 at 18:32, PatMc said:

Similar to Don except I weigh them down on an old wardrobe mirror. The weights are old batteries & lead battery connector straps spread evenly along the length. I have also used books &/or magazines as weights with solarfilm backing plastic to protect them from the glue.    

While I am taking the wardrobe door from its hinges, do I charge my battery's up first, and are model magazines better, also do that have been read first ?.😄

[Cuban8]

2 hours ago, Christopher Wolfe said:

I am surprised that nobody has mentioned traditional balsa cement.

 

After straightening the edges and taping them together then a bead of acetate based balsa cement into the seam is excellent for joining balsa sheets.

 

It shrinks as it dries (pulling the joint closed), much of it evaporates with the solvents and it sands beautifully.

 

The resultant joint is stronger than the wood and may be re-glued if a whoopsie occurs.

 

For comparison, cyano does not evaporate, soaks into and locally hardens the area making for a inflexible and heavy joint.

Also, a cyano joint is almost impossible to re-glue as it is not solvent based whereas a balsa cement (and also aliphatic) joint may be actually stronger if it requires re-gluing.

 

Maybe balsa cement is not as readily available in the U.K. as it was in the past but it's still readily available here in Australia C23 balsa cement

 

Ask any builder of indoor competition Free Flight models what works for them - some people even apply it (thinned) with a syringe as weight is critical when building a 1.4 gram F1D model designed to fly for tens of minutes indoors using rubber power.

 

* Chris *

Clearly works for you, but from my memories of the balsa cement that I used back in the day, for joining sheets it might set far too quickly and give a dry/weak joint. You mention acetate balsa cement - is that different from the old balsa cement of our youth that was also popular with glue sniffers before shops got wise to all that?

[Roy Thompson]

On the subject of which glue is best for butt joining balsa sheets, my recommendation is Deluxe Super Phatic! It’s thin, so wicks in easily and doesn’t leave a rig to Sand down, it also grabs faster than Aliphatic.

[leccyflyer]

I also like Super Phatic for this job, but would give a word of caution - very very old Superphatic can stain the balsa as it wicks into the grain and that will be impossible to sand away. I made the mistake of using an old bottle that had gone dark on a tailplane recently and it has left a visible stain that shows through the yellow tissue covering.

[Simon Clark]

I like the idea of Super Phatic and have heard some good thigs about it - just a simple question: do you just wick the glue with the sheets already pushed together like you would for cyano or do you open up the joint and apply the glue in the same way as for normal aliphatic. I assume it is best to wick it in but I have never used this stuff!

 

Thanks

Simon

[Don Fry]

Wick