Thoughts on gap filling please

[Graham Bowers]

Almost finished putting together an ARTF Black Horse Twister that's been lurking for some years, and now have to confront those easily put off final details.

 

The fin is epoxied into the fuselage however to get it square meant I now have a highly visible fuel residue attracting irregular gap where the fin slots into the fuz, that needs addressing

 

Comments sought on how best to do this please, and not end up with a horrible mess. It's glow powered so needs to be fuel proof. That leads me to think filling with epoxy of some sort. And half thinking of masking tape - being pretty sure I'd end up with masking tape epoxied to the model. There must be some tried and tested tricks to do this neatly and elegantly ???

[leccyflyer]

For a gap like that I'd be mixing up some 30 minute epoxy with microballoons to make a stiff-ish creamy paste applied to just fill the gap, then put tape over the top, smoothing down with a fingernail - which should stop any runs or unsightly mess. If you haven't used the technique before you could practice on some scrap. You're aiming for a nice smooth fillet, with no unsightly runs and you're ensuring that the gap is nicely filled.

[Graham Bowers]

1 minute ago, leccyflyer said:

For a gap like that I'd be mixing up some 30 minute epoxy with microballoons to make a stiff-ish creamy paste applied to just fill the gap, then put tape over the top, smoothing down with a fingernail - which should stop any runs or unsightly mess. If you haven't used the technique before you could practice on some scrap. You're aiming for a nice smooth fillet, with no unsightly runs and you're ensuring that the gap is nicely filled.

Thanks for that. It's not something I've tried before to will give it a go on some scrap, as you suggest. 

[Paul De Tourtoulon]

I mix Humbrol paint into the epoxy to match up the colour then smooth it down with my finger.

[Engine Doctor]

I've used epoxy mixed with Humbrol paint to match the covering . Apply along gap and work in with  a old credit card or similar. Wipe off excess with kitchen roll and methylated spirit. Job done. 

[Engine Doctor]

1 minute ago, Paul De Tourtoulon said:

I mix Humbrol paint into the epoxy to match up the colour then smooth it down with my finger.

You beat me to it 👍.

[leccyflyer]

That's a good tip - mixing some colour into the epoxy. 🙂

[Graham Bowers]

11 minutes ago, Paul De Tourtoulon said:

I mix Humbrol paint into the epoxy to match up the colour then smooth it down with my finger.

I like that- humbrol enamel presumably?

[Steven Hurd]

I wouldn’t worry too much about glow fuel getting that far down the fuselage, I’ve only ever wiped the the odd drop off that part of the plane, however if you want to seal it, and not have a different colour of filler to deal with, I have used clear or coloured silicone bath sealants  to good effect. 
They stick very well to degreased films and you can get a very small fillet in there, they are also glow fuel proof. 

[kc]

PVA might be neater as it can be wiped off whilst wet.  Perhaps a tiny sliver of balsa to fill the gap.

[Graham Bowers]

21 hours ago, Steven Hurd said:

I wouldn’t worry too much about glow fuel getting that far down the fuselage, I’ve only ever wiped the the odd drop off that part of the plane, however if you want to seal it, and not have a different colour of filler to deal with, I have used clear or coloured silicone bath sealants  to good effect. 
They stick very well to degreased films and you can get a very small fillet in there, they are also glow fuel proof. 

Fair point about the glow fuel spatter. I only ever oil on the tail, and usually not in that specific location. I just can't bear gaps !

 

I checked up on silicone sealant, and was surprised to find out how good it is.

 

My new problem is I now have too many repair ideas to choose from 😉

[Graham Bowers]

Thanks for all responses, I've learned a few things!

[Mike T]

After the gap has been filled by whatever means, I cut 6mm strips of covering, which when folded down the centre to create an 'L' shape, can then be ironed over the joint to act as a fillet/finisher.  Not the best pic (or workmanship ☹️) but this is my Precedent Funfly - of which the Twister is a blatant copy!

 

On ARTFs where there is unlikely to be any spare covering material, you can 'harvest' some covering (usually from the wing centre section where it seats on the fuselage) and cut this into strips.  Scrape off any remaining wood fibres and coat with balsaloc or similar, then iron on as above.