Crossover v-tail fins

[Jerry Lunt]

Is it normal for this plane for the fins to be permanently attached? - i.e. glued on.

Having broken one off (the joiner that is) at the Open, I find the other one will not come off.

Also, is it normal for the "joiner" apparently to comprise 2 pieces of channel section carbon with balsa inside as it looks like there is a longitudinal joint?

It may be that the joiners are 6mm x 7mm box section with balsa inside but I cannot find such rectangular carbon section available anywhere.

I've emailed Aer-o-tec a question.  Awaiting response.  The aer-o-tec web page appears to show solid carbon joiners.

[Andy_B]

I dont remember them being hollow Jerry  and no not glued in 

[satinet]

Pictures

[Jerry Lunt]

You can see the rectanglarity here - just, and I have drilled out most of the balsa to 5mm dia., in fin and fuselage.

Inside can be seen the remains of the "joiner" which is splitting toward the opposite side from the fin mount

I found some 5mm round solid carbon rod which fits in my 5mm drillings and the fin fits tightly without glue.  The rod sits firmly in the opposite side of the fuselage.  Camera ran out of battery at this point.  Picture of rod later, when it's got some charge. 

I don't think it will be safe just to glue the rod into either the fin or fuselage only.  I think I need to glue both side and make it permanent.  The other fin is fixed anyway.

The incidence pins were frayed at the ends so I applied some cyano and squeezed it tight with polythene over so as not to fix to my fingers permanently too!!  This firmed up the pins but seemed to expand them as they would not then go into the fuselage holes - each separately, let alone as the pair.  The 5mm holes were not exactly aligned but I opened up the fin hole slightly and the fin goes on now.

[Darren_O]

https://hobbyking.com/en_us/hardware-accessories-1/tube-rod-carbon-glass-fiber/carbon-fiber-glass-fiber.html
Square tube available here, but no rectangle

[Jerry Lunt]

Thanks Darren, I'm aware of lots of carbon suppliers and as you say, no rectangular available - unless you want 20 x 30mm of course 

No, I won't use square tube anyway.  I think aer-o-tec supply solid carbon joiners, judging from their website.  I'm going to use some 5mm round which fits the hole pretty well and will be well epoxied in both sides.  This will be stronger than it was before which means that next time, it will be the fin that breaks instead - I guess. 

[satinet]

Looks like the crossover uses removable carbon rather than the more normal Vee that is epoxied in to the fuselage.  Looks like it's been crashed at some point. 

[Jerry Lunt]

It does have some small repairs on a wing but nothing serious.

[Martin Church]

Reading this thread with interest so I've just checked my new to me 2nd hand Crossover & one tail half joiner is glued to the fuselage & one isn't. Yes it's been crashed, probably a lot. Hope I don't have to ever replace it. Picture of the one that wasn't glued fast to the fuzz.

 

[Jerry Lunt]

That's a strange looking spar/joiner Martin.  What kind of composite construction is that?  Looks like a piece of carbon tube not even near the centre 

Is it definitely rectangular?

[Martin Church]

Without checking I'd say it was square.

[Martin Church]

Right ive managed to get my tail plane off with cyno debonder. Unfortunately now the second part that holds the tailplane the correct angle hasn't enough depth so I'm going to have to rebuild up the area on the fuselage with something like JB weld.

Will post up pictures later.

[Jerry Lunt]

I got a response from Stefan at Aer-o-tec.  He confirmed what I had been told (the joiner is an extension of the spar in the fin) and that it is not normally glued into the tail of the fus 

If the "joiner" is broken, one needs a new fin ................ unless it gets sorted another way of course 

[satinet]

Uff. Bad design.

Can it be repaired?

[Jerry Lunt]

I've mended mine with 5mm dia carbon rod, but it is again fixed in a permanent fashion.  Very solid though 

[Martin Church]

19 minutes ago, Scram said:

I've mended mine with 5mm dia carbon rod, but it is again fixed in a permanent fashion.  Very solid though 

Any pictures mate just interested in how you've managed to fix yours as I may need to do the same now.

Dont know what your thoughts are on the Crossover but it's my number one plane at the moment 😎

[Jerry Lunt]

I did not get a picture of the carbon rod installed.  The spar/joiner was broken flush with the fin root with just some small projections which I filed off to flush on both the fin and the fus.  See pics above.  I drilled out as near to the centre of the joiner/spar as I could with progressive sizes till I got to 5mm dia and fitted a 5mm carbon rod.  I had to open out the hole in the fin to get it to get the incidence pins to go into their holes.  The rod went into the fin about 2 inches and was a reasonable fit and went into the remaining bit of spar/joiner in the fus.  This had clearly been glued previously because I just had a 5mm hole on the far side of the tail to the fin seat and the carbon rod just went into here flush.  I then mixed 30m epoxy with some milled carbon fibres and applied this generously into the fin and fus and installed the fin.  I added the epoxy to what remained of the old joiner in the fus - luckily this was the rear one which was accessible.  These pictures show this:

I had to avoid gluing the  pushrod into the tube 

It looks like you had a carbon tube inserted into your spar.  If it is no longer long enough to go right through the fus, I think I would find some way to lengthen it rather than try to build up the socket inside the tail.  That should give better strength and maintain your removability.