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Empennage Build Questions8 months 2 weeks ago#594

·         Wayne Eckertson

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I have a few question of the build instructions for the empennage of my J230.

The "Fit Horizontal Stabilizer" section of the construction manual shows glassing the tail cone. My tail cone appears to be different than the one shown in the manual's photos. See attached photo, Hor_Stab_1. I assume I do not need to glass the cone with the foam block. Do I need to add glass layers to reinforce the tail cone to horizontal stabilizer? If so, what weight of glass, what dimensions, what orientations, and how many layers? The pre-cut fabric did not come with my kit.

The vertical fin spar is not sitting flush with the rib in the tail of the fuselage. The vertical tail spar touches at one corner and has a 6mm gap at the opposite corner. You can see the gap locations in the Ver_Stab_x photos. I assume I can fill this gap with flock but I am concerned about the amount of flock required. Is there another recommendation for resolving this mismatch?

The instructions call for a flush rivet on the front of the strake. Can I use a temporary screw instead?

The Fit Vertical Tail Fin section shows applying reinforcing layers of glass over the vertical fin and fin stub. Is this needed? My fuselage does not have peel cloth below the joggle step on the fuselage. If so, what weight of glass, what dimensions, what orientations, and how many layers? The pre-cut fabric did not come with my kit.

I don't see a set of instructions for filling the hole cut in the rear of the fuselage for the vertical fin spar. Are there any special instructions for filling this hole? I was thinking about putting down a layer of 2.5oz cloth over the hole which will give a slight concave shape. Then I will fill the cavity with micro-slurry that I will shape to the match the round fuselage shape. Lastly I'll top the slurry with another layer of 2.5oz cloth.

Thanks for the help.

Wayne

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Empennage Build Questions8 months 2 weeks ago#599

·         Doug Smith

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Hi Wayne,
Can you tell me your kit number please? There are a few variations on those parts and I want to make sure I give you the correct answer for your aircraft.

Re the vertical fin/spar, if I'm reading your notes correctly the fin is touching the rib in the fuselage at the bottom but has a gap at the top? If so, the gaps you've mentioned aren't too outlandish... You may have already done this, but often there will be some little dags of flock or something that will be holding the parts apart and a little light sanding can make the fit a lot better. I'm talking about a few strokes with a medium sanding block there, not ripping piles of material out of it!

A temporary screw is fine there.

Again, I'm pretty sure you don't need to glass your fin to the fuselage but if you can give me the kit number I'll confirm.

What you've suggested for filling that hole will work ok... but if you have any spare 3-layer plate you should be able to cut a piece that's a little too big for the hole - so that you have to arch it to get it in there. With a little tinkering you should be able to get the arch of the patch to match the curve of the fuselage pretty well and then it will just need layer or 2 of glass and a little cosmetic filler. It's not a structural patch so does not need to be very thick.

Regards,
Doug.

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Empennage Build Questions8 months 2 weeks ago#601

·         Wayne Eckertson

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My kit number (Batchcode) is 847.

Yes, my fin is touching on the lower portion of the fin channel and the gap is at the top. I have cleaned up as much flock as I can without damaging structure.

I assume I can use all self tapping screws all along the vertical fin instead of clamping it with the aluminum angles described in the construction manual.

Wayne

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Empennage Build Questions8 months 1 week ago#603

·         Doug Smith

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Hi Wayne,

Thank you for that, we're having a look now and will get back to you soon.

you can use individual screws but you will get a dent where each screw goes in. It will end up looking like the surface of a (big) golf ball, making it harder to fair and paint later. The Aluminum angles/strips are all about spreading the pressure from the screws over a larger area while the glue is wet so that the parts end up relatively smooth when the glue dries. That way it's easier to finish off later. Obviously you can substitute other materials for the Aluminium, you just want something reasonably stiff that you can prepare (wax or similar) so that the glue won't stick to it.

Regards,
Doug.

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Empennage Build Questions8 months 1 week ago#604

·         Wayne Eckertson

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Thanks for the update. I am anxious to fit the vertical fin. It is starting to look like an airplane!

Wayne

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Empennage Build Questions7 months 4 weeks ago#607

·         Doug Smith

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Hi Wayne,
Please have a look at the attached file for current directions on fitting your empennage.

Basically, for your serial number aircraft, the horizontal tail is held in with the flock bond around the socket only - with just small cosmetic patches in the corners where it meets the fuselage. You'll see that the drawing calls for a minimum of 90% coverage/bond area - obviously being a structural joint you need to be fastidious in your surface preparation and flock application. There's no need to fit the foam block inside the horizontal tail channel on your aircraft but - depending on how tight the fit is - you might find it worthwhile to fit a packer of some sort in there just while to glue dries to make sure the middle section of that channel is not "pinched" by the fuselage - which would make it harder to get your elevator clearance later. Obviously the packer will need to be something that resin does not stick to - a bit of waxed plastic or even wood wrapped in tape for example.

The vertical tail is a similar story: the fin is bonded to the canted bulkhead (fibreglass rib) in the tail and to the sides of the fuselage socket using flock. Again, 90% coverage is called for, so you need to make sure all the peel ply is removed and that surface prep is right (make sure the surfaces are not contaminated by oil, dust etc.). You'll also see a notes on there about how to fit the fin without wiping all the flock off the parts. As I said previously, provided you're happy with how everything is aligned (fin to fuse, rudder to fin etc etc) the gap you mentioned between the canted bulkhead and the fin spar is acceptable - fill it with flock.

These are the sorts of jobs where spending a little extra time setting up pays dividends. Also keep in mind how you're going to have to make it pretty one day, so keep all exposed flock and glass as tidy as possible (it's a lot easier to removed excess when it can be wiped off rather than sanded!) and, when you attach the fin, pay particular attention to how smooth you can make the overlap between fin and fuse: you'll thank yourself later when your're sanding and filling!

Regards,
Doug.

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TOPIC: Empennage Build Questions

Empennage Build Questions7 months 3 weeks ago#609

·         Wayne Eckertson

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Thank you for the PDF file Doug. I noticed that it mentions not to use this method for the 700Kg fuselage. I would like to build my plane to the 700Kg standard. Can you provide me with those build instructions?

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Empennage Build Questions7 months 1 week ago#625

·         Doug Smith

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Hi Wayne,
Apologies for the delay - I had some time off on leave.

The trick here is that the 700kg J200/J400 aircraft have higher loads on the tail than the 700kg J230/J430 or J250/J450. It's a function of the ratio of wing area to tail area: smaller wing gives higher tail load, all other things being equal.

When we introduced that new tail the J200/J400 models were already effectively obsolete and so the new design was only tested to the 700kg J230/J250 loads. So the installation detailed on that drawing is correct for all current 700kg models and will be fine for your aircraft.

Regards,
Doug.

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Empennage Build Questions7 months 1 week ago#630

·         Wayne Eckertson

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Thank you Doug.

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