Straitening Tip Up Cabin frame?

[RudiGreyling]

Hi Guys,

Wow is it my week for asking questions this week?embarrassed

Busy with the tip up canopy Cabin Frame I have 2 queries regarding the highlighted ? Round Cabin frames (F-631)


Q1) Putting it on a flat table upside down I see I have 1/8? deviation in the middle away from the table. The problem the bend curve is already to the inside. If I understand it correct, fluting the flanges like when we did it on the ribs works well on an outside curve, since it shortens the material and the hence the rib becomes straight. What did you guys do here the get the frames to lay flat? How do I fix an inside curve deviation or am I over thinking it. Should I just clamp it straight, drill it right, and when riveting it will be straight?

Q2) Why are there 6 frames in the kit, I see only need for 4 in the plans at this stage, what am I missing?

Thanks in advance,
Kind Regards
Rudi

[fodrv7]

Rudy, Maybe it's the Southern Hemisphere Coriolis as I had the same problem in Australia.
I simple leant on them to take most of the twist out and then ensured it was clamped tight to a piece of board before I drilled them
As it ends up as a box section it has very high torsional stiffness and so won't twist a bit.
So if it is drilled whilst clamped flat it will be straight.
Attached is a picture of how I used a Vernier Dial gauge to ensure it was of constant thickness. It is a little difficult to get the final width consistent as the flange varies in width quite a bit. So I used the dial guage to ensure that the top of the inner strip was a constant height above the bench- an hence the face of the roll bar. It was then easy to just drop the other sections on top and drill them.

The other two frames are for the canopy itself- so don't throw them away.

If you miss drill them like I did you can use them as a throttle console and order two more.

Good luck,
Pete.

[RudiGreyling]

Originally Posted by fodrv7

Rudy, Maybe it's the Southern Hemisphere Coriolis as I had the same problem in Australia. <SNIP>

Hi Pete, thanks, that is exactly what I was looking for in an answer, and quick at it too. Nice looking console also.

Regards
Rudi

[Pmerems]

Rudi,

Don't flute these frames (all 6 of them). 4 are used to construct the roll frame (never flute) and 2 are used in the canopy frame.

Even though Van mentions fluting (while building the canopy frame) I recommend against it. I fluted a set (canopy frame) hoping it would help with the warpage but it didn't have an effect. Purchased a new set (appeared to have less warpage out of the box). Didn't flute and worked out great.

While assembling the canopy roll frame, clamp to a flat surface (lots of clamps) prior to drilling. When riveting also clamp to a flat surface. My frame once complete had about 1/32" of twist/bow when completed. Also check for the right final width to match the fuselage. Keep checking as you drill and rivet.

Best of luck.

Paul

[RudiGreyling]

Hi Guys,

Thanks for all the feedback, I did complete mine this weekend and used your advise. It came out perfect.

1) Bend by hand as flat as possible, it comes pretty close to flat.
2) Use a flat table & lot of clamps, mark the required width on the table as reference, and start with the bottom (Rear half) channel.
3) Bevel/Radius the strips, mark their position before drilling to bottom, measure the height as you go, it will try and rise out the channel on the bend.
4) On the top (Front half) channel measure the height with a vernier and clamp to compress to right size (i think it is 1 1/2") as you go before drilling the final set off rivet holes.

The result a perfect width, perfect thickness Cabin frame, that simple needs to be cut to perfect height.

Thank you, Kind Regards
Rudi
PS: I'll see if I can post a picture of mine later the week.

[RudiGreyling]

As promised: