Tip Up Canopy Fitting Questions - 7

[BillL]

Hello All, I am building a 7 -tip up and have reached the canopy fitting stage prior to the "big cut". I have looked everywhere (it seems that way) but can not get a clear picture of where the cut on the front of the canopy will end as it meets the canopy skin.

1. Is it at the tangent to the radius where the canopy is parallel to the skin, in the middle, or the tangent to the radius at the top? in other words, will the plexi sit on the skin with a crisp angle, or will the formed transistion radius of the plexi remain? I have still about 1" over the roll bar, and want to get it fitted to the canopy skin before I mark for the big cut.

2. After addressing question 1 I need to understand fore and aft positioning, so, where is the 1.75" measured? at the projected intersection of the plexi to the skin? Or somewhere else?

Thanks in advance,

Bill

 

[BigglesRV7A]

Canopy

Hi Bill,

When trimming the canopy to fit around the front skin, you will want to aim for the completed transition to be flush with the skin and the canopy in it's relaxed state with this achieved. To accomplish this you need to 'bevel' the plexi edge where it rests on the fwd skin and have the line of the plexi running E/W in a straigt line at the front. The 1.75" measurement is taken at the middle of the fuselage running from the leading edge of the canopy fwd skin to where the plexi is trimmed to. You will then fibreglass this area to effect a smooth transition from the skin to the plexi.

Hope this makes sense for you,

Greg

 

[jmjula]

The big cut isn't that critical. Just make sure the front of your canopy somewhat follows the curve of the skin (for now) and is no more than 1.75" back from the front of the skin at the center before cutting. Once the cut is made, it will drop down to the roll bar, and then you will trim the sides and any further trims needed along the front. I trimmed quite a bit after the big cut in the transition from sides to front.

 

[BillL]

Thanks,

Thanks for the replies. I will be cutting the next trim and the big cut this weekend. Have addtional eyes on the question is a help -much better than guessing and reordering.

 

[Pmerems]

Thoughts on the cut

Bill,

I too was concerned about the "Big Cut". As mentioned it wasn't that big a deal.

When I started trimming the canopy to fit I wanted the canopy as close to the roll over structure as possible. The thought was that if I were able to get it to rest on the roll over structure I could make the "Big Cut" and have a really consistent gap between the rear section and the front section, requiring little adjustment. So I slowly trimmed the front of the canopy to mate with the top skin until the inside of the canopy was about 1/8" away from the roll over structure. So I made the "Big Cut" and I still had to trim some to get a good consistent gap. However what I didn't realize was that by continuing to trim to fit the front skin to have the canopy closer to the roll over structure I was actually lowering the middle of the canopy (right where my head would be). If you look closely at the side view drawings of the tip-up you will see that the front canopy doesn't transition to the rear section on a straight line. Mine almost does. I sure could have used any extra headroom I could have gotten.

The moral of my post is that you don't have to get the canopy very close to the roll over structure before you "Big Cut". I think Van's says within 1/2" is fine then make the "Big Cut".

Maybe my RV will be a few knots faster since I lost a little height in the canopy.


Food for thought.

 

[Rupester]

If it makes you feel any better...

...I too sweat bullets over the front canopy edge question. Basically I just kept carving at it a little at a time until it seemed to sit reasonably and conform to the rounded contour of the front canopy skin. It didn't fit perfectly, understand - just close enough I was confident that a few more trims after the Big Cut WOULD make it fit perfectly. It did too. What makes the canopy such an ordeal are the huge number of on-the-fly decisions and the lack of clear measurable dimensions for so much of it ... all the time knowing that a big screw-up will set you back over $1000. Gulp.

 

[AltonD]

... will set you back over $1000. Gulp.

$1200 with shipping to south Alabama, to be exact. Been there, done that. I am just finishing up canopy #2.


The 1.75" from the front is the maximum. My thoughts:
1. That puts the canopy bend, in a high stress area (turning the corner on the frame.) Move the canopy a little more forward and the stars do not line up.

2. 1.5" gives you a quarter of an inch to adjust after the big cut. You can sand down any irregularities in your cut and still have the roll bar line where you want it.

3. I will not make the final trim on the aft edge until the forward skin is riveted on and the gas struts are installed. For some, the Canopy moves forward when the struts are installed. Personally, I think it is with the front skin cleco'd on. Clecos just cannot hold the skin as tight as rivets.