What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Canopy windscreen spacing

J

jay.pearlman

Well Known Member
I finally have the sliding canopy on the frame and all the skirts are done (whew!) I started installing the windscreen and realized I could not find the gap dimension specified between the rear end of the windscreen plexiglass and the canopy bubble forward edge. I believe that some rubber or gasket material needs to go between then so that it doesn't rain inside the cockpit. What gap between the two pieces have people used?
 
I must be at aboutthe same stage as you as I have just finished the canopy.
I have left the windscreen for latter since I still need to finish all of the panel before I rivet the front skin.
My understanding is that the two touch with no gap. However there are many that use a seal here to help with wind and rain.
I think I will go with no gap and see how it does before trying a seal. If fit well the fiberglass fairing over the top should keep most of the rain out.
All of the others I have looked at did not use a seal.
 
On my 9A, drawing 43 section K-K shows it to be about 1/16" gap. The top of the gap is covered by a fiberglass fairing that attaches to the windscreen and the canopy slides under it.

Notice that I didn't say my canopy has that 1/16" gap - I wish it was that clean... :(
 
further information

Tech support at Vans suggested 1/16 to 1/8 as a gap. Direct tight contact might create problems when there is thermal expansion. Not clear what people are doing about rubber gaskets under the fiberglass cover strip above the junction.
 
I haven''t drilled the windscreen yet so I can sand to a perfect fit. I may plan on the 1/8" gap so that there is room for a seal. Jay, thanks for letting us know what Van's recommends.
 
I'm thinking the easy seal solution would be something attached to the fiberglass overhang reaching downward, that would contact the top surface of the canopy as it runs forward under the fiberglass overhang.
 
airguy said:
I'm thinking the easy seal solution would be something attached to the fiberglass overhang reaching downward, that would contact the top surface of the canopy as it runs forward under the fiberglass overhang.
Click to expand...

Try surgical tubing................
 
Gasman is that what you have used?
It seems like that would be a good solution.
Fit the canopy with a 1/16" gap, split the tubing and glue to the rear edge of the windscreen. That way it doesn't rub as it closes.
 
filling the gap

Interesting question. If the rubber seal goes on the fiberglass covering the seam, the fibreglass would have to be stiffer and the rubbing, rather than compression, would cause some where on one surface of the other.
On the other hand, there is only one position where the handle pulls the canopy tight and thus coming down the sides of the canopy, the canopy would not compress the seal as much. Then again, the rain at that point is sliding down the canopy. In the end of this, I don't get an obvious solution. Maybe just too much philosophy.
 
I'll chime in here since I am on my second canopy build on my -7.

I suggest that you make sure there is no contact between the two canopy halves when the canopy is shut abruptly. The top of the canopy will tilt forward slightly while closing. if there is any impact between the two halves this could obviously cause stress and cracking.

As for the seal, I didn't have a rubber seal and I really never had any issue with the canopy leaking around the roll bar during flight even in heavy rain. When my plane was a -7A, I had some issues with leaking on the ground from water rolling forward and under the fairing lip on the downward slope of the canopy. When I converted to a -7 this problem went away since the sloap of the canopy tilted back and now the water just runs backward.
 
More thoughts

I put the windscreen on with a 1/16 spacing with about 1/32 or so variance. When I put on the seal, I will let you all know. It sounds like a seal is necessary if the canopy sits out in the rain even once. Living in the northwest, that once comes fairly often.
 
I went to the Love's Landing fly-in Saturday and spent most my time looking at wheel pants and canopys. Seems like about 50% had no seal and the others had some form of seal but none were the same. I may try some sort of seal but have not made my choice yet. The canopy is done but I have not drilled the windscreen yet. I have plenty to do before I rivet the front skin.
 
another silly opinion

Jay,
you don't say if you have an 'A' model, but I do, and the canopy leaks a LOT more than I'd like when on the ground, no cover.
the fit varies around 1/16" to who-knows-what in those little areas where one can't really tell. If I were doing it again, I'd leave MORE gap, and that would allow me to glue in any number of soft, deformable gaskets.
I have a soft clear plastic window seal, kind of a 'D' section that I'm going to try, but there is so little room, I may have to adjust the latch incrementally until it has just the right 'crush'.
Right now, the glove fit is a bad thing, as it expands in the heat and sometimes 'sticks' closed, and I can't get in!
 
Look at a car door seal. It is hollow and thin wall usually D shaped. Surgical tubing is easy to find and is thin wall and has an easy crush. With the right space for it to fit into, it will adjust to the varied gap and make a good seal.
 
It is an -A model

As you appropriately ask, I am building an A model. I looked at the Canopy yesterday and when the aircraft is level, it clearly sloped forward in the area nearer the windscreen. So I may as well bite the bullet and address the matter soon. As gasman says above, there are D seals - I think they are used on cars and elsewhere, which have an air gap and compress easily for an eighth inch or more. I used them on the previous airplane I built. Here is a sample from a google search: http://www.simolex.com/html/d_strips.html. But, they need more than 1/16" to be installed.
I haven't screwed the windscreen on yet and can trim it further. Be interesting to know what you think of this as a solution.
 
I saw a lot of solutions last Saturday and I doubt that any of them are perfect. I can think of flaws to all of them.
It looks like the best seal would be to have the seal on the bottom side of the fiberglass fairing. This way you are not sealing the front edge of the canopy but the top front edge. Downside would be the rubbing each time it was moved.
Putting the seal on the canopy would mean that the seal would get rubbed each time you touched the canopy. This means it would fall off in no time.
So the best place in my mind would be the rear edge of the windscreen. This is a very thin piece so getting anything to stay would be difficult. Not to mention knowing which adhesives wouldn't react with the plexi.
Your D molding looks good but the gap between the plexis would ned to be large and the adhesive surface would be small. I doubt it would stay.
I like the idea of round tubing cut lengthwise with a inside diameter a little smaller than the plexi. This would give it a clamping effect with a little 3M adhesive to hold in place. This method would require a perfect fit between the two plexi's as there would be very little collapse like a D molding.
Luckily I don't have an A model.
 
Mark,
Use of split surgical tubing raises the question of the fibreglass cap strip. The surgical tubing and some others age and will need replacement. It sounds like the fiberglass strip should have a small vertical gap at the edge of the windscreen to allow placement of the tubing. Probably something that can be smoothed out on top so the air flow is not interrupted.
 
You must log in or register to reply here.
Back
Top