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Sliding Canopy anyone?

patterson

Well Known Member
Patron
Hello,

By way of introduction, I am an RV-4 builder in Northern California. Like those on this particular list, I believe the -4 to be Van's best design. That is all except for the tilt up canopy. To that end, my building partner and I have set about doing a new kit (#4446) with a slider. We're working on the canopy now. :cool:

In my opinion the RV-4 is WAY too hard to build in it's current configuration (a bunch of aluminum and some drawings that are often contradictory). :confused:
I too have inquired as to why Van's won't consider reverse engineering those incredibly confusing 25+ year old RV-4 plans to 'accomodate the market that would opt to purchase a QB-4 over the -8'? Answer is the -8 is a replacement for the -4 (and a better airplane overall for the mission) so there are few actual customers. In short, Van's doesn't feel there would be much real demand for a QB -4, and the cost to turn it into a QB is, as I understand it, prohibitive.

His plane, not mine, so even if I had ton's of $$$ to try turning out QB-4's.... not my plane to start with. The whole design just can't be re-done. :(

But what about just a new, sleek, -8 style design for a Sliding RV-4 Canopy??? :D I wonder if there is any real interest, or is it just me?

So here's my question to the -4 community. If there were good (canopy only) plans, or if you could order as an option, a complete slider canopy to slap on your RV-4, how many potential builders / buyers of this particular complete(d) kit might there be???

Anyway.....Howdy! Glad to be a part of the group!
Ron
N8ZD (reserved)
[email protected]
 
If it ain't broke...

I recently finished installing my canopy and don't yet see what its shortcomings are. IMHO the uninterupted lines of a tip-out bubble look the best of any RV. I know the slider looks cool while taxiing, but I built my plane to fly, and for that I think the bubble will work well.
 
Canopy Plans

I would be interested in Sliding canopy plans, or photo's of anyones installation. I agree that the flip over is great for visability, but I have spent too many long taxis in the sun not to wish I could taxi with the canopy slid back. Besides looking cool counts for something as well. I have been in an 8 and I don't think the roll bar/windshield reduces visablility that much.

Joe Hine
C-FYTQ
 
There have been some RV-4's done with sliders already. As far as getting plans I could not tell you where to get them.
 
RV-4 Slider

I just completed the second rendition of a sliding canopy on my -4. I do like the sliding canopy better than the original. If Van's had offered a sliding canopy option, I would have purchased it.

I started with blue prints offered by John Haehn (Van's may be able to supply a current Phone #) and then did some customizing. It was quite a project and I needed some help from those who know how to weld aluminum and work compound curves in aluminum. For those who have not built their -4, these skills are not necessary to build a good looking -4 from the kit supplied by Van's. Several builders have used fiberglass or carbon fiber for their skirts and eliminated much of the trouble I encountered with forming aluminum skirts.

John's plans use a dorsal fin for the rear canopy sliding block to track on. I have seen other builders use the rear track from the -8 kit, but John developed his plans well before the -8 was available. John used a single wrap lexan windshield, but after 14 months flying with mine I decided to replace it with a plexiglass windshield made by Gee Bee Canopies, Van's supplier for the -4 canopies. Glen has a buck he uses for F-1 Rocket windshields and that worked well in this application. Other builders have simply used the forward portion of the original canopy after they made the cut.

I decided to go with a slider to feel cool rather than look cool. I live in Arizona and though my home field is 6700' msl and carved out of a pine forest, I fly to PHX for work. Considering the greenhouse effect, a 72F day in January leaves you really hot taxiing with the canopy closed. Later in the year you are even more uncomfortable. None of the partial canopy open devices I researched looked robust enough to work. If they had, I might have tried them. I met two -4 owners whose devices failed while on the ground and though they did not crack their canopies, most of the metal work had to be repaired or replaced when the canopy suddenly slammed open.

Though unlikely, an unexpected inflight opening is a possibility, too. Bundled up for a winter flight from my home field (yes it does snow in AZ) I reached for a chart and found the extra clothing I was wearing caused my shoulder to bump the canopy handle. I have a microswitch wired to the only red light on my annunciator panel and it is adjusted so that just a slight movement of the handle will illuminate it. It worked as designed and I resecured the canopy handle, but it did get me thinking. A firmer bump may have unlocked the canopy and, as designed, it would have departed the aircraft. An unexpected, 165 kt blast of air in the face could be disorienting and maybe even bang your head into the rollbar with enough force to knock you out. Aircraft controllability may also be a factor. After many thousands of RV-4 hours flown without any such incidents reported (to my knowledge) this is probably not a major concern, but it did almost happen to me.

I am still experimenting with the canopy open in flight. I use 80 kias as a maximum speed and only crack it open enough to get some air moving in the cockpit while entering the pattern to land. This really does make a difference when the oat is 110F and you have slowed enough that the cockpit vents are not as effective. The air forces will slide the canopy closed without a partial open stop.

Form an appearance standpoint, I prefer the rake of an F-1 windshield to the more rounded look of the -4 and -8 windshields, but not enough for that to be a deciding factor in this conversion. What looks "cool" is purely subjective and has to be decided by each builder.

After going through the process, I have concluded that an RV-8 QB would have been a better choice for both the money and the time, but that too is a personal decision.

Based upon my experience, I would recommend considering the following before installing a slider on a -4:

The rollbar must be lowered/shortened and mounted to the side of the fuselage. A safety compromise? Perhaps. The windshield and canopy bows are reinforced, but who knows?

Rear seat access is slightly more restricted since the forward edge of the canopy extends forward of the rear seat bulkhead. This is also a factor when accessing the baggage compartment. Neither has been a problem for me, but think about it.

My installation is heavier than the original, though perhaps not more than the -8 canopy.

I fly sport aerobatics. Will I have a problem with emergency egress inflight? I don't think so, but it won't be as easy as with the original.

Forward visibility will not be as good as the original, but I do not see it (no pun intended) as a safety consideration and it has not been a factor in landing or formation flying.

For me it was alot of work and, because I chose to hire some services, more money than I would spend if I had it to do over again.

All that said, for me the slider has improved my RV-4. But, as I have tried to make clear, this is a very subjective evaluation and I recognize many arguments against the conversion. I'll try to get some photos onto the site, but my computer skills are somewhat limited.

Jim Graham
 
Ventilation

Having not finished my 4 yet, I have no idea what the greenhouse effect will be, but the posts of others lead me to believe I'll cook in the summer. A slider would be great but too much trouble to do now. I think the canopy partial open thing is less than perfect. It seems that a nice fix for this would be some clever forced ventilation. I'm planning on naca vents below the cowl cheeks, but am picturing some small electric fan somewhere in the system. Anybody ever done anything like this?
 
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