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Re: Model IV smooth cowl
I'm doing the same thing as Av8r3400.... considering the conversion to a smooth cowl on an IV..... Is there anyone out there that has done a conversion and can speak to any:
1) challenges in the conversion (fit, changes etc.)
2) performance differences (cruise, top speed)
Cheers,
Ackselle
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Re: Model IV smooth cowl
One thing I just learned from talking to Deb while at Airventure: the conversion requires a different motor mount.
That could be a game changer for me... :(
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Re: Model IV smooth cowl
Hmmmmmm.....ditto for me. That may be a clue as to the lack of replies to the conversion difference question.
Well...change of plans.... I'm thinking we may need to fabricate our own!
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Re: Model IV smooth cowl
I changed cowls during my rebuild but I am running a Jab 2200 so it was an easy transition. Can't help with the speed though as I never flew it with the round cowl.
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Re: Model IV smooth cowl
I would like to revive a dormant 6 year old thread regarding model 4's and smooth cowls to see if there is any current info..
I could call Debbie at Kitfox for details regarding the needed parts but want to know if the visibility significantly improves on the model 4 since it is a shorter cowl fore-aft than the model 5's and up with smooth cowls?
I was at the 2018 High Sierra and saw Trent Palmers new smooth cowl and one of his friends has a yellow model 4 with a smooth cowl.
Someone mentioned a new motor mount.
Does the new mount raise or lower the engine.
The cowl is ~$1000, how much is the motor mount?
Any other major changes like the exhaust or relocating the oil tank.
I realize the firewall will need to be changed.
Does the radiator end up in the cowl like the 5-7's?
Please share any new info..
Thanks
Herman
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Re: Model IV smooth cowl
Herman,
I mounted the radiator flat in the bottom of the cowl so the air has to exit over the radiator as it exits the cowl. My smooth cowl didn't have enough room to mount the radiator like the model 5-7's. I had to open up the bottom of the cowl to do this. Otherwise, I think you would have to mount the radiator similar to conventional Model IV mounting. There is a picture in my album where you can see the radiator mounting.
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Re: Model IV smooth cowl
Visibility with the smooth cowl doesn't seem much different to me on the ground compared to the round... still have to look out the side and S turn. Maybe better on approach, but by the time I pull back to a 3 point attitude or even for wheel landings, my eyes are out the corner of the windshield (for better depth perception in my opinion) or side windows anyways even if it has theoretically better visibility.
Basically same opinion as Cubtractor on the radiator. Could be wrong, but I don't think it's big enough without modification for the radiator and on a model 4 I also believe the initial design is for it to still be on the belly. My HKS 700T is air cooled, but I do have an intercooler that is similar in size to the Rotax radiator. I modified the bottom of my cowl and stretched it for the room I needed.
As far as I can tell the thrust line is the same for both cowlings. If I had to guess I would say that the mount is probably mostly the same or could be modified to work since the thrust line is the same. Fore and aft may be slightly different, but I would be surprised if it was. I f I had to guess at the difference, it may be that the smooth mount has a provision for radiator mounting and perhaps it does fit in the cowling?
Firewall changes are just the top half and exhaust is what it is - you cut a hole for the pipe.
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Re: Model IV smooth cowl
Scott Palmer's plane (Formerly DesertFox4 - Steve's) is a model IV smooth cowl. The engine mount is totally different and not interchangeable without modifications to the firewall.
Scott's (Steve's) plane has a modified instrument panel, but the standard instrument panel is the same between the two cowls and this is where your visibility is restricted. Changing the cowl alone will not improve your forward visibility.
My log term (5-year) goal is still to rework the firewall forward on my IV to include a smooth cowl and Rotax ring mount system similar to the new model planes. This will probably mean a boot cowl and engine cowl like the newer models. When I get to this project, I will document the process thoroughly.
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Re: Model IV smooth cowl
How is the engine mount totally different and not interchangeable?... We keep hearing this but no one can say how. As long as the thrust line is the same, which I'm pretty sure it is and the length is adjusted what does the mount matter to the cowling?
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Re: Model IV smooth cowl
That is what I was told by Debra McBean. I will defer to her knowledge of the subject.
I believe the length of the mount is shorter, necessitating recessing the oil tank into the firewall. I can not confirm or deny that the thrust line is the same.