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Here we go again. Another marathon, mega thread. I will be helping and mentoring Brad as we (he) builds the prototype 4 seat Javron Cub.
I will try to post helpful info and make this a manual for the 4 seat cub (4S), as much as possible.
The following are our goals:
1) Keep it as close to a Cub as possible
2) Shooting for an empty weight of 1150 (I will be happy under 1200) with a gross of 2400
3) Have the plane at Oshkosh 2023
We will be using an 0-360, carbureted for simplicity and weight. Trying for 260 pounds or less with all accessories, except exhaust. Looking at magnesium sump, lightened cylinders, 9 to 1 comp ratio, Pmags, Skydynamics flywheel, B&C Alternator on the back, EarthX battery, Conical mount, no swing, built in thrust line. I am currently getting bids on the engine.
What I think I know so far.
The Javron fuselage is 44" wide and is a clean sheet design by a well known cub engineer. 19" longer overall. I believe it weighs, with powder coating, 138 pounds, but that will change as we are still working on finalizing the configuration. All other parts, other than the fuselage, will be standard Cub parts. All the angles will be standard Cub to keep the flight characteristics as close to a "Cub" as possible.
The other 4 seat fuselage is available from Airframes Alaska. It is 40" wide, and weighs in at 155 without powder coating. Further options are the PA14, and Bushmaster versions of the Pacer/Tri-Pacer, which are much narrower (about 36"), and probably smaller in length and corresponding cargo area.
The cargo area of the Javron 4S (I will here after refer to this plane as the 4S) is huge. Unlike the Airframes fuselage it does not have the dogleg, or shelf tubes. From the rear of the front seat, (rear seats will be fold up similar to a Cessna 180, and easily removable altogether), to the back of the cargo area is 7'. It is huge. Right now the door is 23" x 24" and does not have a lip. So you will be able to slide things in and out. It might be possible to increase the door size but my understanding is that to do so, and maintain structural integrity, would require a truss under the door and thus a 4 to 6" lip. So the door would be bigger but stuff would have to be lifted over the lip as opposed to sliding stuff. The right front seat will be easily removable to allow loading cargo through that larger door. Everything is a compromise. Lack of the shelf tubes could be looked upon as a negative as it does not allow an upper and a lower baggage.
Due to goal #1 it will have dual cub clamshell type doors. My understanding is this may actually make getting in and out easier than with the seaplane doors, but I do not know that for a fact yet. Remember.....this is the prototype. In the future I am sure you could get Javron to make seaplane doors if that is your preference. One of the great strengths of Javron is the flexibility Jay offers to customize a kit to your specific mission, and desires.
Float fittings
Electric trim
Structure for bolt in lead to adjust CG
Lots of cargo net attach hooks (very necessary with such a large cargo area)
Baggage floor will be on longerons
Easily removable right seat to allow loading cargo through that larger door
Metal belly under front floorboard to facilitate cleaning
We are still working on the stick, rudder, and brake configurations. My preference is in goal #1..... thus dual stick, floor mounted rudder pedals, and heel brakes. But sometimes the monkey motion required for this may not make it the best option. We will see. Brad would like full dual controls and I agree with that.
No pictures yet.
So the first thing we need to do is acquire tools. I will post a list as soon as I can.
Next we need to build a paint booth.
PAINT BOOTH THOUGHTS
Having been down this road a few times in the past here are some of my thoughts. I do not particularly like plastic (visqueen) booths for the following reasons. I was painting the rocker boards on a VW many years ago so was kneeling down on my ankles. When I stood up I lost my balance a little and put my hand out to steady myself and pulled the entire flimsy booth down on the wet paint car. Fixing that was a LONG process and made a more rigid booth a top priority. Plastic gets static electricity and attracts dust which then falls off when the plastic flexes which it will do every time you turn on the fans or turn them off. It might be fine if just using the booth one or two times but when building a Cub there are a TON of times you will be in the booth. 40 or 50 would be my guess. Way too much for a flimsy plastic booth. I know many have used plastic and gotten a perfectly good job. I'm not that good. I have to use every trick in the book, the very best gun, compressor, filters etc just to get an average job. I know, and envy, the folks that can get a 39 dollar gun from Harbor Freight, paint outside, and the darn thing looks like a Lexis finish. I can't do that. So......I will be building a 12x24x8 paint booth that will be fairly permanent so to speak. I will post that as I go.
After a little internet searching I found this....
*You need full air exchange twice per minute
*Calculate your area LxWxH (24x12x 8' ) = 2304 .....x2 = 4600cfm needed to attain that
*A one hp motor can usually move about 1800cfm which means I need about a 2.5hp motor (or a couple of lower Hp units)
*For the intake filter area you need 1500 sq in per 1000cfm, so I will need 6900 sq in or.........12 24"x24" filters
*For exit filters you can use 1000sq in per 1000 CFM so I need 8 24"x24" filters or use fiberglass rolls
*Positive pressure is best thus would also need an intake fan......best number positive pressure is .3 wc
*3/8" couplers flow twice as much air as 1/4" couplers
*Lots and lots of light. Can't have too much light.
Not sure I really need to hit all that but it is certainly a goal and will be much better than my last booth.
Let the games begin........
Hope this helps
Bill
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Originally Posted by Bill Rusk
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