Building a 4 Seat (4S) Javron Cub

[Bill Rusk]

This is a general look at the what the removable rear seats look like. When they are not in place the rear cargo area is completely flat with no cables and no protrusions. 85" long and 44 inches wide - tapering to 35 inches at the rear. It is HUGE. We have 6 tie down locations in the floor and 4 in the top for cargo straps or nets.



Trial fit of the tail feathers. All control surfaces are oversized.



We are using the Air Tech fabric system. First parts in the booth and in primer.


More to follow and thanks for following.

Bill

[Bill Rusk]

ENGINES

After much consideration we ended up going with a Penn Yan rebuilt 0-360. Penn Yan has a long history and an excellent reputation and it was a pleasure dealing with the owner Bill Middlebrook. Bill is a long time cub owner and is VERY familiar with Cub mods and engine requirements. He was able to give us an excellent price, and delivery time, both of which are greatly appreciated. This will be a stock engine. Not an 0-370, 0-375, 0-390 etc. Just a well built stock 180 to 190 hp engine. It will have conical mounts, dual Emags, Carb, Magnesium flywheel and sump, B&C 20 amp alternator on the rear case, and lightweight starter. We elected a rebuilt engine to save weight. The new engines have put on several pounds.
I anticipate we will be using the Sutton exhaust and possibly the Sensenich ground adjustable prop.
We seriously considered Aero Sport Power for the engine, and several others. My understanding right now is Titan may be the best price but their lead time is 12 to 14 months.

We will weigh the engine when it comes in and post the engine weights that we know at that time

Hope this helps

Bill

[Mudofficer]

Thanks for the update @billrusk ! This seat configuration makes for a very versatile and large space. Will it be sleepable? Now that you have sorted out the revisions, do you think that they will also be adopted by Jay? Also, will your build be using a performance STOL type flap from Keller & Javron?

[Olibuilt]

Very nice build. You realize it is a big airplane when you see 2 grown men in the back seats!!

I would have looked for a stronger engine to haul all that weight?


Can't wait to see more progress. Thanks for sharing!

[Bushmaster1]

Is there any good reason not to use a UE520T other than cost and new to market?. Would make a huge difference on a float plane on on higher elevation lakes. 60hp more at 5000 feet would be a game changer for short lakes and strips.

[skywagon8a]

Is there any good reason not to use a UE520T other than cost and new to market?. Would make a huge difference on a float plane on on higher elevation lakes. 60hp more at 5000 feet would be a game changer for short lakes and strips.

This one? https://ulpower.com/en/engines/ul520...t#3-dimensions Other than the higher maintenance for the turbo system, look where the turbo is mounted. To complete the installation connections to the turbo will be aft between the turbo and the firewall. This will require pushing the engine forward creating a forward CG situation. Particularly with the extra 64 pounds for the turbo components.

[dirthog4]

High pressure fuel injection more you know about it in a airplane less you want to. Need small diameter usually 3 blade controllable propeller inefficient rpm range.

[Bushmaster1]

Yup that’s the motor.269 lbs which incudes alt and baffling and starter it looks like.Needs a intercooler which I will make up weight of of 15 lbs almost which is about the same weight as a o-360 carb engine.There will be some added weight for fuel pumps and return fuel lines.should be far less weight than a angle valve engine which I would think many people would consider on a 4 place. Not sure what problems you are referring to on high pressure fuel injection I’ve only heard of good I guess I few guys around here running it.Tuneable injectors,no carb heat,no primer,no mixture,better fuel consumption and starts better.It has a list of props that are compatible which includes catto and MT.Maybe something like a Catto 86/43 should push a four place bushed out cub at 105+ mph and super short take off.The only real big negative I see is it’s not a time tested and short tbo of 1200 hours

[Bill Rusk]

Bushmaster

Why not the UL520?......and the answer is......never heard of it before. Interesting. It seems to have potential. 1500 TBO is a little low. For simplicity I am not sure I would want the turbo, but obviously that has advantages as well. Sure more power is always good. After all we could go to an 0-470 or 0-520 or even a 0-550.
But here are my thoughts on why not a bigger engine.

1) Weight...... bigger engine means bigger and heavier prop. I will need more fuel = more weight. I will need to add more structure to handle the loads and weight = more weight. It is a massive snowball and pretty soon we have Mike Patey with Draco and Scrappy.

2) This is somewhat subjective but try not to focus so much on the 4 seat concept, but look at the gross weight and empty weight. We can use "useful load" to carry people, fuel and/or cargo. We are hoping for an empty weight of less that 1200 pounds and a gross of 2400 pounds, thus a useful load of 1200 pounds. My current cub performs VERY well at 2300 pounds with an 0-360. This 4S cub should perform the same. Same engine, same airfoil, same incidence, etc. and roughly the same weight. On floats, at max gross, I am off in 18 to 20 seconds. On wheels at max gross I am off in 175'. How much more do you want and at what price? So with 1200 pounds of useful we can haul 48 gallons of gas = 288 pounds, 4 x 200 pounders and 112 pounds of baggage. Ok....so maybe not enough useful load to haul 4 full size adults, all their gear (400 pounds) and we want to haul out the 3 moose they just shot? Now we are in a totally different aircraft category. What we will have is a 2 place side by side aircraft that will carry full fuel, 2 adults and have 512 pounds of cargo capacity. Or 2 place plus room for the grandkids. Or 4 adults around the local area. Or 4 smaller adults, say.... 2 guys at 200 and 2 wives at 150 gives 212 pounds for baggage or camping gear which should work pretty well.

For comparison the Bearhawk model 5 uses the 540-580 engines (6 cylinder engines) with an empty weight of about 1500 and a gross of 3000 for a 1500 pound useful load. Cruises faster but I guarantee it will not get in and out as short as a Cub. It all depends on your mission. One of the builder/owners in our project is a serious sheep hunter and so his mission includes some pretty short and rough strips in the mountains of Alaska. Most hunter outfitters in Alaska are using Cubs because they can go where 185's 206's etc just can't go. So they ferry in hunters one at a time. Still tough to beat a Cub.

Probably a little late for this build as we have Penn Yan building the engine now. I am very pleased with all the communication we have had from Penn Yan. The owner/CEO is a cub guy and has been great. I anticipate we will get the engine in the next couple of weeks.

Thanks for the input on this engine. It looks like it is certainly something to be considered and perhaps it will work out for someone who has not already committed to an engine.

Mudofficer
Yes....in the 2 seat configuration it will sleep 2 people. 85" long and 42 inches wide tapering back at the feet. It would be a little cozy for two but huge for one person.
Jay is adopting most of our changes unless you want something different. I believe he will still be offering it as a single stick,or two stick, toe brakes or heel brakes.
We are going to start with stock flaps but may certainly opt for Pstol/Keller flaps in the future. Starting on Goodyear 26" tires because of airport and local area, but it will likely end up on 31's or probably 35's in the near future.



Paint scheme to be gun metal gray with yellow stripes



Brad in the paint booth spraying Airtec primer.


Hope this helps

Bill

[Bushmaster1]

As you might guess I’m Bushmaster type guy. I agree keeping it light is very important because once one thing is heavier you got to make everything heavier like wings,gear legs,struts,and structure.This is going to be a fantastic build to watch and a hard one to beat. My mission is pretty much the same as the sheep hunter fly 600 miles North with 2 guys and hunting gear for two weeks on floats or wheels and use super cub strips or lakes and ferry flight to longer surfaces and fly home. Pretty hard to put that much stuff in a cub even with a pod.It just looked interesting similar weight engine with 60hp more. I think on floats it could be beneficial like 2000’ lake at 5500’ and a couple stone sheep on board. Thanks for documenting all the cub builds many of us reference back to it when doing our own stuff extremely helpful. What is the wing and struts good for. 2400lbs?

[hunt/trapak88]

Bushmaster

Why not the UL520?......and the answer is......never heard of it before. Interesting. It seems to have potential. 1500 TBO is a little low. For simplicity I am not sure I would want the turbo, but obviously that has advantages as well. Sure more power is always good. After all we could go to an 0-470 or 0-520 or even a 0-550.
But here are my thoughts on why not a bigger engine.

1) Weight...... bigger engine means bigger and heavier prop. I will need more fuel = more weight. I will need to add more structure to handle the loads and weight = more weight. It is a massive snowball and pretty soon we have Mike Patey with Draco and Scrappy.

2) This is somewhat subjective but try not to focus so much on the 4 seat concept, but look at the gross weight and empty weight. We can use "useful load" to carry people, fuel and/or cargo. We are hoping for an empty weight of less that 1200 pounds and a gross of 2400 pounds, thus a useful load of 1200 pounds. My current cub performs VERY well at 2300 pounds with an 0-360. This 4S cub should perform the same. Same engine, same airfoil, same incidence, etc. and roughly the same weight. On floats, at max gross, I am off in 18 to 20 seconds. On wheels at max gross I am off in 175'. How much more do you want and at what price? So with 1200 pounds of useful we can haul 48 gallons of gas = 288 pounds, 4 x 200 pounders and 112 pounds of baggage. Ok....so maybe not enough useful load to haul 4 full size adults, all their gear (400 pounds) and we want to haul out the 3 moose they just shot? Now we are in a totally different aircraft category. What we will have is a 2 place side by side aircraft that will carry full fuel, 2 adults and have 512 pounds of cargo capacity. Or 2 place plus room for the grandkids. Or 4 adults around the local area. Or 4 smaller adults, say.... 2 guys at 200 and 2 wives at 150 gives 212 pounds for baggage or camping gear which should work pretty well.

For comparison the Bearhawk model 5 uses the 540-580 engines (6 cylinder engines) with an empty weight of about 1500 and a gross of 3000 for a 1500 pound useful load. Cruises faster but I guarantee it will not get in and out as short as a Cub. It all depends on your mission. One of the builder/owners in our project is a serious sheep hunter and so his mission includes some pretty short and rough strips in the mountains of Alaska. Most hunter outfitters in Alaska are using Cubs because they can go where 185's 206's etc just can't go. So they ferry in hunters one at a time. Still tough to beat a Cub.

Probably a little late for this build as we have Penn Yan building the engine now. I am very pleased with all the communication we have had from Penn Yan. The owner/CEO is a cub guy and has been great. I anticipate we will get the engine in the next couple of weeks.

Thanks for the input on this engine. It looks like it is certainly something to be considered and perhaps it will work out for someone who has not already committed to an engine.

Mudofficer
Yes....in the 2 seat configuration it will sleep 2 people. 85" long and 42 inches wide tapering back at the feet. It would be a little cozy for two but huge for one person.
Jay is adopting most of our changes unless you want something different. I believe he will still be offering it as a single stick,or two stick, toe brakes or heel brakes.
We are going to start with stock flaps but may certainly opt for Pstol/Keller flaps in the future. Starting on Goodyear 26" tires because of airport and local area, but it will likely end up on 31's or probably 35's in the near future.



Paint scheme to be gun metal gray with yellow stripes



Brad in the paint booth spraying Airtec primer.


Hope this helps

Bill

I’m following this closely as I too have money to Jay for his kit. Had a 1150lb 0-360 cub with a long dong very well performing propeller, Keller’s etc. Cub flew and performed well. I’ve always wondered how this 4S will do loaded with a 360 based engine.

Am I reading this right Bill? Your 0-360 “standard” Javron cub is/would defy gravity in 175’ at a gross of 2300lbs in a no wind configuration!!?? 175’!!?? If so, I have second thoughts on my cub. Which I thought was a performer….

[Bill Rusk]

Folks

A little update. Going slower than hoped for but that is pretty much always the case. It seems this spring Brad and I have both been gone a lot. tough to build an airplane when you are not there.



Carbon Fiber floor board material came in. 2 ply on top and one ply on the bottom, comes in at .565 pounds per sq ft.



We got our alternator(generator) from Monkworkz. This is a relatively new unit designed by an electrical engineer. Primarily used in the RV community as a back up power source. I am very impressed by the construction and customer service. I think this will be a winner. It weighs, with the regulator 2.6 pounds. That is 3.5 pounds lighter than the B&C direct drive units. Produces 15 amps at 1000 rpm and 30 amps at 1800 rpm.




Just for a size comparison. That is a standard can, like a can of corn, soup etc. So it is much smaller than the B&C , and cost the same as well.




The engine came in from Penn Yan and looks great. This is without a starter and generator so add abut 9 pounds and we are at 257 with carb, mags, plugs, wires, starter, generator, and oil filter. It came in at 196hp, and plus 35 pounds torque. 9/1 pistons. I am VERY pleased. We did get some damage on the flywheel so ordered a new one. Checked to make sure that was all that was hit.




Bill Middlebrook at Penn-Yann was, and is, awesome to deal with. Great guy and a cub guy as well.


Engine and prop test mount. We will be doing some prelim testing of W&B to adjust motor mount if necessary.


Hope this helps some

Bill

[Buschpilot]

Looking great Bill! I hope to get out your way for a visit sometime before you guys finish her up. Our kit is due to arrive in August or September, and I would love the chance to soak up a few good ideas before we start building!

[Bill Rusk]

Buschpilot - Happy to have a visit anytime.

Bill

[Bill Rusk]

We will be doing some early, best guess, W&B/CG calculations in order to make sure we have the right length motor mount.






Bill