Updated photos of Twin JAG

[jimdc8]

Here are a few new photos of my twin engine project. More to come shortly at www.homebuiltdirectory.com (http://www.homebuiltdirectory.com).

[jimdc8]

Newest photo as of today (bottom photo)! Engines being built shortly.

[64wing]

Newest photo as of today (bottom photo)! Engines being built shortly.

That is a very interesting project! I have been toying with the idea of designing a light twin for some time now, given the rapidity with which engines are growing more efficient, airframes are getting lighter and stronger, etc...

Looks like you've adapted an RV-7 or something(?)

Would love to see more photos! Keep up the good work. Can't wait to see that fly!

[jimdc8]

Thank you for the kind words! I will be adding more pictures very shortly. I am currently finishing the instrument panel/center console installation, minus avionics for now. Used to be a RV-6A. Now it is called a Twin JAG.

More coming soon.
Jim

[RV8505]

Thank you for the kind words! I will be adding more pictures very shortly. I am currently finishing the instrument panel/center console installation, minus avionics for now. Used to be a RV-6A. Now it is called a Twin JAG.

More coming soon.
Jim


Now that's thinking outside of the box! COOL Project. Best of Luck!!

[jimdc8]

Here are some more recent photos. Trial fitting the burlwood panels on the center console. More pics coming soon...

[wildhorsesracing]

What engines are you planning on using?

[jimdc8]

What engines are you planning on using?

I am building custom 120hp Corvair based flight engines. They are direct drive 6 cylinder air cooled and are very smooth running engines. They contain a fifth bearing to handle loads imposed on the crankshaft by the props. My engines will use the following brand new custom parts:

1. 4340 billet ion-nitrided crankshafts
2. Custom pistons & cylinders
3. 4340 connecting rods
4. Falcon machine heads
5. High volume oil pumps
6. Weseman 5th Bearing
7. ...much more!

I will begin building these engines in the next few weeks.

Jim

[Bob Dingley]

Very nice project!
.
Your Dec 17 post included a picture of your console with the #1 & #2 PROP BRAKE controls. I had only seen passing reference to brakes in obscure texts. A recent forum thread regarding the Bally B-17 replica had pictures of those powerplants and some folks thought the brake drum looking things aft of the props were freewheeling devices. There were some opinions expressed that a free wheeling prop on a shut down engine was desirable.


Could you bring us up to speed regarding the relative drag of a feathered prop vs a braked prop vs a free wheeling prop. I can't wait to see pictures of your brake system. It could turn out to be lighter than a cs feathering prop. As if there were one even available for a 120 hp Corvair. Can't go wrong with the Corvairs.


Bob

[jimdc8]

Thanks Bob!

As you know, a constant speed prop is both heavy and complex. It is also a failure point and it's weight puts stress on the crankshaft. My concept of a prop brake is a simple one...I will install a mechanical brake caliper, identical to a bicycle's, which will stop the windmilling prop using the machined surface of the flywheel (just under the teeth where the starter meshes with).

Here are a few of my thoughts for this setup:
1. A feathered prop, using a constant speed prop, effectively reduces drag approximately 97% compared to an unfeathered windmilling prop.
2. A stopped unfeathered prop, using my proposed braking system, effectively reduces drag approximately 93% compared to an unfeathered windmilling prop.
3. I feel that with a simpler and lighter setup, I would be willing to live with the 4% degradation in performance. I can makeup the difference by setting limitations to the operation of the aircraft (ie. minimum runway lengths).

These are just some generic thoughts of mine that describes why I am choosing this route. It is much more in depth than I can describe on this forum. Hope this helps.

Jim

[jimdc8]

3646
Panel shot...
interior pieces just in place temporarily.

[jimdc8]

Panel with Dynon templates taped in place...

[jimdc8]

Here is a pic of the left motor mount. Due to the shallow geometry of the firewall hardpoints, a truss style mount is required. Weighing in just under 10 pounds, I over-engineered the mount but am confident in the strength. It passed a 6 g load test.

[jimdc8]

Recent photos with engine mounts installed. Powdercoated pearl color.

[jimdc8]

Just fabricated and installed landing light enclosure. Also streamlines upper portion of nosegear leg. Landing light is Aveo LED...very bright and low amps! Airframe just about complete...just waiting for engines and avionics. I am just starting to build the engines now and hope to have them installed late summer or early fall. Also taking advantage of the warmer weather to finish the filling and sanding of all the fiberglass work.

[Frank Giger]

Holy crap.



http://media.tumblr.com/tumblr_mdc65v0gPk1ruhd6j.gif

[64wing]

Made my night, Frank! Too funny...that movie is most excellent

[jimdc8]

Filling & sanding....about 80% complete.

[jimdc8]

Painted cases bolted to mounts for sizing purposes. Building shortblocks very soon...

[jimdc8]

Both engines have cases closed with ARP case studs with cam & crankshafts installed. Should have both shortblocks complete within next 2 weeks. Fifth bearings installed on both cases last week. Virtually everything other than the cases and head castings will be brand new parts.
41634164

[jimdc8]

http://eaaforums.org/attachment.php?attachmentid=4266&stc=1
Right engine almost finshed. Left engine also in same stage of completion. Bringing both engines to Corvair College first week of November to test run and break in.

[jimdc8]

Front view of engines mounted temporarily.

[Bill Greenwood]

It seems very hard to believe that just stopping an unfeathered prop cuts 94 of the drag, or else it would have been used in other planes, cheaper, simpler than feathering.
Obviously, once you get to flight testing you can, at a safe altitude, shut down one engine, brake the prop to a stop and try it, and you will know how it flies on one engine. A premium would then be on getting the brake off and restarting.
It may work, but I'd sure wear a chute and be able to get out. A chute won't help if an engine is lost on takeoff,though.
You sure have put some work into it.. Good luck.
Note, I am not any kind of expert on this, and don't even have a multi rating.

[FlyingRon]

Having studied some twin conversions (I'm on the board if the organization that actually holds the TC on one of the twin Navion conversions), did you increase the size of the tail? Rudder trim?

[jimdc8]

Yes, the tail is aproximately 30% larger than the original tail. No rudder trim.

[jimdc8]

Bill, you are correct. It is not truly 94%...I was just trying to quantify in simpler terms the reason for my thinking. A feathered prop is more streamlined than a flat blade. Stopping the prop does make a huge effect on drag although my props will probably stop on their own due to low inertia below 100kts. It is just a simple way to reduce drag if the crankshaft broke just behind the prop hub for example.

[jimdc8]

Some engine details....still fabricating intake, exhaust, baffling, oil cooler, etc.

[jimdc8]

4701
Designed & carved this 62" x 74" test prop. I will use this prop to test run my engines. I will then tweak it for flyable props. Hope to run the #2 engine on the aircraft before Airventure. I will run the #1 engine shortly after I return from Oshkosh later this summer.

[crusty old aviator]

You may see a baggage shelf, and you did a nice job of designing and fabricating it, but I see a rumble seat! I'm not sure how a "light" person would affect the W&B sitting up there, but with a little bubble canopy on the nose cone, instead of just the door on the side, that would make a cool perch!

[crusty old aviator]

Aerodynamically speaking, a spinning prop has the same flat plate area as its entire disc area. This was confirmed by Fred Weick of NACA in the 20's, which is why the feathering prop was developed, as props have little tendency to spin much when feathered. Yes, the blade presents more flat plate area in cruise configuration than when feathered, but only if if it's not turning. What if you have a severed crankshaft, a compression ratio of 20:1 won't keep the prop from turning in flight. If you feather the blades so there's minimal aerodynamic forces acting upon them, you won't have the drag of the entire disk, just "6%" of it. Feathering props are wicked complex and heavy. Jim has created a simple, lightweight system here to help minimize some of the yaw problems associated with an engine-out condition.
I appreciate other homebuilders posing questions to those showcasing their projects here: it's how we all learn lessons from those who tried and learned something new. The only stupid question is the one that hasn't been typed...that said: what color will she be painted after flight testing?

[jimdc8]

Hi Crusty...I'm leaving the paint up to the wife lol. We are going to use a pearl basecoat vs white though.

[jimdc8]

Photo right after successful first run of right engine on the airframe. I fabricated a cooling baffle to direct air through the cylinders. I could not be happier with the first run. The Ellison TBI performed flawlessly! I will be fabricating the subsystems for the other engine over the next few weeks now that I know there are no major issues with the right engine. I will be doing many more hours of engine runs on both engines over the next several months. Back to the hangar...

5055

[jimdc8]

Here is a link to first start of right engine...

http://youtu.be/pcImWpnbb2M

[Frank Giger]

Sweet!

[Blue Chips]

That had to be a rather momentous occasion after all the work to that point, sounds strong.

[DaveP]

I have heard of issues with the Elison TBI providing unequal mixture to both banks in the split intake scenario. Have you compared head temps? I heard the spray bar should be fore-aft instead of cross ways. I know of someone who balanced theirs with a "Tornado" insert. Also, is one engine reverse rotation?

[jimdc8]

I have heard of issues with the Elison TBI providing unequal mixture to both banks in the split intake scenario. Have you compared head temps? I heard the spray bar should be fore-aft instead of cross ways. I know of someone who balanced theirs with a "Tornado" insert. Also, is one engine reverse rotation?

Hi Dave,

Both engines turn the same way. Too many cons vs pros in having counter rotating props. I made my own swirling device similar to the "Tornado". I feel they should swirl the air fuel mixture downstream of the Ellison so when it reaches the "y" in the intake, there will be even distribution. All the builders who have done this report very good results. I don't have all of my engine instrumentation yet so the verdict is still out. The Ellison can be mounted in any attitude. You should avoid having the spray bar vertical as g forces can affect the diaphragm thus affecting fuel delivery.

Jim

[DaveP]

Hi Dave,

I made my own swirling device similar to the "Tornado". I feel they should swirl the air fuel mixture downstream of the Ellison so when it reaches the "y" in the intake, there will be even distribution. All the builders who have done this report very good results.

Jim

I see you have done your homework, then again, I already had that impression. Will you be using a Plenum system like M Langford? ( http://www.n56ml.com/corvair/phoenix/ )

Dave

[jimdc8]

I see you have done your homework, then again, I already had that impression. Will you be using a Plenum system like M Langford? ( http://www.n56ml.com/corvair/phoenix/ )

Dave

Yes. Very similar to Marks. Using a K&N air filter with a flapper door selecting either ram air or carb heat.

Jim

[jimdc8]

Links to videos of left engine's first run on airframe...


https://m.youtube.com/watch?v=UcaaDl3ch2U
https://m.youtube.com/watch?v=xx1iTqUEXnU

[jimdc8]

5098

Photo with gear leg fairings installed. Wheel pants next...

[Frank Giger]

She's really coming together nicely!

[jimdc8]

5261
Very rough beginning stages of top cowling mold...hope to be fiberglassing in a week or two.

[jimdc8]

5275

Top view of rough top cowling in place. Lots of filling and sanding!

5276

Another view...

[DaveP]

Nice work, looks like they will be low, sleek cowlings.

[Mike B]

Looking good!! I've been wondering how your project was progressing.

[jimdc8]

Thanks guys for the kind words! I am about halfway finished with the lower cowling mold. The recent cold weather is slowing me down so I switched to doing wiring. I am fabricating harnesses now for a dual VPX system. I will have a few recent photos soon. Hope to have avionics & wiring completed sometime this summer. I will be working closely with Craig Catto to build my props. I will be using 60" 2 blade wood core with carbon fiber coating and stainless leading edges. Craig does amazing work with props and look forward to working with him.

[jimdc8]

5409
Installing Dynon Skyview.

[Mike B]

Looks good. The wood grain reminds me of my sons Jaguar!!

[jimdc8]

5479
Beginning stages of fitting lower cowling.

[jimdc8]

5536
Prepping for finishing "bodywork"... I will be making second cowling and ram air scoops in next few weeks. About 90% done and 90% to go!

[Mike B]

Looks like it's coming along, looking forward to the finished project.

[jimdc8]

5607

Fitting spinners with props. Should have first video shortly of both engines running at same time on airframe.

[Frank Giger]

Can't wait for that video!

[jimdc8]

https://m.youtube.com/watch?feature=youtu.be&v=RTQC2PEPv6g

Video of both engines running at same time. Cowlings structurally complete...just need finishing cosmetically.

[jimdc8]

5640
Just received the tinted canopy. Will begin installation this weekend. Then more cosmetic fiberglass work.

[Mike B]

Coming along quite nicely!!!

[Frank Giger]

I have a feeling it is going to be a monster (in a good way) of a plane.

[jimdc8]

5762
Almost finished with canopy. After that, it is time to start finishing the fiberglass work. A lot of testing and tweaking over the next few months. 90% done...90% to go!

[jimdc8]

https://youtu.be/_OzyMpqTsHA
Short video of lighting check. Shot at dusk just after engine runs.

[jrollf]

Sounds great!

[jimdc8]

5848
Recent photo just before engine runs. Canopy complete other than fiberglass skirt around windshield. Should be riveting top skin in about 2 weeks. Still lots of fiberglass finish work left to do.

[Mike B]

I like the way it's turning out. Can't wait until the finished product!!

[Frank Giger]

LOL, it's starting to look like a prop driven Me-262.

[jimdc8]

Top skin riveted in place. Next step is LOTS of fiberglass finishing work. Just finished some very successful engine runs!

5993

5994

[FunInAviation]

Extremely Cool!

[jimdc8]

6181
6179
6180

Basking in the setting sun after very successful engine runs on a cold blustery day.

[jimdc8]

6187

Photo of panel. Still installing interior and securing wiring...

[jimdc8]

I posted 2 movies that I filmed today on youtube. The first is just a walkaround of the TwinJAG. The second is a taxi test showing back taxiing a few hundred feet down the runway followed by a 180. I then advance the power to about 3/4 WOT for a few seconds back to idle. The acceleration was amazing.

https://m.youtube.com/watch?v=zy0jYcKDR4Y

https://m.youtube.com/watch?v=CZ70GrBjWwk

[harrisonaero]

Great job innovating- very exciting. Please be extra careful and SAFE- blessings on your first flights. Really want to see what this plane can do! :)

[Mike B]

Curios minds want to know, do you have an update on this project?

[jimdc8]

6559Hi Mike. The aircraft is just about finished. Still doing some cosmetic finishing but mechanically complete. Extremely pleased with ground and taxi tests. I will be moving the aircraft over to another airport by truck for phase 1 testing. I've been on the road the last 2 weeks at Oshkosh and Georgia so I can't wait to get back home and finish. Below is a photo from a month or so ago. I will post more recent photos & videos when I get back.

6558

[Frank Giger]

Sweeeettttt!

Way too much aircraft for me, but she looks like a rocket.

[Mike B]

Thanks for the pictures, plane looks great!!! Can't wait to see it in the air.

[jimdc8]

6687

Just a few weeks to go...I'll be moving the aircraft to a larger airport nearby shortly. I will also be making a detailed walk around video discussing my thought process behind my project.

[Mike B]

Can't wait to see it in the air.

[jimdc8]

67596760

TwinJAG is finished! Just completing paperwork and setting up DAR inspection. First flight in next couple of weeks...

[Frank Giger]

Gonna be a rocket!

[wyoranch]

Best of luck.... Be safe
Rick

[Frank Giger]

While prop driven, it almost begs for an Me-262 paint scheme (less swastika).

[Floatsflyer]

I'm thinking that a Sky King scheme would be perfect.

[jimdc8]

Just trucked aircraft over to larger airport for signoff and phase 1 testing!
6837

6838

6839

[Mike B]

Getting close!!!

[Frank Giger]

That is just full of awesome.

[jimdc8]

7449

TwinJAG received its Airworthiness Certificate on 8/18/18! First flight coming shortly!

[pylon500]

Got that Wing-Derringer look going on it.
7460

[Mike B]

Congratulations!!! Looking forward to seeing it in the air.

[jimdc8]

Got that Wing-Derringer look going on it.
7460

Dimensionally, a lighter fixed gear (with wheel pants & fairings) version of the Wing Derringer.

[tfulwider]

Really excited to hear how it performs!

[jimdc8]

The TwinJAG is complete! On the final stage of my phase I!

Walkaround
https://m.youtube.com/watch?v=8n3PkrziSJE&t=2s

Taxi for takeoff
https://m.youtube.com/watch?v=F8QEz78mNSc

Takeoff
https://m.youtube.com/watch?v=AciTO2fwvr4

8011

8012

[Frank Giger]

That absolutely rocks!

[n6233u]

Sweet looking aircraft! Very nice work.