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Verner Scarlett Radials FWF Corner: The Oil System

The Scarlett Engines have really been making a splash in the community over the last few years now, with their real radial sounds, the simple radial architecture, and the excellent performance we have seen from these round engines. Many classic aircraft designs only look right with a classic round engine shape on there, and only sound right when that engine is a real direct-drive radial.

As a result we’ve had numerous people asking us questions about installation options and how this engine might fit their birds, which often was designed for a different engine solution originally, and what needs to be changed. In general there’s 4 major things to consider: Engine Mount, Exhaust, Oil System, and Cowling/ducting. In the FWF corner, we’ll be giving overviews and eventually more detailed looks at the situations and solutions surrounding a Verner installation, whether you’re designing a new aircraft to take the engine, modifying a design, or retrofitting an existing aircraft to make the switch over to a Scarlett.

But today, after answering this question in detail for a potential customer, I decided it was only right to put this information out for everyone to see as I imagine for everyone who takes the time to send an email, there may be many more passively thinking about what they might do down the road. My hope is that over the next few months I can get enough information in this blog that it will be able to answer a lot of questions up front.

So onto the big concern for many who are considering the Verner, especially the replica builders:

The Scarlett Radial Oil System

The engines are designed as a pump supplied, gravity drained, dry sump to a remote reservoir type oil system. In other words no scavenging pump removes oil from the engine.

A mechanically driven pump mounted inside the front of the case draws oil up from the reservoir tank and forces it into the engine passages, before it finds its way through the engine and back to drain into the reservoir. Optionally an oil cooler may be installed in this loop.

There is a pair of main drain holes in the bottom of the case, as well as the drains from each of the valve covers of the lowest cylinders. The design intent for the engine, the purpose for the dry sump, is that in case of any pump or other mechanical failure, oil should always drain clear of the engine to prevent buildup and eventual hydraulic lock in operation. It is considered better by the Verners that a pump failure should simply deny the resupply of oil, in that a drained engine should still operate on residual oils for some window of time before an emergency landing, vs creating an oil flooded engine which could cease quite suddenly if not violently. While many successful engine designs have safely incorporated various oil scavenging systems, they generally come at increased cost, weight, complexity and so on. Verner subscribes more to the theory that if it's not there, it weighs nothing, costs nothing, and cannot fail. And if gravity fails, we have other issues.

Now, this is the theory they are operating under, and as explained to us. However, yes, many have asked about alternatives to the oil situation. And many would like to move the tank out of the way, which I appreciate. We can suggest it is physically possible for someone to incorporate their own system to move it higher, with various check valves and overflow valves to keep oil from building up inside the case and cylinders. However, as of now all of this is theoretical; the Verner company so far has stated they are not interested in incorporating such solutions at this time from the factory.

As dealers at ScaleBirds, we don't currently have the design or engineering experience with those types of systems where we can say what exactly is required or how to implement it beyond the scope of the original design from Verner. So we have not attempted any such systems and all of our customers have opted to find a way to incorporate a gravity fed tank solution. In most cases the tank is contoured to the bottom of the fuselage, and painted to match the scheme to blend it with the rest of the plane. We have worked with various customers on gravity drain oil solutions following Verner's criteria, and come up with what we think are some pretty good solutions at maintaining faithful appearances without having to invent any complex systems.


The absolute upper limit for tank placement, as told to us by Verner, is that when the aircraft is parked on its tailwheel with engine off: the level of oil in the tank should sit below the valve seats of the lowest cylinders. Now, they do prefer that the oil level sits a bit lower if possible, as in below the lowest intake and exhaust ports on the engine when the aircraft is level, but again the limit does allow a little tighter setup if required. Also while the tank requires some headroom for air space above the oil, that doesn't have to be in any particular proportion, it could be in the form of a tall funnel or an oddly shaped extension of some kind. Other suggested options have included moving the oil tank into the fuselage and running longer drain and pick-up hoses to the tank, making faux radiator scoops that are actually oil tanks, or even a small drop-tank or bomb shaped tank hung from the fuselage, with lines hidden up in the fuselage.

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Certainly all of these solutions are possible, but of course the best location is in front of the firewall and in a location easily accessible to check and fill the oil when the aircraft is parked. An oil tank that requires climbing under the aircraft or removing multiple components just to simply check the oil condition, is a solution more likely to go neglected.

For our replicas, we’re finding that many WWII aircraft luckily have ample cowlings and various vents and exit air ports in which we can easily fit a tank within the natural lines of the aircraft. However, we anticipate there will be cases where we are not so lucky, and in those situations we may have to do some creative work to integrate the tank geometry.

In any case, this is but one element of the overall picture, but I hope it has shined some light on the problem for those looking into the prospect of putting a Verner on their aircraft. Let us know if you have any particular questions, ideas, observations, or otherwise!

Tried and True

A little update as we are getting ready for Oshkosh 2019. Wow, time flies! Faster than most airplanes anyway. After SNF19, we had as our goal of building and testing our wing structure. This is what we have been doing for a while now. I always think things will go faster than they do. After a lot of effort, we did it! We had to build a wing and a test fixture as well. Our engineers crunched the numbers and developed a test regime. Our team successfully tested the wing panel to it’s design limit load of 4.4 g’s with no permanent deformation. We then tested her to design ultimate load of 6.6 g’s plus as much extra weight as we could scrounge. +300?? Measurements all along the way, but after the last loading there was about an 1/8” of permanent deflection in the spar and some slight wrinkles in the upper surface of the skin at the spar flange rivet line. Compression loads were crazy high during the test and you could see diagonal waves in the upper skin. Those were about a quarter inch to their crests. This was expected and within margins. Really cool tho! The test started after work around 5pm and went into the evening till about 8pm. Many hands makes for light work and we had a great crew. Lots of 40 pound gravel bags to put on and take off the wing multiple times. After the test was over we celebrated with champagne and beer (ok, some of the beer and pizza happened during the test). The wing panel weighed 31 pounds and held over 2800 pounds. Paul mentioned after the test - “we can lighten it!” I said, “lets up the g loading!”. As of now, we are working very hard to get to Oshkosh with as complete an airframe as possible. We removed the landing gear and the unfinished center section wing panel. Scott machined some of the internal landing gear components we needed to finish and I welded up the scissor link mounting lugs and misc. gear parts. After fit-up, they are ready to paint - this weekend. The center section unfinished wing has just been skinned and we are getting ready to re-install it. We will need to cut-out and drill the two major plates that join the two wings together at the centerline of the aircraft. Then ream the mounting holes to their final size on the aircraft. Our goal is to build at least one additional outboard wing panel for Oshkosh and have her back on gear and engine installed. Then as much detail as we can add in time. Since SNF, we also covered the rudder and elevators with silver Oratex fabric. I still have to rib stitch and tape the edges. I want to paint the rudder in red, white and blue stripes if we have time. We are pushing for it! Talk soon! Will add some pics from the test over the next couple days. Happy 4th! God Bless America!

Sun N Fun 2019

Hi friends. ScaleBirds attended the 2019 Sun N Fun airshow and had a great week. We had booth N68, right next to Viking aircraft engines. Our team pulled a lot of late nights and then all nighters to get the P-36 up on gear and to the show. We did it with no time to spare. We missed the setup day on Monday and arrived at 4:30am with the show starting at 9:00 am. Then, they wouldn’t let us in to set up till 8:00 am. Wasn’t expecting that, so we managed to have a minimal setup on Tuesday and then did the full setup after hours. Steve Wolf arrived Wednesday morning with SAMSONmite and we parked her up front and center. Our P-36 stood nearby and we had the red tent again thanks to Frank Johnson.

Our project was very well received. We are so stoked! Many commented how the lines looked right and that this was just the kind of next project they are interested in. We had the skins on the Port side of the wing center section and the exposed wing structure on the Starboard side. A lot of people liked that and made comments as to the construction method we are doing. Super positive responses from the engineers, DAR inspectors and experienced builders that stopped by. As well as the other airframe makers and engine builders too. That was a real boost to our engineers and to the build team. We are building it well and designing it right. It validated the decisions that were made two and three years ago.

We had so many people interested in the P-36 and P-40 variants. I think 50/50. The cool factor of the radial is a big seller. I would say we have a dozen very solid leads for a kit as soon as it is available. For other models, the crowd favorites at SNF are FW-190 and P-47. A Spitfire is in the running too. One lady was very interested in doing the Rufe after we have a Zero developed. She had a water rating and would love the Zero. A Rufe has never been replicated before as far as I know and I might just do it for that reason alone. But it would be really cool! Just think, we could have some fun and terrorize the seaplane base!

The Verner Motor engines are selling well and it’s starting to take on a business life of its own. WW1 replica builders and other antique aircraft builders/restorers are finally starting to pull the trigger after waiting for a couple years to see how these engines go. That is really great news as it helps us fund the project and gets some really cool airplanes into the air. We have a welder now and can make exhaust and mounting rings for the various engines. We had a couple engine mounts and various parts on display for people to pickup and check-out. I gave two forums at the education center building on the internal parts and main systems of a Verner engine. Very well received. Scott had to buy a laptop pc for the slide show to run on and then when we got there - didn’t work - wrong cable port. It turned out to be an IT project to find a student laptop that had the connection - and then to get the file downloaded with the content blocked by the school. Crazy stuff happens at SNF! Insert other choice words at your leisure. WE did have a good forum each time.

I will try to make a habbit of writing more blogs. I know many of you guys are interested. Will add pics over the next night or two. Tailwinds! - but not on take-off/landing.

Some Progress!

Hey everyone. Sorry its been a long time since I did a blog entry. Been very busy with design, engineering and engine sales work. Also, with the winter weather getting closer and closer - its here now, I had to do some scraping and painting on the house and some chores that I was putting off. Did I mention raking leaves? Aargh!

The engineering effort has been in full swing. Centered around the structural loading and design of the main spar, aft spar, ribs and mounting points for the center section of the wing and the outboard wing panels. Paul made a great report for us and has been cross checking every number. This just takes time. Paul has had to figure the material and thicknesses, rivet patterns, bolt patterns and sizing for all of it. So we have been patient and keeping busy with other parts of the project. Over the next few weeks, we will be adjusting the CAD models and getting ready to make wing parts. I will be finishing the last bit of work on the tail fairings effort.

Design wise, Scott has been making progress on the prototypes’ fixed landing gear. Our approach is to make their mounting and components as much of the retract design as we can do. The down-links will likely be long fixed bars instead of articulating. Some of the swivel assembly will not be installed and the retraction/extension motor and brackets will not be installed yet. We will get it going with that and then after the flight testing is done and we have some time to work on it, we will modify the wing and gear to retract and swivel like real deal P-36. Then see how that affects the performance and make any adjustments as needed.

During late September, Scott and I went to Florida to visit one of our nine cylinder customers - Steve Wolf. We took a lot of video and still imagery of him and the Samson Mite biplane. We even bought the new GoPro Hero 7 camera and Steve made camera mounts. That arrangement worked perfectly on the wing strut for views of the fuselage. We have a couple of the easy to edit videos posted already on our YouTube channel (ScaleBirds). The harder ones to edit are going to take a bit longer. Mainly the air to air stuff. We had a lot of vibration and auto-focus adjustments that happened. Scott was riding in the second seat out in the open of an AirCam twin engine aircraft while Steve was flying formation and rolling off. The constant air blast was moving the camera a lot more than we figured. The engine and air noise was deafening too - so the audio is not likely to make the final video. We can dub in some good radial engine sounds or music. Or like some Hollywood movies, we could dub in some jet engine sound for added realism! Haha, or something crazy. We are trying to recover as much of the video imagery as we can with stabilization software. So we will be posting more videos and I promise you will like it!

Getting Back at it

Hey everyone.  We've been back now for a few weeks and getting back in the groove.  To be honest, had to take a couple of weeks off and regenerate.  Oshkosh was a fantastic experience for our team!  It was an ordeal as well.  The straight-through drive to the show .  The non-stop work to set-up, arrive early each day, work the booth, stay-late each night and then tear-down the booth, load the trailer and drive straight-through to home was rough.  Our team did get to experience the excitement, energy and enthusiasm for our project first-hand.  That was super motivation!  We met so many people who are interested in the engines and also our replicas.  We also gave two well attended forums at the Replica Fighter Association HQ building during the week.  We then had to get in on the RFA bbq on Friday after the show.  That was fun!  

Getting back into the game now.  Since getting back, I made the fairings for the tail surfaces from composite e-glass.  Hand shaped the foam and glassed them.  Coming along nicely.  Paul and Aaron are busy crunching numbers to finalize the wing structure.  We will be ready to make a test wing - thought we would be done by now but the summer got so busy for everyone that it just didn't happen.  Scott is busy with some paint-ball design projects he is involved with.  Very cool stuff!  He will be getting back into the landing gear and wing cad to finish those up.  We have several engine mounts to be fabricated for customers and for our prototype.  I will be adding some images to this post so hit it again in a few days.

Heading to Oshkosh 2018

We finally secured a booth space at AirVenture 2018.  Booth 917 is in the Ultralight area - also known as the "Fun Fly Zone".   We were there in 2016 and got a good amount of traffic.  The Homebuilt exhibits area was full so we took the spot we could get.  A mixed blessing, the North exhibits (Homebuilts) get more foot traffic, but the Ultralights exhibits puts us next to the action.  It allows us to fly the Avenger and keep it in the booth.  There is a good chance that two Legal Eagle ultralights with Verner 3VW engines will be there and flying.  We also will bring our 9S and have it on a display stand in the booth.  IF we can arrange a good trailer, we will bring the P-36 as well.  We may display it in the Replica Fighter Association area.  The RFA hq building is near the Warbirds, but closer to the Forum Buildings.  If you are going to AirVenture 2018, please stop by our booth and the RFA!  

Since Sun N Fun, we have been working on the landing gear design and calcs for the wing structure.  We designed an engine mount for putting the 5Si onto the P-36 firewall.  I'm ordering material to make that.  We plan to add some more detail to the fuselage of the P-36 and make it nicer to display.  Meanwhile, I've been repairing some damage to the Avenger from trailer rash and some things I wanted to change out.  I'm about ready to fly her again and plan to get some good video for the site and YouTube.  We are also working on securing a good trailer and a truck to pull it.  Talk soon!

At the Show!

We were all set up and running at Sun N Fun 2018!  Located at booth space N68 in front of the exhibit buildings, we were getting huge interest and great comments from the attendees.  Many unsuspecting people were snagged by the shape of our P-40/36 tail hanging out the tent.  Then were impressed by a closer examination of our prototype.  We had a brand-new 9 cylinder engine on display and  we also had the sharpest biplane I've seen at our booth.  It is a work of art!  I can't wait to see more and more of our customers aircraft installations.  Each is it's own work of art.  Then, to add to the spectacle, we also had my Fisher Avenger with the 5 cylinder located at the LSA Mall in Paradise City flying field.  I was flying the pattern there most evenings and letting everyone hear the sound of the engine and see some of its performance.   We took pics and video and will post shortly!  

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