Getting There

Howdy folks! Sorry for the long pause. We went to Sun N Fun and what a week! Always fun and warmer than here in CT. Everything worked out great for the show. Steve Wolfs’ P-47D project was a huge hit! We could have sold 15 of them for real if we had a kit. More on that later. Terry Allred allowed us to display his 3 cylinder Verner Motor in the booth as well. I hope we will see a number of sales from the effort and that is the whole reason for going this year. We want to help Verner Motor keep busy building engines. In addition to the engine focus of our trip, we managed to re-kindle some old contacts we had and build some new relationships. Networking in a small industry. We have our work cut-out for us getting into the kit production phase. One of those relationships is with a kit industry big name. He knows the Verner family very well and is interested in helping us transform to production. Can’t get any better. He also is very experienced with getting ASTM certification for SLSA aircraft. We will see where we can go with that.

Steve Wolf is progressing very nicely on the P-47D replica. It will be a huge hit when it is flying. Jim Busha the marketing VP for EAA stopped by and wants to stay in touch with the progress - Sport Aviation feature article coming! The 47 features fully functioning cowl flaps, sliding canopy, actual 47 throttle quadrant, gun sight and stick grip. It has the turbo exhaust and inlets in the rear fuselage. Fully retractable landing gear - tail and mains. Will have guns, drop tank and bomb racks. The Verner 9S fits nicely in the cowling and with an adjustable prop will give it a great sound and good thrust. Steve is amazing with sheet metal fabrication - despite being a rag and tube aircraft builder mostly. He is having fun re-learning his metal skills. The finish is first rate and the plane looks like a production version. Amazing!

After Sun N Fun, I took a week off. I was exhausted and felt like a zombie. Maybe a bit too much heat down there. Finally started feeling normal and got back to work on the P-36. Finished up the modifications to the trailing edge ribs and added the flap spar sections after installing nut plates for mounting the drive tube hinge blocks. Each side of the wing gets four of these blocks. This last week we test fit the flaps after riveting up the flap spars - we could not test fit them while we had a bunch of clecos in the way. Found that our flap ribs were a smidge to high to nest clear of the torque tube. So we modified the fwd inch of each rib to clear. We will incorporate lessons learned in the kit flap design and they will fit up much better. The Devil is in the details! Sometimes, its just a discrepancy between the cad model shape and the actual shape after bending and then riveting parts together. Production parts would be much closer to the cad shape as rivet holes and forming jigs would be better located and repeatable. Anyway, the flaps should be installed this week and then the drive system over the following week.

After the flaps get done, we will tackle the landing gear legs. Scott has an important job to get done over the next couple weeks and then a planned trip. AFter that, we will get the landing gear leg parts completed in quick order. So I have some time to get the flaps done and then mount and adjust the propellers. We are also making cylinder head baffles to try to help with additional cooling of the heads. We may have to modify the cowl inlet shape to allow more air to move outwards to the cylinder heads with less restriction. Another lesson learned. When installing a full cowl on the Verner, allow as much distance in front of the cylinder heads as possible. We kept it fairly tight - maybe 2.5 inches from the nose bowl to the front of the heads. Steve Wolf has about 4 inches on the Samson Mite and has no cooling issues at all. Moving our cowling at this point is not easy and would likely require a whole new cowling and frame. We really want to spend the time on the next airframe if possible.

So we are getting there. Slower than anticipated and some of that is even though we didn’t have to bring the plane down to show at SNF, it still took time away from the project that we don’t get back. I was thinking we would only be about a week away from the effort, but it actually was still three weeks off from working it. We used about a week before leaving getting everything together, making new signage and printing brochures, etc… I didn’t anticipate being worn-out for a week after the show. So we are quickly running out of calender before AirVenture. We are working as hard as conditions allow. Back to work!

It's a Go!

Hey folks! We are going to Sun N Fun ‘23 after all! We have a booth space reserved - not the same spot unfortunately. We gave that up earlier when we were not planning to go. Verner Motor needed to have representation at the show and we need to help them out. So now we are in North exhibits - booth 21. It is straight out between building C and D almost to the main avenue and one spot in from the end cap.

We will have Steve Wolf’s 60% scale replica P-47D fuselage and tail on display. The wings are not done yet. He just finished the cowling and has the Verner 9S mounted. If you can make it to the show, you will not want to miss checking this out. Steve is a Master Craftsman and is not holding back. It is a tribute to his friend Jack Hallet who flew P-38s and P-47s during WW2 in Europe. Jack’s P-47D was nicknamed “Frigid Midgit” - the painter misspelled it and Jack didn’t have the heart to bother him about it. On the cowl, it had a large Snow White character - Dopey giving Hitler the middle finger. This replica has a real gun-sight, throttle quadrant and stick grip. Jack helped on the project while he still could and donated his actual flight helmet and goggles as well as a bunch of pictures and memorabilia.

Jack’s P-47 had a unique paint job. One of the plastic model companies even made a model of it with decals to match Jack’s plane. It was an olive drab painted early D model without the dorsal fin. That fin along the top of the tail fuselage was added in the field and left unpainted. Jack had made contact with some trees during a low-level prank during one of his first flights in the P-47 and the wings were replaced - they were un-painted too except for the US roundel. Jack said: “The P-47 didn’t pull out of a dive like the P-38 did”. “Pulled the nose up and it just kept going the angle it was!” Their transition to P-47 was - none. Just jump in and fly it - no manuals, instruction, nothing. The very first plane their squadron flew was damaged on landing. Jack was second or third to fly their new mounts.

Jack was a real fun guy and thanks to Steve and Kathy, I am proud that my wife Karen and I were able to meet him several times. He told us many stories and always had a good laugh. A very humble and genteel guy. One interesting thing is that General George Patton had given him a pistol for bravery. Jack was almost embarrassed to talk about it. A real Patton Pistol. He was that kind of a guy. Best generation.

Along with Steve’s Frigid Midgit, we are going to have Terry Allred’s Verner 3VL engine on display. We could not in good concience tear apart the P-36 even more and trailer it again. We need to jump right into completing it after the show. Not bringing it was the only way we could attend. Steve and Terry stepped-up big time for us. Thank You! We have the best friends!

Flap work continues and the landing gear modification to Oleo struts is waiting on a few machined parts to get made. We are going to be ready to fly in April - early May at the latest. So testing in May/June. Then, get ready for a long cross country for AirVenture ‘23 late July. That will be fun- or at least a great adventure!

March Already!

Can't believe it is March already. February was jam-packed so I guess it just flew-by. SNF is almost here! We are in discussions on sharing a booth with Myers Aviation. We were not planning to go this year, but Verner is concerned about representation, so we are gonna try - last minute! If we go, it will interrupt our flight testing, but not too much if we don't trailer the P-36.

We are on-track for completing our flap installation and the oleo strut conversion by early April. The flaps are built and ready to install. The flap actuation torque tubes and drive arms are fabricated and ready to install. The wing modifications are under-way. Those modifications involve removing the aft, lower skins and modifying the ribs to make room for the flaps. We will also install a Z bent spar for the hinges to mount to. The hinge blocks will hold the actuation drive system. The flap actuator is electric and will mount behind the pilot seat bulkhead and below the baggage space. The flap switch will be mounted to a small box that will fit on the left side-wall of the cockpit - between the throttle and the arm rest. We will have a circuit breaker mounted into the box there also.

In February, I made a trip down to Florida to visit some customers and give/receive advice on FWF installation of the Verner engines. That was a very productive trip and fun too! At the end of the month, I took a full week off to go on a Caribbean cruise with my wife-where I am writing this blog from. Yah-Mon! My first cruise - very fun! I did get sick the first night, but felt good after that.

Standing in line for a show, met a married couple-both airline pilots. He flew airshows in a Bede 5 micro-jet he built. She has an RV-8 they built. He is retired, she is still working. They know my wife’s sister who is an airline pilot. I also donated my BD-5 project to Art Nall - the same guy he sold his micro-jet to. Mine will be converted to a jet with the larger engine after his. So two of the fastest BD-5J’s. You never know who you will meet. Aviation is a small World in the sense that you meet people and they know your friends from some crazy interaction. It’s cool! Planning to meet up at SNF and for sure Oshkosh.

Just before leaving for this cruise, we got our new replacement propeller blades from NR Prop of Kiev, Ukraine. They sent it parcel post and USPS delivered it here. Only took two weeks - from a war zone! They are still in business. It is important for their economy to keep moving along so business is encouraged. They have mostly scheduled power outages from the damaged electrical grid. The blades look great. Very good quality and finish. These are not the exact same blades we had. These are going to have a smaller over-all diameter of 68". The old prop was 72". We are re-using the hub. We wanted a known performance blade and tip design for flight testing. These are a standard propeller model for NR Prop so they know the performance it should provide. Designed for 125 hp and 115 to 135 kts cruise speeds. The shape is slightly slimmer than before, but it looks WW2 in shape but with squared tips instead of rounded. I'm very eager to check the balance and install this and the 2-blade wood prop from GSC for static pull testing.

Our plan is to get you real performance numbers ASAP. March and April will be very busy! Flight testing in April and May.

Update: Trips over - Back to work! I wasn’t able to edit the website blog from the ship - internet was spotty for andriod phones. Sending it from home. Promise to update you on any SNF plans and if we get a booth.

Fresh Start

Happy New Year! Best wished to all of you and your families. We made some progress, but not as much as I was planning for - but that’s what plans are for! I didn’t plan on getting a nasty cold for Christmas. Must have been getting it right as I was writing the last blog entry. Wife got it and gave it to me - I want to blame somebody! The gift that keeps on giving! Then Scott got it and it ruined the first half of our work week. Christmas was delayed, but good enough thanks to Dayquil. The rest of my family didn’t get sick or were just finished with it and we had a good time none-the-less. Plus, it was like Artic here for a few days over Christmas and after. I’m glad we didn’t get the snow that many had to endure. Just some rain and then freezing cold. Glad to be working inside!

The flaps are designed to be split flaps like the P-36 and 40 had - except at approx. 50% of span. On the next airframe they will be closer to 60% like the real ones - since we have more aileron than needed. This thing rolls quick! I am planning to use the electric drive motor out of a Pulsar build that was never finished. We are using a square tube for a main spar and then z-bent stiffeners, piano-hinge and .125 inch thick bar stock at trailing edge for the span-wise members. Triangular ribs made of several pieces riveted-up are spaced at normal intervals to make each flap rigid and transfer the airflow loads to the hinge and the drive assembly. We are adding in z-bent spars for mounting the flap drive system hinge blocks and the piano hinges. We will be modifying the inboard and outboard wings aft of the rear spars to accommodate the flap spars and the space needed for the flaps to fit up in there. The modified ribs will get stiffeners.

Over the week, Scott worked on tweaking the CAD models and 2D patterns and then the cut path files - trying to catch-up. I spent a lot of the week working on cleaning-up parts lists (not a very glamorous job) and cleaning/organizing work spaces - basement shop and office, our industrial shop and the hangar. Trevor helped with the organizing too. Also we have been rounding up tools and equipment from our multiple spaces and getting them to the locations we will need them (haven’t been making parts in a long time now). I keep telling myself to buy tools for all the spaces so I don’t have to drag them back and forth. Someday!

On Saturday and Sunday, we did cut-out most of the flap parts and the two skins with rivet holes on the 3D router table. Will be able to finish cutting the rest of the thicker parts out over the next few days. Then will bend the parts up with the box brake we have at our shop. The steel lasered parts have still not arrived - hope they show up soon. Then can get busy welding up the flap drive system parts. I have been chomping at the bit to build the flaps and we are going to hit it hard this week and likely a few more. Then attack the landing gear mods. At least that is the PLAN now! Fresh start to the new year!

Also, here is a pic of the wood prop we ordered from GSC Systems, Inc. in Canada. This is going to just be for testing purposes and likely just a few flights. NR Prop is still alive - literally! They are working when they can on making a new set of carbon fiber propeller blades for our hub. God bless them there in Kiev.

Happy Holidays - Merry Christmas!

The ScaleBirds crew want to wish you all a Very Merry Christmas and Happy New Year. Happy Hanukkah and any of the year end/beginning holidays you practice and enjoy. God bless you all.

Many of you know that most of us on the ScaleBirds crew work a day job for General Dynamics, Electric Boat Division here in Southeastern Connecticut. The ship building industry and Electric Boat in particular shut-down the yard and design facilities between Christmas and New Years. We call it “shut-down”. Unusually creative I know. That means a whole week off from work and enough time to get a serious amount of work done on the plane. Ready for that! There are some friends and family activities to make room in the schedule for.

We have been preparing for this week for a while. The design work is done on the mods we are going to do. Some final 2d patterns to make and then we can start cutting metal. We have ordered our materials and have sent files off for laser cutting the steel parts - hope we get them this week. Planning to fabricate the flaps and flap drive assemblies, cut the wing skin and ribs and then add in the flap spars and hinges. Test fit and then paint everything. Scott will then work on landing gear parts in the machine shop. Will see how far we get in a week.

Designing Mods

Been working on designing the flaps and landing gear mods. Taking longer than anticipated - mainly due to the day jobs we have. Sorry, but the Navy wants it’s toys and really needs them. Also, its that time of the season where everyone is busy and has social things to do as well. Can’t be anti-social. That said, we are just about ready to order material and parts. I can’t wait to start the fabrication and modifications to the wings. I really like working on airplane sheet metal because it goes fairly quickly and you see the results right away. I have the week off between Christmas and New Years - gonna work on the plane as much as possible.

Scott has the landing gear changes modeled and will get to ordering parts and material this week. The lower leg/struts are going to be chromed steel with a .125” wall thickness. They are fairly short - about 12” so wont weigh too much. The rest is going to be delrin and aluminum internal parts which will weigh a lot less than the heavy springs we have in there. So hopefully we will loose weight overall. Having oleo (oil and compressed air) gear legs will dampen the landing bounces much better than the spring gear legs. Hopefully!

I am modeling the split flaps and actuation assembly. The flaps and wing mods are designed. Still working on the actuation. I have an electric flap motor that Im thinking of using, but my engineers want me to put in a manual flap handle. One less thing to fail at the wrong time - although I’ve never had electric flaps fail on me in my Cessna and Grumman flying career. Trying to find the space for it between the seat and side wall - as it wasn’t there when we put other stuff in place. Manual flaps are fun - flown with them in Cherokee’s. They are great for feedback and quick action. Flap position indication is intuitive as well and less parts. Gonna try to make that work. Either way, almost ready to start cutting sheet metal. Yah!

Elliot Seguin said he would be available in the Spring to help us out. We still have the stall and envelope expansion flight testing to do. I want to do the next flights after the mods to make sure we iron out all the issues so Elliot doesn’t have to. Way more productive to have him flying those test cards and not managing temps, pressures and stuff. More productive is more cost effective too!

We have elected to skip Sun and Fun 2023. First, we will be in the middle of flight testing and that is top priority. Getting all the test results as soon as possible helps get the Beta airframe design finalized. Second, because of the modifications, we don’t have the three to four weeks we loose by going to a show. It does take that long as the show is a full week. Sorry to all our fans that go to SNF. I love SNF and we will be there for sure in 24. Might fly down for a day or two as a tourist. Oshkosh will be our show priority for this year. We want the Beta tail kits ready asap and before Oshkosh. We have to focus on finalizing the design. With the P-36 flying, we can likely visit other regional shows after the big one.

One of the big comments we hear every year is “can you fire it up - want to hear it run”. That is a very large drawback to the Homebuilt area booths, they don’t allow any engine runs or aircraft movement during show hours. So we have decided to change our booth location for Air Venture 2023. This year, we will be in the Ultralight area. A mixed blessing/curse. There is way less foot traffic during the show. The booth spaces are larger which helps a lot. The big benefit though is we can run the engine and possibly fly the plane if we can get her in and out of the short strip. I know she can take off fine from there. She gets off quick and climbs right out. So far, my landings are too long. The flaps should help a lot. I do think we can figure out how to land her in much shorter runways once we know the stall behavior better. It will mean a lot of practice at a similar flying field - I don’t mind! Back-up plan is to push her across the fence line and run the engine. Just hearing the engine roar to life will sell engines. Seeing the P-36 buzzing around will generate all kinds of interest!

Will wrap this up here. Planning to write a Holiday entry and project update before Christmas. See you then.

Oh Shoot!

Been an eventful month of October 2022. We have been flight testing and working on temporary wheel pants and leg fairings in order to speed her up on cruise. That required attachment brackets to be fabricated and fitted to gear that were not designed for pants. We need to find out if the wing is good for stalls and for high cruise speeds in order to develop the Beta/kit version. We just need a few more flights to get that information. We need to determine if wing area, washout, stall behavior are good or need refinement. We have been fighting high engine temps which has kept us slower and lower. The cooler weather now is lowering the engine temps a little. We will get her to altitude and try some stalls and dives to check the control forces and behavior. Before doing that, I needed to get some spin training.

As mentioned before, we skipped adding flaps to the prototype. That was a mistake as landing and approaches are not a fun experience - cant see the runway over the nose. I have been holding it high for the lift needed from the slower wing, or it drops like a rock. So power and nose high attitude. I was discussing this with Steve Wolf and he was saying there are several non-standard approaches that he could show me that will help keep the runway in sight and allow for the higher angle of attack. Round engine tail-draggers have to be flown differently than a Cherokee. I took him up on it and booked a flight to Florida. Awesome trip and I am super grateful for that instruction! One of the best weekends I’ve ever had! Camaro convertible, perfect weather, some flying with an expert, hanging out with aviation friends and seeing their projects. Great food, great beer. Hard to beat!

I got back home and back to the landing gear project. The mounting brackets were not fitting correctly. The angle needed to be changed - requiring they be cut and re-welded. So instead of mounting the wheel pants, took her up for a flight to get back in the groove. We had borrowed an Ilevel BOM unit from a friend and had mounted it on the wing. Planning to get some data over the next few flights to calibrate our pitot sytem in flight. Kept the cowl flaps closed and she was climbing out at 1400 fpm at 90 mph. Started getting close to temp limit and I lowered the nose and power. Cruise climbed at 100 and the Verner’s 2000 recommended maximum continuous rpm. Got her up to 2500 feet and cruised around the airport area at different speeds and rpm settings. Did some turns and banks, dives and climbs. Was having a fun flight. She really is going to be a fun machine when we have the heat and speed issues fixed. Alas, fuel getting lower, I decided to bring her in for a landing.

Well I was a lot more at ease with the landing after Steve showed me the approaches. I chose the diving one where you stay high and dive toward the numbers and then transition to flying a few feet above the runway bleeding off speed. Well, I messed up and got her a bit too fast in the dive and was pretty fast over the numbers. Bled the speed off over the runway - its 4000 ft long so not an issue - and then bounced it, corrected and stuck the wheel landing by pushing the stick fwd. She jerked a little but other than that it rolled out straight and the engine idled along just fine. Parked at the hangar and got out. Gary was pointing at the right wheel. Bent the right lower landing gear leg and clipped the very tips of the propeller. Oh Shoot! Plus words I can’t repeat here. Didn’t seem that bad (I’m actually lucky the leg bent and didn’t break - that would have been bad). The landing didn’t seem any worse than previous bounces and I never felt the prop hit. I did raise the tail - maybe a bit too much but didn’t feel the prop hit. Well the plane is sitting there in the hangar. Still looks great - just don’t look at the wheels. Even the prop looks fine - just don’t look at the tips. All in all, lucky. It was all my fault and I should have gone around and planned the approach better.

Guessing that the extra speed added to the forces applied to the axles and our stainless steel lower leg wall thickness was insufficient. Found the weak spot! The lower leg on the Curtiss is a full cantilever unlike a Mustang where the wheel is directly under the strut. Currently, the right tire is tilting toward the gear leg about 20 degrees and almost rubbing the leg. Looks like it did rub it for a revolution or two. The left lower strut is just starting to deform - slight hint of it. But looks normal. The rest of the landing gear is fine, straight and un-damaged. The yellow tips of our NR Prop are abraded down about 3/8 from the very tip - they are rounded and so just a little material is gone - but being carbon fiber blades - they are toast. The engine will be fine - but we will pull the prop and check the hub for concentricity and square to centerline, if within tolerance and fine - will re-torque the hub bolt onto the crank-shaft. When it happened, I was trying to slow down - the engine was at idle and the prop was wind-milling. The Verner radial is very robust. She was running fine after the strike so the split crank didn’t get spun. We will have to do some ground runs and verify integrity once we get a new propeller.

Ah. A new propeller. Well the existing one was likely not the right prop for our airframe. We knew pretty quickly that it wasn’t perfect. Ideally we need an inflight adjustable to get a higher cruise speed and good climb. Also, after discussing propellers and reading everything we can find about selecting propellers, we are thinking a good part of our issues with landing and approach may be due to the propeller being a huge air-brake. A gentleman graphed various speeds and blade angles on his Zenith 750 Cruiser and found that higher blade angles caused excessive sink rate (sounds familiar) and terrible flare on landing (sounds familiar). He also plotted a 50 mph difference in 5 degrees of blade angle. This may be one reason we are much slower than expected. The wrong prop. We have a bit too much diameter and who knows if the twist in the blades has any efficiency for our speed range. We really need a purpose designed propeller from someone we can communicate with.

We are not getting responses from NR Prop - they are at war and out of power. So we have been contacting a number of propeller manufacturers. Most of the Worlds prop makers are 3 to 9 months out for delivery. Yikes! We can’t sit here for that long! We may try a fixed-pitch, 2-blade wood prop specifically designed for our flight envelope, diameter and rpm for a datum for comparison with other propellers. GSC in Canada can carve one in 10 work days. Sure, it won’t look right, but its for testing only. We want to see if it has less vibrations and runs smoother as well as the performance range. Ultimately, we want an electric three blade WW2 looking prop for the Verner as well as the other engines that will be used in the P-40. We are looking - most of the manufacturers will not supply their ground adjustable or in-flight adjustable props for Verner or other direct-drive engines. Some do and we are finding out who and what the difference is that allows it.

So we are down for a while. Likely the winter. The flying season is quickly wrapping-up here in New England - as the days will be cold and windy most of the time. During this time, we are going to mod the wing and add half-span split flaps. Scott and I are designing those right now. We will fix the landing gear and are deciding if just making new thicker walled lower leg struts or if we switch to the planned oleo gear legs and get rid of the springs. We also discussed with our engineers about re-making the wing center section to add wheel wells, flaps and 10sf of wing area or if we need to make new outboard wings with less washout twist. This all is doable, but takes more and more time. We have decided to fly her first with just adding flaps and maybe oleo landing gear legs. Might eliminate or reduce the bouncy landings. Then, get more data with this wing and then decide if further, incremental mods are required on this machine. Ideally, we want to start work on the Beta airframe asap. This delay is also a delay to our planned production start of the Beta kits. I will keep you up to date.

Going to School

Been way too long since our last update. We have been flying the Hawk and making adjustments. We are trying to find out what is causing all the drag we are seeing. She is not quite getting up on step for cruise without using a lot of power - which is keeping the temps up to the limit on the engine. If we can reduce the drag and lower the power we can see how she really flies and handles. She is designed to fly at a much higher cruise speed. If we can get her there, then we can determine our control surface sizing and forces, see if the angle of incidence is correct, look for flutter and dive speed, etc… Right now we are just flying large patterns around the airport. The oil tank mods are working perfectly. Not a drop of oil out the breather. The inter-cylinder baffles are helping a lot - we are likely going to try to add a little more baffling around the cylinder heads to help them cool better. She still gets hot, but much easier to manage.

Our main issue now is that she is way slower than expected from the drag calculations. We have several drag producing features to work on. First is the landing gear - they are fixed down. We did that to get flying as fast as possible. The retracts are a big project all their own. The current fixed gear have 600x6 wheels and tires with a thick vertical gear leg. The leg is very similar to the retractable version we have designed. Looking at old NACA wind-tunnel studies, we stumbled onto the absolute worst combination. Large tires with a thick vertical strut tight to the wheel. Then, add in the down-link and braces protruding out right next to the fairings that imitate the retractable look - and we have some serious drag penalty going on. Even in the 30’s when it was more of an art than a science, they knew to add fairings to the wheels and gear legs for a fixed gear. Curtiss added spats to the Hawk for fixed-gear export models. We are studying how Curtiss designed them and are fashioning our own gear leg and wheel fairings to see how much drag the landing gear are producing and if we can speed up the plane. We are fitting wheel pants right now. Will see how much the pants do for speed, then add the spats to the legs and see how much more. So Steve Wolf was telling me that the legs are the real culprit. He was Van’s Aircrafts first employee and learned a lot from them. He told me that when they first put landing gear fairings on the RV-4, the wheel pants gave them 2-3 mph, the gear leg fairings gave them 8 to 10. The round cylinder is the most drag producing shape due to the eddy currents it creates - an order of magnitude more drag than a tear-drop shape. Our drag calcs included a factor for the fixed gear - but may have under-appreciated the drag this gear configuration makes. Gotta find out! Retractable gear are the plan - this reinforces that for sure! The fairings we are adding now are for testing purposes only. Some customers have stated that they want fixed gear. We will develop a purpose built fixed gear and fairings that are more historically accurate when we have the airplane we want.

The next drag producing feature is the cowl flaps. I never really appreciated how much drag they can produce. We are going back to school on this drag thing. There is a reason that all the radial cowls had adjustable flaps. I always thought it was for getting the best speed possible on the fast planes. Nope. Round engine cowl flaps are draggy at all speeds. I have been talking with various warbird pilots and they all tell me the same thing: they close up the cowl flaps right before or after take-off or the plane just mushes along. A B-17 doesn’t take-off with the cowl flaps fully open. They are only fully open on the ground. Most of them have a setting that is barely open - “in trail”. So we closed ours up - they are ground adjustable on the prototype. We found that we are 7 to 10 mph faster with them closed. They are still open a little, so some exit air still gets out. The engine got hot a little quicker in the climb, but I could cool it quicker due to the faster airspeed. Just that bit of drag reduction helped to get her about on-step at high cruise rpm. Full throttle and she is behaving nicely. I just cant keep her at WOT. It is giving me a glimmer of hope that combined with the wheel fairings, we will be flying much better! Going to do more testing at different open settings to get the best compromise of drag and cooling. Ahh, flight testing!

Another drag producing feature is the wing itself. Airfoil, wing tips, root fillet, area, washout, incidence, rivet type and aircraft weight all play into the drag being produced. We have to clean-up the first two large drag buckets to understand how much of the excess drag is left to blame on the wing. Paul is thinking that our wing tip design is about as bad as it gets. How big are the wing tip vortices? The curving tip is terrible for allowing the high pressure air beneath the wing to swirl up and around the tip shape. Basically forcing it into a vortex. We are trying to do a replica, so I’m not too sure how much of that we can change before it isn’t a P-40. We may just have to learn to live with it by adding more required power or at least thinning up the trailing edge for more of the curve. Same with the wing root fillet. We made the trailing edge shape close to the P-36 Hawk’s fillet shape. It isn’t perfect, but pretty close. It starts out very thin out on the wing, but gets a larger and larger radius as it blends into the fuselage. State of the art in the mid 1930’s. On the later P-40, they kept it sharp a lot further along it’s way to the fuselage. We may find that we have to sharpen our fillet to reduce drag. Can do! If you noticed, a P-51 and all the later WW2 aircraft designs don’t have that big fillet. The Spitfire does (it’s a 30’s design), but they keep it sharp all the way. The rounded trailing edge is bad because it allows the air from the wing to mix in eddy currents with and along the fuselage. We will add yarn tufts and see how bad it is. Video coming!

There is of course, many areas on the fuselage and plane as a whole where we can reduce parasite drag. Gun sights, canopy, rivets, skin laps, paint finish, etc… However, we are trying to make a replica fighter from the 30’s. Gonna be draggy if we do it right! So we are going back to school on drag and learning some hard lessons. “They did it that way for a reason”. We will be able to clean her up and keep the look. An inflight adjustable propeller will also help with the performance effort. There are several electric options and we will be studying them for the best fit for this machine.

The good news is the plane flies nicely at higher speeds. The engine cooling is better, the handling is nice and crisp and seems very solid. This really points us to needing retracts with an adjustable prop and cowl flaps. Wing flaps will be a must have feature as well. I have no doubt we can adjust the wing design as needed to compensate for 30’s aerodynamic shaping that made the WarHawk an ICON of WW2. Back to work! Flight Testing!