Airdrome Sopwith Tabloid

[Joe Perkel]

Originally Posted by drrivah

Wonder for the Tabloid-related Baslee seaplane designs, whether fuse will use different corrosion resistant alloys. Since they will be primed and painted, it may not make much difference.

You bring up an interesting question which I would like answered as well.

Where Al tube and gusset construction is concerned for float plane considerations, would it be effective to treat the interior tubes as one may do with 4130 tubing and linseed oil??

I have recently become aware of one failure of the main fuselage tube on an aged Drifter due to unseen internal corrosion. This was an aircraft that had been routinely operated in seawater.

In addition to corrosion proofing issues, (If at all possible) I think it would be prudent to provide for the occasional bore -scope access point for the main members, i.e. longerons, if such access would not compromise the tubing in any manner.

I will concede that the above issues are primarily applicable to float-plane issues as the inherent alloy corrosion resistance to my knowledge is more than adequate for landplane use.

[j ferguson]

I had recent need for a borescope and found that i could make an effective one using an auto-focus video camera intended to fit on the screen of a notebook and enable you to project your face o'er the web.

Mine needed only fit in an 1 1/2 inch ID tube, but could have been smaller had there been a need. Your's will need to clear the rivets.

I added an LED light and a target placed about 7 inches in front of the lens which forced the autofocus to that range which was what I wanted to inspect the interior surface of the tube. Then added a long stiff wire and a very long usb line so I could push it through the tube while monitoring, and recording the view with a notebook. I also lay a steel measuring tape in the bore so that I could locate the corrosion I thought I'd find.

It worked great and cost about $75. And like the usual things we run into with machinery, the possession of this wonderful tool and its use revealed nothing wrong with my tube and I could go on to finding the real problem which was much simpler - Occam was correct as always.

Building one to inspect tube and gusset might be tricky to prevent hanging on the rivets.

Or you can always say that your bird is video equipped - the borescope you were unable to extract from one of the longerons.

[drrivah]

Looks like many of the aluminum tubes are open ended in Baslee designs, so
inspection would be easier than welded steel closed tube system.

Luscombe had some aluminum corrosion issues with the carry through spar
overhead of the cockpit. The fittings essentially plugged the ends of the aluminum box spar so you couldn't readily look.

Open ended tubes mightbe a good thing, or perhaps an end cap that is easily removed.

BTW, the above home-built boroscope is way-cool.

[j ferguson]

Maybe I should post a photo in the never-go-away tools section so you can all be heartened by how much better your craftsmanship is than mine.

I'm continually amazed at how often the elaborate tools, jigs, fixtures and so forth that I whip up turn out to be time-wasters because I didn't think about the problem long enough.

I might add that I love this forum above all others even though it's unlikely that I will ever get to actually building anything that could be flown. Everyone here is intelligent, resourceful, droll, and mostly working on really worthy projects.

Thanks all.

[RobW]

The other half of Great War Aerodrome is Shelly Wells. She is the driving force behind the company... constantly pushing me out of my daily daydreams into actually doing something.

Here Shelly is burnishing the foot rests... 4 total.

She also cut out the floor board. The intent was to make it a single piece, but in the end we had to go with a two piece floorboard in order to make it easily removeable.

Here you can see the installed rudder bars, floorboards and one foot rest on each side. For the time being, the inside foot rests are not installed. If you look below the foot rests you can see the rudder and tailwheel cables heading back to the rear of the aircraft. The rudder bars are attached to the front face of the forward spar.

[

This photo shows the interconnect between the rudder bars. As I described before, the right side rudder bars control the right side rudder/tailwheel cables. The left side rudder bar controls the cables on the left side. The circuit is completed by the silver interconnect tube.

It was important to us to have rudder bars instead of rudder pedals. Several pilots have commented to us about the perceived differences in feel between rudder pedals and rudder bars. How much of a factor, well, that is debatable, but enough folks highlighted that difference to lead us to this decision.

[RobW]

Why the heck are we doing a Tabloid replica?

Hmmm... well, first off, replica is probably overstating things a bit... John M., Jeff Brooks, Paul from Golden Age Air Museum... and many others... they are all doing replicas, and great replicas at that...

What we are looking for is something that has the look of, and similar flight characteristics to a WWI replica, two seats, dual controls, affordable, and maintainable.

Any solution to that statement is a compromise.

This Tabloid is probably better described as an Imposter. From a short distance away it'll look like a Tabloid, or at least a conglomeration of the various Tabloid derivatives. Once you dig a little, you find that it is a light sport plane doing an impersonation of a WWI replica...

Engine: After much discussion, and looking at alternatives, we've decided to go with a Valley Engineering 2332cc VW (the biggest one Valley makes) with a 2.30:1 belt driven propeller speed reduction unit. It puts out about 115-120 HP at 3800 engine rpm. This allows us to swing a 92" propeller. This is not too far off the original 101" propeller and is the only solution we found that allowed us to get that close. The Tabloids cowl is completly enclosed... therefore the engine is hidden... a 80HP Gnome rotary would be wonderful... but since I don't have one laying around this is the best I could come up with.

Airframe: The original Tabloid was a work of art in wood. We've gone with aluminum tube and gussett. There are probably other ways to have done this, but since our designer is Robert Baslee, we stuck with what he is comfortable with. A great learning point with this airframe has been how easily it is repaired or modified. From an engineering and maintainablity standpoint it has proven very adaptable to our requirements.

Controls: the original Tabloid was a wing warper. Later variants, specifically the SS3 model had four ailerons (and metal struts between the wings). To keep it simple, and somewhat familiar... and make it like the vast majority of WWI aircraft... ours has four ailerons.

There were no dual control Tabloids that I know of. In fact, the only two seater was the prototype, plus and an indeterminate number of Norwegian Baby's modified as two seaters. This is another concession on our part. However to introduce folks to WWI flying... dual control is a must.

Most Tabloids had a wheel instead of a joystick. We went with a stick. Again, most WWI aircraft had a stick... sticking with our mission statement of providing a WWI like experience... A wheel would be a cool touch, but in our case, a stick is a necessity. In the Tabloid drawings, there is a drawing for a stick. Additionally, there is an interesting drawing for a stick handle with two parallel grips, sort of Dr.I ish... but that handle is marked "Cancelled". The stick however, is nice and ours will resemble it.

The Airfoil: This is the tough one. Robert Baslee knows what he likes and what he is comfortable with. Sometime in the next few days I'll post some work I've been doing comparing the original airfoil design with what we actually went with (basically a Cub airfoil).

For the time being we are going with this style airfoil. To us it is the biggest deviation from the original aircraft. Because of this, the aircraft's flight characteristics will be significantly different from other period aircraft which violates one of our principle mission descriptions. From my initial analysis, the biggest difference will be the point at which this aircraft stalls, and how it behaves once it stalls.

For instance, at 90mph, Tabloid airfoil stalls at an AOA of about 8.5 degrees. A cub airfoil at the same speed stalls at something closer to 12 degrees. When the Tabloid airfoil stalls, it has a sharp decrease in lift... the cub, well, it is like a cub... a more gradual loss of lift. Drag wise, they both have what appears to me to be about the same amout of drag (at least through normal angles of attack). Near the stall, the Tabloid drag increases dramatically. The cub... not nearly as dramatically.

I'll share more about this airfoil investigation later on the technical talk thread. I'm still looking at my data and will share it soon.

So, there you have it... where we are going, and some of the why.

Rob

[RAF56_Ball]

Hi Rob,

While there is a lot of academic discussion about the "break" at stall for early airfoils, the early Sopwith's all seem to have had good reputations. I would nto be afraid of having it on the Pup, a 1-1/2 Strutter or a single place Tabloid
.

Having said that, I think you, Butch and Russ are spot on using the modified Clark/Cub like airfoil. You all have the idea of sharing the experience with others, and although the wing loadings are likely to be light, (making a break much more gentile BTW) the overall experience for a passenger is surely to be more comfortable, so as the move said, "You have chosen (pause for effect) WISELY".
Have to get the Pup certified and flying first, but am looking hard at following with one of these. Yours are all a real encouragement.

[Dart]

This Tabloid is probably better described as an Imposter.

More gently, I'd refer to it in the same way as I do all the scale or modernized versions out there - representations.

It represents a Tabloid, but isn't a precise replica.

[RobW]

Representation is how I've referred to these in the past... and in my WWI replica database... I use that term to categorize the various replicas into groups of aircraft with similar aspirations...

Imposter is a more recent development... it is certainly more descriptive and in many respects... honest.

[RobW]

Originally Posted by RAF56_Ball

Hi Rob,

While there is a lot of academic discussion about the "break" at stall for early airfoils, the early Sopwith's all seem to have had good reputations. I would nto be afraid of having it on the Pup, a 1-1/2 Strutter or a single place Tabloid

Glenn,

I completely agree. Especially after my recent assessment, I wouldn't be afraid of a Tabloid airfoil either, and would probably consider, once we have gained some experience with this one, building new wings with an airfoil that more closely resembles the tabloid one given the structural limitations I have to live with.

Being able to consider that option... is a testament to the adapability of the basic Baslee design.

Rob