1911 Curtiss Ely Project Progress

N44VY · 18 September 2009, 03:38 AM

The above photos show center section development, and highlight the slightly different path I've chosen. The control stick has been modified so that the wheel controls the ailerons via pulleys and cable. There will be rudder pedals and "de-tuned" Cleveland brakes. The engine is a 400 hour TT C-125-2 with a 6" Saber Mfg. Hub Extension driving an Ed Sterba pusher prop. The radiator will be a clad shell only and will probably house a few circuit breakers and relays, maybe a radio and transponder. (It appears I'll have to add those concessions to satisfy TSA. The Curtiss could possibly be confused as a terrorist weapon, otherwise.) The remainder of the airframe is built to replicate the exact configuration of the Ely-Curtiss Pusher, as flown onto USS Pennsylvania on January 18, 1911. I am using archival US Navy photographs to authenticate the design, along with assistance from the Curtiss Museum in Hammondsport and Vet Thomas' extensive research and experience. The Ely-Curtiss Pusher of 1911 was unique in several ways, which I will initially replicate. If test flying proves design or performance flaws, I'll have to make changes. That's for next year. For now, the front elevator will have the top sail only, a single bamboo rod from the nose wheel fork and tip mounted brace wires. The main wheels will have forked radius rods attached to one of the front wing panel bolts and a second straight rod attached to the other bolt. The engine bay will be as with the "Military Model D", with steel tube X-bracing supplementing the wire rope and turnbuckle bracing. The wings will replicate the Ely-Curtiss and the "Military Model D" with the addition of two 30 inch wing bays between the two 60 inch bays on each side. A glaring omission, though, will be the two well dented floation tanks under the lower center section. I will wear the bicycle inner tubes, of course, but I just cannot hang a single additional ounce on that center section! The Continental weighs less than an OX-5 with all its radiator and plumbing, which helps. Still, I am amazed at the delicacy, to put it mildly, of construction. Since I dream of flying the daylights out of this plane, some original touches, such as the floats, will have to go.

This replication might cause some to cringe. I think it would make Glenn Curtiss proud. After all, his early Pushers were all unique, evolving, flying experiments. If you're wildly incensed, I'll throw you a challenge. Build an absolute exact duplicate, perfect in every respect, and come fly with me!

Note to realists: I have no doubts that this adventure could end in the trees, so to speak. Of that I harbor no illusions. The important thing is to try. If it flies, it will fly - and a lot! What say you? Bob

ulpilot · 19 September 2009, 05:13 AM

Looking really great! I hope I answered some of your questions over the phone. Had to cut it short as I was at work, so wished we could have chatted more.

Don't get too upset at the purist's out there. Every individual has their own reasons for building what they do, and why. Unfortunatley there are a few narrow minded people that can not accept another persons point of view.

I have similar discussions with Jeff Brooks about his DVII. But it boils down to it being his plane, so he can do it the way he wants, and I respect that. Only when I see something that can effect safety do I insist he deviate from the original.

By the way, are those Cub or T'craft cowls in the background? Reason I ask is I'm lookig for a decent used cowl for my Cub.

N44VY · 19 September 2009, 10:14 AM

Vet: after I talked with you, I did talk with the prop maker, Ed Sterba. His point, based on experiences with other pusher-types he builds props for is this: If the prop is too close to the trailing edge on a faster plane and/or one turning a higher RPM, there is a pulse every time the blades cross the trailing edge. Depending on the relative strengths of the prop or the trailing edge, one will crack after it reaches its respective fatique cycle. At 60 MPH and about 2500 RPM maximum, we do not figure to encounter pulses proportional enough to cause damage on my Curtiss Model D replica. Still, as Ed says, very close monitoring is required. We determined that the closest I could place the prop to the trailing edge is 3 inches, with 4" better. You and I discussed the possibility that the engine itself might flex fore and aft with power, based on the way the engine is mounted. There are plenty of cross tubes and diagonals, but there is still a possibility for shifting. It sure would be helpful if someone with Curtiss Pusher experience would sound off about this topic!

Back to the shop. I have all the leading edge cuffs formed, so today is scheduled for bending the turnbuckle and cable ears. I still haven't welded the sockets for the interplane struts, all 32 of them. That will be a good job for the winter.

Those cowls are Taylorcraft - one is Andrew King's, the other is for our T-craft project, but it's for a Lycoming, so we'll have to cut some, weld some, shape some more to fit the A-65-8. Regards, Bob C.

David Paule · 20 September 2009, 02:34 PM

Your project is a fascinating one! I enjoy reading about it.

I don't have any Curtiss pusher experience, but I once had a Kolb Firestar with three inches clearance between the prop and the trailing edge. The vibration was noticeable but not extreme at around 2,300 prop rpm. That was stock for that airplane and a lot of them were successfully flown that way.

The folks on the Matronics Kolb list figure the more clearance the better, and sometimes added prop extensions to gain more clearance. I don't remember the numbers for sure, but think you'd be fine with six inches. Also, the more vertical distance between the trailing edge and the prop center, the better. Apparently the worst situation is to have both blades within the wing wake at the same time.

They also had a prop tip clearance issue with the tail boom, and the same clearance issues and dimensions were observed there, too. They frequently used a three-blade prop to get more tip clearance and get better prop efficiency. Of course a lot of that might simply be that the three-bladed props were better-designed props than the standard two-bladed wood prop, some of them, anyway.

N44VY · 21 September 2009, 02:12 AM

David: Interesting corroboration from the Kolb camp. Ed Sterba also said the 3-bladed prop was the solution for a lot of the pulse, clearance and vibration problems modern pusher designs encounter. As you indicated, I anticipate there will be one or two RPM zones that are either uncomfortable or down-right dangerous. Test flying and ground runs will have to watch this carefully. Still, Dale Crites had a lot of fun in the 70's flittering around in his Curtiss at OSH, so we know it will fly.

Spent the weekend building some of the engine bearer tubing supports. Will try for this week to get the dozen or so other pieces cut, bent, welded and drilled. Working on the aft elevator, too. When I get tired of bending steel, there's always woodwork! I'll post some photos later in the week if I can. Cheers! Bob C.

David Paule · 21 September 2009, 07:06 AM

Actually, that 2,300 rpm was about the maximum I remember. It was cruise for that plane. I don't remember if there was vibration above that, there probably was, and below that it got better.

I wasn't meaning to imply that there would be certain rpm bands to watch out for, just that at typical rpm that you'd have on the Continental, there would be an effect.

Interestingly, the change in airflow was distinctly noticeable from the ground. That particular Kolb had intake and exhaust silencers and the dominant noise was the prop beat.

N44VY · 23 September 2009, 02:10 PM

Don't know if you've heard the unique sound an OX-5 with straight stacks makes, loping and clacking along at low RPM, but that is the sound I want to work towards with this Pusher. We are going to have straight stacks, except one reserved for carb heat. I'd like it to sound like one-half of a Merlin, which can be done if we work at it. No silencers for me! The only drawback on a modern engine is that HP comes from higher RPM and fewer cubes. Without a reduction box I can't get the prop down to OX-5 rev's. Still, who cares, as long as it flies. Working on the bamboo front outriggers still. Couple of stumbling blocks, but no drama, yet. Bob C.

N44VY · 22 October 2009, 03:35 AM

Gents: I have hit a small snag in building the horizontal stabilizer on the Ely Curtiss Pusher. Included are stab photos of the dark blue USMC Triad and a second Pusher. The Triad has the rudder hinge post going simply thru the stab spar. The cream colored Pusher has a large, built-up gusset at the juncture where the rudder hinge post passes thru the stab spar.

I am building this replica with the Schultz drawings, which show a gusset at this juncture at the center of the stab main spar. However, it appears from the Schultz drawings that the rudder gap as listed in the drawings does not account for this build up.

Has anyone done some homework on this or built their way out of the conundrum? I favor the gusset because it obviously would strengthen the spar where it is drilled for the rudder hinge post. What I want to avoid, though, is creating inteference with the rudder hinge and/or rudder free travel left and right.

Assistance, analysis and advice welcomed! Bob C. BTW: I'll post some progress photos as soon as I get a bundle of parts back from the powdercoater. Not much to look at with everything disassembled, now.

N44VY · 22 October 2009, 03:37 AM

N44VY · 22 October 2009, 03:45 AM

Note the wider gap in teh rudder, above the rudder control horn, as well as the large gusset at the rudder hinge post.

This replica was built for the USAF Museum at Dayton in the late 1980's, I believe. Note the tacks and upholstery nails used to attach teh fabric. The wing fabric was fastened to the ribs with rush strips nailed thru to the ribs with the same button-head upholstery nails.