Jim's XL build D-25

[liteflyt]

Tom H: Wrote in #74

"We had to >SNIP<....  It flew and landed great; just did not have enough hp for climb."

 Could you put some estimates on this, i.e, rate of climb ( feet per minute ) at what was the all up weight...
Thanks;
Rodger

[Tom H]

Rodger, our LEU, Treehugger, was heavy, showing 273# on our scales, which we think were reasonably accurate, maybe reading slightly on the high side.  But, the airplane was heavy, no matter the numbers.

We were going to carry a vertical speed indicator to measure the rate of climb to help with improvements, but never got to do it.

I would say with our lightest pilot, about 150#, it would climb a couple hundred feet / min.  This was with a 54x20 prop, full throttle about 3200 rpm.  He could get to cruise and throttle back and maintain altitude.

With me, the heaviest, around 225#, it would climb maybe 100 - 150 ft/min.  I never could throttle back and maintain altitude.  I tried for max altitude one fine, clear, dry day, and the highest I could get was 1000 ft AGL.  That was it.  

Our engine, at full throttle using the wood bar dynamometer, produced 29 hp at 3400 rpm. 

I believe other LEUs experienced similar lethargic climb, and now most of the guys seem to be going for the bigger displacements, getting mid 30 to mid 40 hp.  We were looking into increasing engine stroke, but, again, never got there.

Hope this helps,
Tom H

[grdev]

Tom I wonder what can be expected with the XL? the 1/3 Corvai is supposed  to put out 35 HP, at 85 pounds but we all know in the real world weights are higher than they are supposed to be and HP is always lower. I'll have to check in with the Ultra Vair group and see what their actual HP and wt numbers are. Don' the XL have a larger wing than the LE and some other differences to accommodate the more robust pilot? There are just two many towers around now that reach 1000" AGL or higher for me to feel comfortable.  I was figuring on loafing around at about 2500 AGL around 24-2500 RPM.
Any ideas why you plane was heavy? Now I wonder should I just go ahead and build mine as experiential and use a redrive or say a 1600 VW? wonder how many problems I would run into there. Gotten a little heavy over the fall and winter, but my goal is 225 by early summer, maybe I'll have to rethink that, but at my age the pounds just don't fall off.

[Jlwright]

Looking at several pictures of finished Eagles I have a question about why there is such a large gap between the bottom of the vertical stab and the top of fuselage. Seems like it would look better if the gap was closed up to a much smaller amount. I'm curious about the reason why.

[Tom H]

Gil, our LEU was heavy for several reasons.  Probably the main reason was it was built by a group, and we pleasantly agreed on things, which led to heaviness, rather than fight to keep it light.  Sort of the "designed by committee" result.  Weight creep.  If we ever resurrect it, I think I could get a bunch of weight off of it.  Didn't listen to the voices of this group that stress "keep it light".

Regarding the hp of the 1/3 corvair - I'd like to see results from a dynamometer test of the engine.  HP results across the rpm range at full throttle.  Or, at least, a wood bar dyno test like we and several others have done on the 1/2 VW, which gives a hp/rpm reading at full throttle, a single point, but better than just a lot of claims thrown around.

I know very little of the XL, but I believe it uses the same wing design, but longer span, but still keeps the weight at legal ultralight.  Correct me if I am wrong.  If so, as I understand it, it should climb better, all other things being equal.

[grdev]

Tom, I'm not familiar with the wood beam dyno, so I looked it up. Now I see basically what it is, but I don't understand just how you derive actual results. Any simple explanation?
Thanks
Gil

[Tom H]

Gil, we're sort of hijacking Jim's topic with this subject of wood bar dynos, so I started a new topic under engines/2 cyl.

Hope you can find it.  I noticed that Les Homan recently posted some results of his wood bar dyno tests there, too.

[grdev]

found it, thanks

[Jlwright]

Looking at several pictures of finished Eagles I have a question about why there is such a large gap between the bottom of the vertical stab and the top of fuselage. Seems like it would look better if the gap was closed up to a much smaller amount. I'm curious about the reason why.

Just wanted to bump this to the top.  It got buried the other day.

[Bob S.]

I filled in the area between the vertical fin and horizontal with thin flashing. It makes that area look more finished. 
I don't really notice much difference in the flying ability of the Eagle..

Bob

[Jlwright]

Thanks Bob.  I wonder why they didn't just make the stab fit closer in the first place.

[Bob S.]

Ease of construction....

[Sam Buchanan]

Thanks Bob.  I wonder why they didn't just make the stab fit closer in the first place.

Jim, install the vertical stab root rib as close to the bend in the leading edge as possible and you will have a minimal gap. You can also move the stab closer to the fuse, just make sure you leave room for the horiz stab.

[Jlwright]

Thanks guys.
The fuse is out of the jig and ready to finish weld. I need to rig up the rotisserie now.

[hvacrbert]

looks great looks like you have been putting a lot of time in there.