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PostPosted: Fri Jun 03, 2005 10:30 pm
by art
Plenty of Views / One Interesting reply.
I'll ask it this way. Has anyone seen a Tricycle gear mod? If so, what do you think? Art

PostPosted: Sat Jun 04, 2005 11:40 am
by Chappy
Before he designed the Vampire, Bill Sadler was a Lazair owner, and then dealer. He was the first Lazair owner, IIRC, that installed a lower control stick, and one of the first to convert to steerable trigear. I think he sold conversion kits. Don't think they were a hot seller.

Personally, I don't think much of converting a Lazair to a nose dragger, as it just doesn't offer any of the benefits usually associated with that mod. Because there is so little mass out back anyway on a Lazair, and the rudder forces are quite good, it's probably no easier to land and takeoff with a trigear setup, so why bother. You lose some rough field capabilities, and it just plain looks wrong too!

But then, who am I to discourage mods. I do love my wide gear, etc. on #25.

Just my opinion,

Chappy

PostPosted: Sat Jun 04, 2005 1:32 pm
by Guest
What Series Lazair are you talking about ?? Isn't a Series 2 already a nosedragger ? One thing about a nose dragger Series 2 is you can land and stop in a short distance on smooth grass.

Chappy with your experience how do you feel about what is apparently a stock Series 2 equipped with F-36's/re-drives, 9' extended ailerons, and wing tanks. Is this asking a bit too much from the original design ? Lazair is strong but come on ?

PostPosted: Sat Jun 04, 2005 11:56 pm
by Chappy
ALL Ultraflight designed Lazairs are tail draggers. The series I didn't originally have a "nose wheel", which is actually an added revolving skid, if you will. Actually, my parts manual dated May 1, 1982 still doesn't list a "nose wheel skid" assembly, but the upgraded tundra tires and Rotax engines are shown. The landing gear is only slightly ahead of the CG. With the boom tube held level, there should be several pounds weight out at the tail. I'm tired and I don't remember exactly how many, so check me up on how many. Early on, several pilots let their planes dig the nose in and flip over, so the wheel was added. The series II had the same main gear placement. It wasn't until the series III that the gear was moved forward a couple inches and a more conventional tail dragger configuration existed. If you own any (unmodified gear) Lazair, and when you get in the seat, it flops forward onto a wheel, you've got a CG problem!

If those are the re-drives I've seen pictures of, I would be much more concerned about the thrust line not being in line with the center of the original engine mounts position. As power is added, the re-drive axis will be pulled out of line. That puts uneven loads on the mounts and nacelles, and wings, plus the thrust line will change when power settings change. All bad things. That was the first item I addressed when I designed mine. There are pictures of mine on one of these Yahoo sights where you can see how the prop is still in line with the center of the nacelle even with the re-drive.

I've flown factory 2 seat prototypes using the NGL/Westlake and the KFM twins mounted on series I .016 spar wings. The wing had a .020 cap added over the spar as with the normal Rotax engine mod retrofit, and may have (?) had the stiffeners added to the drag box assembly, I don't remember. Don't know how long they would hold up, but my Pioneer re-drives have over 400 hours on unmodified, uncapped .016 spar wings. I look for cracking, haven't found any. (OK, I confess, they are modified - I replaced the original aileron cables with pushrods).

9' long ailerons - why? You want MORE adverse yaw?

Chappy (Wishing people would sign their posts so we know who's who!)

PostPosted: Mon Jun 06, 2005 9:22 am
by xgary
chappy,

here is what i wrote ont he CAREL topic over a year ago.


http://lazair.com/forum/index.php?showtopic=103


Sorry carel, but I have invited you her a few times to help you out and learn about your lazair that is extensively modified. Hope it works for ya man but heck be careful..

Hell chappy musta read my post to have smae thoughts? or are u just a knowledgeable fella?

SIGNED BY SHORTY :)

PostPosted: Tue Jun 07, 2005 10:25 pm
by Chappy
shortnaked @ Jun 6 2005, 10:22 AM wrote:
Hell chappy musta read my post to have smae thoughts? or are u just a knowledgeable fella?

SIGNED BY SHORTY :)



Well, Shorty, since I designed and built my re-drives almost 25 years ago, maybe it's more likely you saw the pictures of them, and then commented on Carol's design last year? (Shorty goading me on again.)


Or, more likely, we both recognized that having the thrust line offset from the centerline of the nacelle mounts was not a good idea for the reasons we mentioned earlier. I'm sure we're not the only people to have looked at that design and know it's "not right".

Chappy

PostPosted: Wed Jun 08, 2005 12:28 am
by JPXman
on a standard nacelle with the rubber mounts in two rows, along top and bottom, as long as the centreline of the thrust acts somewhere between the two, I would think this would be satisfactory as well. this would only induce a tiny moment on the D-cell due to thrust if it was between the top and bottom mounts.

PostPosted: Wed Jun 08, 2005 6:54 am
by xgary
tyler -- this year you think it not good to have the centerline trust off center?

I say torsional twist on spar/D-cell could be a problem. But i standto be corrected upon flight testing.

:)


JPXman Posted on Jun 8 2005, 01:28 AM
on a standard nacelle with the rubber mounts in two rows, along top and bottom, as long as the centreline of the thrust acts somewhere between the two, I would think this would be satisfactory as well. this would only induce a tiny moment on the D-cell due to thrust if it was between the top and bottom mounts.


last year it was ok ?

JPXman Posted on Mar 9 2004, 12:02 PM
it seems to me that people have been flying on redrive 185's with 44" props for 20 years in British Columbia. The fact that the thrust centreline is actually lower will help reduce pitch/thrust sensitivity in my mind.

of course, simply my opinion! I think they look sweet and will work fine - we're not flying the space shuttle here with ultra-fine tolerances.

I would however hope that Carel incorporated the "long bolt" modification to his engine mounting strategy, and incorporated a method of distributing the new longitudinal torque about the D-cell from the hefty amount of additional off-centre thrust - could be in the form of the extra plate on the top and bottom that is added as part of the long bolt mod. But if his craftsmanship is any indication, i think its all great.

I say giver Carel.


Tyler

PostPosted: Wed Jun 08, 2005 9:42 am
by rayjb60
Some redrives can be rotated for either a top or bottom centerline orientation, but I wonder if a left or right side is also possible....or you could turn the whole engine sideways in the mount perhaps.

if the thrust centerline is still in line with the wing, it would be best.....although you would still want to reinforce the spar attach points, but at least you avoid the torsion on the spar.....I suppose its a bending force now instead, but probably less problematic in the long run.

Ray