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PostPosted: Thu Mar 13, 2008 7:50 am
by Shannon
Hi Mick, the front clevis modification (extra two bolts) is definitely something to consider. The F-9's hardly had any problems on Series 3's unless the plane went up on the nose ect.. It woud be a judgment call on you to either go with thicker metal or go back with original.
There are quite a few minor mods that can be made in certain areas. George's plane incorporated many (if not all) the improvements below. You guys can help me out with any I miss or others you feel are good.

Compression tube motor mounts with improved motor mount pads
R-3 rib doubler
Capstrips (We have always stripped top and bottom all ribs)
Box section stiffeners
R-8 doublers
Sharp trailing edge
Improved throttle cables (and engine attach brackets)
Throttle quadrant rear cover
B-7 bushing doubler
G-25 (end of the wing plates) strengtheners

If you have looked at pictures of George's plane you will notice he also has a different type bucket seat, self retracting (reel type) shoulder harness, and upright mounted fuel tank.

One question I had was what caused your engine failure ? Some common reasons for failure include carb coming loose, sparkplug cap popping off, or compression release failing.

PostPosted: Thu Mar 13, 2008 9:31 am
by mickbroom
Thanks for that.
I have got a lot to learn about Lazairs ( and am looking forward to it).
The engine failed due to fuel supply, it had not been run for some time and it stopped just before the hedge at the end of the strip. Dave managed to zoom it over the hedge into the next field which was full grown rape and while he could maintain hight on one engine he could not climb and with no open gates to fly through had to put it down in the crop which flipped it onto its back <_<
He always had trouble with air in the lines and still had the primer and two tanks which did not help. We needed the tanks to increase the range to qualify for the Championships.
When flying the Lazair I like to keep things simple both in operation systems and instruments as to me its part of the planes charm , chuck the radio and a bit of string for the instruments, OK a compass for cross country and Verio when hunting thermals is handy.
Will check out your list so I understand it.
Its good to have as we have not got the air hours over here to find these things out.
I would guess that Dave has the most hours when he did about 100 the year of the competition

PostPosted: Sat Mar 15, 2008 11:09 am
by Shannon
No problem. You can use the "search" function with keywords to look up information. Type in "rivets" for example and set up the search parameters..i.e "All Forums"... "Any Date"..."Including Words" ect.. and you can pull up posts that contain the keyword you put in.

Faulty fuel systems have been responsible for many Lazair accidents. My Dad for example had a forced landing on his second flight because of a faulty primer bulb. After that greater attention was paid to the fuel lines and primer bulbs were never used again.

I wanted to mention that if you made the front fitting modification (extra two bolts) you could possibly utilize nuts on the backside of the front fitting (like the existing bolt) rather than using drilled and tapped holes. The drill/tap method was developed for front assemblies that were not going to be removed from the boom tube.

Definitely nothing wrong with a minimalist approach with instrumentation. I know of many Lazairs that were flown with nothing more than a Hall indicator.

One thing I've been wanting to ask about is the apparatus attached to your front fuselage down tube. You have what appears to be either some type of trim system or control adjustment mechanism. Could you give details on what you have there ??

PostPosted: Mon Mar 17, 2008 10:48 am
by mickbroom
Thanks for the search tips.
We have a pitch trim lever on the front, basically a stiff lever connected to a spring.
I have never flown it without so do not know how nessessary or effective it is.
All these cool pictures of Lazairs in the snow I am afraid I cannot match, we have no mountains very little blue sky and not a lot of snow for the last few years in our winters. hopefully the summer will be a good one with less rain than last year (and the Lazair flying).
The picture of your front assembly is completely different to mine in the thickness of the metal and extra plates and support brackets, scary!
While the safe thing to do is to beef all the bits up I need to watch the weight as it needs to stay under 115Kg dry but ready to fly otherwise the paperwork and silly requirements make it a no go.
Unfortunatly I have no actual weight for this machine but its listed as 95Kg but is probabaly more.
What is a typical weight of a Lazair?
A good tip on the bolt arangement, what about two steel rivets instead?

PostPosted: Mon Mar 17, 2008 12:20 pm
by Shannon
The front assembly in the picture belongs to Karl Petruch. He re-worked the front assembly on a project plane some time back. He may have used thicker than standard metal "all around" on the re-worked assembly. I included the picture so you could see the additional two bolts that were added into the center of the assembly. Here's the earlier discussion on the assembly by Karl. ... #entry2970

The picture of the Lazair in the snow with the beautiful blue sky and mountain backdrop is of George's plane.

Upon closer inspection it does indeed appear you have a front assembly quite different than normal. It appears your F-9 is not a seperate piece like all that I've seen. You may need to replicate exactly what you have there as a replacement. How best to strengthen and modify your front assembly would be totally up to you. Best I can do is provide a few ideas/info on what I and others have done. By the way the extra two bolts in the front assembly was a factory modification I believe. If nothing else you could make the connection and ship your front assembly off to Karl for total rebuild (if he was interested in doing it).

In the case of weight being a super critical issue obviously it would be advised to not add any additional weight. If there were any reserve capacity for extra weight some of the upgrade modifications, compression tube through-bolt motor mounts for example, make good sense. The weight of this modification along with several others would surely be less than that of an extra fuel tank and the non-factory fuselage brace tubing on the plane.

Earlier you had mentioned some dents in the leading edge of the wing(s). Typically damage of this sort can't simply be pushed out. Damage usually requires that an overlying skin doubler be placed over the dented-damaged area. To keep things symmetrical a corresponding doubler is placed on the other wing.

The typical bare bones (factory stock) Series III should weigh in around 210-220lbs (95-100kg).

It would be super if you could post some pictures of the pitch trim lever for viewing.

PostPosted: Mon Mar 17, 2008 1:57 pm
by Shannon
Now for a look at how I reinforce the front assembly. "L" brackets are placed on each side of the boom tube to help prevent clevis rotation. The F-9 doubler is visible on the bottom of the boom.

PostPosted: Mon Mar 17, 2008 1:59 pm
by Shannon
Later (when I get the chance) I'll be drilling and tapping the fitting to accomodate the two extra bolts.

PostPosted: Mon Mar 17, 2008 2:01 pm
by Shannon
Bottom View. We have never really cared for how this assembly was made. It's my opinion that modifications to strengthen surely can't hurt. Guys with Series 2's that are constantly on the nose should pay special attention to the F-9's as they can and will break from repeated stress.

PostPosted: Mon Mar 17, 2008 6:07 pm
by russell

As for the solid rivets securing the F9, look at the head of the original rivet. There will be either no symbol or one of many. Go to this website to see the different symbols and the type of material they represent.


PostPosted: Mon Mar 17, 2008 6:19 pm
by russell

I really like those pieces you made for the added support for the F9 and the clevis. This is something I plan on incorporating. I've had the boom plug out twice now and I'm concerned about the small tabs on the plug that fold back into the boom tube that accept the rivets. This "L" bracket and the F9 strenghtner bracket will give me a great deal of confidence that the wings won't leave me. The clevis on the series I can't be modified with the two bolt setup as is so this will work as well. Thanks for sharing.