Larry F

Hi Guys,
Don, first I hope you read this, PLEASE don't stop with your posts, I think they have been great. Rating someones comments is not a great idea. OK enough said.
Here is my next concern with the Viper. As I said in my earlier post I was a day behind getting my Viper because I was waiting for a backplate motor mount from LCS Performance, The reason I went with his or the stock mount is I did not like the idea how is was made to accomidate the differnt size engines. Well I am glad I did. We now have 7 viper out at the field, and all but one is having a problem keeping that mount tight. If you need a fix for this and you are going to fly an OS or TT engine, get the one from Lewis. Well worth the price and if you get a bunch of guys together, he really gives you a great prices.
By the way, now that we have learned from all the Viper posts on here and from really helpful emails from Irl and Lewis, the last 3 coming out to the field flew perfect off the baord


Larry

PylonWorld

Thanks Larry.

What are you seeing with incidences? Are you doing any shimming on the engines, wings, or stabs?

luv to race

My Feedback: (1)

Why would the mount from Lewis not come loose? and the mount in the kit come loose? Are they not the same style? Does Lewis' have built in "lock washers"?

There must be an explanation.....

PylonWorld

Randy,

I'll post a picture in a little while ... I have to pull my engine off.

There are four slots that the bolts go in. Because of the slots, there is not as much surface area for the cap head. Less than half as much.

I used blue thread locker on my backplate bolts. That may be why I haven't had a problem. Plus my plane doesn't have a lot of flights on it because of trying to get incidences adjusted.

PylonWorld

For those who haven't seen the Viper backplate mount up close, here is a photo that shows the slots that allow for different sized engines.

Unless the engine is the maximum or minimum size, the cap heads don't have a lot of surface, and the aluminum is probably distorting on the sides of the cap head.

luv to race

My Feedback: (1)

I see.... I was thinking the motor mount was coming loose from the fire wall. I can say that I don't care for the backplate after looking at Don' picture. But, I can see what Great Planes is trying to accomplish there....

Maybe use some blue or even red locktite...?

Larry F

Hi Don,
Yes you are correct, there is not enough surface bit for the screws to hold. I really hate to use loctite on any aluminum surface for fear of hurting the threads. We learned that years ago in the aircraft industry. If you are going to take something apart, find a way to keep it tight other than some type of thread locker, I think it is great they tried to make a universal backplate, but it just does not hold up.
Anyway, here is what were are flying with

.5 degree positive wing
0 engine
0 stab

All the planes needed some adjusting, the most common being the firewall and stab. Some of the stab are out by as much as .040" and most of the firewalls are coming out of the box at -2 degrees. Square everything up to the numbers above and it is a super flying plane.

Larry

PylonWorld

Larry,

Thanks for letting me know about the other planes. Mine was one with the stab way out, and the engine at 2+ degrees negative. I guess I was just lucky.

Now that I've got the engine incidence pretty much worked out, we're starting on the stab. At least it's adjustable ... For the time being anyway.