ETLB Squawk Forums — Archive

A MiniMax builder from Texas gave me (for free) the empennage unit of his under-construction V-Max, after he had abandoned his build some time last year.

I am planning to install this heavier stabilizer in my Max 103, which presently has a tail group of light, weight-saving construction. My Max103 has a 5 lb dead weight in the tail for making W&B. I will obviously remove the 5 lb weight when I replace the stabilizer.

While checking the innards of the new heavier stabilizer, I notice there is a gap of 1/4 inch on either side, between the (rear) wood cross member and the central longitudinal rib piece ( see picture for details. )

I am wondering if this is the correct way to build it, and the gap is intentional.

Thanks for any suggestions / ideas.

Here is another view.

The plan shows only one RS-10 crossmember.

Walkabout , thanks for that picture. I saw my copy of the Max 1100 plans, and they are same as the one you posted.

I doubt if the builder has modified the stabilizer from his V-Max plans, so it is probable that the V-Max plans have a slightly different construction. (Just guessing, but not too sure on this.)

I am attaching a picture of the Max 103 stabilizer from my Max 103 plans. ( Not directly relevant to this discussion, but just for comparison. )

Are not all the plan sets still available on the TEAM web site? (By which I mean a FREE download?)  I seem to remember downloading all of them some years back. Maybe I am just imagining it. OR maybe V Max was not included at the time??

Oh boy, Now I am going to have to start searching through old portable drives to see if I can find them.
O.K. It looks like what Walkabout has posted is the same as what I have for Page #8 for 1550 V Max Plans.
The plan set for the 1650 Euros (page #9) seems to show an Identical photo for the same section! (ONE Cross member).
Maybe the previous builder thought there was just to much (notching) in that RS9 & decided to "modify" it for what he (thought) was more necessary strength? (Though kinda hard to imagine just adding stuff like that, it certainly would not be the first "modification" made to a Max! This site is FULL of them!
But almost ALL have been closely scrutinized by other members with LOTS of experience in the specific fields of the modifications. Be it air frame, Hardware or engine... Personally (with NO experience), I cannot see the harm in the extra cross section other than weight (which it seems you will still need some of).
I don't think the heavy tail is 5 lbs. heavier than the light version.  
PS: Nice catch to notice such a small addition. I could see where one looking at that , knowing it's the "heavy tail" could just assume that's one of the parts/pieces that make it a heavy tail. Neither the 1550 or 1650 plan sets seem to include an extra RS9 cross piece.

TTT, Thanks for sharing your thoughts on the stabilizer question. I guess you are right about this extra piece of RS-10 not being there in the V-Max plans. ( I think the cross-member is RS-10 even for the Max 1100. It seems to be RS-9 only for the lighter tail of the Max 103.)

The only reason I could think of why the original builder added this, may be because the two holes he drilled for the AN-3 bolt that attches front of the stabilizer to the fuselage, came out too close to the rear edge of the only RS-10 member. (If this indeed were the issue, I would have simply added a wood bracing or RS-10 doubler at the rear side of the hole to hold the bolt more securely, rather than add a whole long cross member.)

The large triangular 1/8 plywood gusset, glued to hold the front of the stabilizer together, did not cover the rear coss member ( picture below of the other un-opened side of the stabilizer.) This also leads me to think that the rear cross member is an afterthought / addition.

Now I am thinking, rather than cut away the rear RS-10 member, I will just keep it, and fill in the 1/4 inch gap on either side and glue both sides to the middle RS-10 rib. This extra piece won't hurt. ( This heavier stabilizer weighs 6.9 lbs; the light weight stablizer I just removed was 3.8 lbs without fabric, so the extra 3.1 lbs will help for W&B )

As a side issue, I am planning to keep other 3 components of the empennage from the light build. Since, the vertical stabilizer, the rudder, and the elevator are all supported by  the horizontal stabilizer, strengthening only the horizontal stabilizer, may possibly help. Even it it doesn't, at least it won't make things less safe. I wonder if any other builder has tried this heavy-light empennage combination.

It looks like he also added plywood to the cross member. Clearly a case where the builder thought he was adding strength but only added weight and/or he wanted freedom in locating the mounting bolt holes. The load here is relatively small.  All the horizontal tail loads are carried by the rear spar. Still this only adds a few ounces. It's ugly, but you will cover it up and we can keep a secret.

Thanks, Bob.
Good observation, about the additional ply glued on either side of the RS-10 cross member.