Mark O: I like the DB quote, hadn't heard that one before. I hear ya about limited storage space. I kinda have the same issue. Keep going on that TT!


WEDJ: Thanks for the link! It's great idea!

I almost have the mock up done. What I did was to build the section of the wing that houses the gear to make patterns. This way, I wouldn't ruin the ribs and could make sure all would fit well. I happen to have a single Rhom Air retract that as far as I could determine, is the same size as the Spring Air. I'll post some pics in a day or two.

FB

Yes, I think Spring Air "copied" the Rhom air footprint to make an "improved" version that fixed the single biggeest Rhom Air problem, namely loss of air pressure caused a destructive landing.

Gear up, gear down, it's a good thing.

Never once did I have a Rom retract fail to retract or extend and I flew them quite a bit.

On the other hand, those individuals that cut the tubing off of their fittings while changing the gear from one model to the next, or who needed to remove the gear entirely from the model for servicing, had problems of blowing off pressure lines, leaking pressure lines, etc.

Learning that one always pulled the tubing from the pressure line and NEVER cut it off with an X-acto knife is one of the best kept secrets in pneumatic retracts. I was grateful that my mentor, Syd Clement, passed along this secret to me. I used to watch the other fellows struggle with their Roms, and other pneumatic gear. I can still hear the sound at the contests on hot summer days, "POW! Shsssssssssssssssss". <G>


Ed Cregger

Weren't the Rohm airs the ones that used monofillament fishing line to steer the nose wheel?

Seems I remember that you had to get the tension just right...
Too loose (LeTrec) and it wouldn't steer.... too tight and the gear would not extend all the way and wouldn't lock down.

A friend of mine had a Banshee, with some rash under the nose...

Yes. It sounds like an awful system, but it was very easy to set accurately and it worked without problems. Very ingenious.


Ed Cregger

Sorry for the delay guys, you know how life and work can get in the way.....[:@] So on with the build.

The J&J kit was not meant to house retracts, so you have to engineer this on your own. If I'm not mistaken, in later kits, J&J included a separate drawing showing how to modify the ribs for retracts. They did do this with the Troublemaker as I have a copy. I'm sure that retract installation in both the Banshee & Troublemaker would be very simular, so I used this as a guide.

Before getting started, the ribs need to be cleaned up from the CNC cutting. On my example, there was some tool chattering that needed to be removed. Because the wing planform is tapered, the ribs need to be sanded in pairs. I used binder clips to hold the ribs together, which works very well.

In this close up pic, you can see how rough the ribs are.

After sanding the ribs, they should be smooth and even. Also while the ribs are clamped together, check the spar slots and adjust them as necssary. All of mine were a little shallow and the spar was a little proud of the rib. It's a lot easier to make the spar fit now instead of later as you build the wing. When you're done, you'll have 11 pairs of ribs that are excatly the same.

Remainder of the pics, file was too large to upload in a single post.

As mentioned, I decided to make a mock-up of the wing section that houses the retracts. Now that the ribs were sanded, I made copies of ribs 2, 3 & 4 and built that section on the plans. I didn't want to hack up the kit ribs, as I knew that there was going to be a lot trail & error cutting up the ribs. Using the Troublermaker retract drawing, I made the ply mounting plate from 1/4" birch ply. I had to change its shape slightly as the Banshee wing isn't tapered as much as the Troublemaker. For maximum strength, I decided to place the plate against the spar and to keep the gear as close to its original position. I cut up ribs 3 & 4 for the plate making sure it was flush with the spar, with the back side of the ribs and flat so there wouldn't be any binding. Next, rib 3 & 2 are cut for the wheel well and the gear leg. I also made a floor for the wheel well from 3/32" balsa. The sides of the well will be sheeted with balsa later during the wing construction. In the pics, ignore the gear leg, it's just a dummy piece of wire to establish the length of the leg for the wheel well.

I now took the wing section apart and cleaned up the ribs. As you can see, the ribs were cut up a quite a bit and a lot of trail and error was needed, mostly on ribs 2 & 3.

Now, I used the pattern ribs and traced the cutouts on to the wing ribs. In the pics, the cutout has already been made in rib #4, there wasn't much to see.

Now it's time to determine the ply reinforcements so everything stays intact. Using the modified ribs, I traced them onto a file folder and drew the patterns for the ply reinforcement plates. On the front, I extended the ply between the spars, and at the rear, past the mounting plate by a 1/2". This should hold up well. I then cutout the patterns and traced them onto 1/16" birch ply and cut them out with a scroll saw. Don't use lite-ply anywhere for the gear installation. Looking at ribs and how thin they had become, I decided to laminate both sides of the ribs for peace of mind.

Here's the ribs being laminated. When this is done and the ribs cleaned up, wing construction can start.

Lookin' smart!

Quite a bit of gear engineering there, good job. Gotta get back to my Perigee.............

Thanks WEDJ - having the Troublemaker print was a big help.

Update: My retracts arrived today! Woo-hoo Also, Don (from Eureka Aircraft) sent me the wood parts
for the canopy. Now I can really get back to the build.

FB

Good deal! Let's see progress, pictures, text, etc.

Oh, am I asking too much?

Hey, throw us a bone - pix of the Primus?

That is an excellent method of building a mock-up first to get the cutout patterns. Great work!

David

WEDJ: Primus pics will happen at a later date. Need to stay on track with the Banshee. Winter is quickly moving on......

David: Thanks for the kudos. First time around for this. All the other kits I've done in the past, retracts were part of the design.



Well, I had planned spending the day building, but I got a call and gotta spend the day at work. [:@][:'(][][&o] Hope tomorrow is a better day!

FB

Bummer!

Today I'm moving the shop around a bit, and cleaning up.

Clay: Thanks for the pic!

OK, I've been playing with the retract setup for the nose and it looks pretty much like the pic in post #17. However, I'll be using a Sullivan 12 oz slant tank (the plans show a Pylon Brand tank & the Sullivan tank is indentical). The problem with this setup is that it raises the tank, which would now be too high for the carb. Would a belly mount gear setup save a little space and lower the tank? Does anybody have an Spring Air belly mount and some dimensions for comparison?

Second problem: If I use an OS 61 engine, it's 1/2 inch longer than the placement of the nose ring. This is with the engine moved as far back as possible on the engine mount. To keep the 2 1/4" spinner diameter, the nose blocks have to be made longer and wider. Would it be easier to move the firewall back the 1/2"? Would there be any CG issues keeping the firewall in the stock location? I really don't want the model to be nose heavy and have to add dead weight to the tail. Does anybody remember if the Banshee had any CG issues?

FB

Both of my Banshees balanced without adding weight, except for the nails in the left wingtip.

Here's dimensions for you:

http://www.retracts.com/Retrax_200.htm

I vote for moving the firewall back. The Blackhead 0.61 was a pretty light engine. If you need tail weight, the servos could go back there. Maybe make for that provision while the sides are open.

Another option that I'm looking at is to use an OS 55AX with a tuned muffler. There's a thread with I believe some numbers
and the combo was going to be used in a Mach 1. The Banshee is a smaller airframe, so the weight savings would be of
benefit. This would probably allow the firewall to remain in the stock location. Thoughts??

FB

Rick:
I am very impressed with Nic's 55 on his Sr. Falcon. Even with the regular muffler it is a real gutsy engine. Have just ordered one to evaluate for my Tiger Tail. I think the 61 is heavy enough that I don't think you will get away without adding tail weight. The 55 should be awesome with a tuned muffler.

Hope this helps.

Peace

Mark O