Hey DaveGee, go to: RC Warbirds and Warplanes under the Airplanes Forum. Go to page 5, scroll down past the middle to Charlie Kellogg's TBM Avenger Build. That is my build, however, I have had a few set backs and all my buddies have finished their Avengers and waiting for me to get my @#$% together and finish. I'm a bad modeler because I am also finishing up on an L-19 Vailly BirdDog also on the same Warbird Forum. Certainly expect to get back to both airframes. The Bird Dog only needs priming and painting now that I have corrected the washout I forgot to initially build into my wing panels. Hummmmm. The TBF Avenger I am building is huge and your hook plane will be perfect. Chic

P.S. The Grumman TBF-1 Avenger landing hook was stowed internally while the TBM -3 Avenger landing hook was stowed externally. Lucky me, I am building a TBF-1. Chic

Hi Chic: looks like a marvelous build! You should have plenty of room to put the tailhook in there. That would really look cool doing the low pass with gear, flaps, AND tailhook down! There may be others who have done this before, but if they have, I haven't seen them. Good luck with your tailhook add-on. Let me know if I can help out at all, and especially let's see some pics when it is done!

davegee

Well, now you know how to build the internal tailhook! It looks cooler, anyway!

Good luck!

davegee

Well, I did an operational test of the tailhook this morning with the magnet, but unfortunately I still don't have a permanent solution to the airloads blowing the tailhook almost straight back during flight. That magnet is powerful, and on the ground you would swear it would hold the tailhook fast to the back of the fuse at a 90 degree angle, but I think the airloads keep it from getting close enough to snap onto the magnet as the hook pays out. I am going to try a small flexible plastic tab that will put a little pressure on the hook to stay close and snap onto the hook; see if that works.

The actual deployment/retraction of the tailhook is perfect. There are absolutely no issues there. I just need to be able to get the tailhook to stay down during flight.

On other warbirds, say, like a Corsair or some versions of the Avenger where the hook is outside the fuse, it is easy. I have already done this on an ESM 85" Corsair that was a display model only, but I wanted to look into the idea for a flying model tailhook in the future. Just having a fulcrum attached to a servo will lever the tailhook down into position without any problems because the tailhook is anchored to a lever arm that keeps it in place.

I still think the tailhook idea is cool, and I will pursue a fix for the Hellcat tailhook.

cheers

davegee

One thing that just occurred to me is the method I used to deploy the tailhook and it not going to the full 90 degree down position from the fuselage. I was concerned that rapid move of the knob on the transmitter might mess something up on the tailhook deployment. I have found that rapidly moving the knob to the full down position for the tailhook makes it snap onto the magnet that is glued on the bottom of the fuse almost instantaneously, and the whole unit seems to be well designed without any damage while doing this.

Next test flight I am going to move the knob rapidly to the down position, in the hopes that the tailhook will grab onto the magnet before the airloads can push it back in the airstream, and away from the magnet so it can't hook onto it.

I also added another rare earth magnet below the first one, this a 1/8" diameter and about 1/2" long that is glued below the first magnet, and into the fuse. The two magnets together really grab onto the tailhook, I just don't know yet whether it will be enough pull to offset the airloads.

More later.

davegee

Hi all: well, the technique of rapidly moving the tailhook down didn't work. It still wasn't enough to counter the airloads while flying to lock it onto the magnet.

I did some more experimentation with trying to find a cable or flexible strap to keep the tailhook from blowing back into the breeze after it is deployed. None of these ideas worked, mainly because of the geometry of a 4 inch tailhook inside a tube that has to come out all the way before it can drop down making a 90 degree angle with the fuselage.

So, the latest is that I went to Home Depot hoping to find a piece of thin piano wire to wrap around a 1/8" diameter tube a few winds to make my own spring. Unfortunately, they didn't have any piano wire, but I did find a little package of assorted springs.

So this is what I've done for this attempt: I found a 5/8" long compression spring that is a little more than 1/8" inside diameter, or in other words, it slides onto the joint that has the robart hinge connecting the tail hook to the structure and cable that winds its way to the servo inside the fuse. I pre-bent the spring at a 90 degree angle at the middle of the spring, so that when I pushed it onto the tailhook, the bend in the spring is right at the joint where the hinge is. So, the spring is going to force the tailhook down at nearly a 90 degree angle once it clears the fuse, but allows it to go straight to fit inside the fuse when it is retracted.

If all this makes sense, I am hoping and expecting that the next test flight will have the tailhook coming out and down, forced to do so by the spring, and the magnet on the back of the fuse will latch onto the tailhook for extra security.

If this latest technique works, I think I have a final solution for both this size foamie and also large models, too. I'll post pics if this works.

I'll try it again tomorrow morning to see if it will work.

davegee

You are the "MAN". Your dedication and ingenuity is admirable. You are going to make my project even better. I thank you. Chic

Thanks, Chic. The ultimate goal of this little project is to allow me and others to branch out a little bit with some potentially cool extras onto scale aircraft. It was a little too windy this morning to take the Hellcat up (at least for me!) so I'll have to wait until I get back from a work trip in about a week to test out the new system with the bent spring to help keep the tailhook down when it comes fully out of the fuse. I really think this type system would work on your plane, especially at its larger scale. You could weight the end of the tailhook a little at that size which would help, and I think the spring idea is one that will hopefully work and make it reliable to use inflight.

I think the idea of making a low, slow pass with gear and flaps down with the tailhook hanging down will be very neat to modelers and others just watching the plane fly. I'll continue working this and report back as soon as I have the chance to fly it and get the results of the latest mod to the tailhook.

Cheers

davegee

SUCCESS!! I got the opportunity to take the plane out today. My friend Leo flew it for me while I operated the tailhook switch and photographed it. It really works great, now! The first pass we did was a little fast, and the hook wasn't all the way down, but was definitely in trail like what you would expect for approaching the boat. When it was slowed a little further with flaps and gear down, apparently there was enough tension on the spring to force the hook onto the magnet, where it hooked fast to it. The result is that it deployed exactly as I hoped. I would say this system is now Operational (for foamies).

There are still some things that could be done for larger planes:
1) A different geared system needs to be developed to bring the tailhook straight out until it can drop down once clear of the fuselage end, with the assistance of the spring. On larger aircraft, getting the room free inside the fuse to swing an overly large servo arm might not work, and is not very efficient.
2) On larger planes, I think a solid metal or at least weighted tailhook on the end of the rod would be helpful.
3) The spring is very important, at least in this model. It is similar to what you see in a ballpoint pen. I bent it to a 90 degree angle at the middle, and slid it onto the tailhook where the joint of the Robart hinge is. It is mechanically able to straighten out to go inside the fuse, but when the rod extends past the end of the fuse, the spring forces the tailhook down almost at a 90 degree angle.
4) For this small model, the magnet is very helpful. It might also be helpful in larger planes to be sure the tailhook stays in place with the airloads, and a powerful but lightweight rare earth magnet could even be put inside the fuse where it would not be seen, but would still have power to catch the tailhook rod. I put a metal screw inside the aluminum rod where the magnet would touch it, and it worked great.

In conclusion, each model probably has a case by case design that will work best for it. Chic, for your Avenger, I think you could probably work something very similar to what I did on this little foamie Hellcat, although you might want to change some things, like the geared mechanism to push the tailhook out and in the fuse. But I think the concept works, and if I get a larger Grumman "cat" someday, I will probably add a working tailhook along with other goodies like working cowl flaps, sliding canopy, etc.

NOTE: I tried to upload some pics of the flight today, but am getting an error message: 501 Internal Server. Not sure what that is about, but I'll keep trying to upload the pics, they look pretty cool!





Cheers

davegee

Hi All: photos finally uploaded ok. Might have been a glitch in the network or something. But as you can see, the tailhook is down where it is supposed to be.

davegee

DaveGee - Thanks for being the pathfinder. Your innovations has given those of us who follow this thread great paths to follow and think about. Me - Well I am thinking about a gear system that you talked about with regard to worming the tailhook out and back along with the magnets in the fuse tail. Thank goodness I will have the room in the Avenger to work it out. Chic

Sounds good, Chic. I'll hand off the baton to you and please let us know how your Avenger comes out, and if you work in a operational tailhook with it. I suppose maybe others have done some working tailhooks before, but I couldn't find anyone who has done a Grumman tailhook before. But I can see all sorts of practical applications for tailhooks, booms, etc., on any number of scale aircraft in the future! Best of luck on your Avenger, I look forward to seeing it finished as many others do, too!

Cheers

davegee