Thank you forum members. I have run the many good ideas by my son, and we have decided to fly her as is early this saturday morning before anybody shows up at the park ( for safety ).

Be aware that our agreement with the city only allows organized club rocketry at that site. Please do not do anything which may jeopardize everybody else's use of the field.

If you show up early when the range crew is setting up and explain the situation, they will give their opinion on whether they feel there will be a problem and if they think there is a likely chance of success, will probably let you try with all hands on deck for fire suppression just in case.


Bill - wearing club secretary hat

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It is well past time to Drill, Baby, Drill!

If your June, July, August and September was like this, you might just hate summer too...

Please unload your question before you ask it unless you have a concealed harry permit.

: countdown begin cr dup . 1- ?dup 0= until cr ." Launch!" cr ;

Give a man a rocket and he will fly for a day; teach him to build and he will spend the rest of his days sanding...

No I wouldnt do any thing like that. last time the local F.D. was at our launch with their permission and guidance we had a successful launch and great time. The next time I will be taking a member of our P.D. and hopefully soon maybe even the folks who run the local boys and girls club will be invited. It's nice to get people involved. And Besides I love to see their faces after a good recovery! I haven't been to your launch area yet, and am not sure where it is? So I have been getting permission from local authorities to launch at our park in Vernon. As always Safety First!

Actually Bill I am not a member of the Dallas Club. I would love to come down and visit Y'all. The club launch I have on the 17th is in Duncan. It may actually be a little closer to home than the "Big D"

Me bad. "North Texas" is bigger than I thought. Some of your fellow club members have visited us before.

If you can, let someone else look at what you have before you fly it. Normally, I would not sweat over a quarter inch, but this is a short and stubby rocket with lots of wood at the tail end.

And add to our collective knowledge however it turns out. Happy flying...


Bill

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It is well past time to Drill, Baby, Drill!

If your June, July, August and September was like this, you might just hate summer too...

Please unload your question before you ask it unless you have a concealed harry permit.

: countdown begin cr dup . 1- ?dup 0= until cr ." Launch!" cr ;

Give a man a rocket and he will fly for a day; teach him to build and he will spend the rest of his days sanding...

Stupid question... Have you tried the old "swing test"?

With regards to motor block not "backing up" the front end of the engine hook... I do recall a lot of older Estes kits that had motor hooks but didn't have a forward engine block. Even on those kits that did have engine block, there was eventually some tearing of the motor mount tube indicating one other cause of the tearing -- the ejection charge. THis is one of the reasons some folks advocate having a engine hook that's longer so that it encompoasses both the motor and the forward engine block. The engine block keeps the motor from shifting forward, and the hook keeps the motor from being spat out, with the forward end being backed by the engine block.

I think one reason for the motor block is to keep the hook from sliding forward. (They can work their way thru the forward slit.) So if you put the ring behind the forward tang, you lose that feature. The implication is that sandwiching the tang between two rings is best

Of course, that adds undesirable cost.

But it does make for a good segue. I prefer to not have any forward tang or motor block at all (and use an aft tape ring on the motor as a thrust ring). That way, I can use any length motor. This applies more so to 24 and 29mm motors - the days of multiple length 13 and 18mm motors are long gone.

Securely mounting a hook that way, with no tang, requires a new approach. So I use piano wire hooks anchored with a little epoxy and glass cloth, or gauze and glue, or even nylon mesh and glue (as shown below). But the key is forming a shape into the forward end of the hook such that it adheres well to the motor tube and cannot easily slide fore or aft.

FWIW, here are a couple examples. Doug .



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YORF member #11

If we simply have a engine hook, the forward tang is inserted into a slit at the front of the motor mount tube. During boost the motor pushes against the forward tang, which then transmits force to the motor mount tube. Upon ejection, the motor kicks back and is "trapped" by the hook -- the load is transmitted through the forward tang to the motor mount tube -- on both boost and ejection, the forward tang, inserted into a slit cut into the motor mount tube is what transmits the forces to the rocket.

In the case where you put an engine block in front of the engine hook, during boost the forward tang is "backed up" by the engine block. So even if the motor hook wants to move forward, it's stopped by the engine block. However, during ejection, the force of the ejection gets transmitted through the forward tang -- and with nothing reinforcing the tube at the slit, the tube becomes prone to tearing at that point.

In the case where you have a lengthened engine hook -- the front end goes in front of the engine block. Durig boost the engine pushes against the engine block, not the forward tang. During ejection, the motor pushes against the hook, which then transmits the force through the forward tang -- which is being backed by the engine block.

Of course, this assumes you're using standard single-use motors. If we're talking reloads then you're gonna use a different retention mode. If I'm not mistaken in this case you opt for a rear engine block for boost loads. For ejection loads, you can simply bend the forward end of the engine clip up so that it hooks against a centering ring. You don't have to worry about the hook sliding forward during boost because the rear engine block is handling that already.

Good point. I agree the block spares the hook from the thrust forces. But it can still work its way loose and slide forward. The smooth, flat metal of the hook tends to keep if from staying put; it doesn't bond well. So I still prefer something which can be anchored more securely.

Doug

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YORF member #11

Good point Naoto.