External motor hooks?

[McKailas Dad]

I have not had the best of luck with friction fitting, so I am looking to use an external hook for a upscale/stretch project I'm working on. Its a BT-20, that I'm going from a 13mm to 18mm power.

Is the hook just set next to the root edge of the fin, and buried in the fillet? Wood would glue hold it (as a fillet), or I've used Devcon 2 ton epoxy for fillets as well, would that be a better choice to keep it down?

Thanks!

 

[Rex R]

as long as you don't get too crazy about the lifting the hook, wood glue will work. I would rough up the hook w/ some 60-80grit sandpaper though.
rex

 

[JRThro]

I have not had the best of luck with friction fitting, so I am looking to use an external hook for a upscale/stretch project I'm working on. Its a BT-20, that I'm going from a 13mm to 18mm power.

Is the hook just set next to the root edge of the fin, and buried in the fillet? Wood would glue hold it (as a fillet), or I've used Devcon 2 ton epoxy for fillets as well, would that be a better choice to keep it down?

Thanks!

Any way you could fit an outer tube/sleeve over the midpoint of the hook? That would make me feel better.

 

[KennB]

Any way you could fit an outer tube/sleeve over the midpoint of the hook? That would make me feel better.

Agreed. It will give you good flexing to get the hook out of the way when loading and unloading and will hold it firm during use.

Just a little relief in the fins will allow the ring under them and an extra drop of glue at the top end of the hook to seal the slot wouldn't hurt, either. No glue on the hook below the ring.

 

[kenobi65]

Any way you could fit an outer tube/sleeve over the midpoint of the hook?

Doesn't the Estes Hi-Flier do something like that? ISTR that there's a sleeve which fits around the outside of the body tube for that reason.

 

[McKailas Dad]

I was wondering about the 'sleeve' as well. I could see notching the fins alittle, but maybe not putting the hook in the fillet. I didn't think about the flex of it, and putting it there may not work to get a full fillet on the fin. I guess I'd better not put in the way of the launch lug either!

I think the Crossbow SST has an external hook, I'll have to see what I can find for that, and how they did it. Maybe I'll PM jpbell, I know he had one...

 

[ScrapDaddy]

I had a crossbow, they used a little clear sleeve over the hook, and the fins had little nooks in order to allow the sleeve to fit cleanly.

 

[plano-doug]

Doesn't the Estes Hi-Flier do something like that? ISTR that there's a sleeve which fits around the outside of the body tube for that reason.

The Estes Sizzler did that. As noted, notches are cut into the fin roots to fit over the external sleeve. You can sorta make it out in this pic. Doug .

.

 

[BEC]

Also the Star Stryker uses an external mylar ring (and the fins are relieved to clear it). Of course there's the old fashioned gauze approach, but it's ugly.

 

[plano-doug]

Of course there's the old fashioned gauze approach, but it's ugly.

It doesn't have to be. A little FnF can do wonders But it's better to not use the regular, smooth, flat motor hook. Piano wire, properly bent, can be affixed much more securely.

The top pic shows a C-bend covered with epoxy and a little glass cloth.

Covered with some smoothed FnF, the bulge can be faired in to be very aero-looking.

That said, the OP wants to use the stock hook. That's probably best secured using a ring, along with having the forward tang. But without the tang, it'll be prone to breaking loose and sliding fore and aft - not good.

Doug

.

 

[hcmbanjo]

Those mylar rings are available through Semroc:
https://www.semroc.com/Store/scripts/prodView.asp?idproduct=1827

 

[McKailas Dad]

Thanks for all the responses! While I do like the piano wire idea, I think I may use the sleeve from another project...

I'm going from 18 to 24mm on one, and 13 to 18mm on another, so I'll have extra pieces and parts to build one from the other.

Plano-doug, with that piano wire, does that also act as a motor stop-style hook? i.e.; Does it poke into the BT, or just surface mount? What size/guage/note is that wire? That does look really good all smoothed in.

I'll show ya what I got....when I'm done!

Thanks again,

 

[Rex R]

methinks it do poke into the tube. I wouldn't go bigger than 0.078" or smaller than 0.062"(which gives you two choices ).
rex

 

[plano-doug]

Plano-doug, with that piano wire, does that also act as a motor stop-style hook? i.e.; Does it poke into the BT, or just surface mount? What size/guage/note is that wire?

Hi, Jeff,

No, it doesn't poke thru like the tang on the Estes hooks. I use a mix of motor blocks or aft thrust rings (3 wraps of ¼" masking tape) to bear the thrust load.

The main advantage of surface mounting it is that there's no tang to interfere with the motor. Any length motor can be accommodated. And the delay well on reloads won't be impeded by the tang.

The wires are on the order of 0.02 to 0.03".

HTH.

Doug

.