Hobie Forums

Broken Comp Tip
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Author:  kevinbatchelor [ Sat Oct 28, 2017 6:22 am ]
Post subject:  Re: Broken Comp Tip

mmiller wrote:
Discontinued product from the mid-late 90's now 20 years old. At some point the tooling fails as is the case here. Last one sold in 2014.
Ok Miller i have an idea, you give me the old mold for the hobie 21 comp tip, and I'll fix it and make a few tips for me and my friends here. :)

Sent from my SM-G930P using Tapatalk

Author:  speed633 [ Sat Jun 22, 2019 1:27 pm ]
Post subject:  Re: Broken Comp Tip

After much deliberation I have finally made progress on my 21SC mast replacement. Over the winter I picked up a hobie 18 mast and I have been modifying it to fit the 21SC. Since the boats share much of the same rigging, it was a close fit.

So far I have constructed a new, taller mast base out of epoxy, glass, and aluminum.

With the new mast base installed I am on to extending the shrouds 6". Anyone got a cable stretcher I can borrow? :D

Thanks to all the good advice I've gotten on this forum. Especially to Matt Miller for sharing mast profiles and such.

Author:  ChuckC [ Sun Jun 23, 2019 8:15 pm ]
Post subject:  Re: Broken Comp Tip

What length are those hyfield levers? Maybe you can add those and end up with shroud extenders... Win-win.

Um...What sail are you going to use? Interesting thread, as these things are getting more like restoring classic cars. Have To be innovative.

No one's tried to mold a new comptip, though? Or is that frowned upon? Not going into business kind of thing; just for yourself. Since it's patented, it can't be produced, but Ive got to Imagine someone's done this.

Of course, the cost of making the tooling yourself would likely exceed the cost of an aftermarket used mast...

All the same, when you want to save these lovely cats...what choices do we have?

Author:  speed633 [ Tue Jun 25, 2019 10:09 am ]
Post subject:  Re: Broken Comp Tip

Good idea on the hyfield levers, but I already have shroud extenders. As an aside, the levers I found have much less travel than the shroud extenders, so if anyone is thinking of shroud extenders or levers, I would recommend the shroud extenders.

I set up the mast such that it will use the 21SC sails. The tang is ~4" higher on the new mast, hence the need for longer stays. The overall mast height is a little shorter, thanks to the space efficiency of using an aussie ring compared to the stretchy halyard setup. That said the mast was still about 4" longer than a hobie 18 mast. The additional 4 inches came from a really tall mast base.

The comp tip was introduced in 1986, so assuming a patent was issued the same year it would have expired in 2006. As Chuck mentioned, the other barriers (cost) would likely be preventative. Also, I prefer a 1 piece mast.

For those that are curious, I chose to go with a H18 mast for the following reasons:
Cost To have a new replacement made it would be ~$5000 + shipping, or driving 14hrs each way to pick it up.
Weight It is light enough to step without a mast stepper system, greatly reducing the rigging time
1 Piece No plastic luff tracks for the sail to jam in, no worries about setting the mast luff track down on cradles during transport.
Strength It is strong enough, I hope. I believe that the 21SC mast was oversized to allow for more casual abuse. I have heard stories about people flying a hull with 2 trapped out, 2 on the wing
and 2 on the deck of a hobie 21 SE (wider boat). I don't need that kind of strength in my mast.

I will try to put up some pics tonight.

Author:  speed633 [ Wed Jun 26, 2019 7:11 am ]
Post subject:  Re: Broken Comp Tip


Author:  Bille [ Wed Jun 26, 2019 9:04 am ]
Post subject:  Re: Broken Comp Tip

The comp-tip for my Hobie 21se , is in perfect shape, and
i plan to sell it , (just the comp-tip) at the ((END)) of November.

I measured my new trailer for my H-21 and found out that the aluminum
part of the mast will fit nicely, on the trailer , from the tong to the back, if
the comp-tip is removed. I will build a PFP mold and do a removable one-off
comp-tip -----for Just ME.

I have no plans to sell the new design , because of the technology involved
it would cost WAY too much to build for other people. Made with uni, and woven
fiberglass, and kevlar uni, with a Nomex-honeycomb core, and LED strip inside.
since it's removable , i want to make the splice longer than the 8.5" it
is now so there is no slop in the interface to the aluminum ; so it kinda has to
be custom built, for the mast it's going on.

My stock comp-tip will be going on craigslist for local pick-up only , if anyone
is interested ? At 9-ft , the stock tip will fit on an airliner ; what
a GREAT reason to come to Las Vegas in the fall !!!!!
I might even take you sailing on Lake Mohave ; but that will cost Ya
a dinner and a Beer , and i eat a LOT ! :D


Author:  ChuckC [ Thu Jun 27, 2019 12:51 pm ]
Post subject:  Re: Broken Comp Tip

Bille -

Would you mind sharing your progress? I intend to do some molding of my own after this sailing season. I want to mold some new, modified rudders first. Something lighter with a better foil along the lines of a true NACA airfoil. That would likely be a hot wire cut, vacuum bagged affair at first to give me something to play with. It's also remarkably easy and quick (I have built a few high performance RC Jet wings this way). If it works well, then perhaps I'll build molds...perhaps and then play with the layup schedule. These old H21 rudders could certainly benefit from some newer technology to get a sharp trailing edge, etc.

Anyway - I LOVE these kind of projects and can't seem to get enough. I'll post my progress as well. I'd like to see your molding of the comp tip, if that's what you plan to o.


Author:  Bille [ Sun Jun 30, 2019 2:52 pm ]
Post subject:  Re: Broken Comp Tip

ChuckC wrote:
Bille -


Anyway - I LOVE these kind of projects and can't seem to get enough. I'll post my progress as well. I'd like to see your molding of the comp tip, if that's what you plan to o.


Yep --- mold it & sell the stock one.

I need rudders , (mine are delamed & Toast) ; sounds like your "Mod" , will
be way better than molding my patched-Up stock one ?

That's where I learned to Hot-wire ; RC gliders.

How about this for a deal :
You wire out your rendition for a rudder , and stabilize it with two layers of 5-oz glass ; then
send it to me and i'll put a shinny finish on it and mold one. Then I'll turn
out two for Ya ----- but made with carbon, carbon uni, and Nomex honeycomb
and a bit of kevlar uni inside the LE; for damage control. I would need the
exact location for the bolt-holes , to mark the mold ;it would need something
really solid, surrounding the hole , (end-grain Oak) or better.

It's a good possibility that i can do a PFP mold, in 1/4 the time, you could
make a conventional one . They are just -- (Really Heavy). For both sides of
a rudder ; 100-Lb + . :shock:
But hydrocal, or Ultracal ,is $25 for 100Lb bag ; + the surfacing epoxy !! :D

We both know ; it's the Dang blank, that takes all the real time !! Gurrrrrrrr

I won't be ready for composite work , till the first of November ; so take your time.
This time of year , i fly Hang gliders, and Paragliders ; addicted to FUN !!!


Author:  Bill 404 [ Mon Jul 01, 2019 4:40 am ]
Post subject:  Re: Broken Comp Tip

(We both know ; it's the Dang blank, that takes all the real time !! Gurrrrrrrr)

I got that covered if your OK with Mahogany as a core to build off of. They typically weigh 4 oz. heavier once finished then my old stock rudders.

I have shaped many before and clad with fiberglass. Right now I have four core parts 50% finished.
I need to have some teflon bushings milled for where the bolts pass through while the parts are still flat ( for drilling purposes )
And then finishing the shaping and start the fiberglass process.

My next run of 21SE rudders will incorporate an updated design. :wink:

Author:  Bille [ Mon Jul 01, 2019 10:51 am ]
Post subject:  Re: Broken Comp Tip

Get back to Ya , in November ; i gotta go Fly a hang glider
for now !! -----------------addicted.


Author:  ChuckC [ Fri Jul 05, 2019 1:28 pm ]
Post subject:  Re: Broken Comp Tip

Cool - I'm in.

I've got a neat software package, that you probably already know - Compufoil, and it does nice, elliptical wings. Got tons of high density foam to play will.

Bill404 - we need to coordinate on design improvements. I have VERY clean rudders now, just they aren't as up to speed with today's composites. A true airfoil, properly vacuum bagged should provide an improvement on drag and resistance to flutter. I should be able to knock out 1 or 2 designs a weekend, including insetting hardwood or carbon reinforcements in the blank. Would be fun to take 3 or 4 designs out and see if there's an improvement on stall in the turn using different shapes in the planform. Airfoil, or I guess hydra-foil shape seems to have been well developed and documented. I see a whole lot less about the planform shapes.

Just re-built those things; new cams, links, bolts, etc. Feels a lot more like rack-and-pinion. Gotta sail.

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