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PostPosted: Thu May 31, 2012 8:30 am 
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Looking across the forums, I saw that a guy mounted a Baby Bob mast float to a H18 all-aluminum mast and said it was sufficient to keep from turtling. I'm looking to see if anyone has done the same for a comp-tip mast, or has any ideas as to how it could be done.

For those of you asking "Why?"....I had my first "knock down" last weekend, and despite my sealing of the mast, it still sank far enough to hit the bottom in about 4-5' of water, packing dirt and sand into the top of the mast and my sail. I'd like to keep that from happening. The Mama Bob just looks too big to me, is twice as heavy as the Baby Bob, and the extra floatation it provides doesn't appear to be needed.

Thanks,

Mark

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PostPosted: Thu May 31, 2012 7:42 pm 
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If the mast comes down hard the bob will tear off a comptip. That will leave you with a soaked tip that will always go turtle. It can, and has, been done.


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PostPosted: Wed Jun 20, 2012 11:01 am 
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I saw someone raise a boat bumper with the sail.

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PostPosted: Wed Jun 20, 2012 11:38 am 
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poolemarkw wrote:
Looking across the forums, I saw that a guy mounted a Baby Bob mast float to a H18 all-aluminum mast and said it was sufficient to keep from turtling. I'm looking to see if anyone has done the same for a comp-tip mast, or has any ideas as to how it could be done.

For those of you asking "Why?"....I had my first "knock down" last weekend, and despite my sealing of the mast, it still sank far enough to hit the bottom in about 4-5' of water, packing dirt and sand into the top of the mast and my sail. I'd like to keep that from happening. The Mama Bob just looks too big to me, is twice as heavy as the Baby Bob, and the extra floatation it provides doesn't appear to be needed.

Thanks,

Mark


Mark, There should be plenty of metal "real estate" at the top of your mast to accommodate a Baby Bob-compatible homemade mount like this.

http://www.thebeachcats.com/pictures/?g2_itemId=79694


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PostPosted: Thu Sep 06, 2012 8:12 am 
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Ok, here's my final method for mounting a Baby Bob on a Hobie 18 Comptip mast. It's a 1" square, 1/8" wall piece of aluminum tubing cut at an angle and riveted to the front of the comptip mast. The top most rivet goes through both the comptip material and the side of the aluminum tip (inside the top), making a very strong connection. I epoxied two small strips of carbon fiber material to the mating area of the mount to make a solid fit against the curved front of the mast. Two bolts go through this square tube at the front to connect to the Bob mounting plates, and another bolt goes towards the rear, through the angled "neck" on the cap plate, with 3/8" plastic cutting board material wedged inbetween on each side. While it looks heavy, the aluminum tube and rivets on the front only weighed 4 ounces.

Image

Image

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PostPosted: Thu Sep 06, 2012 9:11 am 
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Looks pretty bomb proof to me. My only comment is that placing carbon fiber in direct contact with aluminum is generally considered a no-no. Doing so will cause galvanic corrosion of the aluminum in much the same way as occurs when stainless and aluminum are in direct contact.

sm


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PostPosted: Thu Sep 06, 2012 11:09 am 
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Captain Mark

Great job, and clear pictures tell the whole story.

I have the full sized Bob at the top of my comp tip mast, and I'd like to add a piece of aluminium sort of like you did, but going FORWARD....so that in turn, I can mount a TeloCat wind vane up there...anyone have any suggestions?

(Yup, I'm thinking of adding a spin.....which means losing the existing bridle mount).

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PostPosted: Thu Sep 06, 2012 11:19 am 
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while on this subject. can anyone tell me how deep into the comptip the top sheave casting goes... 1", 1½", 2" ?

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PostPosted: Thu Sep 06, 2012 11:29 am 
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John, I'd have to see your Telocat Wind Vane to get some ideas how to mount it up there.

OlderBowman, there was a H18 comptip casting for sale on Ebay a few days ago, and from the picture it looked like it extended about 1.5"-2" down into the comptip. You might check to see if it's still there.

Hope this helps,

Mark

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PostPosted: Thu Sep 06, 2012 11:40 am 
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Go to the Forum....Help with Repairs, and see the great article (with pictures) by SRM, 'Can I repair a comp tip.'

That should give you some indications, or better still, ask SRM...he is the Wikipedia of the Forum.

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PostPosted: Thu Sep 06, 2012 11:47 am 
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OlderBowman wrote:
while on this subject. can anyone tell me how deep into the comptip the top sheave casting goes... 1", 1½", 2" ?


The aft bottom halyard hook rivet hole is right at the bottom of the mast head casting. The bottom edge of the casting is about 1/4" below the center line of the rivet hole (give or take). All of the halyard hook rivets pass through the mast head casting.

sm


Last edited by srm on Fri Sep 07, 2012 6:13 am, edited 1 time in total.

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PostPosted: Fri Sep 07, 2012 3:55 am 
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great, thanks.

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PostPosted: Sun Sep 09, 2012 7:18 pm 
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poolemarkw Have been working on this problem for quite some time. (baby bob on 18 comptip) .Have seen many suggestions--I like yours best..Question......what length, diameter do you suggest on those rivets AND what is the length of the aluminum bracket??????Thanks in advance...DJ


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PostPosted: Mon Sep 10, 2012 10:44 am 
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Hi DJ,

I didn't measure the length, but rather did the "That looks about right." method. Looking at a ruler now I'd say its between 7.5"-8" long. I installed it using 6-10 rivets with the rivet caps for a water-tight installation. The part numbers for the rivets and caps from www.mariner-sails.com are shown below. You'll need one of the larger rivet tools to install them, and I actually had to grind down the sides of the head of the rivet tool a little to get it to fit between the 1/8" sides of the square aluminum. I bought my riveter from Harbor Freight, part #66422. Once you get one of these, you'll be looking for other things to rivet together!

HC 8010121 6-10 Rivet
HC 8011291 Rivet Cap

Mark

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PostPosted: Tue Sep 11, 2012 9:47 am 
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Poolemarkw, Am planning to follow your bracket plan for the baby bob but I have reservations as to whether the "baby" bob is adequate to prevent turtling of my 18 comptip on a windy day.Have you tried it out yet? I think the next size up is the one used on the getaway and I wonder if the bracket on the getaway version is the same size and configuration as yours. Any help is appreciated....DJ


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