Comptip R&R (2017-2)

by John Bauldry and Matt Bounds, Hobie Hotline Spring 2017 (Volume 46, Number 2), pp 12-13

Almost since its inception, the Hobie Cat Company has waged a running battle against accidental electrocution caused by mast contact with overhead power lines. In 1976, mast warning stickers were made mandatory for class racing. In 1979, aluminum tillers were replaced with fiberglass and there was a free retrofit program. There was the “Bounty Program” of the early ‘80s that gave Hobie goodies in exchange for letters written to power companies about their low-hanging lines. The Comptip, introduced in late 1984, was the culmination of this effort. Free retrofit kits were offered for many years after and the class rules made it required equipment from 1990 onward for class racing in North America.

Fast forward thirty-plus years and many older Comptips may be loose from improper support while trailering, bottom contact capsizes or just normal wear and tear. The drawing below from a Hobie 16 shows how the Comptip/aluminum extrusion joint is put together. (All Comptips share the same general details.) If your Comptip is loose, the epoxy resin has probably failed and the joint needs to be taken apart and reassembled with fresh epoxy.

To get started, place a couple of sawhorses or other supports within the length of the mast extrusion. Leave the Comptip unsupported for now. Drill off the heads of the twelve stainless steel rivets that secure the mast tang and drive the tails into the Comptip with a punch. For 17’s that are 1994 vintage or older, remove the single thru mast nut/bolt/washers to detach the mast tang. With a helper holding the extrusion, gently wiggle the Comptip back and forth while pulling away from the aluminum part of the mast.

Once the Comptip is free, remove all the old glue [1] from the male mating surface and clean [2]. Do the same for the extrusion, removing any old glue from the inside [3]. Inspect the Comptip end for any damage or cracks. The Comptip is made of fiberglass so any reinforcing repairs can be made using polyester resin and fiberglass if necessary. This is also the time to check the integrity of the mast sealing plug and plate. The factory uses Sikaflex 291 sealant.

[1]
[2]
[3]

After cleaning, it’s time to do a fit and alignment check. Rotate the extrusion so the mast track is facing straight up. Secure the extrusion in this position using wood blocks, clamps or vises so it doesn’t move [4]. Insert the Comptip in the extrusion and support with a third sawhorse. Using wood blocks stacked with wood shims, adjust the stack/wood shims under the Comptip until the Comptip mast track and extrusion mast track are level. Then eyeball the entire length of mast track to be sure the Comptip is aligned perfectly straight – not trending to one side or another. Once you have completed the set-up, alignment and fit check, mask off the extrusion end and the Comptip with masking tape [5]. Remove the Comptip.

[4]
[5]

The factory uses West System epoxy to bond the Comptip to the extrusion. Pump enough epoxy into a container to coat both the male end of the Comptip and the inside of the extrusion. Mix in some colloidal silica to thicken the epoxy to a toothpaste consistency. Then mix in some graphite powder or pigment to give it a very dark gray/black color. (If your mast is clear anodized you do not have to add the pigment.) Mix thoroughly and apply a liberal amount to the inside of the extrusion [6] and coat the male end of the Comptip.

[6]

With a helper holding the extrusion, re-insert the Comptip, pushing hard to work out any bubbles and wet out excess epoxy. The Comptip will be fully seated when you can place a 3/16” rivet in the top hole on each side for the mast tang. For older boats with the mast tang thru bolt, keep working the Comptip until the bolt holes align. Fillet the epoxy around the joint [7], then clean off any excess epoxy and remove all masking tape. Now rearrange the wood blocks and shims supporting the Comptip until the mast tracks are level and straight [8]. Let the epoxy cure at least overnight.

[7]
[8]

Once fully cured, remove any excess epoxy (file – a small diameter rat tail works best) so you have a smooth, consistent joint between the Comptip and extrusion. Chase out the rivet holes with a 3/16” drill bit (or 5/16” for the thru mast bolt) and re-install the mast tang using stainless steel rivets or the bolt/nut on the old style tang [9].

[9]

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