Do I Repair or Replace a Damaged Composite Skeg?
By Tad Stetson, Service Technician
Inspection: While this may sound like a self-explanatory step, with only a few minutes of checking over the lower unit for small cracks with a sharp pick or knife, you could save hours of work performed in vain. It is also important because water intrusion into the housing will most likely result in a failed repair.
How bad is it?
Is the skeg broken off clean? Is it cracked or chipped? Whether or not the drive needs to be replaced all together depends on what else took the impact. If the props and shafts took a shot, maybe this isn’t the place to begin. These drives have an aluminum internal housing that keeps internal parts aligned, with a composite “clam shell” housing affixed around it in some secret Volvo fashion. A tear-away seam is designed into the bottom of the drive just below the lower pod. I haven’t seen many that split further up the housing when just the skeg was hit.
If repair is your chosen route, it is advised this be performed by an experienced fiberglass specialist (Volvo actually recommends this), or at least someone with some successful glasswork under his or her belt. Just about any full service boat shop could glass a new skeg on, but, depending upon the severity of the damage, this isn’t out of the DIY realm. (Alternatively, you could ship it to us!)
Options: Many people out there have an opinion on this matter, and, I suppose I just made myself one of them. On the two that I have repaired for a customer, the skegs were cracked badly but still attached and straight. I decided to repair the crack with Vinyl Ester resin (more on this process in a bit) instead of molding a new one from scratch. I have read on other blogs and forums that chop mat can be used and is plenty strong enough for the lower skeg. If there is enough material left, a metal skeg guard by Volvo or a composite replacement Blackfin could be attached with screws and/or a urethane based adhesive, such as 3M Window Weld or 5200. Both replacement skegs are approximately $100.
The repairs I did were on cracked skegs, one of which wasn’t even noticeable at a glance, so the repairs really weren’t very extensive. Just the same, here is how I did it.
I first cut back some delaminated material and got a good look at how deep and how far fore and aft the crack was; on one of them, the crack was almost all the way through. I checked it for straightness by sighting down the skeg and prop shaft. If necessary, a jig can be made from wood and tape to hold its position while you work. I used a small metal grinding bit in a die grinder to gouge out the damaged area, working on only ONE SIDE AT A TIME. This kept the skeg in position while I built up my repair. It is important to give hard sand with 80 grit at least four inches in all directions around the ground out area. This is where the repair will be “feathered out.”
After I was satisfied that I had gouged out the crack sufficiently I used long strand Tiger Hair from NAPA, working it into the gouged area while making sure to work any air bubbles out and to really set it deep into the etched surface. Working quickly, I didn’t try to get it all in one pass. I stacked a couple layers of long strand, sanding in between with 60 grit and giving plenty of time for it to dry between applications.
I roughly shaped it down to a nice cove between the skeg and the bottom of the drive using 60 grit and 80 grit sandpaper by hand. I then spread a skim coat of Bondo body filler over my long strand. Remember, Bondo has no structural purpose and contains talcum powder and will absorb water. Body filler is only for filling tiny air bubbles and scratches to make a smooth surface for paint and should NEVER be used exclusively in a repair. Ideally, the Bondo filler should be only about 1/32 of an inch thick and as long as the surface is smooth—sanding through it is not a problem.
I then went through the same process on the other side, matching my coved profile left to right. Once everything was sanded and feathered, I gave the whole lower a scuff with a Scotchbrite pad and then a wipe with a mild solvent to remove dust. Check your product for what solvents are compatible with the products you are using. I didn’t gel coat it when I was finished, although I could have. Instead, I chose a spray can of sealing enamel designed for fiberglass and plastics and gave it four or five good coats of paint. Paint is protection! Love the mils!
I followed up the paint job with a good polish using NuFinish but you may not want to do this if you plan to put bottom paint on the drive. I hate bottom paint on composite drives; it never looks good and it really makes them harder to clean. I like to wax them with a polymer-based product like Nu Finish or Awlcare. You may have to reapply a couple times a year but this may be done in the water without much trouble.
Good luck! Work safe! And happy boating!
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April 7, 2014 / Thomas Stetson / 0
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