Glass wrapped mahogany gunwales

Im fitting new gunwales to an IP24. Plan is to build them up out of mahogany to mabye 125mm wide and 140mm deep and wrap them in fiberglass. As the stern is round I’m planning on steam bending a few layers of 6mm mahogany. My question is that the mahogany I’ll be using will have been kiln dried and I’m worrying that the moisture I introduce whilst bending will cause problems with the fibreglass layup and it de-laminate through time.

The other option is to just to leave them natural and oil.

Photo isn’t of my boat but it’s something similar I want to end up with.

 

Are you planning on a very light layer of glass so it is almost transparent?

 

No, couple of layers of 450 an white flow coat.

 

I have three questions for you:
1. If you throw a kilo of glass over it why mahogany?
2. If you laminate why steam bend?
3. What is this flow coat based on, epoxy or polyester?

For glassing over a cheaper wood does the same trick, you don't need the expensive mahogany.
Laminations don't need any steam bending, you pair them down until you find the thickness that will bend dry.
Polyester doesn't belong on wood and epoxy needs paint over it, not pigment.

Steam bending mahogany is always a hit and miss operation, mainly because of the wide variety of species sold as "mahogany". Steaming is actually a drying operation, it removes moisture from the wood.

 

Polyester flowcoat is painful to get a reasonable finish on, requires a lot of sanding where it clogs gear, then requires a lambswool buff, cutting compound and finally polish to get a gelcoat like finish. It is brittle and chips easily so you will be forever patching dings on a gunwale. A varnished mahogany gunwale will be a nice feature, especially if you have other bright finished timber. It will take a bump and be easy to touch up, I feel that you are making unnecessary extra work for yourself both now and in the future if you use fibreglass and flowcoat. Wooden Boat forum might be a handy place to ask your questions by the way.

 

OIL!
Don't even think about any other option.
Oil.

 

Apologies for the thread drift, but @hardguy007 did you see this thread where a chap in the Med is asking for help in identifying a boat that he saw - I was thinking that it looks rather like an IP 24.
Do you know what boat she is? https://www.boatdesign.net/threads/do-you-know-what-boat-she-is.68678/

And can you post some photos of your fine vessel please?

 

Any particular reason for a section as large as 140 X 125? It will be quite expensive and rather heavy to add all that to the boat.D section rubber would be gentler on neighbouring boats and easier to wrap round the boat,not to mention easier to source for less money.This sort of thing: https://www.wilks.co.uk/product-category/marine/boat-fendering/d-profiles-boat-fendering/

 

Mahogany 125mm wide sounds like a lovely cutting board. Oil or varnish would be the least work to maintain / repair after, you know, when your mates wanted to go fishing, or someone 'helps' you. Or you could embellish it with scrimshaw; you wouldn't do that if glassed over.

 

I am swaying towards just mahogany and oil.

In addition I’m also adding a new wheelhouse. I’ll be making a mould out of melamine and laying the wheelhouse up inside it. The forward deck however, I see no easy way of doing it other than plywood and glass with a nonslip finish. I suppose I could take the extra time and build the wheelhouse, forward deck etc as one moulding. Would take a lot of time but may well be worth it for the better finish. For the sake of a few sheets of melamine it might be worth a try.

 

By the time you have painted it with a good non skid finish, I think that you are most probably not going to be worried about the quality of the finish on the fibreglass.

 

Hard heartwood mahogany is a wonderful underlayment for a skin of glass. It has the toughness to take a hell of a beating without crushing or dinging. Two Honda Civics committed suicide against the transom of my trailer sailor and failed to leave a mark. One was doing about 50 mph when it hit my boat. Totally destroyed the steel trailer the boat was sitting on.

What you want to be able to do is peel the fiberglass off when you decide it's time for a refresh. What works for me is to use Minwax Red Mahogany stain and don't be shy about it. It is quite waxy and will release the fiberglass when the time comes. Put one coat of clear epoxy resin over the stain (wait about a week after staining, if possible). Then use 6 oz deck weave over this. You can go two thicknesses and still have it invisible. Fill the weave with three or four more coats of epoxy then sand smooth. Then lay on the spar varnish - 20 coats or so in the tropics. Give it a cut back every 4-5 coats. In the tropics, you'll need to cut back and reapply about 3 coats of varnish every 3-4 months. It will last forever. I've built stuff like this out of salvaged mahogany that had already been at sea 100 years.

Another helpful trick is to cut a groove in the bottom of the rail very near the hull and use standard round window screen spline to hold one edge of the glass in place. This will save your sanity if you are doing this by yourself. You can trim the glass in the groove with a knife and have a clean edge.