Dynel vs. Fiberglass - as wood strip sheathing

[Robert Miller]

What are the technical and practical advantages and disadvantages of sheathing a wood strip plank hull with epoxy/fiberglass vs. epoxy/Dynel? The sheathing should be considered structural, in addition to abrasion resistance.

Searching the forums has brought up rather little.

Thank you.

Robert Miller

[Not A Guest]

You can look at Gerr's book on boat strength.

Dynel is a very loose weave so it takes a lot of resin to provide a smooth surface.

[PAR]

Dynel does cover compound surfaces much better then typical glass layups and provides more abrasion resistance then same. I'd skin the hull in glass and hold the final layer for Dynel if you really require the additional help. It depends on the layup schedule meant by the designer. Decks are an area you see Dynel for obvious reasons, but there are better materials available for abrasion resistance. What are you building?

[Anthony DeLima]

What are the technical and practical advantages and disadvantages of sheathing a wood strip plank hull with epoxy/fiberglass vs. epoxy/Dynel? The sheathing should be considered structural, in addition to abrasion resistance.

Searching the forums has brought up rather little.

Thank you.

Robert Miller

It is a matter of modulus the glass will give you the stiffness and strength required to hold the boat in the desired shape. Dynell is very strechy and will tend to do so when the hull is strained. If you have abrasion concerns I have used dynel strategically with MAS epoxy in the areas of the for-foot subject to the greatest abrasion. This is a nice way to go as it is easy to repair. I find I doo the most dammage to a loaded boat when padling areas of Maine where every landing is a rock one.

[Jim Kartz]

Read a story about atrimaran in a collision,broke off 3 to 5' of port ama bow, dynel kept bow atached,minimal leakage. Boat saflt returned to port.

[DBRbrunei]

Hi Robert

Don't know if you have already been sorted out but I introduced Dynel Sheathing into the Far East 30 years ago.

If you are definitely needing strength and not just protection Glass Cloth is obviously the way to go but Dynel does help a little.

If you regard your hull strong enough for your needs I can assure you that Dynel is a great sheathing process. I sheathed 3 20M naval vessels 30 years ago and they are still operational today with the same sheathing on. People think they are constructed in GRP. Dynel being a polyester cloth is easy to use and non irritant.
David

[JEM]

Dynel does not wet out clear. So it'll "fog" the look of a natural wood finish.

[thomas mattson]

From what I have read Fiberglass can be too stiff for wood, and may delaminate. While Dynel or some of the other products from Defender Industries will be able to. If you are going to use fiberglass then you must use one of the more flexable epoxies.

Thomas.

[JEM]

From what I have read Fiberglass can be too stiff for wood, and may delaminate. While Dynel or some of the other products from Defender Industries will be able to. If you are going to use fiberglass then you must use one of the more flexable epoxies.

Thomas.

Tight weave fiberglass can be a pain to apply. "Regular" weave is very easily installed and forgiving to tight bends. From what I understand, polyester cloth (Dynel) drapes arouond corners a little better then standard weave cloth.