HRP construction

[fisherman]

An old fisherman stopped for a yarn this week and recalled when GRP first was used for commercial boats. (in fact I remember when the White Fish Authority insisted that a GRP hull be fitted with wood frames fastened through the hull. By 1972 they more or less got it right).
Then this chap said he once fancied buying a nice looking small boat which had been moulded by the owner, only he was warned off by someone who told him they hadn't used glass, they had used hessian sacking instead. On reflection, hessian is harder to tear up than CSM, but would it survive?

 

[jwilson]

An old fisherman stopped for a yarn this week and recalled when GRP first was used for commercial boats. (in fact I remember when the White Fish Authority insisted that a GRP hull be fitted with wood frames fastened through the hull. By 1972 they more or less got it right).
Then this chap said he once fancied buying a nice looking small boat which had been moulded by the owner, only he was warned off by someone who told him they hadn't used glass, they had used hessian sacking instead. On reflection, hessian is harder to tear up than CSM, but would it survive?

I once moulded a small interior tray type fitting for a boat with polyester resin and some cotton cloth, as I had no glass cloth or mat to hand, but a can of resin. Worked fine, though I might not have used it for a hull.

Have seen hessian-reinforced concrete, used as a quick cheap method to build temporary shelters, basically a hessian-covered tent over bent bamboo frames with a very thin coating of sloppy mortar just to fill the holes in the weave. The resultant structure lasted years instead of the month or so it was designed for as an emergency shelter as is needed now in Nepal.

 

[fisherman]

Instead of the ubiquitous Elastoplast repair for my specs, I fixed the earpiece with a winding of cotton and superglue, the result was rock solid and impregnable. Similarly, the heater control knob on the Saab, a hollow spindle which splits, glue and cotton wound round it.

 

[Scotty_Tradewind]

I've made a few repairs over the years using cotton and lightweight lines wrapped onto a smearing of Araldite.

Very strong and resilient. Worth having a tube of Araldite aboard!.

S.

 

[pcatterall]

I've made a few repairs over the years using cotton and lightweight lines wrapped onto a smearing of Araldite.

Very strong and resilient. Worth having a tube of Araldite aboard!.

S.

is one tube any use??

 

[TimBennet]

I would recommend you look out for a copy of 'Heart of Glass' by Dan Spurr (International Marine / McGraw-Hill ).

It's a history of the early years of composite boatbuilding. It recounts the use of all sorts of reinforcing material before glass became ubiquitous. Just of fascinating is discovering how many of the 'modern' techniques (resin infusion, high temperature cures,male and female closed moulds, etc) were quite common in those early days.

 

[Scotty_Tradewind]

is one tube any use??

smart a*se!

S.

 

[reeac]

I once moulded a small interior tray type fitting for a boat with polyester resin and some cotton cloth, as I had no glass cloth or mat to hand, but a can of resin. Worked fine, though I might not have used it for a hull.

Have seen hessian-reinforced concrete, used as a quick cheap method to build temporary shelters, basically a hessian-covered tent over bent bamboo frames with a very thin coating of sloppy mortar just to fill the holes in the weave. The resultant structure lasted years instead of the month or so it was designed for as an emergency shelter as is needed now in Nepal.

I recall that when we lived in California in the early 1960s we had a guide book to the area where we lived (across the bay from San Francisco) and one of the older house construction styles mentioned was timber frame with sand/cement mortar impregnated hessian nailed onto the exterior. Seemed to work in that climate

 

[JumbleDuck]

Then this chap said he once fancied buying a nice looking small boat which had been moulded by the owner, only he was warned off by someone who told him they hadn't used glass, they had used hessian sacking instead. On reflection, hessian is harder to tear up than CSM, but would it survive?

I doubt if the hessian fibres are anywhere near as strong as the glass ones.

 

[rotrax]

In the Burma Campaign in WW2 Slim's engineers used a rubberised hessian material as an all weather roadway across a notorious range hills that were impassable during the monsoon.

It cost 2 gallons of oil products per yard but did the job.

When making special bits from lightweight GRP for racing motorbikes I often used shaped wires to add shape and stiffness. Push bike spokes were good-nice stiff material with fatigue resistance and easily bent to shape by hand. Seat backs were a good example of where this worked.

 

[William_H]

Resin when simply molded into a block mold has quite a bit of strength. It can however be broken or cracked. Use of cotton or hession for resin or superglue will if nothing else increase the thickness of the resin holding it in place until it hardens. I doubt the hession or cotton will add very much to the strength or stiffness of the final product. Glass Kevlar carbon fibre or similar materials will add in them selves huge amounts of stiffness or tensile strength. Indeed to get the best strength to weight they go to some trouble to get the minimum amount of resin that adequately saturates the reinforcing. olewill