weight-saving techniques

[afreegreek]

*puck

[afreegreek]

you know,, foam is basically a spacer to keep the two skins separated and keep them from moving in relation to one another. it isn't much of a structural component on the whole and unless your building something like a wing, pretty much any rigid foam will work.. you just have to make sure the glue or resin won't eat it away.. I'm not saying there is no need for true structural foam, it's just that for something like a TD it just won't matter..

[eamarquardt]

I think one important consideration in the GRP/foam construction technique is making the GRP thick and strong enough to resist denting to begin with. If you dent it and damage the GRP/foam bond then the delamination has a "foot in the door" and can progress more easily. More is more expensive and heavy but "everything in life is a compromise". My friend's fishing boats are pretty robust construction (but as they are displacement hulls, weight wasn't a big considerstion) and they, after 30 years of commercial fishing in the Santa Barbara Channel (pretty rough by some standards) are doing well.

I agree with AFREEGREEK that the strenght of the foam isn't that big a deal but you want to get the best bond between the GFP and bond you can and protect the integrety of the bond by making sure the GFP/foam isn't easily dented.

I also think keeping the completed tear out of the weather to the extent practical would go a long way towards maximizing it's lifespan. The heat/cool cycle and resulting expansion/contraction can't be good for the sandwich. Not that you can't take your trailer out in the sun, but even if it was used 2 days a week that still gives you 250 days a year you can keep it out of the weather (mostly the hot sun). Doing that might extend the usefull life by a factor of 3 (well beyond our practical lifetime).

Cheers,

Gus

[kennyrayandersen]

The heat/cool cycle and resulting expansion/contraction can't be good for the sandwich. Not that you can't take your trailer out in the sun, but even if it was used 2 days a week that still gives you 250 days a year you can keep it out of the weather (mostly the hot sun). Doing that might extend the useful life by a factor of 3 (well beyond our practical lifetime).
Cheers,
Gus

I agree with most of what you said to a point. The skin needs to be thick enough that it can withstand abuse loads and some impact damage. However, not every place on the tear is exposed to the same hazards. As Glassice suggested – the door and the hatch are areas that get ‘abused’ more than others. The galley area would probably be more prone to things being dropped or ice chests being slid around etc. I’d also add the lower front (where things get kicked up by the car), and the underside aft of the fenders (though the fenders should catch most of it). It would probably pay to put an extra ply or two in those locations. Small delaminations (under a nickel size or so) shouldn’t make too much difference unless you get a bunch of them). You would want to protect so that you could drop a butter knife hilt first, but perhaps not a hatchet.

[afreegreek]

little delams can be fixed if caught early too.. you just need to drill a small hole and inject some resin..


if you're smart, you can do it with your vacuum cleaner..

[afreegreek]

you can also drill holes in the foam and thread strands of glass through them.. (pull bundles from roving and use a crochet hook to thread them through- trim them an inch long on each side) this creates little piers between the layups.. the glass give some stiffness and helps wick the resin through.. this gives a lot of strength and stiffness for the work involved. it's really worth it around corners and openings.

I just use a piece of peg board and go to town with the drill

[glassice]

When I was poorer I put 10ea 20 d nails in a 1x4 to pock holds in the foam. It work great under leaves at the door to stop thieves

[eamarquardt]

I agree with most of what you said to a point. I really don't see than you are not agreeing with anything I said.. The skin needs to be thick enough that it can withstand abuse loads and some impact damage. Agreed. However, not every place on the tear is exposed to the same hazards. Agreed. As Glassice suggested – the door and the hatch are areas that get ‘abused’ more than others. The galley area would probably be more prone to things being dropped or ice chests being slid around etc. I’d also add the lower front (where things get kicked up by the car), and the underside aft of the fenders (though the fenders should catch most of it). It would probably pay to put an extra ply or two in those locations. All seems like common sense to me. Small delaminations (under a nickel size or so) shouldn’t make too much difference unless you get a bunch of them). You would want to protect so that you could drop a butter knife hilt first, but perhaps not a hatchet. Everything in life is a compromise. No such thing as a "perfect compromise" as all compromises trade one thing for another.

Cheers,

Gus

[afreegreek]

When I was poorer I put 10ea 20 d nails in a 1x4 to pock holds in the foam. It work great under leaves at the door to stop thieves

good idea on both..

[kennyrayandersen]

I agree with most of what you said to a point. I really don't see than you are not agreeing with anything I said.. The skin needs to be thick enough that it can withstand abuse loads and some impact damage. Agreed. However, not every place on the tear is exposed to the same hazards. Agreed. As Glassice suggested – the door and the hatch are areas that get ‘abused’ more than others. The galley area would probably be more prone to things being dropped or ice chests being slid around etc. I’d also add the lower front (where things get kicked up by the car), and the underside aft of the fenders (though the fenders should catch most of it). It would probably pay to put an extra ply or two in those locations. All seems like common sense to me. Small delaminations (under a nickel size or so) shouldn’t make too much difference unless you get a bunch of them). You would want to protect so that you could drop a butter knife hilt first, but perhaps not a hatchet. Everything in life is a compromise. No such thing as a "perfect compromise" as all compromises trade one thing for another.

Cheers,

Gus

Gus -- I was slightly disagreeing about the thermal damage you were suggesting -- I don't think it is there. Of course -- how would you know what I was thinking -- since I forgot to write it down!!

[kennyrayandersen]

little delams can be fixed if caught early too.. you just need to drill a small hole and inject some resin..


if you're smart, you can do it with your vacuum cleaner..

yep -- just like them cracks in the windshield!

[eamarquardt]

Gus -- I was slightly disagreeing about the thermal damage you were suggesting -- I don't think it is there. Of course -- how would you know what I was thinking -- since I forgot to write it down!!

I wasn't making any "dire predictions" but having owned GRP boats, with a cat in the back yard right now with some delamination between the glass and foam (started before we got it), and having seen surfboards damaged by the sun I am convinced that any effort to keep thin GRP/foam out of the weather to the extent "practical" is a good thing. A friend has a "junkyard" at his place. Motorcycles, boats, jetski, etc. Most of it has been rendered "junk" by the effects of the weather (and it's MILD here in Ventura County) compared to the rest of the country.

As I'm sure most who read my posts agree, I do things a bit differently than most. I do my best to keep everthing out of the weather simply because doing so makes things last longer. If I weren't married with children I think I'd have an acre or so with a big butler building on it. The exterior of Butler buildings are pretty maintenance free. In the building would be a small home facing a BIG ROLL UP DOOR, a huge open shop, a huge inside storage area/work area, with the cooking area outside the home near the door to exhaust the fumes. Never have to paint the exterior of the house, never need a new roof, all cooking fumes and vapor go outside, and everything out of the weather. On good days I'd roll up the door and enjoy the view (gotta be on a hilltop with a view) and during "inclement weather" I'd close the door and carry on with business as usual out of the weather. Heating an a/c costs would be minimized with the house out of weather. Odd, yes. Functional, yes. However, I don't think it's gonna happen as Suzy has vetoed the idea.

Cheers,

Gus

[eamarquardt]

little delams can be fixed if caught early too.. you just need to drill a small hole and inject some resin..


if you're smart, you can do it with your vacuum cleaner..

yep -- just like them cracks in the windshield!

How do you get a "sucker" to "inject"? What's your technique? I've done the "windshield miracle cure" several times with excellent results!

Cheers,

Gus

[afreegreek]

little delams can be fixed if caught early too.. you just need to drill a small hole and inject some resin..


if you're smart, you can do it with your vacuum cleaner..

yep -- just like them cracks in the windshield!

How do you get a "sucker" to "inject"? What's your technique? I've done the "windshield miracle cure" several times with excellent results!

Cheers,

Gus

basically you use the vacuum to suck out the air.. suck hard enough and the cavity will become a vacuum chamber.. you get some resin at the entrance to the cavity and release the vacuum.. the cavity will suck the resin into itself as it tries to equalize it's pressure with the outside pressure..

it's a poor explanation but it's the best I can do

[eamarquardt]

basically you use the vacuum to suck out the air.. suck hard enough and the cavity will become a vacuum chamber.. you get some resin at the entrance to the cavity and release the vacuum.. the cavity will suck the resin into itself as it tries to equalize it's pressure with the outside pressure..

it's a poor explanation but it's the best I can do

I can see this working with a small delam. The one on the cat is pretty big (maybe 6" in dia). I'm thinking this would be an "ideal" location for one of those small circular access hatches. Cut the circle, inject resin into the delam that's left around the perimeter, use multiple clamps to hold it together while the resin goes off, and then fill the hole with the access port. The thing that bothers me is that only one hull has a problem and if I only put a port in one hull the hulls would then be "asymmetrical". I'm big on symmetry so I'd have to put a port in the hull that's ok to keep the universe in proper balance. However, since the hulls are aysymmetrical already (but mirror images of each other) maybe I'd be ok with a port in just one hull. I digress.

Cheers,

Gus