Help! Sliding Hatch flew off while trailering!

[BOAT]

Yeah, but where do you get the mold?

[RobertB]

A mold is easily made with a borrowed hatch.

[BOAT]

Oh, I guess I don't know how to do that. It's not like making surfboards I guess. (With blanks and stuff). So I can't just shape a part in foam and then glass it up huh?

I might need your guys help to build my removable hard top.

[RobertB]

You can do it anyway you want. Making a pattern as you describe is another way.

[BOAT]

Oh! Well that's good to know! Thanks Luna! I can't decide if the hard top third row raccoon pilot house should have a flybridge type sun shade overhang in the front or not. If I do the flybridge overhang then the appropriate method to me seemed to be a foam blank but if I go with a smooth round top like the rest of the deck I thought a plexi top might be better - with the plexi glass top I just shape the top in foam like a surfboard and take it to the airplane shop and they send it out to the windshield place where they put a bag over my blank and mold a plexiglass windscreen over my blank. I think I might go that route because it's easier, but it's more expensive. (We have a little hobby airport over here in my town where the guys can help me get an airplane windshield made). The guys at the little airport are real nice - they have a little breakfast every Wednesday morning and some of them have sailboats - very helpful. Seems like the pilots and the IT guys are always the smart guys when it comes to making stuff. All I know is shaping.

[RobertB]

A mold for thermally shaping Plexiglas needs to be rigid and able to withstand the heat. You may need to mock up in foam, make a negative mold, and then cast a rigid mold in plaster or something similar.

[BOAT]

I can make a rough shape but if I need to have it done in the harder foam like you say then I will go to one of my guys to have them convert my shape into hard foam. I have seen them work that stuff - I can't do it but they can. We have some of the greatest and best shapers in the world here where i live - they are real helpful and they do airplane parts all the time.

Here are some of the guys:

http://visitoceanside.org/blog/the-shap ... oceanside/

[RobertB]

OK, can your hard foam take the heat and pressure? Some can, most commonly available cannot.
We molded 4th generation composite parts for aircraft out of a very hard foam-like material. Actually better than steel since it was not as porous as steel in the autoclave. Would not know where to find the stuff today.
I had plastic parts molded as you describe for the YF-22 (the F-22 prototype) wing edge covers - we made wooden molds that easily withstood the heat needed to make the plastic pliable and could take the pressure using vacuum bags to force the plastic to shape.

[BOAT]

I'm not sure Robert, I do know they use a plastic bag but as for the rest of the stuff all I can tell you about the hard foam is that it's very muck like a pumice stone or a flow stone. When the guys shape it they use high speed grinders and special sand paper. I'm pretty sure it's flow stone because the very guy that invented the whole process back in the early 60's lives in North County and he is Hawaiian or Samoan or something like that and FlowStone is something that comes from the islands ( I think? I'm pretty sure you need a volcano to get it). I have it in my front yard and my back yard and it's like this grey stone that is really light weight and porous but like a pumice it can go right into your fire place. We saw it in the pit where they cooked the pig when we were in Hawaii. You can really easily carve tiki heads in the flowstone with a small grinder, but don't breath the stuff, it's like glass. I saw big Tiki Daddy carve one at the beach in like 4 minutes with a small power grinder. (He did a bunch of palm trees along Oceanside Blvd too with a chain saw but he got in trouble for that one).



I don't know all the details, but I don't have to because of all the guys here that already know all about this stuff. I think they make flowstone in a factory now too. It's really cheap stuff. There is a similar stuff that is cut into tiles to cover the skin of space ships they build up north in a town called Downey, CA. (I think they stopped making that space ship a while ago but you can still get the tile material) I don't think that is flow stone.

[mastreb]

Hit 7.3 MPH under sail...speed over ground according to the Garmin Chartplotter.

MPH: Speed over land. Used when trailering a MacGregor. Useful for comparing velocity to trailer tire ratings.
Knots: Speed over water. Used when sailing or motoring a MacGregor. Useful for navigating, comparing race speeds, and all other purposes.

(7 knots ~ 8mph. More importantly, 1 knot = 1 nautical mile per hour. 1 Nautical mile = 1/60th of a second of latitude or longitude at the equator, which means you can calculate passage times on a chart trivially.)

It's a setting on your chart plotter.

Let the controversy begin!

[BOAT]

Hey Matt, did the word come from the knot's the guys tied into the rope when they threw it in the water with a float on the end?

[mastreb]

That's what old sailors say, if you trust them.

[Tomfoolery]

That's what old sailors say, if you trust them.

Form Wikipedia, if you trust it (or them who wrote it ).

Until the mid-19th century, vessel speed at sea was measured using a chip log. This consisted of a wooden panel, attached by line to a reel, and weighted on one edge to float perpendicularly to the water surface and thus present substantial resistance to the water moving around it. The chip log was "cast" over the stern of the moving vessel and the line allowed to pay out.[6] Knots placed at a distance of 8 fathoms - 47 feet 3 inches (14.4018 m) from each other, passed through a sailor's fingers, while another sailor used a 30-second sand-glass (28-second sand-glass is the currently accepted timing) to time the operation.[7] The knot count would be reported and used in the sailing master's dead reckoning and navigation. This method gives a value for the knot of 20.25 in/s, or 1.85166 km/h. The difference from the modern definition is less than 0.02%. [A fathom is 1/1000 nautical miles, roughly 6 feet]

[BOAT]

I have not met any sailors from the 1850's (mid 19th century), but if we find one we can ask him. (Is highlander around?)

[Catigale]

When you gently correct pretentious sailors who insist that sailers only use nautical miles, remind them that Chapmans states differently.

Nautical miles offshore
Statute miles inland, lakes, coastal waters