The Ship Model Forum

Hope everyone had a happy thanksgiving. got this model on hold as I have some new drawings coming and hope to be able to get hull correct because after checking it is way off. in the mean time I finished downloading 643 odd images of PT Boat Microfilm and started on that. (will make seperate thread for that once I finish the hull which is almost finished and everything is coming along great and matching up with drawings so looks like this will be a fun oine.

I will model it after PT 658 a late war Higgins 78' design because it was cool and loaded to the gills with cannons, rocket launchers, depth charges and the works

Ok tonight I got the main Hull Lofted and thickened. it turned out really good and smooth. now the PIA will be setting up the transom guides[attachment=2]LCVP-07.png[/attachment]

Ok I got a nicer looking Chine Profile, However I need to tweak the top view of the chine. then do some more adjustments and I will ignore the Buttocks unless i really need them for the loft and use the loft to create the new buttocks.

Once I get that all complete I will then create a new tables of offsets and might possibly create a table of offsets for each Bulkhead Station just to practice creating a table of offsets which will down the road probably make it easier on me when I have to adjust a table. so basically for a learning experience.

well last option didnt work. the lines look good but when you try to do the bulkheads they come no where close to the profiles. so I am back to square 1.

I also tried to trace the bulkheads and use them but then my keel and buttocks are really wonky (really technical scientific term)

So I will go back to my plane way of doing things and that is trace the profiles and then tweek both the lines and the bulkheads and find a happy medium. lol or switch to something like the Higgins PT boat that I have 550 drawings for and do this as a semi-scale R/C job and do the PT as a full fledged detailed build as there is so much on it. I dont really want to do a PT boat would rather do the 100' sub, MTB Killer for something different but havent found but 1 sheet referencing it in the collection.

Still trying to find info on the Viet Nam Era Pibber Mk II if anyone has any info on the boat

Forgot to post the link to the swimming restoration Boat [url]https://www.youtube.com/watch?v=ZQzeaj0BCg0[/url]

yea i misread a couple other lines so what I am going to do is use the keel buttocks chine and sheer lines and surface loft them and use that to get my formers since the drawings really wont show enough. and yes the way the thing is sitting is how it sits on the water there are some videos I saw of one in calm water that was restored and that is how it sat.

Joe,

The drawing you linked to doesn't show a water line, so I can't tell if the orientation in the drawing is how the boat was supposed to float. Remember, the base line is just a construction reference and doesn't have to be parallel to the actual water line.

Phil

well looks like I will have to make a few liberties on the LCVP since missing a lot of crucial dimensions plus the raised sheer and sheer lines are off from all the reference I have. the both come out horizontal and clearly they aren't. plus they don't even match the profile views on several pages of the microfilm. thus another instance where maybe changes were made on factory floor not showing in the offsets

yea remember the Fletcher it wasnt too bad only abt 4 numbers and they were only like 1 or 2 inches and a couple 8ths

just got home from work I found a page online to all the higgins PT boat plans was hoping had some more LCVP but nope though does have like 690 pt boat drawings :)

[url]http://cdm16313.contentdm.oclc.org/cdm/search/collection/HIC/order/date/page/2/display/200[/url]

I have never seen a Table of Offsets that did not have errors. The numbers were calculated by someone with an adding machine and recorded by hand. These lists of numbers were compiled into the Table of Offsets in the drawing by hand by a draftsman. Lots of numbers and plenty of chances to transpose numbers and for other mistakes. Especially with large ships where there are thousands of numbers.

But when you run them trough a CAD program the errors are obvious. Normally they are either a mistake in the feet, or inches, or eighths. So the erroneous point will be out of place by X feet, Y inches, or Z eighths. In one case I found an error for one value in both the feet and inches. Had to scratch my head a minute or two on that one.

Phil

Ok seems was an easy fix. station 4 was off by 20". even though all the offsets were correct according to the documents they were in fact wrong

Ok got the chine and sheer curves up they look good top down however the chine has a lump in it I need to double check some figures

[attachment=1]LCVP-04.png[/attachment]

Ok Got the Buttocks in place

Ok so I got the keel Curve file in and it is looking good

Ok dog needed out so took him for a walk and getting away from computer screen lot of my table stuff came to me.

Ok the stations which the first is 15" and the rest 30" will give me my first data input in my curve table.

The Heights from Baseline Will take the Place of the Waterlines in the table.

and for the width data it will be the offset from center.

the Keel, B-1, B-2 this will be like setting up curve table for plotting Buttocks

For the Chine, Sheer,and Raised Sheer The curve table will be the same with the exception that for the width I will use the Sheer and Chine Half Breadths

thanks yes i spent most the night trying to figure out how to set my table up.

Stations I got from the line drawings

[url]http://www.proflooney.net/Offsets-1.tif[/url]

Joe,

Here are my guesses:

Data in the Table of Offsets (TOO) is based upon "stations" or transverse cross sections of the hull. No distance is given for the spacing of the stations along the length of the hull. You will have to get this from the drawings.

NOTE: [b]The distance between stations is not the same for all ship and boat types.[/b] For larger ships the length between the "perpendiculars" (where the design waterline crosses the fore and aft end of the ship) was divided by 40 and this was the distance between the stations. But the dividing number can be anything.

Station positions are not necessarily related to the frame spacing in the hull. Stations are just used to calculate the hull shape as defined in the Table of Offsets. After the hull shape is defined the actual shapes of individual frames are calculated or determined in the hull loft floor. In some cases the actual frames were assembled to fit inside hull plating that was already in place in the ship.

The top half of this table contains elevations above the base line. The bottom two "Sheer" and "Chine" rows contain the transverse offset from the center line. Since these boats had slab sides the sheer and chine define the top and bottom of the sides.

Without the drawings I can only guess what B1 and B2 are. But these appear to be butt lines between the keel and the chine, perhaps defining a slightly curved bottom. Maybe the transverse distance between the keel and chine is divided into thirds (keel to B1, B1 to B2, and B2 to chine).

Maybe the "raised sheer" is a splash board mounted on the sides above the top edge of the sides. I seem to recall that the Higgins boats had something like this.

The table doesn't give any water line dimensions. They really aren't needed on a slab sided boat. Just draw lines between points on the sheer and chine lines and use these more or less vertical lines as template lines to stretch a surface on. After you have the side surfaces you can generate water lines if you want them by finding the intersection of the side surfaces and horizontal planes at various elevations. But I think you'll find you don't need them.

Ditto for the butt lines. Other than B1 and B2 for the curved bottom surfaces, butt lines for the flat sides really are unnecessary.

****

I see three things in the table that are different from larger ships that I have studied:

1. The Base Line is somewhere below the bottom of the keel. The Base Line is just an imaginary horizontal longitudinal reference line, so it can be anywhere and not necessarily related to any actual piece of the construction. All vertical dimensions are referenced to it. In this case it may be the bottom of a framing fixture that the hulls were assembled on - something easy to measure from.

On larger ships the Base Line is often on top of one of the keel plates - actually above the bottom of the keel. All construction vertical offsets are referenced to the top of this special keel plate. This provides a fairly easy place to measure from.

2. The transverse offsets are to the [i]outside[/i] of the hull planking. On larger steel framed ships the transverse offset is often to the [i]inside[/i] of the hull plating.

3. this table actually calls out 1/2 fractions of the eighths part of the distance, instead of having a "+" after the eighths as some Table of Offsets do.

Phil

Ok guys after I adjusted my excel file and got everything linked to the proper data I think I at least solved 1 problem.

the half breadths for the sheer and chine will give me the width and the stations the position along the centerline for each plot point and thenI believe I need to use the heights above baseline sheer and chine as my waterline dimension for the plot.

I still need to figure out the plotting of the keel, b-1, b-2 to set the offset distance from center.

it looks like the raised sheer might be straight up from the sheer wo can use the sheer as my width for that

then I still need to find a table or something for the hull stations and so far I cant seem to find them on the sheets I have they may be missing

I am wondering if someone can point me into the proper direction to set up my excel file as I am used to seeing waterlines on top row stations on the side. also for the B1 and B2 and chine lines how do i set them up in a table so it will draw them offset properly from centerline

thanks
Joe

Ok so now I am ready to get started on this thing here is my first Hurdle. the TOO for this is in a different layout than I am used to. the stations are on top and I dont see waterlines listed but rather heights above base for things so I am not sure how to set this up in excel for my curve table to import