building a 25 ft Tug

Just getting started. 1.5":1ft. scale. just laying it out.
Stay tuned for more.

 

tug 27 ft

hey guys-- do you like this design?
wont say too much about it other than it was originally flat bottom and i added a keel--not my design. the wheelhouse and the keel v bottom added-is my modifications to the plans.i used a half level under the wheelhouse and kept the wheelhouse low. this gave me full 12 x 5 ft for accomodations a v-berth and whatever i can get in the wheelhouse...the headroom below the wheelhouse is about 6 ft 2 inches. the wheelhouse is about 5 ft x 6 ft- the cabin and engine trunk is one level and is 12 ft long.


what i wondered is--if i built it this way - would it be hard to plate up?..i could just build it to the plans which has a flat bottom but wanted a bit more accomodations in her... view the pics...
got the steel for the frames-- 1/4 x 3 inch fb. ill use 13 frames.
see my pics--would like to hear what you guys think on doing it with the v hull instead of flat bottomed? using iether 1/8th or 3/16th plate on the bottom and 1/8th plate for the rest- its in fresh water so rusting is not as big an issue as in salt water- so lighter plate can be used...plus im adopting a glen -L method using shrink wrap technique.

Doug

 

Gee, what is shrink wrap technique ?

And the shape of your tug looks good.

 

Looks pretty good to me. Skegs for the props/shafts?
The shrinkwrap method would be a natural for this. If possible,
build upside down and let gravity help.

 

Thanks Michael--i was thinking the section at the bow where the chine meets the stem might be a bit difficult--but ive asked a lot of people and even an N.A. who i have yet to hear from...but will respond by monday i hope... all say its doable...there are advantages to a flat bottom as well..
shrink wrap is just the name given to welding the plate "only" to the stringers. (from my understanding) the stringers stand proud of the frames abouit 15 mm- the plate is welded to the stringers but NOT to the frames--check this out..
http://www.glen-l.com/designs/hankinson/steel-shrink.html

positive feedback is always very much appreciated...thx!

 

Yea--exactly--i had to turn my last hull and it did damage the hull but in the long run--because im not a pro welder- doing mostly flat position it works to my advantage...i love the hankinson design "fred murphy' shrink wrap method--but what turned me off to it was that tug has canted inboard topsides...a real tug has flat topsides to allow for working on the hip...if it werent for that design flaw id have got those plans--
it calls for 20-50 hp so im hoping i could get away with a smaller diesel. for economy...ideally id like to do the occasional tow off the books..but mostly have my character liveabord tug. even though the space is small. I really love the tugs design ..the 45 ft'er was too big - the 25 ft'er a bit too heavy disp. for my needs so this should do just right and it has all the features i like- there is no perfect boat--but this is as close to perfect for me as it gets...
r u doing the Mal Low design? did you get the cutting files??? they sure make easy work and a fair hull!!https://www.boatdesigns.com/Fred-Murphy/products/741/
Geln-l's reputation as a plans supplier is first rate and i have bought many plans from them--they come highly recommended

also yes the shafts need struts or use two skegs-- i was think of protecting them with a shroud or maybe a kort nozzle but i think they have to be like an aerofoil shape?....

another nice design is the salty here in pdf- it is available from reliable steam for 50 bucks!

 

Steel is very versatile that, in the stem areas the plate can be pulled into position by welding a ("U"-bolt/muffler clamp) to the inside of the plate for pulling with a come-along, etc. Another advantage of building upsidedown. Think about a conical bow section which makes life easier as well.
If placed well, the plate will conform without any heat. Grind off the muffler clamp later.
I haven't got Mal's cutting files (yet). Another project to finish first.

 

I know he is offering them for a great deal right now--i hope they will stay at a low price for a while..600.00 for cutting files--is well worth it...

 

Yes, great price and you can purchase in "modules" too.

 

No comment on the hull mods as I've no expertise there. You're adding to the hull volume so hopefully you've figured this in.

WRT shrink wrapping weld technique, should work fine. I've far more welds along the stringers than I do on the transverse frames.

My 4mm hull plate has been really nice to weld up as compared to 3mm. I'm happy with it. I'd use 4mm again.

The butt joints on your 3mm plate are going to require care in clamping to minimise distortion when welding.

I built my hull right way up. If I were doing it again, I'd do it the same way. Or I'd build it in ring frames and rotate it to the most convenient position. I did consider this but decided it was too much hassle for a single build.

Previously I said you could do it all with a stick welder. This is still true but after welding all my hull plate up using a MIG, I'd recommend getting one provided you can use solid wire & shielding gas. If you have to use flux cored wire it's going to be expensive. The MIG is faster, cleaner and I was able to get sound welds in all positions so I'm happy with the quality of the welded joints. I used 0.9mm wire and a welder rated at 250A 60% duty cycle so I wasn't working it hard. I've also used it for stick welding using E309 & E316 electrodes without a single problem. It weighs 40kg loaded with a new 15kg spool of wire.

PDW

 

This isn't a benefit of building upside down, it's a benefit of using steel. I did much the same thing on my hull built right side up. I could also use a 10 tonne porta-power ram to apply force from the ground underneath to spots where the plate wouldn't lie fair.

All in all I found it a lot better to push than pull. I welded 2 tabs to the plate & lifted it to lie fair against the frames then tapped it into position along 2 edges (usually the bearding line & previous plate edge for bottom plates), leaving the other 2 free . Tack these then work away from the tacked edges applying pressure as needed until the entire plate is tacked in position. Repeat until finished.

Cutting files will save a lot of time if you don't get any distortion in the building process. The way I did it, I could adjust for distortion from plate to plate until the last plate each side closed in the hull. That was the only one which had to fit perfectly on all 4 edges.

PDW

 

Cant wait to get underway- this boat is small to most but still a huge build to me...
when you did you welding -did you have to move your welder a lot?..i.e. do one weld on side then the same size on the other to balance out the distrotion on the hull?
also-- if there is some distortion im not phased by it--the boat is a tug after all--its not meant to look like a yacht but ill do my best on it regardless--i doubt it'll be anything near perfect...

 

Study up on welding sequence and you should be okay.
PDW, Wedges and bits of steel cut-offs can also be used to push plating. I agree that
it is easier to push than pull the plate.

A really good reference is Tom Colvin's "Steel Boatbuilding". Years ago I had the pleasure of visiting Tom for an entire two days, learned so much! Very practical. BTW, Tom tack welds with stick and finishes with fluxcore MIG. He say's it's better if outdoors, so the welding gas
for conventional MIG won't blow away from the welds.

 

thanks - I know about using the pull-in methods but how do you push the plate?

I would have loved to have met MR Colvin- i am assuming he is getting on in years but he is like an elder statesman of steel boats- sadly i have never seen a Colvin powerboat and they-especially tugs- are designed much differently...Did he build them? The other guy i read was Gilbert Klingel who did build in steel and did powerboats...

so fess up- how did you meet Colvin? where?
how?... more details on that little excursion...

 

thanks - I know about using the pull-in methods but how do you push the plate? I would have loved to have met MR Colvin- i am assuming he is getting on in years but he is like an elder statesman of steel boats- sadly i have never seen a Colvin powerboat and they-especially tugs- are designed much differently...Did he even build them? The other guy i read was Gilbert Klingel...need to read it again...