slowglowflyer

I am going to start a scratch build of a tugboat here shortly and would like some advice. I have a very scale set of cross sectional drawings, (bulkhead templates), of the real boat and I am trying to come up with a plan of action. I think I want to cut a keel (what type of wood???), cut my bulkheads from plywood (what thickness???), assemble the bulkheads to the keel upsidedown on a building board, put a few stringers through all the bulkheads, sheet the outside of the hull (balsa or thin ply????), fiberglass the hull, then build all of the upper deck stuff. Does this sound like a good plan? If anybody can answer some of the above questions please feel free to speak up!


Thanks for any help,

Slowglow

LtDoc

Slowglow,
Certainly sounds like a workable plan to me. Depending on the size of the boat, that ply sheeting may be a little 'much'. And then it also depends on how much fiberglassing you plan to do. The sheeting is typically done to provide 'shape', the fiberglass for strength. (I have much better luck shaping balsa than ply. Just depends on what you find easiest to do I guess, and of course, don't run into stuff.)
And at least for me, the best advice is to do the 'inside' stuff before putting the 'lid' on the thing.
Have fun!
- 'Doc

mfr02

The bigger the model, generally, the thicker the ply for the frames/keel. Apart from that the answer is "yes" to everything, including where you have indicated a choice. Planks are generally easier on curved areas, sheet is easier on flat areas. Some parts may be better built up bread and butter style, then sanded back.

rcgreenhornet

hey thinking of buliding a boat this winter never bulit a boat have exp in planes but got into big gas boating thinking of the chris kraft plank wood or somthing like deep/vee or hydro but want to go big any body got some good thoughts

slowglowflyer

I am planning on makeing my tug 26" long. I have changed my "plan" a little as of last night. The cross sectional drawings have the keel included and as it goes from the stern to the bow it tapers to nothing. I think it would be easier to build the keel with the rest of the boat instead of trying to cut out a keel and attach bulkheads to it. I would connect all of my bulkheads with a pipe through drilled holes in their centers, get them all aligned properly, sheet with balsa planks (possibly use light ply sheeting on keel??), apply fiberglass to the outside and inside of the hull, cut out the alignment pipe and have a nice looking hull! My only question is would 1/8" fiberglassed balsa be enough? I also plan on making my bulkheads 1/4" baltic burch ply. (1/4" so the planks will have enough to glue to). Does tugboat plan version 2.0 sound good to you guys? Green hornet I have never built a boat to this extent before either, but like you am experienced in rc planes. I just decided to contact the manufacture of this particular tug and ask for drawings. Luckily I talked to a very nice guy and he sent them to me. Don't know if you would want to go that rout or just draw something up. If you look under the name dreaminhemi, or something like that, you will come across a very skilled man who just scratch built a gas boat and did a very nice job.


Thanks,

Slowglow

cyclops2

The 8' WW II Higgins PTB below was my first scratch attempt. ALL structural parts are 1/8" Birch ply. Both sides ARE Birch. Why?? If of different woods, The sheet CAN WARP badly.

The hull fell 3' to the floor with only a 1" spot of dented wood. It requires 59# of ballest to reach the true WL.

slowglowflyer

If that beast was built using 1/8" birch ply then I think that 1/8 balsa will be pleanty for my little tug. That is an awesome boat and you did a great job for your 1st scratch build. I hope mine turns out that nice.

Umi_Ryuzuki

You have a sound grasp of building technique.
Here is a quickie photo set for hull construction.

Typical_Ship_Hull_Construction

cyclops2

Tug boats are usually way too light when completed. So do not skimp on the highth of the keel anywhere. The PT has a full height keel, viewed from the side. The frames are 1" to 2" wide & excess center material removed. The 3 bow frames, 2 engine & car battery area frames and the transom are all solid. Add beef where there will be impacts or weight stresses.

slowglowflyer

Do you have an picture of the inside of your pt boat? I think in the end I will add lead balast in needed to get her to float at the waterline.

cyclops2

Not really.

But if you will enlarge the lower left picture of the boat, you will see a 72" ASR framed out for a 18# thrust trolling motor. 1/8 " ply again. It is on the bottom shelf of the boat rack.