bertram31.com

Bob

I am amazed at what you learned from your racing days. I would assume that someplace in your back ground you learned engineering to understand all this stuff. While, for the normal boater, this may not be were we would put our money, its interesting to see and understand how everyone tweeks there boats. Every bit of information we all share, both good and bad helps us select what is best to meet our individual needs.

Bob, I follow you so far...the final step, say we are using 1 3/4 shaft would be to fab a custom strut to match the lower shaft angle. Strut material would be 304 or 316 stainless 1/2 thick? Tack together and tig weld off boat. No mufflers needed with 6" exhaust? Thanks for shedding light on shaft angles and all the time you spent figuring all this out.....BH

Strut material would be 304 or 316 stainless 1/2 thick? Tack together and tig weld off boat.

316 would have enough strength at 1/2" for the plate, & 5/16" for the tubes. I wouldn't trust the penetration of the TIG as much as I would with stick. Heavy double tapper on the each end of the leg, almost to zero, then bulid from the root. Use the TIG as a final cosmetic smoothing after any grinding of the stick welds. That's the technique used by my machinist on my rudders...

If you are going thru all the expense of custom fabricated Struts go with 316L on the stainless and welding wire. 304, not a good alternative.

TIG would be fine, but as Capt Pat says not as much penetration with TIG so you would want to groove out areas to be welded to a larger degree, then weld away. I prefer several passes and allow to cool awhile to avoid overheating the SS.

tony thank you for the compliment i went to university of maryland for mechanical engineering but mainly there to get my ass kicked as crease attack on lacrosse team.
moving right along sim you are my hero by owning a machine shop and driving a tunnel boat.i know damn well your pulling my leg you could do this conversion in a heartbeat!!and have a need for speed.
the bulkhead position is not moved back! what we did in the beginning was to remove rotted plwood bulkhead and replace with a azak brand pvc bulkhead at the top of the bulkhead (to support cockpit floor) we laminate 5/4 azak by 2" on stern side and 2" titanium strip on front side there will be alarge cut out for the gears that is why we need top strenth.at this time i want to make a note the primary use of boat is 100 miles offshore fishing so i make changes that are not nescessary for engine installation and we are going to put a "belly band around cockpit" i will include photo at end of post.now we have this huge hole in bottom of boat after removing shaftlog we could make measurements or use the law of sines to find lenth of shaft after knowing shaft angle adjacent side from radius of prop plus 2" clearance and center of shaft added together i don`t want to lose anybody so lets go to the dumbf-ck way.we buy a laser flashlight and we take that template harry made for us put template in place with a 11/2" freeze out plug with1/16" hole drilled in center we mount the laser on rudder withlaser light going thru 1/16" hole shining on main bulkhead this our centerline of SHAFT not engine center line.remove structs grind down bottom flat in area remove shims i don`t know old shaft size had no input but lets say 13/8".remove cutless bearing you have to anyway and install freeze out plugs one front one rear hold them in position until laser goes thru both plugs and harrys template this may be tricky you will have to shim make note of shim and give harry the structs to bore out to 11/2" cutless bearings-that right brothers we are using old struct because of the sleak contour.----- continue tommorow

LOL...Bob we are talking about different tunnel boats...really differnent boats!

As far as getting motors in, lined up, fabricating struts, mounts, running gear etcetera....yeah I can do it, have done it for others, but money and time are not on my side and don't see them coming over to my side in the near future.

I can do some glass work such as glassing in new logs (with Capt Pats insrtuctions ) or I could fabricate logs, again not a problem other then time.

Tweaking the hull strakes and chines...out of my league. Wouldn't trust anyone I deal with either.

I really do like the exhaust running on the outboard stringers...a project for down the road.

Carl

sim i am talking about the tunnel boat that is 20' long like a 3 point hydroplane but a tunnel thru center like catamaran.power by a single mercury outboard reving 9000 rpm with nothing in the water but prop.extremely dangerous because they blow over backward from excess trimm going into turn.they race in a circle about 175 mph in straigherway.
is this what you races---alot of balls ????

btw sim all kidding aside you have my higest respect driving one of those tunnel boats .thats the top of the class for "round de round " racing ,most of them were daredevils.

Bob I kinda had a feeling you were thinking along those lines...

Nope no racing other then indurance go-karts in my youth, the Tunnel Drive I refer to is the kind that draws 14" of water, made by Penn Yan back in the 70's. The ones that threw out that ridiculous roostertail at trolliing speed and if you ran a prop without rake the boat wouldn't do over 16mph or so at WOT... no matter what kind of hp you had. Put a Nibral wheel on that had substantail rake at the boat would easliy cruise 20-22 and top out over 30. Defintely not the tunnel boat you are thinking about.

So I guess I'm back to "No Respect"....

Carl

nah sim your still in " the band of brothers--bertram style" sim think basics thats how i true up strakes on my bert. concrete workers have these perfectly true metal "2x4" about 20' long that is what i use for trueing strakes on my bert.i don`t want to get capt. patrick into convusions lets just say i had the time and wanted to keep my mind off the american iron horse in the garage and the digital speed/rpm on the bars.when the readout says 200mph the need for speed has ended so concentrate on something here on earth!!! '

i don`t want to get capt. patrick into convusions

ROFLMAO!!!

Bob

From what I can see, you have a great mechanical engineering background and really know your stuff. But I think your typing is killing Capt. Pat.

Naw, I know his code. Bob types just like he talks: 90 miles an hour, extreme intensity, & very few pauses. His mind has alreay raced forward by 2 or 3 sentenances by the time any given word has been exhaled. The mechanics of typing and speech only slow him down. I love him!

Capt. Pat

Given Bob's love for speed I figured he's typing at 200 miles an hour. Got to love it though. I actually enjoy reading about his methods. In fact I am looking at his companion way set up for my boat. I love the idea of no screws to hold the engine panels in place. That's why I said, great mechanical background. Would love to meet Bob some day. I bet he has some great tales to tell.

If you ever get to meet him, he talks like he types.

The guy's a walking caffeine rush.

bruce
thats an under statement, lol bob. we love ya

Yeah, but it's good coffee. I spent an afternoon with him the other day and learned an awful lot. He's doing a job on his front windshield and interior that has to be seen to be believed. Walter