BB3 Modified Transom - Maiden Voyage (Pics Added)

K

Kevin T

Active member
Last Saturday Tom Scholberg and I took our boats out on a shake down cruise - Tom in his Broadbill and me in my new BB3. If you've followed my build posts you already know that instead of the standard Devlin motor well I decided to go with a more conventional transom design incorporating a splashwell. After we got some motor issues worked out (thanks Tom) we hit the lake...I was pretty nervous.

The boat was empty except for me and a few gallons of gas. I started the trial with the motor pin set in the middle hole. I had built the transom with plenty of rake (about 17 degrees) so I was thinking this would be about right. The cavitation plate sits about one inch above the keel. The boat came out of the water easily and got on plane, but it quickly became apparent that porpoising would be an issue at full throttle. The boat turned easily, but the prop would let go in a tight turn. After moving the motor pin in closer one hole things improved, but when hitting a small roller or boat wake at top speed it would start to porpoise a bit and I'd have to back down.

Tom was showing me a new lake so we motored around for a while and checked out several bays. Before going back to the ramp Tom suggested I try the last pin position as only about a third of the keel was in the water at plane. I switched it and took it out for a spin - what a blast! The porpoising dissapeared, I was able to slice through boat wakes without worry and the boat prop would continue to bite in tight turns at speed. It pops right out of the water and is very dry. I didn't have a GPS, but I would guess the boat is hitting 28 or 29 mph - plenty for duck hunting.

The weather was gorgeous and Tom and I had a great day on the lake. It was fun to be out there with another member of this site.

I'll post pics of the transom and splash well tonight - I was too busy having fun to get pics of the boat in action!

Kevin T
 
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Glad it turned out well for you. I am thinking about building the BB3 (some day) but didn't know if I liked the well. I'm glad to hear the standard transom went well.
 
At rest, do you think you lost any freeboard at the transom due to your modifications?

Looking forward to seeing the pics.
 
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Chris:

If I understand your question correctly - no I didn't lose any freeboard. On most of the BB3's I've seen the transom is below the deckline an inch or two...perhaps because the builder added crown to their decks. On mine I left the deckline unchanged. If you were to span a batten across the sponsons of a traditional BB3 you would have a good idea of what my transom looks like. You may be able to see it in the build pic below...I'll post pics of the finished boat tonight.

View attachment 000_0195.jpg
 
Kevin, Thanks for the post and story. I haven't had a chance to post a pic and being somewhat retarded on posting pics it may not even work but I will try tonight. I got a couple goos ones. It was a fun day and I have almost gotten the damage repaired.
 
Chris:

If I understand your question correctly - no I didn't lose any freeboard. On most of the BB3's I've seen the transom is below the deckline an inch or two...perhaps because the builder added crown to their decks. On mine I left the deckline unchanged. If you were to span a batten across the sponsons of a traditional BB3 you would have a good idea of what my transom looks like. You may be able to see it in the build pic below...I'll post pics of the finished boat tonight.
Click to expand...

I would speculate that a conventional transom set up versus the original Devlin design could give MORE freeboard, due to the additional hull displacement.
 
Chris...not sure where you're going with that question, but Tom isn't all that big - he's in a broadbill - a smaller boat with very little freeboard. The BB3 is more my size...
 
Kevin,

I have found that the motor mount screws like to loosen when trailering, something about the vibration I think. What I do is zip-tie or rope together the ends of the 'crankers' after I get them tight. I haven't ever had one jump off but I had one that totally loosened up after a 150 mile trip.

Nice job on the boat.
 
Pete, I also have heard of motors coming off. Kevin is planning on bolting her up tight when the sweet spot is determined. I think he has found it, it really gits with the program
 
Kevin

Congratulations on a fine job. You are going to love hunting and being in your boat.




DeWayne


I would speculate that a conventional transom set up versus the original Devlin design could give MORE freeboard, due to the additional hull displacement.
Click to expand...


Not more rear freeboard in my estimation, less. It's basically a teeter-totter problem. Moving the motor forward 16" takes torque away that causes the rear of the boat to dip. The further forward you move the motor the less the rear of a boat dips. I suspect the motor well loss in displacement is more than offset by the shift in the motor's weight forward. Move a 120 pound motor forward 16" and you just reduced it's torque by 160 foot pounds. At 63 pounds per cubic foot a 120 pound motor displaces almost 2 cubic feet of water. For the life of me I can't see the submerged portion of the hull, of what would be the motor well, being greater than 2 cubic feet when the motor is hung all the way back. Nope, the whole back of the boat dips more because the weight shift backward is greater than the gained displacement from omitting the motor well.

Eric
 
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Kevin/Tom - didn't realise it was a pic of Tom in a different boat. Nothing wrong with being a man of substance unless it helps water come in over the transom. This is why I asked if you lost any freeboard with your design mod. I swamped my boat last December because myself and a buddy should have lost a few pounds and not added those extra 4 dozen burlaps to the load.

WRT to bolting a motor on - If I had heeded my neighbors warning about bolting my motor instead of using the zip tie trick, I would not have planted a brand new Yam 25 on the bottom of a Potomac tributary creek. I ran up on a log floating just below the surface (spring rains moved it out of the creek). It pushed the motor up and off the transom of a Carolina Skiff into the muck. I used every rescue diver trick but never found that motor. I should have flipped out the gas tank instead of hanging on to the gas line which broke.
 
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Chris, Thanks for the post now I don't have distinction of being the only guy here who has deep sixed a motor. It does happen FAST doesn't it?? My motor is now bolted tight and I added a lip to the outside of the transom. I may be slow but I do learn. Last Sat when Kevin and I were out I hit something really hard and the motor stayed put.
 
You guys have me thinking now. I really should bolt my motor on. With all the crap I hit every year I'm surprised it hasn't jumped off already. I do make darn sure the crankers are tight before taking it out though.

BTW Tom, I forgot to tell you the other night after your shear pin story. I broke 3 in one day myself years ago. It was 3 hp on a canoe and everyone was broke after dark while coming back to the landing - at Goose Island. I used to carry a chunk of brazing rod and side cutters because I ran through shear pins so often.

New Power Pac should be here by noon today. Ended up having to call Sierra for the correct cross reference for the PN I had. Turns out it shows that it's an '85 not an '86.
 
I haven't bolted my motor on, but after reading Tom's story a while ago, I have been using a 1/2" wire cable from the motor to the grass rails. There's not much slack and should keep the motor from going in the drink if it were to lift off.
 
On my Broadbill I use a cable from the motor to the back grab handle should the motor ever try to pop off it won't go to the bottom. If it came off going down the highway I'm not sure if the cable is short enough to keep it off the pavement. I think the liklihood of the motor popping off trailering is substanatially less than hitting something going down the river and jerking it off.

The motor on my Brant is bolted.

Eric
 
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