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Tramson boarding options


Tom Lathrop
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This is a question from Steve Smith in Port Ludlow, WA that I am moving to the forum for everyone to see.

 

Hello Tom,  progress report on BJ 28 hull #11.  The transom suddenly looks very big as seen from an approaching dinghy.  Has anyone given any thought to providing an access door to lower the hurdle required to board the boat from a dinghy?  I'm imagining a small door that would be above the level of one of the seats next to the engine box.  I can't claim to the knowledge of engineering required to design something myself but if someone has already tried it and has some experimental information I'd be more comfortable. 

We're still having fun, but the cooler weather is making itself felt.  I'm thinking of delaying the first turnover until next spring and prefabing some of the interior fittings.  Steve

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The main issue with having a door in the transom to make boarding easier is the stability that is left on the side.  That results from tension developed by the tumblehome in the aft topsides that will have a side force that could allow the side to open up.   Having said that, I think that there is room for a door from the deck level to seat level if it leaves some transom structure to hold the topside in place.  If the door is , say, 12” wide that will leave about 8 to 9 inches for a supporting web for the topsides.  The transom is ½” thick here and if well bonded to the topside, that should be adequate support to restrain the tumble home from moving any at all.  Actually, I think that is conservative and the door width might be expanded a bit.  Since anyone wanting a transom door may want to use the cutout as the door to preserve the curvature,  the decision is not changeable.  That assumes that there is no remaining springback which may not be true and a new door must be constructed.  In that case, a builder could creep up on the best width to satisfy the conflicting demands for enough boarding room and enough web left for topside stability.  I think it might be wiser to take the second option.

 

Some sort of boarding platform, whether fixed or folding will be needed in any case.  There are some stainless folding units made to fit such boarding platforms.

Of course if a builder should decide to construct the boat with an extended motor bracket, the opening can be in the center and no chopping of the transom is required.

 

Of course if a builder should decide to construct the boat with an extended motor bracket, the opening can be in the center and no chopping of the transom is required.

 

Tom

 

A photo of Steve's transom is attached.

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Food for thought...

 

I had great success with my boarding ladder that I actually fabricated to fold up. It was really sturdy with a metal frame on the bottom side of the teak platform. I liked it because I did not have to worry about dinging in while trailering either. All the line did was to help me fold it up. The pad eyes folded beside of each other and I used a snap pin across the two to secure it in place for traveling or running on plane.

 

With the higher transom you will need a wider platform than most of the off the shelf ones so that you can step over and into the boat if you do not cut out a door. I used inboard engine box hinges. If anyone needs more details I can post the shots.

 

I have also done a great version of an improved boarding ladder with one pipe insert into a zero degree rod holder. Few aluminum welders have ever done this, but it can be done by a seasoned welder. Push pins keep the two pieces secure with male and female brackets welded to the main tubing.

 

 

That style worked  for the dock or sandbar and then in deep water with the fold down section. The fellow carried a great Honda generator that's really quiet and when on anchor and he would use it at night, he did not worry much about fumes or any of the tiny noise, which is almost none from it.

 

 

I also generated one for a side of a big flared hull and the duel steps when folded up made a solid platform for stepping up and over the sides. I also added a tee support on the top so that the boarding person could steady themselves as they crossed either way. I created a handrail that also helped when boarding the high freeboard to the top.

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I am thinking about a door on the starboard side of the cockpit.  It would go from the top down to the belt stringer.  Reason for starboard side is to use the boat also as an RV when traveling.  Also helpful for boarding a dinghy.  On the side of the boat there would be plenty of space to add framing around the door to keep the hull curvature in shape before cutting a big hole in the hull.

 

There is a MJM 36 boat that has doors on the side of the cockpit.   

36z_SideDoors_1-141-600-450-80.jpg

 

Egbert

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Mike,

 

I had your platform in mind to bring up later but wanted to give an answer now.  Some detailed photos would be great as I know your aversion to paperwork.

 

Egbert,

 

A door on the side could work also but satisfying the structural necessities would still be needed to make sure it does not result in an unfair sheer.  Can't use a platform there of course so a ladder would be needed for boarding from swimming.  We could all search for more possibilities.  Handholds on both sides of any door are usually needed for many with low upper body strength. 

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I have tried three times to link a couple of photos from photobucket and its impossible. I tried to zoom in on the shot In the water, but it does not show detailed enough.  I also typed a small detailed description with two close ups but it also will not post after it went thru the editing. I will send you a couple of shots and the description and see if you can figure it out. I hate computers and all these options to click on. UGG!!!

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EJDS,

One of the rescue boats I worked on had a door in the starboard side of the cockpit and the new crew (myself included) had to be constantly reminded not to step on it when boarding from a high dock or when going forward on the starboard deck.  If you put a side door in, make sure it can handle people jumping onto it from a high fuel dock.

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The additional detailed shots are not on my 'puter sir. And I tried to copy them off of the  crappy photobucket site that's been modified and updated to the point of being dysfunctional and cannot copy them back to this 'puter. The closest would be to pull out tens of CDs and go back thru them and see if I can find that section. I was using a worn out camera at that time with a small memory card and would have to delete pictures after I loaded them to get more room. So I am not sure if they are even on them. I really never thought that I would need them again. I got LLoyd to take those aged shots for me.

 

 

But FWIW, the photos are recorded in my own "hard drive" memory of the Cranial CAD program, if that would work for you along side of the boat plans and drawings. ;<}

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Thanks Ken for pointing out people jumping on top of the door.  Possibly some cement and glass shards would do that.  I was planning on locating the door midway in the cockpit between the aft seat and a cockpit locker behind the cabin.  Hopefully most people would board just  behind the cabin where you can step on top of the locker and there will be a handhold on the back of the cabin.

 

I wasn't really thinking of boarding from the water.  The door should be able to be used that way also for good measure.  One way would be a double duty boarding ladder that can be used at the transom or someway hang on the door opening providing a handhold and steps.

 

Egbert

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The tumblehome sides above the cockpit sole will need side framing created to hold the shape before you cut the opening on both sides, which also will need to stay in place, if that is your plan.  I would also think that you will need to double up the sides from the aft cabin bulkhead, laminating the secondary piece in place before you fit the framing. But also think that you will get some spring back or at minimum some distortion in the sides. Its not like the fiberglass hulls and the thickness with liners.

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  • 2 weeks later...

Attached is a picture of the cockpit area where I plan on locating my door between the forward and aft locker.  The area is already reinforced at each end by the locker walls.  The door will start just above the belt stringer up to the cockpit coaming.  More reinforcement of the area will come from a honeycomb like structure on the hull side and in front of the door.  Hopefully that will be enough reinforcement to avoid deflection of the hull shape after cutting a big hole in the side.

 

Egbert

 

 

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  • 3 weeks later...

Finally I managed to cut the opening for the door in the cockpit starboard hull side.

I reinforced the area by adding plywood ribs where the door goes and in the area adjacent to the door.

When I cut the door out today there was no visible distortion of the hull side.  Hopefully it stays that way after crossing the Atlantic Ocean.

 

Egbert

 

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