Visit our Popular Forums

Thumbs Up · 06-12-2020, 18:07

Quote:

Originally Posted by MicHughV

I must have missed that.....old age...bad eyesight....

I don't read thru' all the posts...my bad

I know you don't work with epoxies, but you could still have a shop fabricate a plate from FRP and laminate it to the tube....same with closing the holes....but it appears you are headed in another direction.

Wishing you the best in your project !

That is what I said. Doing it in frp (resin), Good idea.

A pair wooden blocks jammed inside the beams and bolted through the top with oversized carriage bolts is what I proposed. I am thinking that it will be good to make them 2' long. They could have a reverse taper top and bottom for flexibility (and saves weight). The extra strength of the wood will more than make up for the big hole in the top. 1- 2x4x8 will do. I suggested Ipe. Or even cut and plane some blocks out of an old fencepost. They should look like this: > : <

Thumbs Up · 06-12-2020, 18:14

Quote:

Originally Posted by Chotu

So boats like this have very little structure holding the traveler. Way less than mine. Why doesn’t the racking force cause issues?

Transferred to the welded SS flanges on the posts. The laminates are reinforced where they are bolted.

Chotu · 07-12-2020, 01:14

Quote:

Originally Posted by Thumbs Up

Transferred to the welded SS flanges on the posts. The laminates are reinforced where they are bolted.

Still, at the angles involved and the area of a high aspect main, seem like the forces would be too great. Apparently they aren’t.

I’ll have to do the same on mine in composite. And more use of backing plates on all of this.

Chotu · 07-12-2020, 01:20

This is the same boat from my last pic. Lagoon 520. There is nothing holding these columns. Do you think it’s the bury in the aft structural beam doing the trick?

There does seem to be a bit of a box beam above them but the attachment points are what confuses me. Basically no resistance to racking.

Maybe the traveler is more in tension than anything else?

Thumbs Up · 07-12-2020, 08:58

The forward connection has triangular struts. Welded flanges on steel posts are incredibly strong. Think about a lamp post, or a flagpole. But looking at more lagoon photos it looks like these posts are buried in sockets at least the lower ends, some seem to on their upper connections as well. The posts are pretty massive.
I am pretty sure that the hard top on that particular model vibrates a lot when sailing.

Chotu · 07-12-2020, 09:08

Quote:

Originally Posted by Thumbs Up

The forward connection has triangular struts. Welded flanges on steel posts ore incredibly strong. Think about a lamp post, or a flagpole.

Ah. Ok. I also have angular struts. They were designed for looks, but provide the same structural support.

As of course, does the entire rest of the deckhouse which it is attached to.

That a relief. I was worried the racking forces would be too much for my deckhouse and the columns. But they have significant less support structure on that lagoon.

My entire deck house is attached to the roof. It’s all one level. There is no separate piece like the lagoon

zstine · 07-12-2020, 09:28

Your racking loads from the main sail (loads athwartship) will be taken by the roof panel... same way the sheeting on the walls of your house keep it from racking. I know you have big windows! The structure holding the roof up will take the twisting of the roof. Hope that doesn't pop out more windows! The columns aft will be in tension when you are close hulled. need to transfer the tension from the sail track to the column and down to structure below.

Chotu · 07-12-2020, 09:48

Quote:

Originally Posted by zstine

Your racking loads from the main sail (loads athwartship) will be taken by the roof panel... same way the sheeting on the walls of your house keep it from racking. I know you have big windows! The structure holding the roof up will take the twisting of the roof. Hope that doesn't pop out more windows! The columns aft will be in tension when you are close hulled. need to transfer the tension from the sail track to the column and down to structure below.

Ok!!!

It’s all starting to make a lot more sense.

I think my deck house structure is up to the task. There is actually a bulkhead, where the salon entrance doorway is that should take a lot of it. Then there is the entire rest of the deck house with angle beams all over the place.

At this point, I’m probably over analyzing. I think I just have to trust it at this point.

At this point, I’m probably over analyzing. I think I just have to trust it at this point.

But it is kind of nice to have the help to realize that those columns will be in tension when close hauled, and the dinghy will actually help with that. A little bit. Ha ha

MicHughV · 08-12-2020, 11:31

Chotu,

Got one last suggestion here....yeah...I know...you won't like it...

but....you mentioned the tube extends over the roof by 7'. I don't think you need to have 7' .

You could cut 2' off and place it over the tube where the tube intersect the roof....say 1' either side...cut the ends at 45 degrees.....

The 2' section....can be attached over the primary tube in many ways..it will serve to cover that hole, strengthen the bending moment and also provide rigidity to help with lateral movement...

it would look kinda cool too....sorta...kinda...'jes sayin'.....

Chotu · 08-12-2020, 14:52

Quote:

Originally Posted by MicHughV

Chotu,

Got one last suggestion here....yeah...I know...you won't like it...

but....you mentioned the tube extends over the roof by 7'. I don't think you need to have 7' .

You could cut 2' off and place it over the tube where the tube intersect the roof....say 1' either side...cut the ends at 45 degrees.....

The 2' section....can be attached over the primary tube in many ways..it will serve to cover that hole, strengthen the bending moment and also provide rigidity to help with lateral movement...

it would look kinda cool too....sorta...kinda...'jes sayin'.....

I like this idea!

Lodesman · 08-12-2020, 15:52

My take is that you won't get the full strength of the FRP tubing by only securing it by one side. And securing from the top side would risk crushing the tubing. Cutting any more material out will weaken the tubing further. If it was me, I'd get some solid square stock of any suitable plastic (acrylic, hpde etc) that will snuggly fit in the tube and shove it down the tube with dab of glue on it - lined up with your drilled holes. After the glue sets, drill through it and get longer bolts - I'd use carriage bolts and secure from the bottom.

MicHughV · 08-12-2020, 16:37

well....if this were my boat...this is probably what I would do given the circumstances....

I said cut the ends at 45 degrees on the upper tube.......just for a more finished look.....but on reflection, I think a full 3" radius would be better...it would be less sharp edges....or a 2" radius on the upper side....this would still leave a 1" vertical piece on the bottom....or a 1" radius even....you got options here...it's your call....

I'd use two bolts , that go thru' both upper and lower tubes in the 1' section over the deck....nice big washers here (top and bottom) to distribute the load...the bolt furthest out should be about 2" from the end, to maximize the lever arm of that upper piece...the other bolt about 2" from the edge of the deck.

On the back 1' section, also two bolts, but I know you have a plate underneath there....if it were me....I'd have at least 1 bolt go thru' both tubes and the plate, (two bolts here would be sweet, either side of the post)....if not, the other bolt can go through the roof....the rear one...also about 2" from the end of the upper tube, but I'd like to see a strong rigid connection here...if you can go thru' the plate for the first bolt location ( and another bolt if possible).....that's the best situation. I don't know how this plate is fastened to the roof at this location, but a good cobalt drill can drill right thru' stainless plate without any drama. So you might end up with three bolts in that rear section, 2 thru' the plate and 1 ...2" from the rear. You want that rear bolt as well, again to maximize the lever arm that upper tube can provide.

You don't want a lot of movement here, so the hole you drill thru' the tubes should be as near as dammit to the bolt diameter...

Finally, that upper piece....I'd use a minimum of 2' length .....but a bit longer wouldn't hurt, so if you cut a piece 2'-1" or 2-3" that is also good.. I know you have holes in the tube back there, but that section of the tube can always be turned sideways, so any holes in the upper tube will be in the vertical side.....or you could use an existing hole in the upper piece for one of the new bolt locations...if it lines up in the right location....

Once this is all put together, push sideways on the tube with your hand, this will give an idea how rigid this tube is....any doubts here, find a way to brace the two arms....many options here, having a brace allows the two arms to share a lateral load....seriously consider a brace....again, if this was my boat, I'd fit a brace...but that's me.....I'm a belt and braces kind of guy....

You are there, and I am here, with your eyes on the situation.
Consider this a guideline.