LB26

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les2021
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Re: LB26

Post by les2021 »

Cheers Dan

All advice is welcome.

In the notes it says about a 1\2 inch radius on the transom but does not mention the chine !!! ( i think ) so do i have to give the chine a radius as well ?

I also gave another look to the laminating schedule. Am I right by saying the following ?

Keel 2 layers of 15cm tape on the outside. 1 directly on top of the other ?

Chine 1 layer of 15cm tape on the outside

Bow !!! the bow has a 40cm radius at the sheer.... how do i give this 2 layers of tape ? horizontal ?

Family arriving from the UK on Thursday so I've been told the boat workshop is out of bounds.....Could be trouble ahead...

Cheers

Les

fallguy1000
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Re: LB26

Post by fallguy1000 »

NEVER lay tapes on top of each other. This creates hard points. In ALL boat work, strength and weakness changes must be gradual. This also helps for fairing. Two four inch tapes are staggered at least 1:2" off each other.

A chine that gets a tape must have a radius, then you build the sharp edge back with compounds. Same for transom. You will get a performance improvement making it so water exits cleanly and without drag. On my boat, the chines were brought back to mostly sharp for the last 15 feet. Further for'd, it won't matter. I use milled fiber on edge build back first pass because I want body in the fill in case I hit something someday. The edge build also protects the core from delamination in a strike of say a floating log. Consider a hammer shot to a taped edge versus a hammer shot to a taped edge reinforced and squared back with milled fibers... you can test it as well to get a feel for what happens...take a piece of tape and laminate it on a core scrap...wait two days and hit with a hammer...reinforcing the edges back to square is a benefit you'll quickly see

The tapes won't lay on sharp edges. Just take the dry tape over to your boat and see if it will lay down dry. If it won't stay down dry, it won't do real well wetted. You'll see the tape edges balloon or puff just off the corners.

Build notes by all designers may miss a fine point here or there. Fiberglass does not lay over sharp edges; the designer is not obligated to tell you these things; the LB26 is not an amateur boat build, so things like not stacking tapes or radiusing corners is expected knowledge. Be kind here. I got lucky I got some really good advice along the way.

If you are taping two different sized tapes, do not fall victim to the idea that shingling is best or that laying the big tape last is wise. It is not. In fiberglass work, two tapes are done for the thickness. Laying the big tape last will result in the potential for sanding it off on the high spot and air entrainment is certain. Bigger tapes are always first by pros. Again, dry check it. You'll quickly see how a big tape last will result in air at the intersection.

I am glad to help you navigate and answer questions. I can also give you my contact info if you like. I am not sure about any of the inboard stuff, though.
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fallguy1000
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Re: LB26

Post by fallguy1000 »

Also, if you reinforce the chines with a tape before laminating the whole hull, you will want to sand and prefill the new tape edges with some thixo to avoid air pockets. The bottom of a boat is super critical. A dime sized void in a laminate gets literally tons of hudraulic pressure and will erode and delaminate. More and faster in a speed boat.

The step in a 1708 tape is 0.050" high. This is too much for the glass to lay down. Take a four inch trowel and ramp the step in four inches. Otherwise, you get air pockets and they could run for several inches.

If you get any air pockets in your hull or tapes layups, they must he ground out and repaired or epoxy injected. To inject, get snub nosed needles 0.065" or 1mm and drill two holes; one is a vent. If they are on the side, put a masking tape and keep the holes high. For repairs, grind out and fill with pb epoxy.
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les2021
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Re: LB26

Post by les2021 »

As always cheers Dan.

Jacques can you comment please. I am finding the drawings fine, it is just a few small details which I need to learn.

Dan's posts are of great help, as the designer would you like input.

This is my first boat build but to be honest I am not finding it very hard SO far. But there are points which I am definitely not accustom to
" fibreglassing " for one. The tutorials are general and I understand the basics but they are not specific to individual boats. The LB 26 has a 40cm radius on the bow ( not easy with a 15cm tape ) So do I cut a fabric triangle 60cm - 10cm and then add on top a triangle 50cm-5cm so the whole bow is then covered and should one be CB1708 and one CM1808 ??? As Dan then kindly points out to me this will need fairing before sheet material is laid. This point I would not have picked up from the notes etc ( or did I miss them )

With regard the keel, is correct to say I am laying 15cm the full length and then 5cm on top then fairing as before, this giving a 5cm lap each side.

Like wise I was pretty sure the chine would need a radius but thought I would ask the question just incase, the notes only mention the transom.

But once again I now know every sharp edge needs a radius and can be reformed sharp later ( cheers Dan )

As mentioned before I am loving this boat build, 103 hours in and learning every hour. And the forum really helps.

Cheers

Les

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Re: LB26

Post by jacquesmm »

The radius situation is simple: you have to end up with a sharp radius at the transom and chine but you can't bend the specified fiberglass over a radius smaller than 1/2" (12 mm) without creating an air bubble..
You will round all those edges to 12 mm before glassing, glass over it with a 12 mm radius and finish the edge later.
After the fiberglassing, you will build a sharp corner with a putty made from resin and milled fibers.

It does not matter if your starting radius is 10 or 12 mm or even 15. It does not matter if the putty is made from milled fibers or silica, as long as it is hard.
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les2021
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Re: LB26

Post by les2021 »

Hi Jacques

It was not meant as a criticism of the building notes or tutorial it was just a comment from someone who is not up on fibreglass laminating.

Sorry if it came across that way.

Could you please comment on the taping of the bow etc as in my last post as I am not sure the procedure for taping something with a 40cm radius. Is my approach listed in my last post the right way to proceed.

Many Thanks

Les

fallguy1000
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Re: LB26

Post by fallguy1000 »

You do not need to worry about the 40cm bow so much. Just reinforce the bow as specified. If spec calls for reinforcing chines with 10 cm tapes, then do so and the glass will do the rest. The thing about the bows is whether you install a tow eye. Then you must use HD foam. But the regular layup will address the flare of the bow.

Sometimes, a question such as this can be confusing because it is rather obvious and to be kind to JM; he may not understand. As a guy who has struggled with drawings and details, I understand your question. The foams in the bow flare are bonded with epoxy and only need the regular layup; no wider tapes are needed. If you wanted to cut a custom tape for the section, you could, but then you'd end up with a hump at the intersection of your custom tape and the regular chine tapes specified for the bow. Make sense?

A new builder may become confused, but keep in mind the chine reinforcements are done because of stress concentrations. A change in direction of hull is one such. And at the bow, the most severe is right on the point of the boat at the centerline.
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jacquesmm
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Re: LB26

Post by jacquesmm »

There was nothing wrong with your question, maybe something was lost in the translation.

For the bow, as Fallguys says, there is nothing special except that you will have the overlaps from the two sides. This is fine, you need more layers there. The bow has to be strong in case you hit a dock during a maneuver.
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OneWayTraffic
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Re: LB26

Post by OneWayTraffic »

When I drilled a hole for my bow eye it was over 20mm thick, not including the backing plate. Definitely strong. 3mm glass, 6mm ply, 12mm fillet, 3mm glass. That was on the C17. All those overlaps matter.

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BarraMan
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Re: LB26

Post by BarraMan »

OneWayTraffic wrote: Tue Aug 31, 2021 9:57 pm When I drilled a hole for my bow eye it was over 20mm thick, not including the backing plate. Definitely strong. 3mm glass, 6mm ply, 12mm fillet, 3mm glass. That was on the C17. All those overlaps matter.
Indeed! On my boat, with all the overlaps, there are 27 layers of 12 oz glass tape or cloth where I placed my bow eye.

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