Stuck On Dagger Boards Trunks - How Would You Build These? (plan photos inside)

Well, I give up. I've spent 20+ hours trying to understand how to build dagger board trunks and I'm still just as dumb as when I started.

Here are the plans for my trunks. Could anyone help me, with a step by step post, to understand how to actually make these things??

Obvious advantages to any method would be:

*Wet on wet all the way through the trunk build to avoid sanding
*Seams on the inside done first, so no need to reach inside an 8' long trunk with a stick and try to laminate that way (poor results, I'm sure)

ALSO...

If anyone has a *better* way to build a board trunk that deviates from the plans here, I'm happy to consider it. These plans seem like a huge PITA to me. Maybe it's just because I'm too stupid to understand how to build them, but they look needlessly complicated to me. How about just taking 12 layers of 24oz and wrapping it around the board and being done with it?

Open to any and all ideas on how to build this particular trunk as shown in the plans, or any other trunk that will fit around my boards and safely enclose them in the event of hitting the ground at 20 knots, as well as allow them to move up and down easily.

Thank you in advance.

 

Gooday 'Cat-b'. I'm sure you're going to get many many answers - so I'm somewhat edgy about getting into this one - as in the past - there are far more intelligent people in here - than I - or so they think. Might be worthwhile extending your thought process about "just wrapping some glass around the board. Of course after adding some 'sheet-wax' as a 'spacer' prior to laminating. Also thinking about adding a sizable piece at the bottom back of the c/b before moulding the c/b case sao as to be able to insert a 'crash foam wedge' that can be easily replaced in the event of a collision.
Don't think that anything will be totally effective at 20 kts though.
It would be interesting to find-out what the owners used in cats like 'Sundancer' (40' - 1967) & 'Sundreamer' (59' - 1983) 'Dreamer is still actively sailing & very quickly at that. And/or any other reasonably quick 40' to 55' multihulls that have addressed this vexing problem. As I recall there was much thought put into this problem area - at those times. Wonder what Nigel would suggest or what he draws when doing his very quick multihulls? I do recall that we allowed a replaceable high density foam compression slab of substantial size - at the back of the c/b - inside the c/b case - - to take-up the impact of the board slamming backwards when it hit something at high speed. Trust you'll find a good solution to go with before you're finished this research. Ciao, james

 

Thanks, James.

I'm happy with Kurt's design (pictured), but I can't, for the life of me, figure out how to build it. It seems nice, but how do you actually make what is pictured above from fiberglass and a piece of plywood?

It seems like a tremendous amount of work with all the layers of glass, then tapered to a tapered piece of plywood (both inside the trunk and out).

I'm truly lost on how to actually make this thing... I'm just shopping alternatives in case the answer is "laminate this, then sand that, then stick an 8ft stick inside and do the inside lamination, then sand with a stick, etc...) That's too much work if that's the only way. I need to find a way to do Kurt's design wet on wet if possible...

 

Hey Cat,
The way I did mine was with a piece of pvc pipe warpped in plastic.

The inside of the trunk can be glassed first and seperately, with 6 oz barrier fabric, then the biax or triax or whatever, then the graphite coat.

then both panels are temp screwed to the pipe, with their edges running a quarter inch or so beyond the centerline of the pipe. cut a two- by the exact width of the trunk and insert it next to the pipe on both sides so that it is touching the pipe, and temp screw it in place. It would also be good to put one or two more inside,in the middle of the trunk to keep the inside width of the trunk exactly uniform.

Then structural bog goes into the gap between the edge of the ply and the pipe, on the outside. When that cures, run the grinder over the outside edge of the panels to form a a rounded edge to match the pipe, roughing up the strip of bog at the same time. You can also pull the temp screws out of the pipe at this time, since the bog holds it in place on the outside and the two bys hold it in place from the inside of the trunk.

Then, layup your outside laminate. As you taper the layups at the pipe/edge you can carefully pull out the temp screws in the two bys as you go. (I didn't do this step and had to come back and grind them out)

 

I'm pleased that your "happy with Kurt's design" - I'm not going anywhere near that subject. I didn't have much luck going down that road. However after inspecting the ply - used in several cats built back in the 60's & 70's - I can asure you there is not way I would ever use ply in a boat where I could not get at it easily - to be replaced as necessary - which it will need to be in due course. I can't see why the ply is required - in any case. With the very high quality of the structural foam's available today - I can't see why anyone would use plywood for anything to do with boats - full stop. Good material - yes maybe - but not for me. I'll leave its use to others, thanks.

I can't see what the ply piece is supposed to do?
Like you I can't see why - when the c/b case is finished there would be any necessity to do anything to the inside of the c/b case. Once it's finished - it's finished & can then be glassed into the hull. All IMHO - of course - what the hell would I know - only been building/repairing multihulls for a living since 1962.
When you get it all figured out - please let the rest of us know. Travel well & keep positive. Ciao, james

 

Charly, thank you for the post. I'm going to read it, then re-read it, then re-read it again. I truly have a hard time with cases and I don't know why. I will probably have a follow up question if that's ok.

James, I don't like the wood either. I'm thinking of using Corecell instead (and was considering solid glass too) so I never have to go looking at rotten plywood in such a difficult location.

 

How I did mine, 10mm strip planked cedar.

* Make daggerboard
* Wrap daggerboard in lino approx 2mm thick (hot melt glue spots)
* Push split garden hose on trailing edge and plasticine thickness difference between lino and hose
* Give it all several coats of pva mould release.
* 2 layers of 440 DB
* Several addition layers at trailing edge
* while green or after light sand, runny slurry and start sticking on planks using weights to hold down.
* Next day roll over and repeat.
* Sand and glass with 2 layers of 440db.
* Allow to cure and then bust off of board

Bigger boat would obviously need thicker core and heavier glass

When I glassed this into the hull I also got some choppergun rovings/uni , cut it into 2 metre lengths and wrapped it around back edge of case and fanned it out through B/h and 1 metre fwd .

This was bulletproof on a 10 metre cat, proven by a grounding on an unmarked bombie with boards down at 14knots hard enough to actualy lift the hull mostly from the water, supported on board.
Damage done to hull was a 1cm hairline crack at back edge of case under the waterline, nothing visible at all on inside.
Board damage was minimal.

 

Whether you use ply or corecell the process would be the same. The hard part with mine was finding a pipe with a suitable outside diameter. Since my pipe was a bit small, I had to cheat a bit and rip some shims to fasten to the outside of the pipe. I just screwed them into the pipe, one on each side, the whole length of the trunk.

 

Charlie - Great instructions - very clear & easy to follow. Thanks so much for sharing all your knowledge. Good sailing. Ciao, james

 

Thanks! Heck. For my next project, I am thinking about an Hadron Supercollider for the backyard. Plywood of course.

 

Ha ha ha! Plywood super collider! Best post ever!

After all this, I decided to go solid glass and keep it close to foil shape so i have less water to carry around with me. Also, I can infuse it that way.

Thanks for all the help. I carefully considered each way of doing these trunks.

 

Cat Ed,s book says to build half molds out of masonite. I can type out all of his instructions if it will help. Rick

 

Instructions & Diagrams

Gooday 'Charly(brown?). Instructions & Diagrams for 'Hadron Supercollider' for backyard - - all 28 pages of them. Please note our 'house yard' is 10.5 acres & is very contoured. I only mention this - so you can adapt the instructions & diagrams to suit. I only have time/effort to do this once & get it right because my goal is set on trying to get to SE Asia to buy a 40' tri to go cruising & I don't wish to waste time or money - - so I'm putting my total trust in your excellent guidance. Thank you for all your knowledge & assistance especially considering your elevated position of experience & abilities.

Thanks again, ciao, james

 

Thanks, Rick. I don't want you tiring out your fingers!

I already have the dagger boards finished, so I'll be using them as a male plug mold for infusing the cases over.

Deviating from the above plans, I can make a case with less water inside it and one that can be more easily built just by wrapping the existing board in glass (with some spacers to keep the case off the board and provide needed clearances).

Thanks for the offer though.

 

Yes! I have I high level position. I have been working off a scaffold all week.

Best of luck with your tri