FAQ FAQ  Forum Search   Events   Register Register  Login Login

Building a ply dinghy.

Page  <1 678
Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 22 Oct 2017 at 9:46am
Steps View Drop Down
Titanium
Titanium


Joined: 14 Oct 2013
Location: Sth Auckland
Status: Offline
Points: 8189
Looks good.. do like the size open hole in the bow seat... thats well thought thru.
Looks heavy for its size.. maybe its the solid supports from side to side on the seats.
 Well done.Thumbs Up
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote mikejf Quote  Post ReplyReply Direct Link To This Post Posted: 22 Oct 2017 at 5:48pm
mikejf View Drop Down
Silver
Silver


Joined: 22 Jan 2012
Location: Paraparaumu
Status: Offline
Points: 112
sweet, that looks great. Now enjoy all that fishing !
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 22 Oct 2017 at 8:51pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
It is heavy for its size. I can still single handed move it around and lift it on our garden trailer though. The extra weight comes partly from the extra fiberglass on the bottom, rubrail, sole and seat tops partly from the wheels. All up it's maybe 35kg where the plans stated 25kg. The motor is another 12kg. Not an issue. It should be built tough.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 26 Aug 2018 at 12:23pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
I've done a bit of refitting so thought I'd post it here.

1. Glued an Aluminium flat bar on the bottom. It was getting slightly scratched up from dragging onto concrete boat ramps etc.This was a regular strip of 20mm by 1.6mm by 1000mm aluminium from Bunnings. Glued with the same Aluminium powder/ West epoxy mix I used to cover the boat. Filled the scratches while I was at it. Works well. Aluminium glues ok if you prepare it by sanding then coat then sand some more to get the epoxy into the surface. 

2. I installed some inflatable pontoons along the sides. The original design is about as stable as a 2.4m long dink gets, which isn't much. OK for just me, or if going for a trip but I wanted more when at anchor with a kid or two on board. These are fully removable in less than 5mins. I haven't gotten them wet yet.

The fabric was from a website in Canada that sells diypackraft gear. I welded it with a clothes iron, so wasn't keen to get all fancy with it.  


Back to Top
Post Options Post Options   Likes (1) Likes(1)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 26 Aug 2018 at 12:24pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2019 at 11:56pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
Thought I would update this with some photos from my iPhone...



Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2019 at 12:15am
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
Having issues getting the text inline, but the first and last photos are from Lake Georgina, one of the Canterbury high country lakes. Well stocked with Rainbows of good size, and they take softbaits well. Our first visit we caught three of legal size and kept two. Nobody else was catching that day. No trolling on the lake, but it is an ideal size for drifting in a little dinghy and then motoring to another spot. 

The middle two photos are from a swamp test on a scout camp. I have strapped two air pontoons to the sides, both home made with an iron and packraft fabric. With these I was unable to capsize the boat even swamped despite leaning well out on a gunwale.  Removing one I could capsize the boat but also with some difficulty reenter. There were pool noodles under the middle seat as extra flotation. The hull material is lighter than water even with the glass on it. 

I would conclude the boat is basically unsinkable- as long as she is used in the manner for which she was designed and built!

I am planning to build a bigger one in the new Year. Flat bottom cabin boat with low speed planing and offshore capable in the right hands.






Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2019 at 1:15pm
Steps View Drop Down
Titanium
Titanium


Joined: 14 Oct 2013
Location: Sth Auckland
Status: Offline
Points: 8189
I really like looking at those sorts of boats.. have a charactor about them... like old 1950s english cars.

looking thru specs etc.. sort of doesnt add up in places.
18 ' 9" 
 Displacement of 1136kg.
 I think from the construction materials it would be rather more than this. Hand laid fiberglas tends to be far heavier than gun/chooer therefor mettered sprayed... getting up around the 1300/1400kg
 Then add say 3 guys ave 85 kg (250kg) then gear fuel batteries etc that takes gross weight on the water up around the 1800 kg

OK assuming that ball park correct..
They say 50hp will WoT about 24 to 28 mph .. lets say 26 mph. That gives a plaining hull efficiency way up with a high  end performance race boat with just the prop in the water..
 Realistically maybe 20 mph, and that assumes the 50hp has enough reserve power low mid range to even climb over the bow wave...very very unlikely..
 And that it will actually plain at that speed.. not still be a displacement or semi replacement hull.

Now IF the calculations are done with just the bare hull.. no ppl , no gear, no engine then yes .. their calculations work.. just.
 To get 26 mph on that hull and weight you will need about a min of 80 hp at the prop, then add another 15% for reserve power at cruise etc otherwise it will be a pig to get on the plain, in crossing a wake or even small chop.
 And that is ball park bare min.

As to 10hp to push her as a displacement hull...this is an area I have next to nil knowledge..
 What little I do know is the longer the hull the less hp required.. a issue that often comes up in these forms when trolling off the plain.
 But 10/11 mph I think you will need about 40hp..???
 Where as if almost 2x the length would 1/2 the hp required ??
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Rozboon Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2019 at 3:37pm
Rozboon View Drop Down
Platinum
Platinum


Joined: 05 Oct 2015
Location: NZ
Status: Offline
Points: 1401
Originally posted by Steps Steps wrote:

I really like looking at those sorts of boats.. have a charactor about them... like old 1950s english cars.

looking thru specs etc.. sort of doesnt add up in places.
18 ' 9" 
 Displacement of 1136kg.
 I think from the construction materials it would be rather more than this. Hand laid fiberglas tends to be far heavier than gun/chooer therefor mettered sprayed... getting up around the 1300/1400kg
 Then add say 3 guys ave 85 kg (250kg) then gear fuel batteries etc that takes gross weight on the water up around the 1800 kg


It says the hull weight is 500kg :/ How on earth did you get to 1300/1400kg unladen, most boats in that ballpark weigh less than that with the trailer still attached.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote phillipcollis Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2019 at 4:08pm
phillipcollis View Drop Down
Bronze
Bronze


Joined: 13 Sep 2018
Status: Offline
Points: 5
My boat for lakes and the inshore fishing...Phillip
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2019 at 5:15pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
The hull material is plywood with epoxy and biaxial fibreglass both sides. Having access to the plans I can confirm that 500kg is correct, assuming I build to the plans. 

The bottom panel for example is two layers of 9mm ply with 400g fibreglass on the outside, and frames glassed in on the top. Similarly sides are 6mm and 9mm ply with a layer of glass both sides, or just epoxy coating where the ply has sufficient strength alone. Bottom panels for vee hulls are typically 6mm or 9mm ply with a layer of glass both sides, two layers for 40mph+ boats, along with overlaps and tape at chines and keel. 

These panels are both stiffer, stronger and lighter than the same thickness of chopped strand/woven with polyester. This is based on both calculations and experience. I built up a test panel and drove the car over it. 

As for the hull weight that is correct, but does not include outboard, heavy livewells, anchor chain, fully enclosed hardtop, water, food, coffee machine... 

Just plywood, epoxy and glass. I would add glass on the sole, all the outside up to the sheer, any surfaces subject to abrasion or the elements, so maybe 550kg all up. 



In this picture, the scupper holes are visible, about 5cm above the waterline. That equates to a displacement of about 1100kg, more or less. The builder stated that scuppers are at the sole, and the PPI is 431 pounds per inch. Max displacement to put sole under the water is 3300lb+- (1500kg.) 

That boat is powered by a Honda 50hp and the builder gets a little under 24mph. Another guy got 31mph with a Suzuki 50hp but switched to a lower pitch prop. I think the bigfoot or high thrust versions would be a better bet for planing. Flat bottom hulls are easy to plane at very low speeds, but pound a lot at speed in chop. 

 
Here you can see one under construction. 



I am still waiting for finances to allow me to start. 
 
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2019 at 5:53pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
The HM19 is a bigger version of the OD18 with hardtop and cabin. 


Here is one in the Gulfstream 20kt wind against the current. 


The OD18 pictured in the study plans, "No Excuse" piloted by the late Cracker Larry
had a few things to say about it...

Quote t does very good if you slow down a little. With 3 of us in the boat, in a 1-2 chop it's comfortable running low 20s. In bigger seas she'll comfortably run about 8-15 into any kind of slop you'd want to be out in, waist-head high stuff and close together. If it gets bigger than that, it's either got to spread out, or you got to go home. She's faster, more comfortable and drier in a following sea than a head sea and requires less attention. She doesn't like much slower than 8 mph, or faster than 15 into a sea, but handles a following sea well at any speed from idle to plane.

 He later got caught offshore in a building tropical storm at night...


Quote It was easy riding out the sound at 22 kts. and we ran about 3 miles offshore to get well clear of the bars and disturbed shallow waters along the beachfront, then set the GPS for the Charleston sea buoy, 85 miles, and turned north. It's 4 pm and dark is at 8 pm, no problem. Also had no problem with running into Charleston after dark if we needed to, it's a well marked, deep, shipping channel.

As we worked our way north up the coast of Hilton Head, the wind steadily increased and the seas were running about 4' with some occasional white caps, and we were getting pretty wet, but the boat was riding easy and we were still making good time, although we had slowed down to about 18-20. I headed a little further out, moving to deeper water. We passed the north end of Hilton Head and Port Royal Sound from 6 miles out. At this point it was getting rougher and we discussed heading into Pt. Royal and up to Beaufort, we had tentative reservations both in Beaufort and Charleston, but Port Royal is rough on a good day and I knew with the falling tide it would be real rough today, so we kept heading north up the coast of St. Helena Island.

As we headed up the coast the wind and waves kept building, now it was blowing a steady 25-30 out the NE and seas running about 6-8 feet. We slowed down some more, down to about 12 kts. A few miles later we started to get into some much larger waves and slowed down more, and more, down to about 5 kts. I knew NOAA was wrong and Miss Jimmy was right, she's always right about weather :lol: Where did this crap come from :doh: 

We soon got a set of waves that made the rest look small. I spun the boat to meet the first one and it was like hitting a brick wall. The second of the set was even larger and I had to keep a lot of power on her to hold the bow up so she wouldn't stuff. When we came off the backside it was like falling off a 2 story building. There was a loud crack and I knew something had busted. The next waves of the set made Dori tell me that I had to build her a bigger boat.She was not pleased, we couldn't see, couldn't breathe and we were taking on a lot of water. The scuppers and pump were keeping up, but if it got any worse, we'd found the limits of this boat.

Then a radio call came over VHF 16. A 65' shrimp boat was taking on water and sinking off Sullivans Island, south of Charleston. I punched in his co-ordinates on the GPS, he was 20 miles north of me and there was nothing I could do to help him. At this speed I'm 5 hours away. Said a prayer for them. We tuned back to NOAA and they'd finally woke up. "A tropical depression has developed off the GA/SC coast, winds building to 30-50 kts, seas building to 12-15 feet. Moving slowly up the coast and intensifying. Small craft should remain in port, yada,yada,yada, great.

Our next chance inshore was at St. Helena sound, but it's shallow, poorly marked and I'm not real familiar with it, and in these conditions we'd have to run it in the dark. Not a good choice, I'd rather stay offshore in deep water than get on some bars in an unfamiliar inlet with these waves breaking in the dark. It was almost 7 pm, an hour before dark. We kept plugging north, now making about 3 kts.

Then we got into another set of waves that left us no choice but to turn around. The boat couldn't take much more than that, and there was so much spay we couldn't even breathe. I keep a mask and snorkle in the boat and Dori put it on to keep the contact lenses in her eyes. Wish I had 2 of them.

We made a 180 turn, timing it careful on the wave face so we wouldn't broach, and headed back south. It was almost instant relief running with the sea. I put us on the back of 1 wave and stayed with it. No more pounding, no more spray, I could get a whole breath of air without salt water. We matched the wave speed of about 8 kts, dried off, lit a cigarette, made a drink, dang that felt good :D The only problem was, we were 8 miles offshore and the seas were still building. I would have kept running south all night, but Dori wanted in, now, the sooner the better. I set the GPS on the Port Royal sea buoy, 8 miles south of us. It's not a good inlet, but at least I'm familiar with it. I figured worse case I'd run her aground on St. Helena and we'd get out and walk. This boat is amazing in a following sea :lol: 

9 pm, past dark, got another radio call, a 49' shrimp boat was sinking 30 miles off Charleston. Said a prayer for them. 930 pm, another, a 65' sportfisherman had broke in half and sinking at the mouth of Charleston Harbor. Said a prayer for them too. We still had a long way to go. I called USCG Tybee, reported our position, situation, and set up a 15 minute reporting schedule. We were riding safe, but wanted someone to know where we were. Called Beaufort Downtown Marina and made arrangements for overnight dockage, called Charleston Harbor Resort and cancelled reservations for the night, called the Beaufort B&B and made sure we had a dry bed lined up, if we made it. I'd promised Dori a dry bed every night :wink: 

10 pm, made the Port Royal sea buoy, couldn't see it but the GPS said it was there. Turned up the north channel and lost all advantage of the following sea, back into it again but only a few miles to go before we'd get some protection. Running completely blind except for the chart plotter and compass. I had paper charts, but no possible way to use them in the wind and spray.

11 pm, made the Beaufort river and turned north, straight into the 40 mph. wind and a slow slog, but making 6 kts towards a hot shower. Wet and uncomfortable but not dangerous. Home free now.



I have no doubts about the hulls ability. I am not an old time charter captain though, and the boat is really designed as a good weather cruiser. It is ultimately very seaworthy however, I would never take it out in worse than moderate conditions. 








Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2019 at 8:18pm
Steps View Drop Down
Titanium
Titanium


Joined: 14 Oct 2013
Location: Sth Auckland
Status: Offline
Points: 8189
It says the hull weight is 500kg :/ How on earth did you get to 1300/1400kg unladen, most boats in that ballpark weigh less than that with the trailer still attached.

I got it as I explained in my post.
Will do so again..
displacement is about 1100kg.. now according to the basic Archimedes discovery a few 1000 yrs ago that becomes the weight of the boat..
Given a modern 18' 19' fiberglass boat, which is chopper gun into a mould, and light construction comes in around the 1250 1450kg gross weight on the water...And this is hand laid glass over ply with substantial framing for hull and cabin/ deck.. 

And again most glass boats loaded , no ppl in the 18' 19' range gross tow weight is still up in the 1250/ 1450 kg ball park range....

That boat is powered by a Honda 50hp and the builder gets a little under 24mph. Another guy got 31mph with a Suzuki 50hp but switched to a lower pitch prop

 And old argument.. basic physics.. this time newtons law.
 A given hp will move a given weight( plus drag) at a give max speed..in practice give or take a couple mph.
 Changing gearbox or final ratio.. eg prop pitch will not change the top speed.. when reaches max, prop slip comes in..
I note here that I roughly calculated a ball park that 50hp would give approx 20mph.. not 24mph.
 Being a 4S honda max hp at the prop will be approx 12 to 15% higher that will put it in the 55/56 hp and in flat conditions in salt water would most properly hit 24 mph as claimed... and I base that on my guesstimate of around gross weight on the water.

Which when reverse engineered pretty well make my guestimate ball park correct.

Regardless, I do like very much the old school appearance of these sorts of boats
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 23 May 2019 at 11:12pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
Yes. The 500kg is calculated using CAD software, with actual usage of ply, epoxy, glass, fillers and basic rigging. It excludes fuel, motor, ice, gear etc. 

It is accurate, but can not of course calculate how efficient a builder will be with materials, or the weight of options. 

Your estimate was a bit high.

Best apples to apples comparision to this hull though would be a Cdory19 which weighs significantly more. (1950lbs)

These boats are lighter than equivalent single skin fibreglass. That's simple Physics, and why large glass boats are often foam core. Plywood core has much higher Physical properties than foam core, so the laminates are thinner, but contribute significantly to strength. 


 1500kg and water is coming in the scuppers. (I have the plans and did double check this.) The boat pictured is fully rigged, one large occupant, and the scuppers are well above the WL. 

That contributes to lesser HP being needed, also the flat bottom is the most efficient planing surface. It pounds more, no miracle. The vee hull version of this boat, similar overall weight, moderate deadrise recommends a 90hp. 

I think that a 70hp would provide better all round performance for this boat, but in calm water would potentially push faster than is safe!

Edit: The quoted displacement is the designers idea of where the waterline should be for a boat in the water with a typical load. Obviously YMMV.

Edit2: Traditional ply on frame boats are a lot heavier, the frames are heavy. A Spira dory is a heavy creature. This boat has two full length stringers (20mm ply tabbed in) and a 13mm ply frame every 1000mm or so. That helps save weight.

Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2019 at 12:20am
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
Steps I really like the look of it too. The wife insisted on a 'roof' which eliminated most skiffs etc off the bat. The water down in Canterbury is a bit colder too so some shelter is a must I feel. 

Here's the other boat I have plans for, you will like this one if you are into traditional:


22' and recommended HP is a 30! 



I am not willing to put on and pay for a 150hp+ motor but want a little more speed than displacment, so that narrows options somewhat. 







Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2019 at 9:32am
Steps View Drop Down
Titanium
Titanium


Joined: 14 Oct 2013
Location: Sth Auckland
Status: Offline
Points: 8189
Your estimate was a bit high.

Yes could be.. have gone to the top end of estimated ball park.
 Do not forget, I owned a fiberglass manufacturing company back in the 80s.. Horse floats , bus/ camper bodies, air conditioning cases.


These boats are lighter than equivalent single skin fibreglass. That's simple Physics, and why large glass boats are often foam core. Plywood core has much higher Physical properties than foam core, so the laminates are thinner, but contribute significantly to strength. 

No.. A 70s/80 glass boat was basically thin laminates with min bulk heads to save weight (SN where way ahead of other boat construction design back in the day) ...the weight came in because the amount of resin the ply absorbed.. and being marine ply, thats a lot heavier anyway...
Glass over ply was always a far heavier boat..the technology of going to moulds back in the early 60s is what turned the whole industry around.
Add to all that.. to get a 3:1 ratio resin to glass laying up by hand and get a 100% wet out is very hard on a large project.. even small stuff.. and even harder with the timber sucking the resin in.
A chopper gun, mixes hardeners and resin, and also chops the roving and automatically meters resin weight and roving into chop strand, mixing the resin and glass in a spray before hitting the mould..Rolling out is quick.

Couple hints when laying up:
ALL external edges and cnrs radius generously .. the glass lays down easy.
Internal cnrs, radius with  body filler.. use this to hold things like bulkheads stingers in place....and when lay up 1st lay a couple lengths of rovings lengthways and wet out.
Makes laying internal radius s easy , no air pockets...and adds some lateral strength... also means use less resin to fill pockets.

The wife insisted on a 'roof' which eliminated most skiffs etc off the bat. The water down in Canterbury is a bit colder too so some shelter is a must I feel. 
 Totally agree m8.. even up here, having the commander cabin and bimini (which I have up permanently) one can always get out of the cold breeze..and if a shower comes over can even still fish well with 'Rodney'
 The other couple esentual things
1/ Portable toilet..private, under a seat and fits well to be comfortable.
2/ A table.. even portable for at least a single burner lpg cooker to fry a little bacon and eggs or a fresh cuppa.

The 18' 9" will suit you and the missus very nice, or 3 guys day fishing... and still tow ok.
 Get bigger and tow vehicle needs to get bigger..gets much heavier..more work at the ramps...
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2019 at 12:55pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
For a glass layup to be lighter than 400g biaxial on either side of 6mm ply it would need to be thin indeed. 

Edit: I’m not just saying this. Ply over frame is heavy I’ll give you that. Spira boats for example have a lot of two by four frames.

Modern stitch and glue boats are a different thing. With directional glass both sides of the ply they become a sandwich. In terms of engineering they are more akin to a cored glass boat than a wooden one. The framing and interior structure is mostly eliminated. Epoxy is mandatory in most of these designs. The glass skins are thin, much thinner than a chopped layup. Browse the bateau forum sometime. There are a lot of building threads where you can see the process and weights of the final product. The Hm19 I linked too is not the best example as the flat bottom needs more thickness.

These boats have more in common with foam core fiberglass than the old Hartley etc.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 24 May 2019 at 6:45pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574
I’ll post a few images from the plans if you are interested. Not enough to break copyright I think.
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote Steps Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 2019 at 10:11am
Steps View Drop Down
Titanium
Titanium


Joined: 14 Oct 2013
Location: Sth Auckland
Status: Offline
Points: 8189
Been down the links and side links off them...spent a bit of time...found quite nostalgically interesting.. takes me back to young childhood days and the old man and his boats/ building etc in the 50s / early 60s
Back to Top
Post Options Post Options   Likes (0) Likes(0)   Quote OneWayTraffic Quote  Post ReplyReply Direct Link To This Post Posted: 26 May 2019 at 12:33pm
OneWayTraffic View Drop Down
Platinum
Platinum


Joined: 19 Jan 2013
Status: Offline
Points: 1574

Here's the Internal Structure of the HM19. Bottom is 2 layers of 9mm, extremely heavy for a Merten's boat. That is probably due to the flat bottom. The vast majority of boats in 2m-6m have 6mm ply bottom. This inlcudes the P19 the moderate vee version of this hull. The bigger boats have biaxial both sides, two layers each side normally if planning to go faster than 35mph. All seams are taped on epoxy fillets.

For this boat Chine panels are 9mm, Hull sides 6mm. Glass both sides on the bottom and outside up to the Style line. All frames/panel joins below the sole taped in with biaxial, above the sole woven tape (biaxial option.) Glass is not specified on any other part. 

I believe that I could build this boat to close to the 500kg hull weight stated. However I would choose to add glass on the outside up to the sheer, on the sole, side decks and possibly a second layer on the bottom for impacts etc. That's all an option and not included in the stated hull weight. 


It's a long way from 2 by 4 framing every half metre or whatever a Hartley glass over ply had. 


Back to Top
Page  <1 678
Forum Jump
Forum Permissions View Drop Down


This page was generated in 0.414 seconds.